/diy/ - Do It Yourself

>>1441528
>>1441876
ok i am home and tried with the samsung tablet
and the charging amperage just jumps around wildly between 0.1A and 0.6A but that is maybe because the battery is 13% so it's trickle charging or some shit
In all other devices no change in current.
I tried both 2x82k resistors and 33k and 10k resistors.

I just don't know what else to try anymore...

but
but those aren't even words

>>1442280
Choose element boundaries such that magnetic flux through a closed path outside the element remains constant with respect to time.

>>1442285
memes aside, in which math/physics course is ∂ introduced? It's for the partial derivative, right?

>>1442292
In almost any circumstance you just treat it like a normal derivative, I've not ever had to do otherwise for any notable occasions when doing physics, and I'm a third year. Because of this it would probably just be glossed over in an early physics class, maybe in regards to springs.

The difference sort of matters in Lagrangian mechanics though.

What would happen if I attached a 60HZ AC power line to the hood of a car? How badly would it fuck it up?

>>1442417
It wouldn't, there is no ground for it to go because it's off the ground and on rubber tires

>>1442419

still, current would flow from live to neutral and would cause some sparking if it found a way thru the paint job. then the breaker would cut off power and you'd have to run inside to reset it. 120V can, in fact, vaporize small sections of metal, say half the size of a grain or rice, but you can do a lot more damage with conventional means: sharp objects, hammers, etc.

>>1442429
Wrong. Unless the car is grounded with a wire, connecting only the phase wire will do nothing.

>>1442429
Only if you have a neutral wire ;)

New thread, same bullshit bingo.

why is EE such an underpaid STEM branch, especially considering the time, effort, and work needed to get an EE degree in the first place?

>>1442483
>why is EE such an underpaid STEM branch,

It isn't. It's competitive with other branches of engineering, and higher than some like mechanical or civil. You might be comparing it to IT which is going through a weird phase, and it's a phase that might never end, but programmers seem like gods because some piece of crap software can be "valued" in billions before it has ever turned a profit. Of course, some pieces of crap software manage to make talentless hacks like Bill Gates and Mark Zuckerberg among the richest people on the planet, so that's where the hysteria comes from.

>>1442276
>I just don't know what else to try anymore...
tell me again what you are using for the 5v source

>>1442439
>if I attached a 60HZ AC power line to the hood of a car?
>connecting only the phase wire will do nothing.

i hope you dont live in a such a shithole country that your power lines only have 1 wire, and you gotta save for a month to buy the second wire.

>>1442419
rubber tyres are full of carbon to make them conductive. same with rubber wellington boots.
dont rely on them to protect you

>>1442483
EE's underpaid? since when?

As a soon-to-be EE major, what gives EE the reputation of being so difficult?
I've asked some of my math professors. One told me it "has some really nasty math", the other one just told me she couldn't tell me because despite being a physics doctor, Electricity was her weak point

from what I can ascertain it's just because it uses integrals. I've yet to find anything explicitly documenting the "really nasty math" of EE, so what are some examples of the difficult stuff of EE? What makes it so hard?

>>1442590

calculus II, eigenvalues, s-parameters, and a bunch of other things that i've been lucky to be able to forget, coz you never need that stuff outside of academia. the diploma just proves you're smart enough, or determined enough, to slog through that BS and come out the other side. they do it that way because that's how it's been done for 2000 years.

>>1442590
here in my uni teachers are either mentally insane or terrible teachers, but both camps (inlcuding the few good ones) are very demanding.

Question for you electronical guys:

Will my DMMs get destroyed by the batteries exploding if I don’t use them daily? Is there a type of battery that won’t assplode? I don’t want to destroy $150 in meters because of cheap batteries.

>>1442608

you're living in a world of delusion. none of what you said is real. stop doing drugs.

>>1442608
>I don’t want to destroy $150 in meters because of cheap batteries.
Take the batteries out when you aren't using them.

>>1442608
exploding batteries are a predictable consequence of tripfagging. stop doing that

>>1442276
did you even consider the possibility that the power path management circuitry is smart enough to feed the input power directly to run the tablet while charging, instead of sucking power from the battery?
here are two things you need to do:
- pass through the D+ and D- lines and measure what they're doing instead of guessing wildly and asking us why you're wrong
- put down the voltmeter and pick up some reading. see the bq24195 and MCP73871 datasheets for examples of what devices are doing in the 21st century. also google for "power path management" and read everything you can find

>>1442609
It happens to all of my flashlights and your mom told me that when I went on vacation and she wasn’t gettin that good D, she took out her vibrator for the first time in a months and it wouldn’t work because the batteries exploded.

>>1442613
Yeah I think that’s what I’m gonna do.

How do I fix this AC unit? The past couple times I used it the compressor would kick on and off and wasn’t cooling consistently. Turned it on today and the compressor ran for like 2min at first, got a little cold air, then shit stopped and it was just fans.

>>1442623
It’s short cycling and tripping on low pressure. You got no refrigerant

>>1442630
Ahh ok. That little portable thing will never get refilled.

Thinking about it too, the AC unit was running like a week ago and tripped the breaker. Never had that happen before and after that it seems like it hasn’t been working right.

The thing is a few years old so maybe it’s trash. Sucks though because those portable AC/ dehumidifier units aren’t cheap.

anyone got a schematic for an electrostatic precipitator/dust collector?

>>1442649
google first, dumbass

>>1442651
they all suck, smartass

>>1442590
I think it's a meme. The mechanical engineering students always worked harder.
There's a lot of math in EE, sure, but ME is a lot of work.

>>1442608
You mean leak salty shit everywhere? Buy some decent batteries for once, like Eneloop NiMH for example.

>>1442590

There's a lot to EE in general. But the most difficult things that I remember were Fourier transforms and convolution.

https://en.wikipedia.org/wiki/Fourier_transform
https://en.wikipedia.org/wiki/Convolution

>>1442608
Maybe you shouldn't be a fucking kike

Hey, I'm looking for books or youtube channels that would teach how to do electronics from scrap metal. We have an old farmhouse from the 1800s that's full of all kinds of junk, and it would be a fun learning experience for both me and my kid to construct something like windmills, water batteries, water heaters, etc. I once ran into a post WW2 book that was filled with good projects but I was stupid not to buy it at the time.

>>1442711
>water batteries

>>1442711
>I have junk, what do?
Take it to the recycler.

>>1442729
As in pump water somewhere high when you have surplus energy, then bring it down when there's no wind. I suppose the correct term is pumped-storage hydroelectricity. Hard to come up with the words since I come from the 3rd world where English is not spoken much.

>>1442731
But I want to use them for my hobby instead of recycling them.

>>1442620
>did you even consider the possibility that the power path management circuitry is smart enough to feed the input power directly to run the tablet while charging, instead of sucking power from the battery?
that can't be it since that would be retarded.
A phone with 13% battery life that draws only enough current to power itself instead of actually charging the battery even though the charger can provide up to 3A? Yeah not even chink phones would do that.

>>1442496
It's a buck converter connected to a 18AH 12V AGM lead battery (the battery can pump out dozens of amps steadily so no problem there)

>>1442740
Have you measured what the current is on an actual commercial charger?

>>1442750
No, but i don't need to because the original charger charges my phone in 2 hours while my ghetto charger takes like 7 hours or so when extrapolated.
The math checks out.

how do I analyse this circuit? like finding the equations that describe it? I am still having grasping as feedback and control.

say I have a preamp in my circuit to drive the signal of my synthesizer to 10+ volts for signal processing
when it's time to be amplified for the speaker, will running it through another amp just double (triple, boost...) the signal again and risk damaging the speaker, or will it just raise it to whatever voltage I set the gain to?

>>1442710
Easier said than done

>>1442679
Yeah and with the circuit boards and shit, I’m concerned how well it will work after that crusty bullshit gets all over. Happened to my Mag Lite recently and it was a pain in the ass to clean and get working again. If Duracells do that in flashlights, I’m afraid of what the cheap generic ones that came with the meter will do.

I took them out for now.

>>1442609
How old are you anyway? You have never pulled an old remote or something out of storage to find the insoded destroyed by crusty white battery innards?

>>1442773
The datasheet for LM317 feedback and control

The transistor is a PNP (read up differences between PNP and NPN, and application examples to get a better idea of how / why this works)
Current is flowing through the LM317, and as you know a current flowing through a resistor produces a voltage drop across it.
When enough current passes through the LM317 (and thus R1), it will cause Q1 to turn on more (due to the way a PNP transistor works), which allows the circuit to pass more current to the load than the LM317 on its own. Usually R1 is picked such that Q1 will begin to turn on sufficiently at certain currents. 100mA for instance, or 200mA

>>1442773
Kirchoff's laws, I_R3 = 1.25V, I_c = I_b*~100. Looks pretty similar to a BJT-assisted Zener regulator.

>>1442773
From feedback and control point of view... You're kinda out of luck, as the datasheet of the regulator omits required information.
You can analyze its basic operation, though, like the other anons said.

>>1442775
Typically you would have a fixed gain power amplifier, which has enough gain to produce its maximum power output at your maximum signal input.
Then you add a potentiometer in front of it to set the incoming signal level. Pic related.

>>1442792
This
Control theory is weird, tedious, and there aren't many resources on it
>tfw using op amps to help regulate power supply voltage
>tfw oscillation
>fuck you ;-;

>>1442740
>It's a buck converter
Are you monitoring the output voltage of the buck converter while the phone or tablet is connected and not charging properly?

>>1442608
The fuck are you doing with a $150 meter when you're asking retarded questions that demonstrate how little justification you have for a $150 meter?

Get the fuck out of our thread tripcunt. Go play with your pieces of shiny metal.

And now.. i become a man.
>b-b-but i-it-
No shut up, too expensive .

>>1442807
Nice
I would still trust a regular scope more. what if something you do causes your computer to get fucked up too instead of just your oscilloscope? But i am excited for you anon
I bought a second hand analogue scope for like 120 bucks. some of the rotary switches were finicky so i opened it up, sprayed some contact cleaner on them (while unit was off and unplugged)
works great now

>>1442801
Yes, first thing i suspected. The voltage is not dropping.

>>1442817
>hat if something you do causes your computer to get fucked up too instead of just your oscilloscope
Not gonna happen. I paid premium for an isolated model, therefore anything touching the probes is completely isolated from the USB ports.
I looked at stand alone scopes, but they were ridiculously expensive, the cheapest decent one costs like 7 times more than this one.
Plus regular scopes take up a lot of space.
Those were two negatives that were not justifiable to me specially since i will probably be using it only like once a week,

>>1442820
Well I hope you provide a detailed review in the coming weeks then (:

>>1442820
old analog scopes definitely take up a lot of space
modern digital scopes don't
Do you live in a cramped apartment anon?

>>1442824
There's always room for a scope. No apartment is that cramped.

