/diy/ - Do It Yourself

this thread's digits brought to you by the famous L293 quad half-H drivers

Because i'm retarded my arduino slipped and fell into a bucket full of tap water, it was not powered, and i put it out in the sun to dry, will it be damaged?

>>1479297
Should be perfectly fine. In fact, even if it was powered it should be fine, at least for a few seconds.

rinse it with 95+% alcohol before letting it dry

>>1479303
this, especially if the tap water is particularly mineralicious

Hey i'm looking to get a few PCBs made and according to JLCPCB's website it's just 2$ (8$ with leadfree HASL) for 10pcs - what am i missing here? Is it really *that* cheap these days?

>>1479318
The not-cheapest-possible factory I usually use wants $5, so maybe.
Plus shipping, which is several times the cost of PCBs.

how is it possible that my clamp meter shows 0.13A current going in and 0.05A current going out? How is that possible? There are no ground connections or any other wires going into the world from the circuit

>>1479323

Which one are you using? PCBWay? I see OSHpark getting mentioned a lot but their prices are about the same as what i can get locally here in the balkans...

is it a bad idea to connect the ground from a device powered by buck converter to the ground of the source powering the buck converter?

>>1479318
yes it really is that cheap. price will increase based on size too. eevblog had a big pcb made and it was like 75 dollarydoos for 5 boards shippped which is cheap as fuck, according to him. I don't doubt it either though
THere are other channels that have shilled for JLCPCB talking about how good the traces are (no jagged edges in any orientation) and how resilient the solder mask is, comparing a different company's ordered PCBs which rubbed right off under 350 degree heat

>>1479365
A buck converter is a non-isolating topology, so the grounds are going to be connected.

>>1479421
Then i guess it was god who fried my arduino, since when i connected the ground from the touch sensor on the arduino, it dimmed and then 3 seconds later a large loud spark appeared in the middle of it and then it went to sleep forever

>>1479336
Yeah, PCBWay.
DirtyPCBs might be a little cheaper if you count in shipping.

>>1474893 (OP)

I bought and gutted two cheap chinkshit adapters for a project where I need 3V and 12V DC.
Can someone better acquainted with PCBs tell me if they can spot something terribly unsafe about them? They work fine and I plan on cleaning them up before use, it looks like they were cannibalized from somewhere else (there were the remains of cut input and output wires above where the chinks soldered new ones.)
Should I encase them (or parts of them) in polymer just to be sure? Put a thermostat between them to cut the power in case shit hits the fan?
Thanks.

>>1479457
Look like standard switching supplies.

How much amperage/power do you really need? If the power to the 3V is low, you could use a linear regulator. Sure, nearly a watt lost for 100mA circuit sounds bad, but it's only .1A off the 12V circuit for some heat and no 3V circuit needed. If you're looking for 3.3V and higher efficiency, you can use the 78xxsr series.

>>1479478
Eh, I already have them both, they cost basically nothing and the 12V one is 500mA so I'll be cutting it close.
As for power requirements, the 12V side will be powering a nixie clock while the 3V side will be powering an AM/FM radio, pretty sure it'll be less than a watt combined.

Can I produce frequency modulation by connecting the clock of a direct digital synthesis chip to a voltage controlled oscillator or does the clock need to be stable? I've googled it but I can't find any examples of someone doing that.

I need a function generator with analog frequency modulation. There used to be chips like the ICL8038 that could do that easily but they're all discontinued. With DDS chips a microcontroller writes some registers to change their frequency which means I'd need a fairly fast MCU and ADC to get the analog modulation throughput I want. If I used a VCO like the CD4046 as the DDS clock I could use a super cheap MCU that doesn't even have an ADC.

>>1479482
What frequencies you talking about here? In the old days you'd use a crystal or otherwise radio circuit.

A normal voltage-controlled oscillator converts analog voltage to analog frequency... not a modulation per-say. Just look up an FM radio. as for rate, someone in the last thread posted a fairly expensive DAC chip that was capable of 12-bit 20 MHz current modulation.

>>1479482
The chip itself allows it, but if you want use a proper output filter (like you should), then you have to set its passband based on the lowest input clock.

I'm back.
So I have changed my design, instead if iuncreasing the sensing distance i connected a wire from the sensing pad on the module to a piece of aluminum tape which gets touched directly by a hand.
This works great in the way that all touches are detected, but i get lots of misfires, when the sensor reports HIGH even when nobody is touching anything..
wat do?

>>1479318
estimate your shipping. i was quoted $13 to the US. i use elecrow personally, but the prices aren't different enough between sellers for single orders to matter. they're mostly shit boards.

Need help IDing this ic
The only results I find for 1508S are bridge rectifiers but the datasheet schematic doesn't match the formfactor of the ic on the board

Can this laser be regulated by PWM or do i need to some gimmick such as voltage regulator?
Basically it says you change the output by setting the TTL to 0 - 5V

>>1479575

Lasers generally don't like PWM at all. They want a driver that can supply constant current, which I'm going to guess is what you have pictured.

What I think you're asking, though, is if you can control the driver with PWM. I won't say it will with absolute certainty, but I'm reasonably sure it would accept a PWM signal directly. If not, you can simply rig up a filter to convert the PWM into a relatively clean DC signal that it will accept.

>>1479568
duuuuuuuude

https://translate.google.com/translate?hl=en&sl=ru&u=http://monitor (dot) espec (FUCKING) DOT) ws/section14/topic269595.html&prev=search

First result on Google images looks like your board.

"Vasilijj0071 , I understand that this unfortunate 1508 has not been identified by you. This is the MX1508 with various letters."

>>1479584
so there is a chance it wont work with pwm, but will pwm damage the driver board in any way? if not i can just try and see

>>1479602

I can't imagine it would. Worst-case scenario (assuming the maximum output of the driver is at or under the maximum of the diode) is that you get shitty results out of the laser from using a PWM frequency too low.

why can't I ever desolder shit properly
instead of melting, the solder just goes into some weird putty-like state, it doesn't flow into my solder wick, and then the flux runs out and it stops melting period.

I'm using a shitload of flux, I'm using the right temperature, what the hell am I doing wrong

>>1479602
Since the driver probably has inductors and things, PWM could fuck with that. Is there an identifiable chip? It might have a pin or two for pulsing vs continuous

>>1479604
Wick oxidized? Dunno, I've had the issue recently. You could try give the wick an acid wash, or scraping it, or "better", trying freshly bare stranded wire, etc.

As always, heat the thing to which you want the solder sticking.

>>1479603
basically what i want to do is attach the TTL to the wires going into my 3d printer nozzle fan (which is controlled by pwm) and then just use gcode to change the "fan speed" which is now actually the laser strength control, turning my printer into a laser engraver without having to take it apart

So basically, what I have is PWM 12V and i need to turn it into fluent 0 - 5V to control the laser

>>1479540
Increase the length of the antenna and rename your 'design' to Ghost Detector.

>>1479336
don't forget to compare design rules
>balkans
have you looked at Aisler? I can't speak to shipping cost, but their prices are about the same as OSHpark but their design rules are somewhat better. iirc their standard service is 4mil trace/space (vs. OSHpark's 6)

>>1479482
how much throughput do you want?

>>1479540
at least put some transparent tape over it so you're not receiving random dust motes
also try increasing C1 in 5-10pF increments. if you run twisted pair wire to the aluminum strip you get this capacitance for free

>>1479604
you've got the wick itself well fluxed, right?
>right temperature
which is?
hmm, larger tip? bump the temp up 10-20 degrees?

what do you all use to stop your helping hands/boards/components/etc from sliding around on your workbench? I'm trying to find a thin rubber mat on amazon but it's proving elusive

>>1479615
Yeah, I use enough that it oversaturates and pools underneath.
roughly 360 C, but I'll try higher, I guess it IS RoHS solder since it's mass produced.
I just ordered a solder sucker so we'll see how that works sunday

>>1479618
I hotglued my helping hands to a cardboard sheet, put some double sided tape on the bottom of the cardboard and ran some fabric across the tape until it didn't stick to the bench too hard but merely provided enough friction to keep it in one place.
It's stable now (thanks to the large base) and it doesn't move around, which is good enough for me.

>>1479618
weight, see Pic related
for the tiny chink "solder station" with two alligator clips, I filled the base with pennies and put some rubber feet on the bottom
cutting mats used for general crafting are commonly seen in videos/etc
also search for anti-static mat
>360°
hmm, that should be enough for any solder in common usage. how strong is the iron? how big is the part? is everything thermally well-coupled? did you sort yourself out? did you clean your tip?
what flux? is it no-clean? (you probably want something a bit more active than no-clean for rework)
do you have hot air? you might try pre-heating the area with it, and/or just using the air to melt solder and pull the component

>>1479615
>twisted pair wire
the second wire floating on both ends? because i can't ground it

>>1479304
a bit of limescale isn't going to short pins

>>1479622
75 watts. The flux pen I have is 100% in chinese so I've no clue what type it is. The wick is no clean though, which is why I've been using so much flux with it.

I do have a heat gun, but it's a shitty chinese one from harbor freight. The first (and last) time I used it, the initial offgas from the plastic and internals set off the fire alarm for 45 minutes and forced my condo complex to evacuate until the fire department could silence the alarm
I haven't touched it since

>>1479627
yes, increases ghost sensing

>>1479627
no, ground on the device end to add capacitance

>>1479629
>chink flux pen
probably pure Vaseline in IPA, kek
hmm, other than trying to maximize tip contact with the wick by angle or a larger tip selection, I don't know what you might do

where do I get the really fine, coated/enamled wire used in inductors and such?

>>1479659
search for 'magnet wire'

>>1479659
if burger, try Remington Industries out of Illinois. they sell magnet wire kits in many sizes, 22AWG-32AWG, for very reasonable prices, also single spools of enamel wire, nichrome wire, bare wire, insulated wire, etc.

>>1479668
I managed to find a really good deal on aliexpress, seems like it's exactly what I was looking for

So I accidentally destroyed a surface mount capacitor on my Logitech M570. How would I find out what the broken cap was so I can replace it?

>pic related, I broke C8, it looked like C7

>>1479767
first, figure out what the caps are doing by tracing out that part of the circuit. it looks like it's involved with Q2 on the other side. you would then read the marking and search for that SMD marking using your favorite search engine or an SMD codebook like s-manuals.com/smd to see what it does, if there are reference/example circuits in the datasheet. at a guess, it looks like a pretty usual voltage regulator with enable. I can't read the marking on the board photos I was able to find, but if this cap is a decoupling cap, larger is better
so now verify the size (you could get out your calipers and measure, or eyeball with a scale if you have a mm scale). to me, based on the tact switch being a 6mm model, I'd say those caps are only 1mm long, therefore probably 0402 (inch). I saw an image that had a pictorial view of the two caps (promise) and showed C8 was somewhat taller than C7, looked to be almost square from the terminal end. 1µF is the biggest commonly available 0402 cap, and will almost certainly do, unless you can track down the code and find that the datasheet forbids that large a cap (unlikely). looks like that's not in a particulary fun place on the board. tacky flux is your friend. happy tweezing
(thanks fjrg76 wordpress com)

can one of u geniuses explain this shit to me, this isnt normal right? its 2018
>dell 56wh standard li-ion battery type 33ydh 15.2v

>>1479782
oops wrong pic

>>1479781
Holy shit. That's why I love this place.