>>1442824
my apartment is a single room
the main issue was the price, plus the portability of this one is great, it's so light i can barely feel in my hand

>>1442825
I think so too
but he said otherwise so i'm curious

>>1442826
You know modern scopes are light as fuck too right? Sure they might not be "barely feel it in my hand" light, but they probably weigh less than 5 lbs. maybe even less than 3 lbs
You're right on price though. They charge quite a bit even for the lowest models. But space taken up by a modern digital oscilloscope is a non issue

>>1442794
>>1442792
guy that asked the question here. Yeah pretty much, most control books use math in a very kinky way (I'm advanced in math but they just do weird, not smart, stuff to fit their lingo) and it bonkers my clonkers. I know I have to find the current that goes to the base, but how do I do that? If I assume constant voltage at the output I can find the current, but no the current that goes through Q1 or the regulator separatedly. Should I only assume that the regulator is maxed and the rest goes to Q1?

>>1442855
If you measure the voltage across R2, you can figure out the current passing through R2 and therefore the current flowing out of Q1's collector.
The voltage across R1 will allow you to figure out the current flowing through R1. Components in series have the same current flowing through them, so that gives you LM317's current

>>1442865
Yes I know that, but I want to do it analyticaly, not using measurements. I want to know if it's possible (or feasible) to analyze circuits like this analyticaly or this is where experience, fairies and electronics start merging.

>>1442880
I'd say it's possible to do while you're in regulation. So find what load will take you out of regulation given some Vin. The regulation current should be fairly linear with load I would think?

>>1442880
Use the datasheet for the BJT in question

>>1442781
>Usually R1 is picked such that Q1 will begin to turn on sufficiently at certain currents. 100mA for instance,

but the complicated bit is keeping the transistor from dumping the entire input voltage onto the load. so, explain why the output doesnt go to, say, 6V or 12V, and stays at 5V.

>>1442807
Nice and clean, doesn't float around at all.
I really like it for the small amount of rupees it cost.
It even has a cute little square wave generator (which the probe is connected to in the pic)
And all i need to do i click auto adjust and it sets up triggering and centering automatically, and so far flawlessly. No manual adjustments needed whatsoever.

>>1442886
Because if the voltage goes higher, the LM317's feedback will sense more voltage on the output and reduce the voltage, which reduces the current on R1, which reduces the current through the transistor blah blah

>>1442888
how to describe this using math?

>>1442895
Use the datasheets provided
And there's equations online - many resources explaining how to determine a BJT's various currents
But if you're talking about the feedback aspect, that's control theory again so you're shit out of luck
Maybe someone else can help you but i swear by measurements and decent guesses using the datasheets
You could have built and somewhat figured out how this circuit worked using measurements and changing parameters in the time it took for us to make these 4 or so exchanges

>>1442895
If you actually took the time to look at the LM317 datasheet (doesn't appear you have at all) then you would have noticed that there is literally an equation there that tells you how to determine its output voltage based on two resistors
jesus christ

>>1442900
Better yet. He could probably just draw the goddamn thing in LTSpice and derive some relationships there from a sweep.
Definitely some kind of student, we're doing his homework.

>>1442895
What do YOU think how it would be done?

>>1442926
>>1442900
I'm making a psu and I was trying to size up the transistors. I would need to know how much each would dissipate and thought understanding how to fully describe the system was a good exercise.
>>1442900
I read the datasheet and aplication notes, what you are saying is not what I'm asking. And the aplication notes have the pnp example but again, they do not give anything to explain it.
>>1442926
I was going to use the block diagram but got stumped there too.
>>1442896
I was going to do that, but I decided to try to understand it, using math. I want to learn (not only gather experience from tests and measurements; which is also very useful.).
>>1442904
>it works because the computer says it works
no shit, I know it'll increase the current capacity, I want to know which paremeters affect that.

>>1442984
>just buy a psu
>just take an old psu, take the psu out of the case and make a new one and call it a day
>just chug it in the computer
This is /diy/, I don't understand why you got so pissed. And to the anon asking about control, I think that's the only exit after all.

>>1442984
There isn't going to be a single equation that tells you what youre' going to get. You have the wrong idea if that's what you thought

>>1443008
I was thinking of a sytems of eqs, but most importantly the current in the transistor.

>>1443009
Have you still not looked up equations on how to determine the current in a transistor?
Because correlating that equation with information in the datasheet would give you that answer
It's been hours

What did you loot today, /ohm/? Picked these out of a Tornado storage unit that we decomissioned at my workplace a few days ago. I'm going back to get some 24V relays, contactors, connectors, rails and more shit over the weekend. I also *really* want the 60V linear power supply that's in there but I can't think of anything I could use it for to justify carrying 10-15 kgs of transformer home (and storing it). What do you even use 60 VDC for? And what are some applications for a RFI filter, except for a VFD? I've been considering putting one in front of my hi-fi power strips just for shits and giggles but can't think of anything other than that.

>>1443029
Also, can anyone tell me anything about this braking resistor? The markings are somewhat cryptic to me. The installation guy told me it was "good to 15 meters", meaning a it could brake a 15 m drop in one of these storage machines, but that's not very quantitative. He also said he thought it was 8 ohms although it measures 30, so... Its physical dimensions are 33x6x3 cm, it was braking a huge motor that was probably around 60-80 kg though our storage unit was like 2.5 m tall.

>>1443029
I can't think of anything really quick that would require 60V
maybe motors or other heavy duty machinery?

>>1443038
Some upmarket audio amplifier kits use 45-60 volt. I've actually been looking for a cheap one.

>>1443036
Let me google that for you.

>>1443044
Oh yeah older electronics might require high voltage. I forgot about that thanks
Was thinking in terms of modern shit we use which tends to be efficient, low voltage, good precision type stuff

>>1443051
Not necessarily older. High-end amps most often use PSU's in the 40-70 volt range for 200-250 watt output.

>>1443036
>braking resistor?
It's just a high dollar power resistor.
It's former application was for braking.
>>1443047
pic related is the rest of the story

>>1443055
Ah okay, didn't know that

>>1443038
Maybe, but DC? Also, if you were to power a beefy DC motor you'd use a proper controller, wouldn't you? Anyways, the only motors in these units were this really large one (which I didn't lug back home) and a smaller brushless AC servo which I forgot to take a picture of that was probably driven by the VFD in the picture.
I'll try to look around and trace where the 60 VDC is going if I can find some time for it over the weekend. It's just such an odd voltage, to me at least

>>1443044
I'd ship it to you if it weren't for the shipping costs ending up being nothing but cheap

>>1443047
Oh fuck, thanks mate. I tried googling some of the markings with no results, I should have tried harder.
Though to be quite honest I'm not sure I understand what I'm reading. I just expected a (continuous) power rating. What does PN mean, nominal power? And what the fuck is max surface temp @40 C supposed to mean?
Am I correct in reading this as it can basically handle 800 W of power at the worst conditions?

>>1443056
I'm considering using it as a braking resistor. If it actually were 8 ohm I could have used it for amplifier testing, but as I wrote
>although it measures 30
I'm a fucking noob but I know how to use a multimeter

>>1443029
>>1443036
I've been toying with the idea of converting my lathe to VFD drive on and off for the last year or two. My lathe's motor is rated to 550W, coincidentally exactly the same as the VFD in the pic. Would this be stretching it, or do I need to leave some headroom?
Ideally I'd want vector control and electronic braking, which I haven't even found out if this VFD supports. If it doesn't, I have a beefier Omron (I think it's a V7) lying around that I know has it, so that's not really an issue. Question is, what do I need to take into account when sizing braking resistors? Is bigger better (in terms of power rating), or can it become detrimental at some point?
Also I'd really like to avoid changing the motor. It's a single phase driven motor which can change direction with the flick of a switch, and I think I remember that it will change direction even when at speed. Does this mean that it's basically a normal 3 phase motor disguised behind a cap? I'd take a pic of the motor plate if it weren't for the fact that the lathe is a two hour drive away.

I'd be really happy if I could just get away with rewiring the motor, removing the fan and replacing it with a temp-triggered 24 V fan or something along those lines.

>>1443065
>maybe, but DC?
I don't know much about motors and controlling them dude. It was just an example.

>>1443065
>What does PN mean, nominal power?
Yes.
> what the fuck is max surface temp @40 C supposed to mean?
The given power value applies if the resistor's case temperature is 40C or less.
>it can basically handle 800 W of power at the worst conditions?
For 40s pulses, at 40C (initial) case temperature.

>>1443080
>The given power value applies if the resistor's case temperature is 40C or less.
But the given value is for temperature, not for power? Hence my confusion, "this temperature at this other temperature". I'm talking about the third column from the left.
>For 40s pulses, at 40C (initial) case temperature.
Explain like I'm more retarded than you think I am - what's a 40 second pulse? 2/3rds of a minute is more than a "pulse" in my mind. Exactly what does "40 s each 120 s" mean?

>>1443085
Right, should have been at 40C ambient temperature, instead of case temp.
The resistor temperature rises to the indicated value at max load at 40C ambient.
And that 40s each 120s = 40s on, 80s off. The resistor has quite a lot of thermal mass, so it won't reach steady state in 40s.

>>1443091
That's what I suspected. Thank you for your patience, senpai.

Hi, guys. I'm making a small FM transmitter but I don't have a transistor (2n3563) and I need an equivalent, would the p2n2222 work?

>>1443170
google first, THEN post
https://electronics.stackexchange.com/questions/211306/looking-for-equivalent-transistor

>order a capacitive touch screen from Adafruit cus y not
>44.95 American toilet paper sheets
>get screwed on the UK VAT because they think USD = Euros lmao
>receive
>pic related
>flux all over the board
>white marks around some of the ICs
>Some joints are just shitty looking
>scorch marks on the ribbon cable
>even a possible solder bridge between pads

Should I complain or not bother? - I can't be fucked to send it back - I'll just reflow the joints.

>>1443183
it's not a Class III assembly, it's a prototyping tool. they aren't gonna clean no-clean flux off of it
as long as it's functional, just deal with it and thanks for the warning

>>1443185
Idk, seems to me that some of the joints are obviously shitty and if the ribbon cable is actually scorched, then seems like something slipped through QA.

>>1443183
/pol/ was right about limor fried

add mikeselectricstuff to youtube list pls

>>1443183
> solder bridge
Looks like a track to me anon..

How do i communicate between fartduino and raspberry pi? I have a simple code on arduino which is reading a thermistor value and i want to ducktape the arduino to the pi as an ADC but how do i make them communicate?

>>1443324
you have many, many options. SPI, UART via expansion port, UART via USB, morse-code-over-GPIO and more. you're the system designer, choose one

>>1443327
What is the simplest one?
I basically want something where i run a wire or two from the arduino GPIO to the rpi GPIO and then in simplr 2 lines of code on arduino i do:
SendtoPi("poop");

and then on pi something like
blahblah = ReadArduino(); # blahblah now equals "poop"

>>1443329
UART over USB, probably. plenty of tutorials on interacting with it this way
UART over expansion port could be physically smaller but you would need a logic level converter if your lolduino isn't a 3.3V type, and you might need to enable the serial ports on each end which might take some digging in documentation

>>1443332
I don't really want to wast an usb port since i only have one
And the other protols seem kind of needlessly complicated, i will just make something like a simple morse code by putting the logical pins up and down and reading them on the PI pins. It will be perfect since i only need to transfer small values

>>1443345
dear god. I was being facetious. read this
https://oscarliang.com/raspberry-pi-and-arduino-connected-serial-gpio/

eya lads
I want to turn this double usb port I took off an old tower into a female-to-female connector
am I supposed to cross the red and black wire or just connect everything by colour

>>1443172
Sorry man, but thanks

>>1443461
Why do you want a female-female connector?

>>1443495
it's forbidden love!

>>1443495
to connect standard usb devices (flash memory, mouse, etc) to my mobile devices
I had a female usb to micro usb adaptor but I guess it got swallowed up by my heaps of garbage

I've tried both ways now and I'm not getting a connection at all.. even on power-only devices like a keyboard light

>>1443503
Just a female-female A won't work for that, you need the ID pin grounded on the Micro USB side to tell the phone to go into host mode instead of device mode.

>>1443504
Oh.
I have a ton of micro usb cables though, how would I go about wiring that to the female USBs?

>>1443508
Match colours, Vcc to Vcc, D+ to D+, D- to D-, GND to GND, ID to GND. You usually won't have ID wired in the cable, you'd usually need to cut open the micro USB end to get to a solder point for it if there is one.

>>1443511
Ah, sounds like that's gonna be a bitch
Thanks for the info though, I'll see how far I get

>>1443515
Ye, for OTG cables it's easier to just >buy it

>>1443518
Opened up one of the micro usb cables and found a strand of copper wires outside the shielding (along with the usual steel(?) wires which I assume are to provide sturdiness to the cable)
Any chance that would be the ID connection?
If not, what might it be?

How do i attach a thermistor to a surface? I need to measure a hot plate temp but the values i am getting are totally off because the thermistor just isn't properly soak in the temperature i am guessing, i tried aluminium tape and that improved it a little but but it is still off by a lot

>>1443597
two part thermal adhesive

I want to measure the power consumption of an equipment that cannot be turned off. Also i dont have access to measure voltages, but i have the three phase cables separated so i can use a clamp meter to measure current. How much error should i expect if i only measure current and use nominal voltages in my calculations?

Ive been dismantling old mp3 players that were lying around my house because I was curious to see the circuitry inside and re use the lcd screens. Every time I opened it the battery smelled like strawberries, and one of them has lead in it. No rohs compliant tags on any of the three players I dismantled. Should I just dispose of everything? Am I getting cancer from prying those shits open? Pic related, it's two of the batteries.

Are these florescent glow starters worn out or is it normal for them to turn black and still work fine?

>>1442804
One was $70 and one was $80, I wanted something I wouldn’t be second guessing without going full Fluke. $7 HF meter got relegated to the car emergency bag.

I will go play with my shiny tools. I used a few of them last night to build a new tool cart so I have more room to store my shiny tools.

Time for stickers!

>>1443558
Likely not the shielding, that's just there to remove interference. The ID line is probably left unconnected, while the shielding should be grounded.

recommend me a soldering iron that heats up quickly, can take off many components at once and can be used for extended periods of time

>>1443741
If they start a lamp - they're OK. If they keep glowing or make new lamp blink - they're fuckered.

>>1443777
Thanks, so the only real way to tell is to start an actual lamp with them? Are some manufactured with black/silvery glass?

>>1442654
Thats because if they posted the proper designs full stop with no drm or paywall, hospitals would receive chink copies and not certifiable pieces of epa approved welds and pixie trails

>>1443773
>take off many components at once
I don't think there are multi tip soldering irons sorry

>>1443836
I assume he means in a row, i.e. not having to wait for the iron to heat up again, i.e. relies on raw power output not on heat capacity.

>>1443773
Hakko FX888 is reputed to have tight temperature control. Metcal-type irons are commonly recommended around here.
cheap Hakko clones work as well if you establish a rhythm

How can a scope measure voltage if i don't connect the krokodile clip on the probe to anything? I don't understand, if it doesn't have a ground as a zero reference, then to what is the show voltage a reference to?

>>1443909
Maybe what you're measuring has a ground instead of a (-) (computer power supplies are an example)
Oscilloscopes tend to have their (-) grounded too, which means it's automatically connected to your grounded device
This poses problems in other scenarios though so be careful. Like being stupid and trying to measure unisolated mains voltage with your oscilloscope - don't do that

>>1443913
>trying to measure unisolated mains voltage with your oscilloscope - don't do that
But the probe has a 10Mohm resistor in it so i don't see how you would even feel anything

>>1443914
It's not you i'm worried about

>>1443782
Yes and yes.

>>1443836
There actually are, and there are also tips which heat multiple joints at the same time.
Not that he's asking that.

>>1443909
Typical scope's probe ground = mains ground.

>>1443935
Well i read a post where it said that if you leave the scope floating and measure the main AC, then the scope's case will be at 200V potential and that to me sounds like bullshit since since the scope had a large resistor that cuts the current to almost nothing. So it should only be a problem if the probe is set to 1x instead of 10x

>>1443939
>Test instruments are connected to the protective ground through the third pin when the instrument is plugged into an AC outlet. The protective ground is generally connected to the chassis, keeping it at ground potential. The instrument signal ground is frequently connected to this point, forcing the instrument to make measurements with respect to chassis ground. Defeating the instrument ground, by clipping the third prong, connecting the instrument to an isolation transformer, or using a "cheater connector," is a dangerous practice that should never be done. In addition to being an unsafe practice, defeating the safety ground can be hazardous to equipment by allowing fault currents to flow through printed circuit boards instead of the chassis. Floating measurements can be made using an isolation amplifier or differential inputs.

Buchla, David, and Wayne McLachlan. Applied Electronic Instrumentation and Measurement. Merrill, 1992.

>>1443761
I stripped the whole thing down to the connector, both the grey and copper wires were connected to the.. shroud(?)
After removing the hot glue or whatever was used to coat the whole mess, turns out there isn't even a connector back there for the ID pin
Once I had that glue off though, I could slip the shroud off which exposes the actual pins what go inside the phone

Kind of looking over my options toward getting a connection between the third and fourth pin now, don't have a very precise soldering set sadly

If i take a pvc pipe, wrap a piece of wire around it, then put a neodymium magnet inside the pipe, and start jacking the pipe off, what voltage and current can i expect? on the ends of the wire?

I'm thinking of make a crude little spedometer for my bike. My aproach to calculating the speed would be getting the arduino to count how many times the spokes of the wheel have passed it per second. What could I use to detect when a spoke has passed the arduino?

Also, since I will likely be using some sort of LCD display, how can I waterproof the entire thing?

>>1443996
A rather common solution would be to attach a magnet to one spoke and use a reed tube or a hall sensor to detect it.

Is the only way to limit current to lower voltage?

>>1444004
Thanks man. I'll look into it.

>>1443973
One wrap? Nothing measurable.

>>1444057
What is some rough and easy way to calculate that? Like 10 loops vs 1000 loops, and a weaker magnet vs 2x stronger magnet etc..
Doesn't have to be totally precise

>>1444061
If you're not useless with math, just pick up a physics textbook
IIRC this was covered in high school physics so it's not that fucking hard, but I don't remember any of the equations

>>1444063
If it's like algebra i can handle that shit, but if needs like calculus and derivation and whatnot then fuck it, it will be simple to just measure it after every couple of loops

>>1444065
It is calculus but the way it is presented in a typical hs text book you only need to handle basic algebra

>>1444068

you wont find any generator calculations in any HS text book. at most, you'll find the formula for inductance, and even that wont help you coz you gotta plug in a couple of constants which you'll have a hard time determining. the only reasonable way is to look at a known device, like a shaker flashlight, or just measuring things.

>>1444040
>Is the only way to limit current to lower voltage?

there are simple circuits that will limit current based on the value of a resistor. just google ''constant-current circuit''

>>1444089
>'constant-current circuit''
Yeah i know those exist, but how do they do it?
For example I have a power supply where i can set 13V and current limit to say 100ma, so even when i short the + and - i will never get more than 100ma, so how does the power supply achieve it? I don't mean the parts it uses, but the actual mechanic, does it lower the voltage?

>>1444093

it lowers the current, which, as a consequence, lowers the voltage across the load. ohm's law cant be skirted around.

>>1444093
it lowers the voltage, which, as a consequence, lowers the current through the load. ohm's law cant be skirted around.

So I bought a "electro shock pen" since it was 77ct and I wanted to use the parts inside. This is what the insides look like. Anyone know what the parts are? I thought that 1 was a transistor (at least functionally) and 2 somehow stepped up the voltage? If so how since it's DC?
since 2 has 3 ports I don't know what it could be.

Also in the sketch kathode and anode are wrong, but apart from the transistor type that shouldn't make any difference.

Thanks for help

>>1444141
I think it simply steps up voltage which chargers a capacitor with tiny capacitance to a high voltage and then it discharges small amount of current, like when you touch something metal and get a static shock

>>1444096
>ohm's law cant be skirted around.
It does not apply to everything. For example, your random switcher draws less current if you increase the input voltage.

>>1444093
If your power supply is set for 13V 100mA current limit then it'll maintain 13V as long as your load draws 100mA or less. As soon as your load tries to pull more current the voltage begins to drop. If you short the output of your power supply the voltage will drop to nearly to zero (the exact voltage will depend on resistance of the connection that's shorting your PSU, millivolt range most likely).

If you have a bench power supply with either an analog or digital readout then try setting a current limit and shorting out the supply. Watch the voltage display, you should immediately see it drop to around zero. Also, if you have the parts try slightly overloading the power supply. Set your supply to 5V 100mA and stick a 20-30 ohm 0.5W resistor on there. Depending on the exact resistor values you have on hand the load should try to draw somewhere between 167 and 250mA but it won't be able to due to the 100mA current limit. You should see the voltage drop.

What setting a constant voltage and current on a power supply basically means is you are setting a constant power is power is the product of voltage and current. Setting the power supply to 5V 100mA as above means the maximum output power it can supply is 0.5W. Let's say you put a 20 ohm load on that power supply. At 5V/20 ohms is 250mA, but you can't draw 250mA because of the 100mA current limit so your voltage will fall. What will it fall to? V = sqrt(P*R), the voltage you will get out is 3.16V instead of 5V.

>>1444161
Thanks that pretty much confirms my assumption.
I was just confused by the fact the voltage readout on the display was showing 12V even though the current limiting was active due to shorted wires.

>>1444168
That's weird, it shouldn't do that. My PSU has an analog readout and I see the voltage needle drop any time I exceed the set current limit. I also have one with a digital display that I believe does the same kind of thing. Sounds like your supply only displays the set voltage and doesn't actually measure the output.