Any suggestions for a cheap, food-safe thermometer? I want a temperature-controlled butter conditioner.

>>1479785
there are a ton of stainless-steel thermocouple probes on alibay, which should all be pretty alright. connect to thermocouple amp/digitizer and enjoy
https://www.aliexpress.com/item/K-Type-Anal-Probe-Sensor-Temperature-for-Ayy-Lmao-with-Wire-Cable-TP-02/32844201839.html

>>1479293
>2nd year ee
>half of lab course is team project to come up with product ideas and then design product
>each team goes up to present ideas, better ones get more funding
>every team is just w-we thought of this great idea
>i-its a sensor that senses temperature
>i-ites a shower curtain that senses light
>i-its this household thing ubt now its internet of things related
this is normal right? my uni cant be that much of a meme, please tell me every uni is like this

>>1479790
The stainless thermocouples are fairly pricy, they're used in kilns and other high-temperature applications. Now that I think about it, a glass diode package is probably fairly food-safe, provided the tin plating is present and clean. But butter could presumably short the two leads, leading to a false measurement.

I'd like to have the butter itself sitting atop a thin piece of stainless with a TEC under it and a heater somewhere too. Since the cooling will come from underneath, and the heating will probably come from above, the butter will keep for longer by way of being soft enough to spread at the top but refrigerated at the bottom. But this requires that I have a temperature sensor at the bottom and at the top. Bottom is fairly easy if I get the right sensor, but the top needs to come away when you open it and go back onto the butter regardless of how much is left, so I'd want it to be flat and on a pivot with some sort of feedback to measure far down the sensor is. But even that pivot needs to be complicated to move up and down without the thing hitting the sides.

pic related

>>1479784
>>1479781
>>1479767
So C7 and C8 are connected in parallel, the trace leading to the IC (ATMEL 168PA 8 bit MCU) is a ground pin so there wouldn't be an example circuit in the data sheet, that's probably why nothing exactly broke when I snipped that cap.
They're connected to the line for TP12 and a small trace that leads to a via that's underneath the switch. TP12 is connected to common pin of the on/off switch, what looks like a voltage divider, and the rest is a rats nest of vias.
C7 measures 1.20 mm on my cheap calipers, so I think you're right about it being 0402
I've been suspecting that the cap had something to do with debouncing because the mouse double clicks.
I'm going to try putting in a 1uF cap like you suggested, if it doesn't fix the double clicks I may try replacing the omron switches

>>1479798
yes, uni is a meme

>>1479807
>The stainless thermocouples are fairly pricy,
well, a probe is the wrong form anyway. anything would do as long as it senses more of the butter than the top heater and is sufficiently accurate
as for the mechanical design, how about a sliding draw bar with a double-pivot, like Pic related?

>>1479813
the datasheet for the voltage regulator Q2 on the bottom, I mean
button presses could be causing the micro to undervolt since that other cap is probably something like 10nF and it might be running at the edge of the recommended Vcc range

>>1479819
The thing would move left and right as it goes up and down, plus it's a little bit of a pain to remove when you want to access the butter, but for that you just need to mount the pivot on the lid.

Now I want to add wifi to it so I can tell it I'm going to make some toast in the next 15 minutes through my phone and it will heat up a little, and I hate myself for it.

chinky-dinky frequency counter actually works well for $10

>>1479834
>$10
How about just use an arduino and your computer's dispaly for 1/3 the price? Not as convenient, but do you really need 8 digits? Do you think that thing is accurate to 8 digits?

>>1479874
Where them $3 arduinos at, friend?

>>1479874
I measured 7ppm against a supposedly 0.1ppm OCXO that has been running for about 24h continuously. have not tested against WWV or GPS standards yet
also a lolduino can't count at 50MHz let alone 450MHz, not very useful for radio
>inconvenience
>fewer digits
>lower performance
sold

>>1479798
>each team goes up to present ideas, better ones get more funding

That is kind of weird. For my earlier project courses we were just assigned what to do. For the third and fourth year ones we had a set budget and wrote multiple proposals the prof picked from. The decision was based on technical merit not how well it would do on kickstarter. There was an informal game of coming up with projects that could use recycled parts like all the CRTs the university was throwing away, pretending you bought things new, buying beer with the difference.

>>1479881
Maybe you could use a frequency divider

I am going to order the laser i talked about.
I found one that is $9 cheaper, it comes with the control board on the left.
But how come the board on the right has so many electronics on it? The parameters of the both lasers are the same, so they should function the same as well.
Is the one on the left some sort of shit?

>>1479798
maybe a bit much to ask of helicopter-parented kids for a 200-level?

>>1479892
Cornell's ECE4760 projects are a highlight of my springtime
apparently of some chink too http://people.ece.cornell.edu/land/courses/ece4760/FinalProjects/Student_Project_Plagiarized.pdf

>>1479893
I would still only get 16 bits of accuracy and not gotten an accurate time base. I could have used an STM32 if I could have figured out the timers on it, but they're pretty intense. maybe over christmas

>>1479895
toroid inductor, larger more expandable frame/heat sink, one fewer pot?
turn over lefty, there has to be more
any difference to the laser body? fan bearings?

>>1479899
There are no difference to the lasers. On paper they are both the same
The are no picture of the dark side of the PCB
https://www.aliexpress.com/item/tfw-no-gf/32914660936.html

>>1479901
the heat sink extrusion looks shorter and further from the laser module on the cheaper one
also no wire loom
just little details, but might be worth considering

>>1479902
Well i guess i will get the more expensive one, 9 bucks won't kill me and if it works better it will be worth it, plus the cheaper one doesn't even have an inductor, i don't know what it does there anyway, but it doesn't have it

>>1479904
yeah it does, it's in front of the left transistor. but it's not shielded
see, little touches

>>1479899
>end of that plagiarism article
das a lot of plagiarism holy fuck

>>1479905
i ordered the more expensive one
i really hope you aren't the person running that more expensive laser store

>>1479906
ikr? I'm not a fan of IP maximalism, but credit where credit is due ffs

>>1479909
kek, no. but I do find that in chinkshit you very often get what you pay for, and I usually prefer the second lowest price to the very lowest

>>1479913
I have ordered close to several hundred electronics devices from ali and i noticed one thing. they are exactly the same quality as the ones sold here except 5 or even 10 times cheaper
reason being that the retail jews also buy them from the same factories in china and then just do a massive mark up

the only downside of the buying from chinks is long shipping time and non existent warranty (technically you get a warranty cover but... let's not be naive goyims here...)

however from all the things i ordered i had exactly 0 non working parts. in fact the only problems i sometimes, very rarely deal with, are shits like bent pins which are easily remedied

>>1479913
>ikr? I'm not a fan of IP maximalism, but credit where credit is due ffs
I hear that
Also one isolated case is maybe possibly forgivable maybe even understandable. but a whole fucking list wow

>>1479916
Like what?
Pretty sure you can't buy a chink JBC station

>>1479926
>JBC station
yes but you can buy YAYBC for half the price

>>1479928
Don't see the brand

>>1479916
as for components and modules, I've had a couple of serious duds out of a hundred. one was a PCF8591 ADC module with a PCF8574 installed. the other was a prototype pc board with a chunk of copper stuck to it under the soldermask and shorting a trace to a ground plane. completed consumer goods were generally 100% ok

>>1479930
When i buy cheap stuff i always buy more. So for example if i need 4 modules i buy 7 since they are so cheap and they usually wall work fine, but if they don't or i fuck them up i have lots of spares

>>1479879
On AliExpress:
$1.20 for a digispark
$1.80 for a mini
$2.30 for a nano
$2.90 for an uno
$8.30 for a mega

But you can get their respective MCUs for like half those prices, at least for SMT varieties. THT packages aren't too bad price-wise either.

>>1479813
I would've guessed it was a timing or debouncing cap. 10nf isn't surprising, but fuck smd

>double clicks
I've replaced like a dozen mouse switches. You can get them in 10+ bags cheap and they're large enough to replace easily. It's probably more coincidence it's logitech because they push such huge numbers, but it's either new mice or new switches, and the switches are a lot cheaper.

>>1479798
My uni was filled with turbo normies. To be fair to your kids, we only did projects at the 4th year, for the "capstone" project.

>most people are doing like a usb sensor scope, layout out a power substation, one group did a synth guitar (basically had a midi controller built-in)
>my group was doing a 1MHz driver for plaque ablation in arteries
>the other three members weren't into it AT ALL, I literally would've gotten more done if they weren't there because they never did anything

Pic related, a possibly confidentiality breaching tank circuit. THREE (all of them) team members didn't even know the schematic symbol for a fucking relay, AND DIDN'T ASK WHAT I DREW. REEEEEEEEEEEEEEEEE

>>1479899
>Chinese
>plagiarizing papers
>mfw

>>1479913
>>1479923
>LITERALLY copies an entire paper
>"credit"
>"forgivable" or "understandable"
The guy and his colleagues should be banned forever from publishing. There is never an excuse for plagiarism. If an institute, business, agency etc is pushing plagiarists, it should be banned permanently from publishing.

Fuck fake scientists, fuck fake science.

Im designing a device with an MCU in it. It has a mains supply for the heavy stuff and a 5V rail is generated from that. For normal operation this is used.
But whenever i want to change settings in the MCU id connect it to a PC through USB. But i dont want to use the built in supply but the USB 5V for the MCU.
Can i use rectifying diodes on the 5V rail to accept either the built in 5V or the usb 5V?

Like this:
mains PSU----5V regulator----|>|----5V rail----|<|----USB 5V----PC

>>1479984
Enjoy your voltage drop, unless you're using low-resistance mosfets

>>1480023
mosfets as diodes?

>>1480027
By tying the gate to the drain, the mosfet will only switch if the source is sufficiently lower than the drain/gate. I forget if you need both an NFET and a PFET to make a decent "module". I could be very wrong. I'm not checking anything atm

>>1480060
http://rs20.mine (dot) nu/w/2013/02/using-mosfets-as-blocking-diodes-reverse-polarity-protection/

Here's a source.

>>1480060
>>1480062
Polarity protection isn't the issue, it's about decoupling two sources from a common load. I would prefer two 1N5817 diodes if the drop matters.

>>1480073
I'm sure there's a way to do it with transistors.

If you use a barrel jack for your DC supply, they almost always have three pins for jack sense, but it's also usable as a battery/power separator. Hook the +5V from your USB through the barrel jack's pin that disconnects if a barrel is in. Use a decent cap so if you plug in or unplug the barrel the chip can run however long it takes to switch supplies. use a 5.3V zener on the main's side if you're worried some residual voltage would fuck up the USB.

who here /cantlearnanythingifnotannoyingthefuckoutoftheprofessorwithstupidquestions/?

it seems like everyone else in the world understands basic electromagnetism but it just makes me wish people could just put thoughts in my head without having to deal with the semantics

I would like to learn a PCB design package for personal and resume purposes. It seems like Altium is the most commonly used professional program, but I've heard that pirated versions have issues with online component libraries. Since Circuit Maker is essentially a crippled version, is it worth using over a pirated copy just for libraries? Any board I would make at this stage would be total baby level, so the other restrictions don't sound so bad. The most difficult thing I'll be making any time soon is curved traces for dumb aesthetic reasons.

>>1479977
That's not science

>>1480115
You know, you can draw your own components. It's not even hard.
That said, I'm kinda wondering the same. It would be nice to be able to use Altium legally, but it is painfully expensive. On the other hand, CircuitStudio seems to be fucked in many ways.

>>1480127

OP pic realted

more like that pls

>>1479972
>team members didn't even know the schematic symbol for a fucking relay, AND DIDN'T ASK WHAT I DREW.

dont pat yourself on the back too hard, when you're doing noob errors like connecting your bridge rectifier wrong.

>>1480115
>I would like to learn a PCB design package for personal and resume purposes.

and during the job interview, they ask how much you paid for Altium, and then you have to lie or admit that you're a thief. use the free version of Eagle. it's more than enough for a noob.

>>1480210
just use kicad

>>1480237
this anon has a reasonable point. if anything, once you understand the *art* of making good layouts, you'll sit in front of Altium and marvel at how many things it makes easy and does *for* you

>>1480246
My first experience was with altium. Can you give some examples?

>>1480246
Guy you're responding to here
What does altium do for designers automatically?
And what sort of artful things should i be looking for / doing when making layouts? I've used kicad a few times before but that was a year or two back, and just connecting traces and pads and shit. making sure high current lines were really wide and to the correct spec, and just general IC design notes like bypass cap really close to IC.

>>1480271
I can't because I have no first-hand experience with Altium. from what I hear, there are lots more libraries for Altium from parts vendors and it's easier to generate IPC-compliant footprints via wizard. also I hear it's got an auto-placer and auto-router which can save a bit of time

>>1480286
>artful things
escaping BGA footprints efficiently, minimizing via/jumper count, designing for testability, recognizing and protecting sensitive signals/components, design for manufacturing (e.g. capabilities of chink with microscope/pencil iron/tweezers vs. pick-n-place robot and reflow oven), A E S T H E T I C S, etc
it's been said that if it looks good it'll probably work good. this is often correct

>>1480210
No I didn't. I don't remember why I had the 100k on the mosfet. I went through so many damn designs, as I was literally the one doing everything except like 50 lines of Python.

>>1480290
>escaping BGA footprints efficiently, minimizing via/jumper count, designing for testability, recognizing and protecting sensitive signals/components, design for manufacturing (e.g. capabilities of chink with microscope/pencil iron/tweezers vs. pick-n-place robot and reflow oven), A E S T H E T I C S, etc
>it's been said that if it looks good it'll probably work good. this is often correct
Cool, I'll keep those in mind
last I used it I was still thinking in terms of one sided PCB, and I didn't know vias were a thing, so the circuit never worked out (if i wanted to keep it on one side). I only later learned that vias were basically like jumpers
stupid me

>>1480297
Not him but the bridge rectifier there isn't oriented the same as the one here >>1479972
So what he said is still true - don't pat yourself on the back quite so much just yet. In fact, the fact that you missed the orientation differences with them both right there is even more incredulous

Probably a dumb question, starting learning about motors and one thing is confusing me. Let's say I have a simple motor with only 2 commutator segments, if the brush is larger than the commutator gap, at some point the brushes will be in contact with both commutator segments at the same time, would the commutator not just act as a short between the brushes?

>>1480346
Phrased that wrong, I mean if a commutator segment is in contact with both brushes at once

>>1480349
Yes. Such motor isn't guaranteed to start automatically, either. I don't remember seeing them anywhere but in hobbyist books and web sites.

>>1480297
but did you actually clean out any arteries with it?

>>1480349
if a commutator segment is in contact with both brushes at once then it would short the motor and disable its function.

>>1480346

yes, and two things might happen, (1) both coils would get current simultaneously in the same direction, or (2) the power supply would be shorted. but it would be very temporary, so the motor might slow down by a tick, but not stop.

in practice, if someone were to use only 2 coils, they would make sure the brushes are thin.

>>1480346
you might note that almost all small brushed self-commutated dc motors in production have no fewer than 3 segments

>>1480373

i built a 2-coil one in high-school shop class. the brushes were just copper wires screwed to the wood base. ran great for hours on end.

>>1480373

i built a 2-coil one in high-school shop class. the brushes were just copper wires screwed to the wood base. ran great for hours on end.

which cheap hot air station should I get?

How does coax splitter signal attenuation work? For example, if pic related is -5db per output does that mean each output is -5 individually (so each device will only get a -5 penalty), or is it -5 per each port in use on the network as a whole (so 1 port is -5, with all 4 it's -20)?
If you have say a modem and 2 DVRs, and of course the modem should have the highest signal possible, can you split the source once for the modem then split it again for the DVRs and give the modem less loss, or is it all cumulative?

>>1480434

It's -5 dbm on all legs regardless of whether you're using just one leg or all. Also if all you have is two dvrs and a modem then you can use a three way splitter. There's one that's -7.5, -7.5 and -3.5 and then there's another that's all -5.5.

>>1480414

* 858 * hot air station

where * = gibberish letters

~$30 + 2weeks from china

>>1480376
I tried to make one of those in primary school, while the commutator was just a single piece of foil instead of two, after fixing that it still didn't work. Turns out the magnets had poles not axially but on either side. I also only had like 20 turns so it probably wouldn't have moved very fast.

>>1479293
I`m trying to make a temperature sensor using two bjts. Both at the same temp (side by side) but one has half the current of the other; shockley eq gives me somewhat precise results if I measure the Vbe`s by hand, even with multimeter insertion error. But I want to amplify the diference and feed it to a MC.(they have a diference of about 15mv from each other). I tried using LM358 and LM324 op amps to make a differential amp but they always return 0.6 - 0.7 V when fed with the Vbe values. What is going on??

>>1480573
Somewhat precise values = +-1 Celsius btw

>>1480573
Post schematic

>>1480434
>-5db per output
That is not possible for a 4-way power splitter. It is always less because 1/4=-6dB.
>>1480438
>dbm
No, dB.

>>1480578
I the amp gain is 10. I tried making both inputs of the diff amp the same and it gave me 0.6-0.7 too. Maybe it`s too small a diference for it to operate on?

>>1480585
What are your op amp rails?

>>1480586
+12v and 0

>>1480589
I don't see anything wrong with your circuit, but it's hard to tell from that drawing. If you make a clean version in a SPICE program (LTSpice) it'll be easier to see your mistake, and you can simulate it to compare to your experimental results.

>>1480594
ok m8, I don`t have time now but I`ll make one later. Maybe it has to do with that CMRR thing? I don`t know very well about those things. But the Sensor part works fine. Thanks.

>>1480597
Doubt it. I'd be most worried about your op-amps railing. Depending on the resistors you're using, the minimum output voltage could be as high .6V but it seems unlikely. Otherwise modern op-amps shouldn't cause any problems here.

Most likely you screwed up input polarity somewhere or miswired something.

I'm troubleshooting a PS Vita Slim motherboard. Bought it on eBay, description said it wouldn't charge. I took it apart and the USB pins were floating, fixed that but it still has issues. I got it to charge once by unplugging and re-plugging a lot, usually it just sips 0.05a, and the USB data connection doesn't work either (device not recognized), but it can sense when it is connected, either to a power supply or to a computer. Everything else works so I'm pretty annoyed. I can't find any schematics or shit on this thing, I can't even find replacements except buying another Vita as a donor.

I'm guessing the chip near the inductor here is at fault (both data and power run through it), but is there anything else I can test?

>>1480629
See if it powers on when you apply the logic level to the board after the switching supply (possibly not a good idea). You'd likely need access to the appropriate test-points to pull that off, and I don't see any. There continuity through the inductor?

Thank you to the anons that helped me a few days or a week ago with this problem. I finally got the time to sit down and do the math. I understand the problem now. I really appreciate all the help!

>>1480650
Well I thought I did but now I see that the voltages are reversed. REEEEEEE, going to check my math

>>1480650
What class are you doing this for anyhow? It's an awfully obtuse question.

>>1480671
I am trying to refresh myself and am doing this problem by choice,

>>1480681
I can't see it being very useful to know, but good on you for being up to the challenge.

>>1480682
I think I am just doing it wrong now.

I have the discharge voltage for the capacitor as Vc= Vo * e^(-t/(2RC)) then I add 10 to see the max voltage.

The charging Vc as Vc = Vin + [(Vc-Vin)**e^(-t/(2RC))] and then subtract 10 to see the lowest voltage.

>>1480692
Where the initial condition is Vc = 10 V.

anyone used a tektonix 2246

>>1480697
Why would you subject yourself to that when you could buy a rigol for less than $300? Spend a little money on your hobby.

>>1480597
the LM358's common mode input range includes 0
low-level output voltage into a 10k resistor is 5mV typical, 20mV max

>>1480585
you really should have posted your resistor values and plotted the voltages on the schematic

>>1480730
because if I ask for advice on a new oscilloscope directly I'll be told to fuck off

>>1480734
Rigol DS1054Z and hack it

>>1480737
I've definitely been eyeing it but $350/$375 is breaking the bank for me a bit

Am I retarded if I try to solder small leads to these pins? They don't have this model with a push button AND solder lugs. I'm trying to fit it inside of this:
https://www.focusattack.com/hollow-aluminum-balltop-blue/

>>1480734
not at all. you'll be told to get a Rigol DS1054Z and enable all features with the riglol keygen
which is good if you can squeeze it. I expect (but am not sure) they're going to be tariffed soon

>>1480745
nah but add some heat shrink tubing over the top for strain relief

What does "d mark" mean and where do these lines lead? The d mark ones are unterminated.