>>1444141
https://www.youtube.com/watch?v=GEH5DSU9L48

>>1444161
20Ω*0.1A=2V

>>1444141
>1 was a transistor
it's a type of multivibrator
>>1444141
>2 somehow stepped up the voltage?
it's a transformer
>>1444141
>If so how since it's DC?
The same way the tried and true points and coil ignition system worked on internal combustion engines for years.
The pulsing DC (actually the collapse of the field when the 12v is removed) causes the secondary of the coil (a transformer) to generate a high voltage to make the spark plug work.
This could also be done with a buzzer in the circuit with the transformer primary and the power source.
The contacts in the electro-mechanical buzzer are opening and closing to make the armature of the buzzer vibrate.
If the primary is connected in series the secondary will have high voltage induced in time with the buzzer contacts.
Ancient auto radios had tubes and needed a source of high voltage for the tube plates.
A special 'vibrator' was used in a similar manner.
<< pic related

>>1444223
>>1444173
>>1444143
Thanks for the answers. I didnt think of a transformer because I was stuck on DC, but if the microchip 1 is a vibrator it makes sense the transformer would work. Thanks guys!

>>1444284
AC is pretty much completely necessary to step up voltages in the first place, barring some weird things like charge pumps.

Why are there so many photonicinduction wannabes on youtube? Some even use the same phrases as him.

can yall reccomend some good fb pages to follow to learn more about electronics?

>>1444361
his projects area cool but his videos suck

>>1444384
Why fb? youtube and forums are where its at imo, afrotechmods is good for beginners as well as electrobooms more educational videos. diodegonewild too.

Just try not to get distracted by people blowing things up with electricity as although its fun you don't really learn a great deal from them.

>>1444387
What makes them suck?

>>1444391
Very amaterish, feel like i'm in the early 90s with them. and not terribly educational (I'd like a bit of educational value)

>>1444393
There's an entire crowd out there making similar "blow shit up with electricity" videos, most of them struggle when it comes to designing something useful.

>>1444390
idk I'd like to just see random stuff popping up on my feed and learn a bit everytime, like a magazine

>>1444285
Yeah, that's where my confusion came from, I'm still very much new to most of this and while I knew how to make DC from AC via for example full bridge rectifiers, the other equivalent DC->AC was new to me. Thanks to the fast answers I understand it now.

>>1444394
Yeah, and I don't like them either for the most part
Electroboom teaches you shit which is why I appreciate his channel

>>1444422
Oscillators are a pretty essential part of modern circuits, and there are various interesting circuits for producing various waveforms. Notably is the 555 timer, op-amp oscillator, 2-transistor relaxation oscillator, a variety of crystal oscillator and resonator topologies. Then there's feedback + phase shift oscillators, which are more sinusoidal than the others, lest you go for something resonant.

>>1444174
I think he steers away from making his videos too educational since most of the stuff he showcases is very high power high voltage and he doesn't wanna be responsible for some idiot trying to replicate the stuff he does and getting themselves killed. He's had years of experience as engineer working with high power electronics like that (think he owns his own company) and knows safety for that stuff inside and out. Hobbyists don't have that experience and these aren't the kinds of projects you should really attempt unless you've made a career out of working with high voltage power distribution equipment.

That said, the video quality is still ass and the last video he did where he whined about committing suicide because the UK won't let him import his pajeet wife was just pathetic. I couldn't finish the whole video, I was like, seriously, grow a fucking pair man. I also wouldn't mind his videos being a bit more educational but I can understand why he doesn't do it.

>>1444393
I think he steers away from making his videos too educational since most of the stuff he showcases is very high power high voltage and he doesn't wanna be responsible for some idiot trying to replicate the stuff he does and getting themselves killed. He's had years of experience as engineer working with high power electronics like that (think he owns his own company) and knows safety for that stuff inside and out. Hobbyists don't have that experience and these aren't the kinds of projects you should really attempt unless you've made a career out of working with high voltage power distribution equipment.

That said, the video quality is still ass and the last video he did where he whined about committing suicide because the UK won't let him import his pajeet wife was just pathetic. I couldn't finish the whole video, I was like, seriously, grow a fucking pair man. I also wouldn't mind his videos being a bit more educational but I can understand why he doesn't do it.

HV capacitor anon here. Was kind of stumped where to find high voltage diode tubes fit for my purpose, but then I remembered our industrious little friends across the river. If I stack all 10 of these in series will they just shit themselves because they're chinkshit?

>>1444438
>high voltage etc
yeah fair enough

>crying
he didn't
I thought he wasn't with his foreigner wife anymore

>>1444443
As of his last video, and maybe stuff has changed since, he was still married but he was having issues getting the UK to approve her citizenship or something. It's ironic considering the UK lets in just about anyone these days. I get that that's frustrating but he was being a little bitch about it imo. He talking about how he was contemplating killing himself after her request for citizenship was rejected for the whateverth time and then I think the video kinda went off the rails and he started talking about some crazy psuedosciencey electronic device he planned to build. I closed the video around that point because it was starting to sound like the ramblings of a lunatic. This guy has some real women issues and it really gets in the way of him making good content.

>>1442590
The professor and grading scheme, imo. The math isn't bad, the programming isn't bad, the analog isn't bad, the theories aren't bad, BUT HOLY HELL ARE THE TEACHERS AND TA'S TRASH. Not to mention if you're not a popular/rich student, i.e. you transferred and are poor as hell, people just won't study or do homework with you. I mean in any fucking classes. With most of the classes, the tests were graded on curve, the homework was too. Except the homework could be five 1-3 hour problems. Most students who were their natively, longer, or had connections, just did 1/5 problems and copied the other four. Literally our professors would tell us to just copy homework in group.

An example is in one of my classes, a professor heard students were copying right from chegg. So they put up a bad answer. More than HALF THE CLASS was cheating. What do they do? Give those students a 0 for that one homework and move on.

Better, I had a mixed 4xx/5xx level class - Photonics of all the damn things. 5+ MS level students were cheating on a midterm, after the one TA proctoring walked out. I reported it to the ethics system, it supposedly went up, came back down to our undergraduate director, they asked the one professor and TA if anything happened. They both said no, case closed. I only found out the following spring, because there was no notice sent to students, nobody was questioned, etc.

And then 3/4 of my senior project partners did nothing for it. Christ Almighty I tore everyone to shit in the review, including the advisor and the school. Product was a medical device without a strict design ready, which had an expected revenue of billions within the first five years. You bet I was fucking furious we didn't get something even prototyped.

The worst part of EE is the people. Period.

So i want to implement a SIMPLE current limiter into my circuit.
So i was thinking that i would use an opamp as current sense and if the current goes above a set value, the op amp will trigger a relay, which will redirect the current through an lm317 in a constant current configuration
What do you think?

what does trimpot labeled UVP mean?

>>1444479
You can implement that natively just by running the thing off the current source all the time, if your resistance is too high it will just hit max voltage and act like a normal voltage source, probably. It works with a current mirror, but that's lossy.

how to get bench psu to swing down to zero volts without using another voltage source to offset the regulators?

>>1444492
The most straightforward way would be to use a regulator which allows you to adjust its reference to zero. LT3080 is one such regulator, or you can build your own from an opamp and some transistors.

Or you can produce your negative voltage with an 7660 or something similar.

Why don't you people invert truly wireless charging?
The inductive shit is gay because the range is like 5mm.
I want my charger to have same range as my wifi router.
Get on it nerds. I'll check back in a week.

>>1444514
https://en.wikipedia.org/wiki/Inverse-square_law

>>1444515
Excuses. Just use more powerful source.

>>1444514
>>1444515
In addition to this, lets say you want 10W charging (5V 2A like USB). Your phone has an area of about (10cm)^2 = 1E-4m^2 for a generous estimate, so at a distance of 10m the intensity needs to be 100,000W/m^2. Power is given by the equation
I = P/(4πR^2) which we can rearrange to P = I*4πR^2. 100,000*4*π*10^2 = 126MW. Personally I'd not stand within a km of something radiating power at that rate.

>inb4 directionality
You'd need something to constantly rotate a dish or laser to point at your phone, which is impractical with ordinary shaky movements. Also anybody standing in the way of the beam would feel it, to say nothing of your walls and

>>1444523
Check & mate egghead boy.
https://www.youtube.com/watch?v=YeNXRD8eziA

I'm trying to build a LED controller that uses a Frequency to V converter for the arduino to feed data to the RGB LED strip.
Here's the project I'm following, https://github.com/DevonCrawford/LED-Music-Visualizer

I'm about to build the freq to V converter in the image but I'm not sure where my audio (frequecy) input would go and what part to connect to the arduino, and where it connects to the arduino.

Also there's a part labeled ".tran 10" what's that?

>>1444528
Kinda works, but the efficiency is terrible https://www.youtube.com/watch?v=2bXjn3wwM8o

>>1444545
V2 is the audio frequency, Vout goes to an ADC pin on the lolduino.

.tran 10 is the instruction to the simulation software to run a normal simulation for 10 seconds.

>>1444484
Any other clues? What's the circuit/device it's in?

>>1444484
wild guess, undervoltage protection

>>1444447
Damn that's unfortunate
>tfw i just realized i missed hex

what is it anyway
>>1444444

Quick question.
O purchased one of those led strip things from china.
Pic related
If one led need 2V 20ma to work and i want to light up the whole belt, which is 300 leds, does that mean i need 600V? Because that seems stupid. Yet when i connect normal LEDs (the ones with two legs) in series i have to add 2V for each new led

>>1444611
white leds need 3V, there are parrallel blocks of 4 in series in strips like this, you need 12V power supply

>>1444627
Are you sure? Seems there are only 3 in the set

>>1444628
is that your or stock photo? if yours then why that first question, if stock then wait until yours arrive

also
>purchased from china
what was written on webpage you got it from?

>>1444633
The second photo is mine.
I never used a led strip before and i am scared of burning it.
The problem is that the page here
https://www.aliexpress.com/item/LED-light-2835-warm-white-DC12V-5M-60led-1-meter-300led-5meter-1roll-3led-1-scissor/32755361323.html?spm=a2g0s.9042311.0.0.15334c4dM37RUp

Says it's 12V DC, but i assume the leds are separrated by the copper contats which puts only 3LEDs in a strip which would be 9V
So if i connected them to 12V the entire strip would dieded

I'm attempting to make this:

https://www.youtube.com/watch?v=lU1GVVU9gLU&feature=youtu.be


Basically create a realtime LED audio waveform based on the pitch and volume with Arduino.

The video isn't super clear on how he made it all work and I'm just winging it as I go.

How do I connect everything to get the desired result?

>>1444650
https://learn.adafruit.com/piccolo/overview

there are hundreds of tutorials to do this. that youtube video is cancer

I'm a bit confused about multi-chamber transformers. Where are they used and why?
Looking for some literature but still haven't found anything worthwhile.

So far only idea I have is that they are used for clearance/creepage and isolation purposes.
Transformer bobbins like pic related.

>>1444628
Cut one 3 LED strip and put 12VDC to it and see how it works. It would be better if you have something to measure current and voltage with, so you could compare to other 2835 warm white LED characteristics to see if it's shitty chinese strip or a bit higher quality chinese led strip.

>>1444650
>>1444653
Yeah pretty aware the video is a piece of shit but that specific project is super interesting to me, I just need to pinout the specifics and I'm done.

I've tried bruteforcing every single connection

>>1444691
>I've tried bruteforcing every single connection

Please don't ever try to design electronics this way. Are you the electronics version of Bepis?