>>1480754
probably "demarc", the utility demarcation point between inside (their) wire and outside (your) wire

>>1480756
Ah. But why would they have unterminated Ethernet lines (forgot to mention they're Ethernet) in my smart box from the street or whatever? I dun get it

>>1480744
Not anyone you've been responding to, but I would've suggested their 4 channel version too

>>1480757
It's to run a phone line to your smart box incase you want phone, or dsl so you can put your modem in there. Or you might even get a food ont that they want to terminate outside your house, and you want ethernet inside

>>1480759
Ahhhhhh makes sense
Cheers

>>1480758
DS1054Z is 4 channel

>>1480650
I just can't seem to get the right answer now. REEEEEEE. Can someone please explain this problem to me? I am having trouble solving the problem. When I make the schematic in LTSpice it oscillates for awhile until it reaches a steady state voltage.

I am confused on how to go about mathematically solving this problem using the natural and step responses for an RC circuit.

I am using Vc(t) = Vinitial * e^(-t/2RC) for the discharging circuit and Vc(t) = Vinput - (Vinitial - Vinput)* e^(-t/RC). But when I try solving as if it is sequentially switching, the voltage just decays down to -20 V instead of hitting a steady state equilibrium.

To solve the problem I have assigned values, R = 10,000 Ohms and C = 0.00001 F. The time constants are 0.1 second (R) and 0.2 seconds (2R). This time constants is significantly larger than the half cycle which is 1 ms.

I think I am screwing up my initial condition. I have been using that Vc initial is 10 V because of KVL but I am not sure if that is correct. I am doing that because Vc(0-) = Vc(0+). After that I have just been slowly discharging and charging.

Given enough time in my excel sheet, it will just decay down to -20 V instead of reaching some steady state. What am I misunderstanding?

>>1480765
Oh okay I forgot what the model number was
Siglent also has a 4 channel too that's slightly more pricey

So this is a dumb question, but i have a wifi module for arduino that is normally connected to arduino by wires and then you give it commands over serial from the arduino.
But if you upload a sketch directly to the module from arduino, to run it as standalone, how do you give it AT commands then? won't the thing on it that controlled the wifi be overwritten by your sketch?

>>1479575
oh shit... ping pong replied to my inquiry saying that the ttl can only be used to turn the laser on or off and not to regulate the output by varying the ttl votlage.
fuck.. maybe i should've waited for him to reply before ordering that damn laser..

d... do you think it would be possible to control the laser output by lowering the input voltage at least?
please say yes...

i mean it will still be able to engrave, but i won't be able to get cool b&w shades without being able to regulate the output power ;_;

>>1480803
um... no
see if you can PWM it, or find a replacement driver that can do variable power, or try using the Z axis to modulate power per area

>>1480805
how about putting a variable voltage divider on the wire going from the driver to the laser and modulating it that way?

>>1480803
If the driver wasn't designed for variable power, changing that isn't going to be a simple tweak.

Anything but the lowest-power laser uses optical feedback to regulate the drive current. A partial mirror splits off a fraction of the beam power to an optical sensor. A servo loop regulates the drive current to maintain the desired beam power. Varying the beam power requires varying the loop's reference voltage.

>>1480815
How hard would it be to change the loop voltage? If i can just solder some resistor onto somewhere thats fine, but if it requires like changing the ICs then there is no way i can do that.

Well the worse case scenario is i can resell this laser for $50 and then order another one that can do regulation for $68 since they are so cheap. I mean I buy $50 AAA games all the time, so I will just pirate one instead.

>>1480731
1k and 10k. R1 doesn`t matter

>>1480821
just for giggles, did you try creating a virtual ground that's offset from the opamp V-? a volt or two off of V- would be enough to get some idea of whether it's misbehavior of the amps. that's why I suggest you annotate your schematic with measured voltages at every node
it almost sounds as if your feedback resistor around the difference amp were shorted

>>1480827
>it almost sounds as if your feedback resistor around the difference amp were shorted
I thought of that. I`m not at home, later I`ll try it again. thx

Is bluetooth easy to work with?
Exploring what an ESP32 can do, trying to get it to interface with a bluetooth gamepad(xiaomi). All the examples are for BLE. Is there much difference between bluetooth and BLE? Does the gamepad have to support BLE to use it?

>>1480803
Assuming the board could be modified to do so, of course. laser diodes are similar to diodes though, in that they don't have a linear I-V curve. So output will change quite rapidly with slight changes

I'm >>1480697 again, might as well ask directly

I need a first oscilloscope. Mainly I'm going to be making analog synthesizers and circuit bending, and eventually other stuff when I start my Computer Engineering upper divs.

That rigol looks really nice but it's rather out of my price range. If I absolutely, absolutely must I could get it but I really want to consider alternatives first

What are the usual go-to beginner used oscilloscopes people recommend?

>>1480883
I am going to try to pwn the ttl to simulate lower output. If it works with electricity and LED then it surely work with lasers too since they are just light as well

My grow lights finally arrived! But where am i supposed to connect the 230v wires? Everything is covered.

>>1480906
Probably the pads that say "L" and "N"

>>1480909
Can't be it. They are just tiny spots and 230v wires are too thicc for them

>>1480910
Are you sure you should be working with 220v?

>>1480911
I bought then specially because they are rated for 230v

I'm looking to get about 5-10 boards made for me. They are about 130x130mm, majority ws2812 smd (about 20), and there will be 3 separate boards that are shaped like letters. Q W O specifically.

The LEDs will follow the lines of tye letters, and I'll have custom diffusers made later. Is there a place that can make this for me with only measurements? What if I designed the board and provided a bom? It must fit inside another enclosure, so size is top priority.

All I have is an idea. How can I get them into my hands?

>>1480921
Also I should add, I built a "prototype" that worked, with ws2812 strips and poured resin, but I want to have a board that drops into place and requires no soldering between segments. This will also help me get better diffusion, as there is about 1/2 in of wasted space after my smd LEDs, the excess strip, and wiring. It does not fill tye letter properly.

>>1480910
Use thinner wire. 220V is 220 watts per amp, so if they're e.g. 44W you only need 0.2A. 230V mains flex is normally rated for at least 3A, and solid cable for 15A or 30A.

>>1480918
>I bought then specially because they are rated for 230v
>>1480911
>Are you sure YOU should be working with 220v?
His concern was not for the lights...

>>1480906
It would be nice if they came with really large plated thru-holes for this stuff. And yes they're meant for soldering on to.

>>1480910
>A BIG NUMBER NEEDS A BIG CONNECTION
>BIG WIRE
>BIG BALLS
>BIG AMPS
>BIG PADS

>>1480925
if you designed the board you could just send off the gerbers. most places will charge based on the size of the smallest square that fully encompasses your design. just draw the shape you want on the board outline layer and (for safety's sake) put some "CUT OUT" text in the middle of your circles
if you want someone else to make the layout, you could hire some pajeet off one of those freelancer sites. pajeet will send you gerber files which you would review using a gerber viewer and then send to your choice of board house
if you want someone to stuff and solder the board for you professionally, that's another $100 or more. maybe you can find some kid in the local university's EE program to do it for you and save a few bux

>>1480885
you could buy one of those 200kHz STM32-based scopes now for like $30. you could also look around for those good old 20MHz dual trace scopes on the order of $100, maybe less by now. a logic analyzer might serve you better for the CompE work

>>1480827
ok I got it working. It was a unlucky couple of bust opamps. How peopel usually measure temperature with diodes or bjts? Now that I got a diff I need to sense the current in each junction reeee

>>1480906
I made a grow box here, you just solder the wire to the L and N terminals. Beware those things heat like hell.

>>1481109
>the current in each junction
No, only the ratio. Look into current mirror techniques. Your choice of 2 is much too small, it leads to ∆Vbe/T=60µV/K. That's a noise level signal.
>>1481111
>heat like hell
Yes, about 15W in his case.

>>1480759
>food
*Fios

I'm looking at these analog tektronix scopes on ebay. A bunch of them say "Horizontal time base out of calibration between 10-100MHz."

is this something that can be corrected/re-calibrated by someone such as myself or is it permanent/prohibitively difficult to fix?

>>1481276
Cheap digital chinese scopes would probably be cheaper.

I got a tektronix scope and I am probably going to spend like $75 in capacitors

>>1480327
>the bridge rectifier isn't mounted the same
No shit, they fucked up transferring my drawing. I was pointing out the relay because they didn't even recognize the fucking symbol. Transferring an entire design they didn't have any hand in - sure, there's bound to be some mistakes. Fourth-year student who at the time had internships for electric CAD? Fucking die.

>>1480364
The company shelved it, probably because of funding or something. As it was, I couldn't even get a prototype done because of how cocked up the team was. I had all the components but there were issues driving the mosfets (needed drivers). Even with the prototype finished we would've been limited to something like 600V pk-pk, less than the goal of 1000. They wanted the wave sinusoidal, single-ended polarity (i.e. +/- and neutral) which made things far more difficult.

>>1481281
I really want an analog for the aesthetic though

I guess pragmatics comes first however. Once I graduate I can spend as much as I want on ancient analog scopes huh

>>1481284
May I recommend the tektronix 7704a?

The screen is smaller than you might hope for, but perfectly workable

>>1481286
I'm sorry to give you conflicting info, but you could also just grab one, expecting to work on it. Old tektronix have great support documents. And having you import scope actually is vital to a lot of the troubleshooting

>>1481284
>Once I graduate I can spend as much as I want on ancient analog scopes huh
They're cheapish anyway. Got my tek for $200 like ten years ago.

>>1481284
With mcdonalds paycheck? Doubtful.

>>1481111
I have couple of old computer cpu alu heatsinks so those will be perfect for that i hope they will be good enough to run without fans, i will attach the leds with some thermal paste and kapton tape.

i wonder though, since the back of the diode is metal, after connecting power will that back become live? because that would mean the whole heatsink would be under live 230, so i would have to 3d print some enclosure to make sure my family won't find my smoking corpse lying on top of my sekkret pot hydro garden

>>1481338
probably not conductive. if you look at it from the side you might be able to see a thin fiberglass insulator. if in doubt, buzz it out with a continuity tester
attachment-wise, you probably want a thermal adhesive or maybe drill the heat sinks and attach with self-tapping screws, using the thermal grease. don't ghetto life safety
that said, I think it's going to want some moving air. maybe build a passive convection tube out of some dryer hose (aluminum type)

>>1481109
>How peopel usually measure temperature with diodes or bjts?
Option 1: feed the diode/transistor with constant current (resistor from power source, if you're lazy), assume the voltage across the diode is offset + temperature dependent part. Pic related. It is/was popular in diy thermometers using display-driving ADCs like ICL710x.
Option 2: use one switched and one fixed current source. Measure the voltage across the diode with two currents. There are ready-made chips with an internal ADC and all for doing this, like LM86. It is used in conjunction with big ICs with built-in temperature sensing diodes.