>>1444701
I've actually been brute-forcing my way for quite some time (way too long considering I could just sit down and read the fucking schematics) I always buy components to spare because I burn them

>>1444691
retard

>>1444712
Like I give a shit

>>1444657
>isolation purposes
You're on the right track, keep on searching.

>>1444657
So i decided to yolo it and connected the strip to a lead acid battery since it's the only 12V battery i have.
It lit up nice and bright and one thing i was surprised about was the fact it was only drawing 0.5A. The whole thing has 300 leds, that means 100 parallel segments which adds up to (or at least should) 2A at 12V.. yet i was only getting 0.5A. So either the chinks lied about the total amount of leds in the 5M reel, or they draw less current than the standard 20ma per led

>>1444650
>>1444653
>>1444691
I only skimmed the video - why is it cancer?

>>1444794
the hair

>>1444794
I'm the guy that posted it.
The fact he says LIT and BRO and doesn't even mention he used FastLED library wich basically takes all the work off his shoulders.

Also he doesn't even explain how it works or finish the project

>>1444498
can you point me int he direction of something like that with opamps? I`m trying some circuits here but I don`t see how to do it for large loads (that cancels out the option o zener`ing the output to zero) and the only option I see is to use a transformer

>>1444657
they are used for EM isolation purposes. If you want to know more get a book on "electrical machines" usually the first parts are about transformers.

>>1444832
Is it possible to just buy a class-d amplifier and use it as a power supply? 2 channels, zero crossing, and I don't think there's any DC blocking in there. Just feed an unregulated input voltage created with a potentiometer or something similar to each input and you've got two variable outputs with pretty low loss. Not to mention the things are damn cheap.

>>1444836
third worlder here, nothing is cheap when the dollar is 4 times your banana money. Also, I have like 10 smps from cellphones, computer and regular led drivers. I`m thinking doing a psu would be good experience after my pletysmograph.

>>1444837
Oh no go for it, I was just spitballing ideas. If you already have the parts then that's perfect. Mind mentioning where in the world you're from?

>>1444832
Pic related is a pretty typical such PSU. The stuff on the bottom right (VT3, R12, OP3...) is for the current limiter and can be omitted.
There's also a small design flaw in the current limiter: the current sense resistor is outside the voltage control loop, worsening the load regulation.

>>1444839
br huehue, I can find most things you can find in the US for cheapish prices, online, and that is the problem because either the shipping (thank you based mail government monopoly protecting me from fast and cheap shipping) is absurd and I need to buy lots of things to make it worth or it's in china and I need to pay them in obamas. I live in a hellhole called florianopolis, and if you try asking for anything better than a 741 on a electronics store they'll look at you like you are speaking some other language or charge your kidneys for it.

>>1444849
thanks anon, the middle part is the regulation one with the zener, the upper is a pass transistor but what is going on with the bottom and VT2 and VT3? (if it's too much hassle explaining I'll look into it later, it's late here.

>>1444442
Don't these types of diodes need potting in epoxy to prevent flash-over? Also putting the in series you have to be careful as they don't always share the voltage equally.

>>1444637
notice the resistor?

>>1444865
VT2 translates the drive current for the pass transistor. VT3 steals current from its base as the output current sensed by R20 exceeds the limit value

>>1444438
Think his wife was just after a greencard?

>>1444443
>I thought he wasn't with his foreigner wife anymore
Really? Where was that posted?

>>1444637
I've got some of these strip lights in my room, they've got resistors built into the strip to limit the current.

I actually run mine at about 10v as they're in my bedroom and 12v makes them too bright for my room (my desk is under them). This dropped the current from 2.8 amp to 1.25 amp in my case.

>>1444887
Each is 20kV, which is about 10mm in air, so yeah definitely. Or just a cardboard tube full of wax, which would be cheaper.

New to electronics and I'm thinking about researching circuits and electricity in general to safely work on tube radio restoration as a hobby. I've been watching a ton of videos and purchased a book on repairing shit, but one thing I don't get so far is why there are often times resistors right before a ground in some circuits. So they'll have a schematic of a DC circuit where power is being fed to a resistor before it goes to an LED, that much I get, but then sometimes they have a resistor AFTER the LED right before ground. What's the fucking point? And it's not just LEDs, I see resistors before ground in all kinds of things.

What's the point of a resistor after the component that the current is powering?

>>1444887
You have that wrong. You don't put diodes in parallel because they don't split the current evenly.

The forward voltage does vary slightly from diode to diode due to manufacturing tolerances and temperature but it's not an issue and the diode drops can just be added when in series. When reverse biased diodes are put in series the breakdown voltages can be added and that'll give you a total breakdown for the whole chain. 5x20kV diodes in series would have a total reverse breakdown voltage of 100kV.

>>1444949
in a simple series circuit such as you describe, the resulting circuit behavior is the same. the designer had a choice and he made it
first see Kirchhoff's Voltage Law and remember the commutative property of addition. also see Kirchhoff's Current Law and Ohm's Law. these are math you will use every day in electronics

>>1444984
Millman's theorem is the most useful theorem.

>>1444814
Oh jesus. I understand now

>>1444894
>Really? Where was that posted?
I don't know. It was something I remember reading a year or two ago on /ohm/

>>1444984
I saw a few videos on youtube about ohm's law and Kirchoff's law, but I think my confusion is partially stemming from conventional flow vs. electron flow. In schematics, we picture the signal going from positive to negative i.e. conventional flow, so it makes sense having that resistor before the LED so that the LED doesn't get blown out; but then there's electron flow which is said to go from negative to positive, so in that case, it would make sense to see a resistor between the LED and ground.

I'm sure this sort of thing will make more sense the more I read and apply schematics in real world use, but for now, it's confusing af.

For a comparator, if Vref is 5v, and the input is a sine wave that goes from 0-3v, the comparator will never output high?
How would I make a comparator sensitive to both larger and smaller input voltages? Would Vref need to be adjustable?

>>1445044
>sensitive to both larger and smaller input voltages
You mean turn something on if it's Vmax>V>Vmin? In that case making a schmitt trigger might do what you're looking for. If it's V<V1 or V>V2 where V2>V1, then you'll probably need multiple comparators and an OR gate.

>>1445046
>You mean turn something on if it's Vmax>V>Vmin? In that case making a schmitt trigger might do what you're looking for.
Yeah, exactly. I'll need to read more. People online say the only difference between a scmitt and comparator is hysteresis, but I guess I don't know what that means in this context.

>>1445060
Look at how you can build a schmitt trigger with a comparator, and how the feedback leads to a shifting reference voltage. It's surprisingly elegant the first time you see it.

But on second thought you'll still probably need two comparators, since the schmitt trigger will only trigger turn on passing up through the reference and off when passing dow through it. A rudimentary OR gate can be built with a few diodes, but you'll need to ensure that anything you're triggering with them can handle Vcc - ~0.7V from the diode's forward voltage.

>>1445030
It doesn't matter where the LED is as long it's in series with the resistor. The total resistance in a branch determines the current flowing through it, the exact position of that resistor is irrelevant as long as it's in the circuit branch in question.

A lot of people who are new to electronics seem to think that current flow is very high right up until the point that it hits the body of the resistor, after all how can the current know that there's a resistor in the circuit until it actually physically reaches it. This notion seems to make sense at firsts but it's not how it plays out in reality.

>>1444964
>You have that wrong.
No u. The reverse breakdown voltage and the reverse leakage current are even worse parameters than the forward voltage drop. If you want to get anywhere close to the nominal maximum voltage, you should add balancing resistors and preferably balancing capacitors, too. Pic related.

>>1445073
Okay, so there are some additional things to worry about with high voltage, whatever. Still right that it's fine to put diodes in series. Putting them in parallel is when you run into issues. You're arguing semantics.

Okay, I need you to check my autistic math on this shit:
So I have a led strip, same as the ones posted above, it takes standard 12DC.

I want to power it with 230V AC.
So here is what i want to do. Connect the power cable with the outlet (2 wires) directy to the led strip.
Then cut the AC wire that goes into the + led strip wire and place this in series there:
a simple diode to cut off the bottom part of the sine wave
a resistor with the value of 436 Ohms

And the simple math:
I need 12V 0.5A going into the leds.
I need the resistor to only allow 0.5A while dropping 218V.
218/0.5 = 436 Ohms

Since the sine wave is 0V 50% of the time, the energy the resistor needs to dissipate is average to 110V
And since the bottom of the sine wave is cut off, this further reduces the energy to be dissipate to the average of 55V per one sine wave.
This means the resistor needs to be able to dissipate 55V*0.5A of power, which is 27.5W

Is this correct? Will that work?

I realize this will make the led strip blink since the sine wave goes up and down, but it will be so fast that it won't matter.

>>1445075
>Still right that it's fine to put diodes in series.

>gets told exactly why it's not okay
>"ur right"
>"but it's still okay also semantics"

hurr?

For fuck's sake, Google exists, there's no excuse for this behavior.

http://www.nutsvolts.com/questions-and-answers/diodes-in-series

>>1445086
It's fine for literally any small signal low voltage application and you see it done all the time in bias networks to drop a fixed voltage.

>>1445087
>any small signal low voltage application
We are talking about high voltage diodes.
>drop a fixed voltage
We are talking about their reverse behavior.

>>1445089
Diodes in series is fine in 99.99% of electronics applications. Your particular situation is the 0.01% where it IS still acceptable but you have to be a bit more cautious. You are being a huge autist about this.

>>1445099
Don't confuse him with me, the guy who wants the diodes in the first place. But getting resistors big enough to use may be a pain. But why are the capacitors necessary anyhow?

>>1445083
problem: your 230Vac rms input actually peaks at 325V
>Since the sine wave is 0V 50% of the time
lol no
>average to 110V
nope, still 230 before you chop it in half
>55V*0.5A of power
no, (325V - 12V) / 2 for half wave = 156V
156V * 0.5A = 78W

>>1445109
You'd need high voltage resistors. While it's not a widely publicized spec, resistor do have voltage ratings and your standard resistors are usually rated to something like 250V, maybe a bit more. As for what values you'd need to even out your voltage drops... I dunno. I'm gonna defer to someone more experienced with HV design than I am.

>>1445111
You always use the RMS value to calculate power not the peak, should be 54.5W. The guy you're responding to IS wrong about literally everything but I figured I'd just point that out.

>>1445083
>>1445111
Anything more than 1W is a failure, considering common resistors can handle 0.25W. Put a capacitor in series instead, and before the rectifier (but mind how you calculate the capacitance value).

>>1445112
Looks like I'll be wanting resistors in the range of tens to hundreds of GΩ anyhow, which the existing parasitic resistance might already cover.

oh fuck i forgot to eat the brazil nuts

>>1445111
>325V
How?

>>1445143

What is the name of the metal bit that plugs the wire on this type of button?

>>1445172
crimp terminal receptacle. It is generic name since it's generic item.
Look up TE FASTON series, like 170331-1 or other depending on actual switch tab width.
Other manufacturers also have something similar

>>1445065
Starting to make more sense, thanks.

>>1445172
That switch looks like 1/4" terminals.
The same type are available in many sizes.