But usually people buy their bandgap temperature sensors ready-made. Or use sensors based on some totally different principle.

>>1481341
I guess i could use a 120mm fan and set it to rpm so low it will be inadible. do the 12v computes fans work on AC? If yes i could just add a resistor and be golden otherwise i guess i could add a diode to make a shitty recitfier

>>1481349
no, that'd just be noisy. you could use a wall wart or its innards
you'll need a PWM generator to set the speed. being a 120mm fan maybe it's pretty quiet at full tilt, or maybe you'll be lucky and it runs at minimum speed with the PWM lead floating or grounded
t.over 9000 hours in captcha for this reply

Anyone familiar with ESP32 or WiFi.h?
Trying to use IFTTT to send an email, when I enter a specific url into a browser it triggers and sends the email.
How can I trigger that url from an ESP32?

>>1481369
looks like you need to add one more line feed to end the request

>>1481370
Tried that, here's some example code I found, I don't see how mine's different and why it's not working.
What's the difference between GET and POST? tried both anyway.

>>1481371
I don't see any client.connect stuff in your code, for one. perhaps you're establishing the connection differently. show all
POST requests typically include a message body after the header. GET requests do not. the remote server will very likely behave differently for each

>>1481367
I guess i could eviscerate a phone charger and connect it to the wires powering the grow light and then to the fan, but it's only 5V so i would have to use boost converter and that is hella overcomplicated just to spin a stupid fan, i don't have anything that can step 230to 12v directly. if i feed the fan 5v wont it technically spin at half speed even without pwm? since i mean fluent 5v should be even better then fake pwm 5v no?

>>1481375
it might not even start
I suggest paying the $10 for a proper locally-sourced wall wart if you're in a hurry to get it rolling, or pay the $3 for one from ali and wait a bit, or locally source a 240Vac fan of sufficient quietness and size

>>1481338
No. It is made of metal for the purpose of heatsinking. It even has holes for the screws

>>1481374
>I don't see any client.connect stuff
It only appears once, returns true if it can connect to that server on that port. Just a test to see if it should continue.
Added it anyway, no luck

>>1481164
uhm nice. I was using a TL431 to make a constant-ish source but that is trashy as hell. I think even a discrete current mirror is better because I can only care about the ratios

>>1481376
What do chinks call a wall wart on ali?

>>1481385
wall adapter, I'm seeing them for as little as $1.86+shipping
if you don't need the big plastic shell you can get just the board
https://www.aliexpress.com/item/DC-12V-Benis-Driver-300mA-450mA-600mA-1A-2A-Power-Supply-for-Benis-Strip-Spotlight/32917883702.html
(they say they're for LEDs but since they're constant voltage supplies they'll work fine with a fan load)

>>1481378
lol no, it performs the act of connecting and returns a success or failure report

>>1481389
I ordered 5 of these, 400ma should be plenty for anything light related
https://www.aliexpress.com/item/1PCS-12V-400mA-AC-DC-Isolated-Power-Buck-Converter-220V-to-12V-Step-Down-Module/32787822604.htm

thank god for chinks. imagine if i had to buy these here, instead of $5 for 5 i would pay $15 for fucking one

>>1481371
y u no use AT commands?

>>1481391
depends on how much you catch the bug and decide to automate it, timers etc
that'll be more than plenty for one ventilation or cooling fan, maybe even two

>>1481392
Pic related

>>1481369
>>1481390
>>1481392
Got it working, gave up on WiFi.h and tried HTTPClient.h

>>1481393
i'm quite serious buddy, i use serial AT commands to run my esp01 and it works flawlessly

>>1481403
sheeeeeiiiiiit
clearly I need to look at the ESP32 SDK since I didn't even know that was there

>>1481404
>wasting a processor that's 30x the tarduino
>on AT command set parsing
>as sent by a tarduino
you know you can write code for the Espressif processors, right?

>>1481403
Is that the whole thing? How do you input the wifi login deets?
I ordered some esp32 as standalone battery powered brains for my sensors and i need to make post requests to my server with the collected data.
It would be really nice if it was this easy.

>>1481409
It still uses WiFi.h to connect to wifi, here's the whole thing. Push button recieve email.

>>1481380
You need no constant current. I would first use two 1% resistors (e.g. 10K and 100K) connected to a known stable supply like 5V. Then measure the difference with a multimeter and see if it follows expectations. The common mode part can be removed with an instrument amp which has hi Z inputs, no buffers required. The differential gain can then be trimmed with one resistor (R2 in the image). Given the common mode signal of about half a volt, you may not need a negative rail for the amp.

>>1481420
can you just use arduino ide or do you need some special addons?

>>1481429
Arduino ide with regular C++ but it needs a little setup.
The one I bought is a heltec "wifi kit 32" with built in oled.
Setup:
https://github.com/Heltec-Aaron-Lee/WiFi_Kit_series/blob/master/InstallGuide/windows.md
Oled library:
https://github.com/ThingPulse/esp8266-oled-ssd1306
The pinout on the website is wrong, but it's printed on the underside of the board.
It was $11 on ebay, went back today to get my brother in law one for Christmas and the listings gone and they're $15 now.

>>1481433
Here's the right pinout.
once it's setup you can swap between boards in the IDE with Tools > Board

>>1481433
Do you really need the oled tho? They have esp32 on ali for just five bucks that is where i got them

>>1481460
You don't need the oled.
I've been working with an uno with the same screen though, love it.
I bought an esp32 without as well but haven't set it up.

>>1481464
I heard that esp32 is very battery friendly and will last longer than you will on a single charge if you use sleep modes
i basically plan to use them as replacement arduinos with wifi, can they handle 5V?

>>1481468
I haven't tried the sleep modes yet, apparently it's a lot more efficient than the previous esp8266
Mine is micro usb so it takes 5v, pretty sure it uses 3.3v logic though.
Also has a jst plug for connecting lipos directly, has a charging circuit for them but I haven't experimented with it yet. Just got it yesterday.
I have a bunch of lipos and different charging circuits just waiting for jst connectors so I can see how it fares.

>>1481428
The problem was the resistors, throwing shit off rails. I have no 1% resistors, I only got acurate resuls when I measured the drop on the resistors and used the measured resistance, otherwise I`m off by 800 K. Fucking exponencials. What are some cool ways to measure temperature easily? If I use a thermocouple I`ll have the cold junction thing to solve, and I don`t want to be a plebeian and use a 10k thermistor.
>>1481346
noice

>>1481473
>measure temperature easily?
The de facto standard since 1999.

>>1481483
>1 british dollar
Welp, -2mv/C diode estimate it is. One of those things is like 10 Reais here in the third world. Ten Reais = 4 crack rock pieces = a lunch = 1/2 of a memuino uno

If I have special LED dimmer light switches, do I need "dimmable" LED bulbs, or will the dimmer work well with regular LED bulbs?

I'm still in my gen-ed/pre-requisite classes at college for CE.
in order for me to graduate kind of on time, next semester I'm going to have to take 18 credit hours:
>Calc-based Physics 1 with Lab (5)
>Introductory Chemistry with Lab (5)
>Calculus II (5)
>Speech (3)

now I know the engineering course load is legendary, but does this sound do-able? I don't want to tank my GPA taking too many courses but I don't want to be behind two semesters instead of one.

what do you guys think I'm in for?

>>1481484
>lunch
what the fuck pajeet? i could barely buy a single slice of bread with that
move into a 1st world country

>>1481502
Br, due to communism one banana dollar = 1/4 dollar. Usually it`s 1/2. And the fucking br mail now charges 7.5$ for ANY foreign imports comming in through mail regardless of taxation or size, so ali is only a option for large quantities.
>>1481496
First semester of EE here has 30 h/week. The other semesters are about 26-28 h/w . Calc ll is ok and physics l too. I think you are ok (for now)

>>1481508
>>1481502
and it`s not my fault your bread is expensive my man.

>>1481508
I think we're talking about two different things
here in the US, college classes are rated for difficulty in how many credit-hours they're worth.

Your average class is 3 credit hours. The average student takes 4 classes a semester, which totals to 12 credit hours a semester

so 18 credit hours is equivalent to an extra two-and-some-change classes over a normal schedule

though, you're the second person to say I'm going to be alright, so at least I've got that going for me

>>1481512
Here one credit = 50 min, your casses are rated by the ammount of credits they`ll give at the end of the semester (how many hours of class you had, in theory). I`m on the 6th semester here, I currently take 24 weekly credits, which with hole sin the schedule and commuting is almost 40 hours). If you are like most people, as you prograss in EE you will basically study by yourself and only go to class because you need, the biggest problems aren`t the subjects or time, it`s the fucking autistic teachers.

>>1481491
regular LEDs will do

>>1481514
>it`s the fucking autistic teachers.
I'm still in community college, what I'm most afraid of is when I transfer to Uni next fall to begin my CE Major courses all my professors and colleagues will be chinese or indian.

Since I'm going to be going to UCF, which has the largest student body in the entire US, it's pretty much a given.

>>1481517
A sikh guy came here from TU (Texas) to give a lecture for us here in brazil about monte carlo methods in fault analysis. He was old as fuck and very nice, had a chat with him about IoT on power systems. The main problem are the angry, frustrated, socially inept teachers that either suck too much for a commercial job or are so rude/annoying/pedantic that they can`t get one. Every field in every academic enviroment has people like that but EE has a higher density somehow. You just have to learn to deal with each particular kind of insanity they have. Studying is easier than that, much easier. Good luck anon.

>>1481517
Some of the best teachers I've ever had were Chinese and Indian. Stop being a bigot.

>>1481540
I want all dirty pajeets and tiens reported. if you want that rice dick so bad then move to china raskeh

>>1481578
You're on the wrong board, friendo. This is the one for people with brains. You're looking for /pol/

>>1481578
>if this guy ever read an electronics book it probably was written by foreigners or their descendants

>>1481578
you have multiple containment boards at this point, go back to any of them

>>1481578
this isn't only true, it's also based and redpilled

I need some tips. Is there a way to look at the capacitors in a circuit and tell if it forms high frequency or low frequency poles?

>>1481740
>high frequency or low frequency poles
By the value of the capacitor and nearby resistor(s)? High and low are fairly arbitrary, sure you don't mean poles and zeroes? Any specific examples?

>>1481772
Here's an example from a midterm. Could you tell which capacitors are high frequency poles and which are low?

Also, when we drawing small signal models, do we short circuit all the capacitors

>>1481781
You don't have any component values, so your question doesn't make sense. Are you asking which ones are parts of high pass vs low pass filters?

>>1481781
Well actually it's not tough at all. Capacitors to ground are being used as low-pass filters, while capacitors in series are used as high-pass filters. Not sure if that answers your question, but it's the most reasonable thing I can see. But that sort of complex BJT circuit is above my paygrade, if I can do it with op-amps I will.

>>1481806
increase your pay grade
https://en.wikipedia.org/wiki/Cascode

>>1481781

Diagram looks like it was transcribed from another source by someone who didn't know what those symbols were.

Funny, all the capacitors are unnecessarily drawn as electrolytic, so you'd also assume they're above 4.7 µF. :-)

Anyway, the capacitors act as short circuits under high frequency AC analysis.

>>1481491
>can I use a dimmer with non-dimmable LED bulbs
Why would you ask

>>1481826
nvm, I thought you meant can you DIM non-dimmable bulbs on it.

Just turn the dimmer switch to max. Probably a small voltage drop or near-complete wave.

>>1481496
Are you in CC or Uni? At CC those classes would be difficult in themselves, but alright load wise (Physics 1 is most difficult, Calc II is second-worst math after pre-calc). At Uni everything was terrible. Somehow covered less material and fewer assignments but had far worse lessons and outcomes.

>>1481517
I see you're in CC. Good luck at uni, it's terrible. Try to make friends ASAP, including paying for them (alcohol, fun, whatever). Some of our courses were literally designed for 5+ people working on one homework, and people cheated left and right and even when they got caught, school looked the other way. I was EE. You either did well and it was a lie, or you did mediocre-ly and it's because you weren't "in". I tore the teachers a new asshole in every review and to the co-director's face.

>>1481816
>all the capacitors are unnecessarily drawn as electrolytic
>what are tantalum capacitors

>>1481816
>electrolytic
nah, just old. in the USA they used to draw all caps that way, and marked polarized caps with a + at the appropriate end

>>1481851
I can't think of a good reason to use tants in 2018

>>1481853
I hear they've got good specs in one way or another, audiophiles might take to them.

>>1481856
ah, yes, I forgot about the microphony of ceramic caps. that's a pretty good reason

Anyone with an EE background help me or help point me in a direction to learn op amp stability shit?

>>1481828
I did mean can you dim "non-dimmable" bulbs on it.

I.e. if dimmable LEDs work with a traditional dimmer (they do), what's the advantage of a special LED-specific dimmer switch? Is it compatibility with "non-dimmable" LED bulbs?

Why would you be snarky before you understand my question?

>>1481882
some work, some don't. a non-LED dimmer driving LEDs may be unstable due to e.g. triac hold current requirements not being satisfied. also, the brightness curve isn't precisely linear

>>1481871
What do you mean?

>>1481886
Systems are unstable when there's a certain frequency w at which the phase difference is pi and the gain is more than 1. This isn't possible with single pole systems but can happen with two or more poles.

>>1481887
Meant you
>>1481871

>>1481887
>>1481888
ah, it isn`t just with op amps. You have good grips with laplace and a bit of control theory? because that is what you need to look into.

Just got my new T12 station, and its working fucking ace, but the slim 9501 handle is just too thin for all my holders (just slips through). Anyone have the same setup and know of a good holder for it? Preferably something janky and cheap from ali.

>>1481890
I did a little bit of both in linear systems, but I learned the rule for stability in electronics 2.

Op-amps specifically used to need external frequency compensation, but since we've gotten better at having caps on silicon it's not really an issue any more. Just pay attention to the stuff outside the amp.

>>1481887
Yes I know the general idea
But how do i analyze a circuit / control loop etc?
like i want to drive a mosfet with an op-amp to control current flow
The basic circuit isn't going to be stable and I want to know how to analyze it and how to get it back into stability

>>1481894
Figure out the poles and draw Bode diagrams for phase and gain. Look for where the phase is pi and see if the gain is 1 or more.

>>1481892
>not adding a washer or something to the holder
the one that came with my Aoyue station has a waist at the entrance end. might be a feature worth looking for. maybe this one?
https://www.aliexpress.com/item/janky-and-cheap/32671938510.html

how do I choose probes for my new-to-me oscilloscope? What I've read is you should get probes rated at least double the bandwidth of the scope
mine's rated 100MHz but I'm having trouble finding 200MHz probes
that and the capacitance/impedance thing doesn't make much sense to me yet either, how do I know it'll be compatible?

>>1481893
Wait I thought you were the guy asking. nvm.
>>1481894
exactly the same way you analyze any other system m8

>>1481896
What the fuck? That looks like cleaning your tip in it would hurt as fuck.

>>1481914
not at all. give the tip the old in-out-in-out 5-10 times and the brass coils pull oxides, solder and other gunk right off without damaging the plating. it's healthier for the tip than wiping it on wet sponge

>>1481896
>not adding a washer or something to the holder
The one I use now is one of these fuckers. It works OK for my old iron, but its absolutely useless on the new thin one. I think jury-rigging something on it is probably a lot more effort than its worth, but I'll check out the ali one you posted.

>>1481918
>in-out-in-out 5-10 times
when i do that, this strange white solder comes out from the tip of my tip

Could someone tell me what kind of motor this is/what they're called?

>>1481944

looks like a very standard DC permanent magnet motor, the kind you find everywhere in toys, shavers, pencil sharpeners, edge trimmers, etc etc.

What's the deal with non-polarized aluminium caps?
Can I use one as a drop in replacement for a standard aluminium electrolytic?

Anyone know a circuit of a current controlled current source? I need pass a current through a bjt that is a constant multiple of another current elsewhere.
>Current mirror
I need it to be a decade or so larger, the only way to mirror it with gain I see is to put n bjts in the current mirror, but 10 bjts would occupy a hell lot of space.

>>1482012

yep. if they fit. they're usual bigger.

>>1482017
Cool, Ordered a few 10uF ones without realizing they were non-polarized.
What's the downside? Are they more expensive?

>>1482019

more expensive coz less volume produced, and as i said, bigger.

Anyone know if these (very cheap) Nanos are usable?
>https://aliexpress.com/item/2014-Mini-USB-Nano-V3-0-ATmega328P-5V-16M-Micro-controller-Board-For-Arduino/32567039076.html
I`ll probably need to make some 5 or 10 things that will record data in a SD card, so they`ll have to have more than 512 bytes of RAM, A PIC that would do the job is almost the same price of an arduino where I live, the nanos would fit the package and I can acess the MC functions regardless of retarduino language.

>>1482012
That they're not polarized?
If price, size and ESR do not matter, you can use them instead of normal electrolytics.

>>1482014
You could use different transistors for input and output sides (leading to difficult to predict gain) or possibly reduce single transistor's gain with an emitter resistor, but why not use opamps? If your driving current source has non-shit compliance, you could use a basic opamp vccs + resistor for converting the control current to voltage.

>>1482027
I have two bjts and I need to make the current through one ten times larger (or smaller) than the other. The value really doesn`t matter. I could use op amps, thanks anon, my sleep deprived brain did not think of that.

>>1482029
>(or smaller) than the other.
What's this bizarre application where G=0.1 is just as good as G=10?
Anyway, there's the Widlar current mirror, too.
https://en.wikipedia.org/wiki/Widlar_current_source

>>1482033
this
>>1480585
Using resistors does not give enough precision and a 10 transistor mirror is too big.

I got sniped on another ebay auction for an oscilloscope, so I gotta keep looking

I'm seeing a lot of listings for analog tektronix scopes where the seller just lists "Turns on, couldn't test further, selling as is"
it makes me think that they're trying to sell faulty goods, how can I be sure I'm not gonna get fucked?

So, if i take an arduino, run a wire from the 5V rail to an INPUT analog pin, then cut the wire in half, strip the ends in the middle and then touch both ends with my finger, thus closing the circuit, with my finger acting as a resistor, will i be able to reliable detect in the arduino code when i have that finger here, without any shitty ghosting issues causing misfires?

>>1481904
>exactly the same way you analyze any other system m8
too vague, because it presupposes that i even know how to analyze stability shit

>>1481895
I don't know how to do that. Otherwise I wouldn't be asking

>>1482148
Get a book on linear systems and start reading. If you want non-linear or dynamic stuff it gets complicated, but linear covers 99% of all op amp stuff

>>1482071
no, because when your finger isn't touching the wire that connects to the input it'll basically act like an antenna and pick up a bunch of meaningless noise. add a 1M resistor to ground. maybe less since i'm not sure what the atmega328p's pin leakage is.

>>1482170
This. Will possibly still need debouncing.

>>1482150
>linear systems
Okay that's one starting point at least. thanks anon

>>1482229
>debouncing
Not him but do I need to debounce every switch?
I see even rotary encoders need debouncing fak

>>1482303
Sometimes you can just put a capacitor on them such that it forms a low-pass filter with the pullup/pulldown. If you really want to you can debounce in software, though it's somewhat a waste of ROM.

>>1482026
you could get STM32F103 bluepills for about the same price, fwtw. 20kB of RAM should do ya

>>1482303
just about any mechanical switch will require debouncing

>>1482148
Here's what I do: Take 30 seconds and build the thing, then play around with the values and watch the results.

You'll eventually get an intuitive feel for how they work and you'll understand that real components don't have things like infinite input impedance.

>>1480692
If the CR time constant is bigger than the period the cap will charge to 10v and boost up to 20v I think. Diode clamp will short to ground either way so wave would look like 0.7v on either side

I'm almost 100% wrong but maybe my rambling helped somehow

>>1482365
That works but it doesn't bring me closer to understanding

>>1482229
What is debouncing?

>>1482426
When you flick a switch or button to act as a digital input (typically with a pulldown resistor), the switch contacts don't just touch and stay closed, they bounce a few times within a few ms. Not anything you have to worry about for a power switch, but if it's a volume button on an MCU with a clock speed in the MHz, it will see each of the ~3-10 bounces as additional button presses and blow your eardrums. This happens since each time the button comes off the contact, the pulldown resistor pulls the voltage at the digital input to ground again. Using an SPDT switch without a pulldown will avoid this problem, as the contacts don't bounce all the way to the other side, they just stay in limbo. Typically schmitt triggers (hysteresis machines) and capacitors are used for the purpose however, since most PCB buttons are SPST.

>>1482430
I see, that won't be a problem then, i will simply add a 1 second delay after the finger is detected, so that any following triggering for 1s are ignored

>>1482431
What's the touch sensor for?

>>1482440
it will be a simple on/off switch
i tried to use a capacitative solution first but it was fucking trash, even with a dedicated touch IC, so i am opting for running two wires next to each other and using skin as resistor which will completely remove tho annoying as fuck ghosting problems i wasn't able to eliminate from the capacitative solution even when i tried fucking EVERYTHING.

>>1482442
Make sure to test it with really dry hands, since that will make the resistance pretty high. Might even want to use a 10MΩ pulldown.