>>1445195
>>1445172
Thanks, I'll look into it.

>>1445178
female spade. fuck are you retarded? quoting specific part numbers for what is an out of patent design available in cheap generics. also i always solder those because spade terminals are for people who dont own soldering irons.

>>1445151
Nah in my country outlets are 230 and by that they mean top of the sine wave is 230

>>1445202
>by that they mean
[citation needed]

>>1445202
>160V AC RMS
Are you from some pacific island?

>>1445216
>>1445217
By your logic top of the sine in clappistan would be crispy deadly 220v

>>1445224
Voltage on appliances is written in RMS. Here is the US mains voltage, peaks are over 150V while RMS is about 110V.
In Europe 230V mains peak is about 320V.
There is a reason why in 230V power supplies engineers use 400V electrolytic caps - after rectification voltage is about 320V DC.

>>1445239
That is very confusing. Does that mean i have to calculate resistor values for my led strip based on peak sine or the rms as the guy said? Seems if i use rms then when the sine peaks at 320 it will fry the leds

>>1445245
Why can't you just buy a normal 12VDC power supply instead of nigger-rigging something that is very likely to kill you

>>1445245
Just buy a 12V power brick. Nearly all of them can supply up to or over 0.5A. You are a lot less likely to die and you won't blow up your LED string. I'd say design your own SMPS for this purpose but since we can't get past basic resistor math I think building an offline switching converter is way over your head. Just buy a premade one.

>>1445245
Yes, if you want to limit current to 0.5A at peak voltage, you'll have to recalculate resistance.
But problem is that you'll need high power resistor. Might as well just buy off the shelf 12V DC constant current power supply and be happy.
Safer, price will be around the same or even cheaper and accidentally touching led strip won't kill you.

>>1445245
>based on peak sine or the rms

you always calculate based on RMS.

>buy a normal 12VDC power supply

this is a very sensible idea. it's way safer, you dont have to worry about having 50W+ of heat to get rid of, and is probably cheaper. i find 12V 2-3A chargers at the thrift store every time i visit for $3.

Are automatic wire strippers worth it, or is it better to just stick with the cheaper, simple cutters?

>>1445257

only you can answer that question, dummy, based on how much stripping you do, and how frustrating you find it, and how much spare cash you have.

>>1445257
Had same dilema as you but in the end decided to buy them and i regretted it ever since because now i stripping wires with knifes regular pliers feels like stating fire by rubbing sticks. the auto strippers basically ruined all other methods of stripping for me

If I'm amplitude modulating audio does an event like pic related indicate I'm over-modulating it? I'm assuming, since it doesn't happen too regularly, that the audio input to the mixer is slightly too high and I need to attenuate it a bit, right?

>>1445273
Maybe, but why are you using a modulator capable of doing that, if you don't want it?

Why do i measure 10V on the output of my buck booster but when i connect load it's only 8.5V?

>>1445283
I'm not, at least I'm not doing it intentionally. I'm using an analog multiplier built with discrete transistors and I think it's not biased quite right. This is the schematic. I'm not using an IC like the NE602 cause I wanna feed in line level audio ideally (though I'm currently taking it off my DAC with it cranked to max). Using the IC the input signal levels aren't allowed to be any higher than something like 68mV due to it being internally biased very near the positive rail. This is probably fine for RF applications but it's just not acceptable for audio. Attenuating the audio to that level causes a major reduction in SNR

>>1445284
This is so fucking weird.

When i connected a 12V battery, the buck boost could easily get up to 29Volts as advertised.

Then i connected 5V wall charger instead, and i am unable to go above 8V with load connected.
Another weird thing was as i was turning the trimpot on the buck booster the wall charger started making annoying high pitched sound. As i kept turning the trimpot the sound kept changing in frequncy, but at the same time the voltage on the output was unchanging, 8.5V or so. So how the fuck was the sound changing and voltage was staying the same?
I checked the spec and the wall charger is 5V and 2.5A which is more than enough, all i need is is about 11.5V and no more than 0.450A on the output. So this comes to about 1A on the input, which is less than half of what the wall charger is rated for.
So why the FUCK isn't it working?

>>1445307
Tried another wall adapter and exact same story... fuck
Pic related, it's the schema for the buck
Why can't i turn 5V into 11V when i need to draw just a meesly 0.450A?

>>1445312
Did you have a load connected? Do you have enough watts?

>>1445172
>tfw my largest problem designing shit is discovering how that kind of stuff is called and finding that shit in catalogs
life is pain. It's actually worse in my native language
>english
>plug "some shit" female receptacle
>portuguese
>mango dog two pole borne
fucking historical reasons

>>1445321
Yeah i measure the voltage with the load connected.
I can't have enough watts when i can't get that piece of shit to produce 11 volts.

>>1445312
Are you using some module or have you built it yourself?
If yourself, what inductor you used ?

>>1445326
It's this magnum opus of electronics
https://www.aliexpress.com/item/MCIGICM-5pcs-MT3608-2A-Max-DC-DC-Step-Up-Power-Module-Booster-Power-Module/32704822301.html?spm=a2g0s.9042311.0.0.7d3b4c4di1CykU

>>1445327
Do the same thing with the noisy charger, but measure current, post results.

>>1445327
>>1445312
Since it's unlikely shit you bought is faulty, I suggest increasing input capacitance. I would suggest increments of 47uF to see if it improves.

>>1445329
>I suggest increasing input capacitance
You mean adding another cap in parallel to the 22u on between the VIN pins?
I do have a bunch of big caps, should u go straight away to a 560Uf one? I pulled it from an old psu

>>1445336
560uF might be a bit too much, but yes parallel to 22uF.
Also, I suggest before putting it to check voltage on VIN with wall adapter to see if it's stable with converter and load.

>>1445338
Ok thanks i'll try it tomorrow and report back, since it's really late and have a rat race to get back to in the morning

Why do you suspect it's the cap at fault here?

>>1445340
Not the cap, but wall adapter.
Increasing capacitance might help with sudden increase in current consumption in buck-boost converter.

It would help to see your actual setup how you connected everything, what wall adapter you are using, what actual power can wall adapter deliver etc.
If it's cheap chinese adapter - most of the time wires are not good enough to reliably deliver 1A without significant voltage drop so
thats why I would also test input current and voltage. I've had many where even at 500mA wires were getting warm

And since your setup works fine with 12V battery, it might also work just fine with 4.5, 3V or other batteries voltage batteries further suggesting that
wall adapter is not very good.

>>1445245
>Does that mean i have to calculate resistor values for my led strip based on peak sine or the rms
If you're just putting a load across normal AC then there's nothing wrong with using the RMS value, that's what you should be doing since it's the AC average based on power consumption. But if you rectify the power then you're making that 330V peak into 330VDC, in which case you need to calculate the resistor for this instead.

Still use a capacitive dropper, it's what cheap LED bulbs do.

>>1445245
>very confusing

It's even worse. The brightness of an LED follows the average current through it and the power dissipated by a resistor follows the rms value of the current.

If you want to limit the peak current to 0.5A you need a resistor R=(230V*sqrt(2)-12V)/0.5A=626Ω. Its dissipated power would be (0.5A/2)^2*R=39W and the average current through the LEDs would be 0.5A/π=0.16A.

Thanks to your half wave circuit this results in a dim LED strip, a nerve-wrecking 50Hz flicker and a resistor producing the heat of a soldering iron.

>>1445390
But in what circumstance would you not use a filtration capacitor?

>>1445392
cheap chinese shit.

>>1445245
Rms = dc equivalent that would dissipate the same average power. Grab a circuit book, or look up videos. the RMS value is there to help you, so you don't need to keep working with sines and cosines all the time, same for complex numbers and transforms. Usually to limit current in AC shit you use something called a Thrystor. (And it's brother the DIAC).

>>1445458
I mean if you were making your own.

>>1445257
>>1445267
can confirm, automatic wire strippers will CHANGE YOUR LIFE, my dude

>>1445294
did you manually match the discrete transistors as to gain and Vbe?
also, if you're creating a ring modulator, the NE567 PLL is really good for that

>>1445322
this is what anglos feel like when shopping on aliexpress

>>1445494
>limit current in AC shit
uh, a thyristor is a switch that turns on and stays on. it allows you to change the total power by allowing a circuit to block the first part of each half-sine, but doesn't limit current

My friend has some american devices and needs to use them in europe, is there any simple way to step down 230V AC to 110V AC?

>>1445674
depends on the devices
electronics that are "universal" (rated for 120V and 240V on the nameplate) just need a simple $2 plug adapter or a local power cord
devices with motors or heaters will probably work with a step-down transformer, but these can be heavy to lug around
devices that are line-frequency-dependent probably won't run well or at all

>>1445676
How about using computer source and connecting it to the inside of the device where ac turns into dc?

>>1445678
It's like old radio parts and such

>>1445603
To some extent LEDs can be run at higher than their rated voltage and current if you PWM them such that the average power over a small enough timespan is below their maximum, but obviously trying to accomplish this with anything more than ~150% the voltage is going to end badly. Not to mention the decreased luminous efficacy from running it above its forward voltage anyhow.

Also I think he meant TRIAC not thyristor/SCR, but the thought still makes some sense.

>>1445250
>>this is a very sensible idea. it's way safer, you dont have to worry about having 50W+ of heat to get rid of, and is probably cheaper. i find 12V 2-3A chargers at the thrift store
you probably mean 5V chargers. I have never seen any 12V chargers that aren't some large boxes intended for car battery charging

>>1445688
But wait i could look for notebook bricks instead of phone bricks, since the notebook ones are usually 12 - 19V and stepping that down is much easier than stepping 5V up and they handle much more current too

>>1445688
chargers ≠ power supplies
>>1445692
or you could just get a 12V power supply and use it directly

>>1445603
>>1445686
yeah TRIAC sorry, I was working with a thryristor and the name stuck on my head.

>>1445715
>12V power supply
too expensive. anything that costs more than $5 is too much
But if i can't one of them notebook bricks for cheap or even free from someone who has it left over after a notebook, then i have a free 19V DC power source than can do 4.5A

>>1445723
that would work, with one of those things >>1445327 links to

>>1445724
Since i only need to drop 5V and the resistance of the load will be identical all the time, then i think a small power resistor will be more economic than a buck converter, since it costs pennies and it only has to dissipate 2.5W which is nothing

>>1445718
What do you use thyristors for anyhow, besides unfiltered rectified AC, which I've seen maybe one or two things run off.

>>1445728
>2.5W
From what, a laptop PSU? Not mains that's for sure. Just buy a cheap 12V power supply from ali, like $3.
https://www.aliexpress.com/item/faggot/32677602188.html
Else try to adjust the output voltage of your power supply.

>>1445746
I was fucking around with one I got from scrap.Trying to find a use for it.

>>1445748
What does it output?

>>1445749
A cut of the upper mains wave with size depending of duty cycle. I managed to do a crowbar thing that detects shorts using a zener and some other stuff, but that is it.

>>1445752
Phase* not duty cycle, sorry.