>>1482026
>Cheapest Ali nanos
I have tons of these around and they all work perfectly fine. Never tried to use them for SD-cards, but they do have 2k SRAM, so that shouldn't be a problem.

>>1482443
I could just increase the input voltage over 5V since the skin resistor will eat it up if i have any problems

>>1482449
Technically, but if you've got wet hands you could fry the MCU. Nothing that a zener diode couldn't fix, of course.

>>1482455
>zener diode
Can it break down fast enough though?

>>1482457
a TVS diode could handle it well, also any static charge you might have built up while walking over to the switch

>>1482462
yeah, static charge will be a bitch damn it, it makes the dione pretty much mandatory. i will try to add a 5.1 zenner since in already have one at home and hopefully it will be able to deal with static. and if not i the arduino only cost me about two bucks so it won't be a huge loss

>>1482463
A 4.7 zener might be a better idea. If you're worried about sharp voltage changes you could always use a low-pass filter.

>>1482475
>low-pass filter
so a cap between input and ground? i am unsure how would that work?

>>1482477
Cap from the input pin to ground and a resistor in between the input pin and the zener+contact+other circuitry. The RC circuit would take some time to go from initial to final voltage, in which time the voltage spike from the zener not handling the ~12V would be already gone. Since zeners are probably fast to at least 10µs, you could go with a pretty tiny cap here. But at that point you could use the RC circuit for debouncing as well, which would require a larger time constant.

>>1482442
>on/off switch
Is it a comedy project?

>>1482498
seasonal kek

So I'm trying to build a battery powered shocker/taser type device, but I'm mediocre at electronics and I really don't want to build something that causes electrical burns. From disposable camera flash circuits I've seen, it looks like a flyback converter charging a high voltage capacitor is my best bet here, but is it even worth building a flyback myself instead of buying a board like the one in the picture from china? I'm also having difficulty deciding on the capacitor to use. From what I can tell the resistance of skin is between 40K and 1M, so I'm unsure of how large a capacitor I should charge to 390V before I start outright injuring people. Ordinarily I would just buy parts and experiment, but something about high voltage freaks me right out.

>>1482563
The source in question, takes 8-32V and outputs 45-390V

>>1481496
Graduating on time is a meme.
What do you think matters more, -0.33GPA or +1 semester.

If i would do it again, I would take extra time to not have three tough classes in the same semester.

>>1481496
For me the only real issue here would be calculus ii, that class was an absolute nightmare. Your mileage may vary, im a bit of a brainlet when it comes to math, so no matter how much I studied I just didn't get it. If you're historically a strong student in math you might be fine, but its specifically know to be a class that weeds out students. I might just accept an extra semester, or decide to take a class or two over a summer at some point. Theres no way I could have taken all of those at the same time and passed them all, but I'm also not a great student.

Is there any advantage to using a bulky soldering iron with that base station?

My soldering iron has only a power cord going directly to the power outlet and it solders just fine

Can anybody tell me what this symbol means?

google reverse image search gives me a circle so ...

>>1482585
looks like a square with two lines in it

what happened to the shortwave general? I wanted advice on babby's first radio but now it's gone

>>1482585
it's apparently a naamloos

Will my solder joints get fucked up over time if I used zinc-chloride flux (and cleaned it off with brake cleaner)?

>>1481882
>Why would you be snarky before you understand my question?
Let's look at your question shall we:
>will the dimmer work well with regular LED bulbs
You either a) asked if non-dimmable bulbs could be dimmed (you're an idiot, but we'll pass since this is an engineering/learning thread), b) if non-dimmable bulbs can't work at all any more (a good question), or c) asked the wrong question (you need to communicate better). I assumed the least insulting things about you.

>>1482563
>how large it should be before injuring people
Use a flash camera circuit

If it burns, try a smaller cap, if not, use that size. From what I remember, I got pock marks from using a flash camera circuit. Remember, it's not the voltage that'll cause the damage, it's the current.

If anyone in the thread wanted some math help, I tutored professionally for six years. I'd be glad to. Drop a line in the thread and I'll try to notice it.

>>1482603
jeez, you don't say.

>>1482611
that "nameless" in dutch, I drew this in paint and that's the default name

/diy/ used to be more helpfull

>>1482563
AFIAK, most such devices are essentially flyback converters without any rectification or output capacitance. This produces a fixed output current which is independent of impedance.

>>1482148
You're gonna need a vector network analyzer for that. Hope you're okay with dropping $10k+. You can get away with a spectrum analyzer and tracking gen for the gain measurement but not for phase and you want the phase info in order to make your shit stable.

>>1482585
>what this symbol means?
>>1482653
>/diy/ used to be more helpfull
I would be helpful if you explained where you saw it used.

>>1482669
On a electronic component, I think it was a reed-contact/sensor thing.

I figured since this was an electronics thread people would instantly recognise it

I checked through the IEC 60617 but I couldn't find it.

High-freq AC or DC for a diy condenser mic?

I have some things I want to solder, recommend me soldering iron, solder and whatever else could be useful. I also need a multimeter, preferably a good one.

>>1479297
Soak it in high purity isopropanol then leave it to dry out/evaporate. I did a Gayberry Pi last week, works fine

>>1482585
Proximity Sensor

Shockley eq temperature guy here. Managed to get it working, now I need to wrap it up on something that is not a protoboard, and can stand being thrown in a lake.
>temperatura BJT = temperature using delta Vbe
>Temperatura DHT = temperature measured using a DHT11 sensor. (I don`t have a thermometer at home)

>>1482768
this btw
>>1480585


The reading fluctuate a tad in a short ammount of time (I still haven`t added power supply caps or fed it from a regulator instead of the arduino source) so I take 10 readings spaced 10ms apart and average them out to get a temperature value.

>>1482633
How about we start with the fact there's no such thing as a non-dimmable bulb, and you should know better than that? Dimmable vs non-dimmable is a marketing term, not an engineering term.

>>1482768
>>1482772
Put caps between the diodes and everywhere else. What are you going to use to seal it? The thing that always put me off using diodes as temperature sensors was that the packages are plastic or glass and hence aren't terribly thermally conductive, plus they're somewhat difficult to expose to a conductive medium without shorting the leads.

I'm tired of having meters I can't rely on.
I want a really nice one, something that's versatile and reliable for general purpose electronics work. I'd spend a few hundred on something that's going to last years. Recommendations?

Brainlet LED project

I want to basically wear Christmas lights at concerts. The LEDs should respond to the music (flash in time with the beat) and have cycles that I program.

Is this good for a first time electronics project? I've built computers before and know how to program and use Linux.

This page makes it look doable. https://www.instructables.com/id/Sound-Reactive-LED-strip/

Any microcontroller platforms I should use or stay away from?

I recently read about a guy who would render phones air-gapped by cutting the PCB traces leading to WiFi, Bluetooth, and GSM ICs so he could use them to 'read sensitive material' without worrying about any kind of remote compromise.

Is it just me or is that just not possible? I've done some work with smartphones and I know they enter bootloops or won't boot at all if these chips aren't working as they're supposed to. Was he bullshitting or what?

>>1482610
>where is /hrg/
I eated it

>>1482667
>VNA
fwiw I've seen plans where you can build for under $500

>>1482672
industrial electrics have their own symbology

>>1482860
reasonably possible, if he cuts the power traces to the RF portions of the chips and leaves the digital interfaces powered, and also uses his own OS build that doesn't know about the chips
now, doing that on a densely packed multilayer board is a whole other question of plausibility

>>1482667
I'm talking about on paper, faggot

>>1482860
just read sensitive shit inside of a faraday cage son

>>1482821
I think I`ll use silicone that people use to caulk sinks and shit like that, they`ll be on the walls of a pvc pipe, with the leads hopefully no tin contact with water. The inner tube will have the turbidity IR sensors I`m making too, and if I make some nice coils and use a low enough frequency the water conductivity sensor will be wound up on one of the ends. But it`s either silicone or liberal ammount sof hot glue.

>>1482883
Linear systems. Any book on introductory control iss good too.

>>1482782
Wrong. Some LED bulbs will produce full output right down to the dimmer's minimum duty cycle. Plenty of them will operate at full output for anything above 50% (the point where the rectified voltage stops increasing). Dimmable bulbs sense the duty cycle and vary the drive current accordingly. That's something you have to actually design in.

>>1482734
>>1482736
Thank you

I see you took a screenshot, can I ask for source?

>>1482922
Sounds good, much luck to you dear.

>>1482929
Thanks my man, it`ll be challenging because it`s my first big boy project (and that will actually be used), I`ll have to learn to solder properly, design a PCB, wind up coils, calibrate all that fucking shit, decide I`ll use a bunch of them + one with a SD card that listen to their wireless signals to cut down costs or put cards on every one of them. It`ll take a couple months but I think the ecology professor will like it.

I need to attach a switch to the cable on my soldering iron, but in order to do that i have to solder it in
Is this what they call irony?

>>1482931
Sounds like quite the project. I'm interested in how the calibration will go, and if you plan on inputting the calibration data by hand or if you plan on writing that directly to program memory with the help of an external sensor you use just for calibration (like I was going to do with a thermocouple and a heater element as a way to use the element as the temperature sensor).

>>1482934
Crimp connectors, man. My last (Goot) iron had all its connections done with ferrules and crimps, made it really nice to take apart and put back together. Too bad it lasted the best part of a month before the element went open-circuit.

>>1482924
Yeah another anon mentioned that. have looked up the pdf

>>1482836
Accurate tempo detection is not trivial and generally can't be done in real time and requires digital signal processing techniques that are way outside the scope of a beginner project.

That said if accuracy isn't too critical and you just want the LEDs to flash within like +/-20% or so of the actual tempo there are simpler methods...
In all cases you need a mic and a pre-amp. Can be a simple JFET or BJT common-source/common emitter amp. This should go to a low pass filter with a cutoff probably around 100Hz or so. The steeper the roll-off the less likely the LEDs are to trigger on signals outside the passband. 4-pole 1dB Chebyshev should be adequate. You can either feed this signal directly into an analog input on the micro and use the ADC or you can use a comparator. Basic idea is when the signal amplitude reaches a voltage threshold you set that will pulse the LEDs on for the duration of the time that signal is high. When it goes low again they'll go off. The signal should only exceed the threshold within the passband of the filter. The effect is that your tempo detector will be sensitive to low bass. Since a lot of songs use some kind of regular drum beat like a bass drum kick to keep time this can be a surprisingly simple and effective tempo detector. But... if there is a part of a song with no regular bass rhythm then this will not detect any tempo even when there clearly is one. And like I said, if the filter roll off is too slow it'll respond to higher frequency signals as well like 200Hz or 500Hz and will give false pulses that are out of time.