>>1445752
Oh so a TRIAC-based dimmer? It will be possible to get it to output 12VDC but pretty tough. By that I mean get it to trigger at 9.98ms out of the half-wave period of 10.00ms, I'd give it up. You'll just get a wonky waveform, not a lower voltage, and once you've rectified and filtered it you'll have like 330VDC anyhow.

>>1445603
>did you manually match the discrete transistors as to gain and Vbe?

No, I didn't bother going through that effort. I did buy these transistors around the same time, the BJTs anyway so there's a reasonable chance they were cut from the same wafer and the parameter spread isn't completely awful. The JFETs are probably not well matched though. I also have some degenerative negative feedback via 5k1 resistors in the lower diff pair. I really just wanna allow enough output voltage swing that even minor variations won't cause issues with overmodulation. Incidentally I did make some small tweaks to the biasing that have eliminated the over modulation at the expense of reducing the average modulation depth slightly.

>ring modulator
Like the diode or mosfet ring modulator? No. I'm operating this mixer at much lower frequencies than those mixers are normally operated it. I can't use RF coupling transformers because they don't have the right bandwidth. I need much larger low frequency audio transformers for the signal input and some kind of transformer suitable for the longwave band for LO input and the IF output. If I get the design off the breadboard I might try for the shortwave or even the lower end of the AM broadcast band though so I can probably use wideband RF transformers in that case.

>>1445728
buck converters are only 1/4 burgerbux

>>1445746
>What do you use thyristors for anyhow
SCRs are good for turning on high-current dc with a small signal and triacs are good for turning on ac with a small signal, but generally cannot be turned off with a small signal (there are special types for that)
I've seen SCRs used extensively in e.g. photo flashes where the contents of a capacitor should be dumped through a flash tube as quickly as possible. apparently they're also used in variable frequency drives, welders, that sort of thing

>>1445764
right, mixer. as I said, the NE567 is pretty good for audio frequency mixing
https://www.diystompboxes.com/smfforum/index.php?topic=46995.0

>>1445769
I've never used a tone decoder before let alone used one to amplitude modulate a signal. Looks like it could work okay though. I don't have any on hand but maybe I'll pick some up.
It won't have any issues with a swept local oscillator on the input right? I will eventually ditch the fixed frequency for the first mixer stage.

>>1445780
Actually, I lied! I have an LM567 in my parts box. That's convenient.

>>1445780
its LO is built in. you could probably just couple it into pin 6 if it's clean but it probably wouldn't mind if you used a digipot or LDR
this looks like another worthwhile thread with some possibly less dodgy designs https://www.diystompboxes.com/smfforum/index.php?topic=104440.msg936560;topicseen

>>1445790
hmm, I might just use the discrete transistor mixer for my swept mixer stage and then use LM567 for the subsequent two stages which will both have fixed LOs.

I also need to get my hands on a VCO to generate the sweep as well. I'd picked up a LM2917 which I thought was a V->F and F->V converter but it turns out it's only the latter so I can't use it as a VCO. I think the LM331 is what I want but that I know I don't have off hand.

>>1445759
Electric showers here in the third world use triacs to control temperature, dimmers too. You get a lower average tension I guess.
It all depends when you start conducting. No idea if the led guy can do it tho.

>>1445338
>>1445340
So i tired adding 200uf caps to both inout and output but there was no change at all

>>1445803
VCxes are good reasons to buy a small collection of LM13(6|7)00 transconductance op amps btw

>>1445323
then get enough watts. you'll need a 2A adapter to cover the load and 10-20% more to cover conversion losses. I would suppose you don't have this

>>1445816
The adapter is rated for 2.5A so i have enough raw power to work with

>>1445810
This shit is driving me crazy. Could the chink buck booster just no be good enough? Because if i remove the load it jumps to 12V and i can set it up to the max 29V no problem, but the second i connect the load it falls to the 8V. Maybe the inductor is too small and can't handle stepping up the voltage with load connected.
But then again the buck is rated for 2A

>>1445819
>The adapter is rated for 2.5A
Keyword here is Rated. In reality it could shit itself at 1A continous drain. If you have multimeter, just test the current that is going into buck-boost and see what it reads. At 1.2MHz speed it should be quite accurate.

>>1445847
if it steps voltage up it's a boost converter
if it steps voltage down it's a buck converter
if it does both it's a buck-boost converter
please use the correct nomenclature
anyway that 2A rating is for the boost's switch. the inductor on the board may not be sufficient to boost to the voltage you need at the current you want, I seem to remember those were only rated for 1.5A continuous

>>1445859
Already did that. My load needs 0.5A at 12V to work properly.
I measured the current going into the buck which was about 0.7A. that is basically nothing. SHitty usb 2 port can do 0.5A easily. The adapter is rated for 2.5A even if the crafty merchant was like "Haha let's label there shitty 1A adapters as 2.5A, the goyim will never know!" then i still would have 0.3A unused reserve.

>>1445327
>>1445862
It's the boost converter the one from the link.
I only need 0.5A from it. So it's nowhere near the advertised limits.

>>1445810
If several capacitors showed no improvements, then there is no point in further trying to add them.
Maybe it's defective unit, for that price point I would not expect quality product.
I also would not expect this device to handle more than 1W applications reliably.

>>1445878
I bought an entire lot so i have 5 of them, i'll try another one, but i doubt it will change anything because one looks perfectly fine and not damaged

>>1445864
they could well have hobbled the chip with the rest of their design. the MT3608 datasheet is a bit shite. it's a good idea to derate chinkshit by 25-50%
that said, other anon inspired an idea: measure the voltage on the input side while powering the device you're trying to power

>>1445880
Did that, with load it dropped only by about 0.5V

I even tried with different charger and same result

>>1445882
Only other solution I would have is to measure feedback pin voltage. From datasheet I believe it should be around 0.5-0.7V. If it's below 0.5V - either regulation is not working or IC is trying to supply too much power. If it's above 0.7V - it sees output voltage as OK and is not going to supply more power. But cannot be sure how accurate readings would be without scope to see relation between input output and feedback.

>>1445887
i have oscilloscope

>>1445887
wait i just noticed something, adding 470uf cap at the input in parallel, made the leds a bit brighter and the output voltage jumped up by 0.2V

>>1445887
>>1445890
>>1445894
this is fucking supernatural

So i turn it out without the cap and it's all dim and shit. Then i add the cap, 470u, on the input and the leds start to blink between their current dim brightness and higher brightness. The the blinking slows and then they stay at the higher brightness.
So, now i remove the cap... and the still remain at the higher brigthness.. even without the cap... until i turn them off, after that they are dim again.

fucking sorcery

>>1445903
Made a quick video here.
https://www.youtube.com/watch?v=pXewHHotPzA&feature=youtu.be
Ignore the mess i am a slob enthusiast.

>>1445890
>>1445894
>>1445903
If you have scope post input and output waveforms with and without capacitor.
Maybe with feedback. Then again having them would probably already give you answer

I have an arduino nano clone and a Arduino UNO with a faulty bootloader, can I re-write the UNO's bootloader using the NANO?

>>1445956
You need an usb programmer for arduino it costs like half a buck on ali. It would be cheaper just to buy a new uno for $1.5
You can probably use nano but you need to connect the right pins

>>1445970
I've ordered a new UNO but I'm in a hurry
This nano clone doesn't follow the same pin order as the original and pin D10 and up doesn't exist so I'm guessing I'm fucked

>>1445938
This is without a cap

yellow is input, red is output

What's /ohm/'s recommended digital potentiometers for general purpose op-amp/audio use?

>>1445975
this is right after adding a cap

if i hold the cap there for a while the lines become both straight

>>1445978
Holy shit, your power supply is terrible.

Your input should not be dropping 3-4V. You have bad supplies. Literally your first image is your input dropping to 0V. You drained all the charge off the stabilizing capacitors. The reason it's more stable in the second case is just that, by having the capacitor you're probably reducing the instantaneous drain of current, so you're consuming slightly less current, which is either preventing full drop off. It's either triggering the current protection in the first pic, or draining the capacitors fully.

Alright stupid question, let's say I have a long, real wire, that connects to a voltage source, and a switch and a light in between. If the switch is on, obviously the light is shining. What exactly happens if I turn the switch off, will the light stop shining that very instant, or will it keep shining just a little longer, depending on the length of the wire?

>>1446006
current is identical in all parts of the circuit therefore it will turn off right away

>>1445808
Lower average power is fine for that. But when your load obeys the Shockley diode equation, having 20 times the voltage for 1/20th the time will still mean far greater power. Such dimmers should only be used on loads that can take the full duty cycle.

>>1445688
>you probably mean 5V chargers

are you implying i cant read, faggot? i'll have you know i graduated Harvard. Medicine. 1904. Dr. Cornelius Benway. Look it up, fag!

>>1446020
Even considering a real wire? I don't just mean ohms law, I mean with the magnetic field the wire creates and stuff, would it still turn off within the speed of light?

>>1446020
>current is identical in all parts of the circuit therefore it will turn off right away

quibble: except that there's thermal inertia in the burning lamp wire which will keep it lit for a sec.
current does stop immediately, so an LED, for example, would turn off immediately (unless it has a phosphorous coating)

>>1446020
Incorrect, the electric field will change at the speed of light within the wire, which is pretty fast but not quite c.

>>1446043
This desu

Also charge carriers have inertia. There's an effect which I can't remember the name of, ballistic something, where inductance results from charge carriers not accelerating quickly enough to match the oscillation of the electric field.

>>1446046
Ah, that's an interesting perspective.

Unfortunately it's not exactly a simple matter to describe the speed of light within a conductor, since this speed is proportional to frequency and any conductor will attenuate EM very rapidly. A straightforward thing to do is derive the speed of light in free space from Maxwell's equations, but in addition you can consider the situation where the light is travelling in a medium not only with non-unity relative permittivity but with non-zero conductivity also. The resulting speed can be determined through the dispersion relation, or by simply v = 1/√(µε)

We need LaTeX on /diy/.

>>1446046
usually for speed on transmission lines you need to go into wave autism. Hint, it varies widely from medium to medium. And in perfect conductors the electric field does not reside within the conductor.

I'm doing a MCU DSP project where I have a big array of pre-calculated kernels that I multiply my signal by.

Along the lines of
out[1] = signal[1] * kernel[1];
out[2] = signal[2] * kernel[2];

I want to use a lookup table to store the kernels in program memory and do the multiplications in a loop. Can I #define an array and then get elements from it like it's a normal array in RAM?

>>1446060
Neither does the magnetic field, though somewhat coincidentally. As I see it a superconductor is like a short-circuit for an electric field, the field propagates through it but stretched infinitely weak. In an extended way that putting a conductor in between two capacitor plates decreases the effective distance between those plates. But with a non-superconductor there's still a faint electric field within, there's still a voltage and therefore a power dissipation.

I have some LED strips I bought that should able to handle up to 12V. I powered one with a 9V and it was just file. I really want to power them from the wall.Should they be wired series or parallel? Would it be best to power them from some type of old wall charger?

How the heck do these hair straighteners work. Is it just a heat thing? Obviously looks like a PWM control

What should I do to clean a potentiometer if deoxit or contact cleaner do not work? On my receiver the Volume pot is extremely dirty or something, because it causes one or both channels to die if I turn it. I know that it is the volume potentiometer because if giving a good tap fixes it. I have tried to use Nutrol or whatever the MG chemicals equivalent of Deoxit is, along with some other brand contact cleaners and lubricants, but it seems that the fix never lasts. I think that it is due to humidity too, since it worked fine during colder months, but now since it is hot out and I have no AC it is a little bit muggy in the room that it is in.

>>1446148
The surface erodes. It's a physical problem with pots.

>>1446148
I put a bunch of pots that seemed to be covered in some greasy oily substance in a container full of distilled water and forgot about them for like 2-3 months. This is what it looks like now. I'll have to get them out, rinse them off and measure them. They're probably no good but I'm curious if they'll work at all, are in spec if they do, and whether or not they're actually clean.

>>1446065
> Can I #define an array
No. To store it in flash rather than RAM, it may suffice to just declare it "const", or you may need another implementation-specific qualifier (which will be described in the compiler's documentation).

>>1445976
whatever's cheap and has the interface you want

>>1446076
parallel
no

>>1446143
yes

>>1446143
>Obviously looks like a PWM control

when dealing with AC, it's not called PWM, but ''dimming'' or ''phase-fired control (PFC)''.

>>1446196
Is that supposed to be a sinusoid?

>>1446200
welcome to mains

>>1445975
>input side drops to 2V
>cutoff for converter is 2V
>power supply recharges capacitors because no load
>rinse and repeat

>>1446200
>Is that supposed to be a sinusoid?

it shows a sinusoidal input and a portion, or slice, of a sinusoid on the output. the bigger the slice, the more power goes to the load.

>>1445987
I'll try to put two chargers in series to see if it helps

>>1446253
I meant parallel

>>1446237
No I was commenting on the shape of the input waveform. It looks awful. Hence >>1446212.

>>1446254
That probably won't work, you'd have to give them a common voltage reference, and possibly other things as well.

>>1446256
You mean connecting grounds? I can do that. And they are both 5v.

>>1446260
No I don't mean that. Let's say that one PSU wants to output 5.05V and the other wants to output 4.95V, which are both well within spec. Put them in parallel and one will do significantly more work than the other, hence not splitting the load up correctly. Worse still, if the power dissipated by the PSU causes the voltage reference to drift even further from 5V you'll have thermal runaway on your hands. This is why I recommend that the voltage references at the least (~5V) should be shared between the two units.

>>1446260
no, internally. without precision matching they're going to fight each other and ultimately only one of them will do any work
series is a much better idea

>>1446265
>series is a much better idea
Well even if he can set them both to 2.5V I doubt he'll get much better ripple rejection, not to mention the inefficiencies of running two SMPS units together like that. I think the problem is that it's one of those ICs that have a poor feedback circuit by default, best thing is to get a better one. Could get a decent one of ali for like $3 if you know what you're looking for.

>>1446268
if the load will take 10V I don't see the problem. isn't that anon just feeding a boost module to get 11V?

>>1446264
How come you can use batteries in series without problems?

>>1446275
Shit, i meant parallel

>>1446275
Parallel batteries are usually fine because they can be expected to have the same internal resistance and follow the same voltage/charge gradient; they're not pumping voltage up to a reference.

When you place two different cells in parallel they equalise to have the same voltage across them (may produce much current, use a resistor if they haven't been connected together before). As you drain them the voltage across each will always be the same because current can go in and out of each cell and there is a continuous curve between voltage and charge. One cell drops voltage, the other one will pick up more of the load until the voltages are the same.

>>1446270
I think he wants 10V, but he's got 2 steps, the 5V (mains flyback converter?) adapter and his boost converter. Should just get a mains-to-12V module and be done with it.

>>1446278
becase they don't have active voltage regulators built into them, they're just chemical reactions

>>1446283
agreed. iirc he wants 11V at 450mA and he doesn't want to spend money on it
only a slight variation on >I have junk, what do

>>1446278
Even more-so, there's virtually no difference between putting batteries in parallel and putting capacitors in parallel, which is done all the time. Only difference is that I ≠ C*dV/dt, it will be something more complicated.

>>1446283
>should just get a mains-to-12V module and be done with it.
Because that would be same as giving up.

>>1446306
so be a curious child working well above your pay grade on your own time

>>1446309
you think Tesla gave up on fucking that pigeon just because everyone told him to rent a hooker instead?

>>1446264
Talking realistic, power supplies will have caps at the output, and they'll balance voltage easily. You'd get some high frequency noise because they'd be charging/discharging at different frequencies. Might also get weird things because one would be trying to charge the others capacitance.

Parallel supplies matter more when they're not regulators, or precision regulators without capacitors. The LM317, 78xx, etc are precision regulators/non-capacitative regulators. Something regulating within a few mV can easily be out of "spec" with another, so those need balancing. Batteries in parallel can cross-charge/discharge easily.

I need 400V for a Geiger counter, the power source is a 4.2V 18650. Although the output current is really low, I think it'd be more efficient to use a flyback transformer instead of an inductor. I'm having trouble deciding what IC to use, I currently have a bunch of 34063, but I was wondering if there's an IC better suited for this task.
I'm also having a bit of trouble with the design of the flyback, I know the Vout formula for a flyback (Vout = (1 / (N1/N2)) * (dc / (1-dc)) * Vin), and I know the ferrite core shouldn't reach saturation, but how do I find the maximum current and the optimal turns on the primary? do I choose an arbitrary (but reasonable) number of turns and calculate a frequency for which the maximum current doesn't causes saturation?

This is the transformer I'm going to use, the core is 4.6 by 3.9 mm, or 18mm^2, the material is ferrite.
https://www.aliexpress.com/item/20sets-lot-EE16-PC40-Ferrite-Magnetic-Core-and-5-Pins-5-Pins-Side-Entry-Plastic-Bobbin/32737490653.html

I'm going to read more on the topic, starting by https://www.ti.com/lit/ml/slup126/slup126.pdf

Also, does anyone know a good IC for usb charging a lithium battery? I have some chinese 4056 5Vin 1A battery charging modules and I could copy the circuit and use those ICs and the extra protection.

>>1446454
You could switch a current regulator for your flyback. Would prevent saturation at the cost of heat loss in the current regulator. I feel you'd want to make sure you have a diode on the inductor output or input, to prevent it from feeding back into the regulation side. If you switch the regulator off, there'd probably be some noise in turn-off that might interfere with flyback. If you use a mosfet at the ground, the regulator would ramp up to max voltage to try and push through the current, but it would fail and go back down when you re-connect the ground.

>>1446460
It shouldn't be hard to tune a frequency that limits the current given the impedance of the primary, current limiters are rarely used in DC-DC converters I believe, no need to complicate things further. I need to do the math and get a hold of some design procedure like the one above.
I might use a circuit similar to pic related, but with a BJT transistor instead of a MOSFET, since they don't work too well below 5 volts gate voltage.

>>1446476
Maybe I could set a fixed frequency and duty cycle with a microcontroller timer and use an OP amp to compare the output voltage with a reference zener diode and another OP amp to let the timer signal pass or not to the primary transistor. Since using a digital input to turn the clock signal on or off might interfere with the program, even if I use interrupts, since I also have to drive an HD44780 display.

I still need to do the math to figure out the maximum input current given the maximum output current that the tubes are going to use and figure out the turns in the primary and the frequency to avoid exceeding that current or saturating the core.

>>1446454
Please calm down Fajiik. It doesn't have to end like this!

I have this IC chip for a stepper motor. Do i understand it correctly that it's just a bunch of transistors inside that trigger larger current into the different wires on the servo, depending into which legs of the ic chip i apply small voltage to?
So i could basically remove the IC and apply voltage directly onto the stepper wires and it work as well, assuming my control voltage and current was high enough?

hello all,
I am ordering from aliexpress the ts100
I want some solder and some flux.
I will do some soldering on laptops and small arduino-like boards if that helps.
I don't care if the solder or the flux is toxic and kills the dolphins, I would like to have a good melting point and not get corroded easily.
any suggestions?
p.s. I'd order them locally but there's a tariff of 3-4 euros on anything for shipping... so it's cheaper to get it from china.

>>1446476
>current limiters are rarely used in DC-DC converters I believe
you're drunk, dude. current limiters are very common in boost converters, if nothing else to protect the switch
>since they don't work too well below 5 volts gate voltage.
you're really drunk, dude. don't buy MOSFETs that don't work well at 3.3V

>>1446490
ghetto af. why don't you just use an onboard ADC and vary the duty cycle ±1-2 according to your voltage reading every ms or so? HD44780s will hardly complain if you drive them too slowly

>>1446454
the TP4056 is bretty gud for low end work. don't try to run your application through the charger, though. instead, use two Schottky diodes to put the higher of the input voltage or the battery voltage into your application, or use a real power path manager IC like the bq24195 or one of its simpler cousins

>>1446512
basically. there are probably smarts inside the IC that prevent stupid things from happening, like shorting the rails

>>1446518
then Sn60 is your bag. get a fine wire (0.5mm or less) solder if you're going to be doing fine repairs
as for flux, most of it on aliexpress is diluted or fake. you should probably bite the bullet and buy locally for quality

>>1446528
>then Sn60 is your bag
thanks man, I appreciate it.

>>1446512
A stepper motor driver IC typically drives the phases in the correct order, possibly including half steps. Some of them also do smooth stepping and/or current limiting (if the coil resistance is particularly low, you can burn out the coil with less than a volt if you don't limit the current, either directly or by limiting the pulse width based upon the coil inductance).

I'm looking at some Hakko FX-888 clones on Ali since I left my soldering station back home. Are there any recommended ones? Don't know how much I should pay for one

>>1446449
I don't think you understand what >>1446264 is saying.

If you put two constant-voltage supplies in parallel, they are unlikely to contribute equal shares of the current. Whichever one has a lower reference voltage (and there will be some variation, however small) will supply most (or all) of the current and the other one will be idle.

Putting a low-value resistor between the output of each supply and the common output will reduce the variation, but will result in a lower output voltage and some wasted power. A higher resistance produces more balanced currents, but also a higher voltage drop and more wasted power.

The ratio of currents will be equal to the ratio of voltage drops. Suppose you want 5V@2A, and have two nominal 5V@1.5A supplies, one of which outputs 4.95V and the other 5.05V. If you put a 200mΩ resistor in each output, you'll draw 0.75A from the 4.95V supply and 1.25A from the 5.05V supply, with an output voltage of 4.8V.

Without a resistor, the 4.95V supply won't supply any current until you're drawing more from the 5.05V supply than it can provide and its output voltage dips below 4.95V.

>>1446614
why not put diodes at the outputs?

>>1446454
Dual comparator IC?

>>144666>>14466655>>1446665>>1446665>>1446665>>1446665>>1>>1446665>>1446665>>1446665>>1446665>>1446665446665>>1446665>>1446665>>1446665>>1446665>>1446665>>1446665

>>1446666
What a fuck up

>>1446666
what is this degeneracy?