I think there are some other analog methods that are more complex involving envelop detectors and analog multipliers but I don't know much about them and it'd probably be a pain to implement.

I need to repair my car. Do cars contain any stepped up circuits?

>>1482971
Ignition. Also, backlights for LCD screens sometimes use CCFL (cold-cathode fluorescent) lamps which need a relatively high drive voltage.

But you aren't going to find high voltages (anything over 24V) anywhere on the wiring harness.

any idea what the uvp does in this step up downie?

>>1479293
What is RSLogix 5000 used for?

>>1482712
Any recs? Please guys I can find stations for 5-5000USD. What is the C2D of soldering?

>>1482994
Yes.

>>1483004
haha you're so funny, hard to believe you're still a virgin

>>1483002
you haven't told us what you're going to solder, silly. tell us more about what you're gonna do
general advice for hobbyists:
you can't go wrong with the Hakko FX-888D
solder: any old Sn63Pb37 if you're not trying to sell it, flux-core. Henkel Multicore is well-regarded in industry and hobby
flux: no-clean if you're working on high-quality, fresh components, RMA otherwise
liquid flux (in pen applicator) is a bit more convenient all-around, paste is better for fine SMT work. chink flux may contain 0-100% vaseline
a 5x magnifier is nice if you're gonna work on smol SMT birbs, choose what fits your workstation and budget
clean your tips with brass wool, not a sponge
solder wick is very helpful

>>1482994
I desoldered the CV potenciometer so i can replace it with a big one that has a knob.
how much current goes through it? can i use thin wires or does ALL current that comes out of the output of that buck boost go through that potentiometer?

>>1483034
I = E/R
if they're using a trimpot > 100 ohms, any power loss through wires will be entirely negligible

>>1483037
I just want to know if the current i am drawing from the converter is passing through that potenciometer or not. The potenciometer is 100K.
For example if you can use a switch to turn on a mosfet, so there is only a small current passing thru the switch, even though you are drawing a large current, so i want to know if this is the case as well.

How do I do flyback diodes? Zener to ground? If so where do I put it in relation to the coil?

>>1483038
It isn't. At 100k, you'd need to put 100V across it just to get 1mA.

>>1483046
A normal diode across the coil allows the switched off current to continue flowing and decay naturally. Nothing is flying back.

Give me the cold, hard truth lads. I just failed my electronics 2 midterm cause i couldn't draw a small signal model. Can i make it as an electrical engineer?

>>1483193
I don't even know what a Thevenin equivalent is and I'm in the second year of a grad program.

>>1483193
You'll probably be fine. Just study more. I fucked up a problem on my electronics II midterms because I didn't know how the fuck to get the AC load line for an amplifier. I was sorta able to figure it out and I was able to plot the maximum voltage swing at the Q point but I ran out of time before I could plot the maximum collector current swing. Still got a 93.

>>1483195
How in the fuck?

>>1482934
>only having one soldering iron
>implying cord switches don't use screw terminals

>>1482821
Strapping two legs of a transistor together = a diode, and you can find a heatsinked transistor in almost everything.

>>1483125
>A flyback diode is a diode connected across an inductor used to eliminate flyback, which is the sudden voltage spike seen across an inductive load when its supply current is suddenly reduced or interrupted.

>>1483193
>>1483195
>>1483319
Engineering should be left to the autists. Ree.

>>1483325
>Strapping two legs of a transistor together = a diode

Wrong. Strapping the collector to the base of a BJT = a diode. Strapping the emitter to the base does not. Also this doesn't work at all for JFETs though MOSFETs do have an intrinsic body diode from source to drain.

>>1483325
>Strapping two legs of a transistor together = a diode
Can you get (common) single package schottky transistors I wonder?

>>1483346
LS TTL and probably some other variants use Schottky clamped transistors very often but as far as I can tell this isn't what you're describing. The Schottky clamped transistor clamps the base to the collector with a Schottky junction to divert excess current when it's saturated. I think you're referring to the Vbe junction being a Schottky junction, no?

I'm not aware of any such devices though heterojunction bipolar transistors are about the closest thing I can find. They're very fast and can be used for RF amplifiers up to several hundred GHz. There's a few different material types for the junctions though InP and InGaAs seem to be pretty common.

>>1483349
I am referring to Schottky clamped transistors, as used in LS TTL. Just wondering if they came in power transistor packages (for god knows why) so I can get a bunch on ali and use them both as (linear-region) power transistors and power diodes.

>>1483351
Oh, my mistake. In doing a quick search I didn't find any discrete transistors like that. Google showed BC337 as a related search for Schottky transistor but the datasheet for it doesn't suggest that it is Schottky clamped at all and it's in a TO-92 package, if you want it for a power application you probably want TO-220, TO-225, or TO-3. I'd say your best bet is getting a normal power transistor and a schottky diode and literally just connecting the base and collector through the diode.

>>1483355
Sounds like what I'd expect. In that case I'd be better off just buying power-package diodes.

>>1482922
Hot glue only looks like it works. It will keep things okay for a few hours in non-critical applications, maybe. If you hot glue a connection and use a continuity tester between it and a free probe underwater, it looks the same as if there were no sealing at all. Silicone is tricky to get perfectly sealed. Epoxy is standard, and you can get thermally conductive epoxy if need be.

Test at the expected depth for triple the expected time, with whatever sealing method you use. A graphite motor brush with a wire soldered and epoxied (with the graphite exposed) works well for an underwater probe to test for leaks. Remember that the cable sheath will draw water straight up it and corrode your wire if it is left unsealed.

>>1482922
>>1483355
As far as creating the void in the center of the epoxy, cast it around a rod that can be removed later. Possibly something water-soluble or that can be melted out. If going the melt-out route, make sure that the melt temp is above that of the curing epoxy and below that of the PVC tube. A low-temp hot glue stick comes to mind.

>>1482931
Most wireless signals travel for shit underwater, the exception being acoustic.

>>1483377
>>1482931
With the complexity and cost of wireless underwater data transmission, don't. It would be much cheaper and easier to put a card in each.

putting two resistors in series is easy as fuck, but how the fuck do i put two potentiometers in series when they have 3 legs?

>>1483377
I suppose that's due to the conductivity leeching away power alla J = σE law? Anyway I though he was just going to have the sensors underwater and the transmitter and power setup above the water.

>>1483368
Oh, and no wires coming out of an epoxy block without strain relief. That's asking for trouble.

>>1483382
I believe so. If the design parameters allow it, that setup would make the most sense. In that case, wireless communication of data may be best, so that collection only has to be done at the master point, rather than traveling all over the lake. He might consider a buoy tethered to the sensor, to house the power setup and to send/receive the signal, but the sensor would have to be anchored to prevent being dragged along. If anything moves the sensor, that sensor's data is then next to useless if it's a location-dependent study.

It also depends on local regulations for tethers and buoys in the lake, and whether or not there are boats, etc.

>>1483380
I know, the arduino/pic/whaterver will float on the surface I think. I haven`t decided yet to be frank. I was really thinking of letting it full of air, put some weights arround it so it stays arround 1 m or so bellow water and have some wires going to the other buoy with SD card/transceiver. I haven`t decided how much time it`ll spend underwater, because I haven`t finished up the sensors so I don`t know how much they consume. Probably a month or so (that`s the frequency of their visits when they take manual measurements). If I go with the SD card thing I`ll probably make a confg.txt file with things like how frequently to measure and other stuff.

The team had a super duper sensor buoy but it was stolen/sunk. Why would someone need one of those idk.
>>1483373
>>1483368
I do not have acess to epoxy where I live. It`s not really used outside of industries here in brazil and the only one you can find are the two mixture epoxy that come in 20g syringes and they cost a fortune(in relation to the scope of the project).

>>1483382
>>1483393
it`s related to conductivity.If you solve the wave equation + maxwell you can see it clearly. (Well not so clearly, it startds getting really filled with parameters at some point). Last time I played with those things I go tthe skin depth for wifi on fresh water was something like 2cm or less, I don`t remember really.

>>1483407
I think I've derived something along those lines, though it was a right pain. I should do it again, since it will help in the leadup to my laser physics and EM exam.

>>1483405
Have you tried boat-building supplies? Epoxy resin is used alongside fibreglass for making/repairing boats. Other resins (like polyester) could potentially be usable.

>>1483409
Nice, I`ll look into boats.

so i have an AD7607 ADC and the datasheet (https://www.analog.com/media/en/technical-documentation/data-sheets/AD7607.pdf)) has a plot of frequency response+phase response. pic related.

i feel like the phase response is fishy though. when i calculate it via matlab, it appears to be way more delay than stated. which would somewhat concur with my measurement.

could anyone possibly countercheck? or did i miss anything obvious

>>1483381
One middle and one outer leg.

>>1483477
all 3 legs are used by the circuit

>>1483485
it's circuit-dependent. post specific schematic
generally you will wire one with wiper shorted to one end and place it on whichever of the three legs of the other makes most sense

>>1483423
How are you calculating it? I don't see any information on the filter besides those two graphs

>>1483532
it says it is a second order butterworth filter. the sample frequency is given as 200khz. so i created a 2nd order BW filter with the given 3dB-Frequency. the magnitude plot is about the same as the one in the datasheet. then i use the function phasedelay() to plot the phase response.

pic related is what i get. y=phase delay in seconds, x=frequency in Hz. instead of ~12µs @ 10 Hz i get ~60µs @ 10 Hz

why do all of the to-92 triacs come with unformed leads, and a gate pin adjacent to a terminal that's going to be as much as 300V relative to it?

>>1483423
>>1483537
>phase delay in seconds
Is this common? I've always seen it expressed in terms of angle.

>>1483682
its somewhat common i guess. see it every now and then. in school we used to do it with angle as well. maybe its particularly handy in seconds for ADCs

>>1483660
It must be a conspiracy.

>>1483716
does jewish treachery know no bounds?

>>1483660
>to-92
>triac
You're getting what you deserve. The only shit that runs off AC are high-power electronics and shitty LED bulbs (which shouldn't be dimmed anyhow), anything else is bound to run off rectified mains fed into a switching converter, so you're not going to get anywhere by dimming down to the first 50% of duty cycle, and past that you're really fucking up the power factor when using a dimming FET after the rectification or a replacement adjustable switching power supply would work better.

>>1483747
i'm driving some incandescent panel bulbs, without dimming. it would be utterly retarded to drive them off DC when AC is available with no processing.

>>1483750
Not him but why are you using a triac at all then faggot just string them all in parallel you dumb fuck

>>1483765
to turn individual indicators on or off independently. this shit is why nobody talks about their projects on here.

>>1483768
/ohm/ is one of the most (for the lack of a better word) toxic generals. expect that kind of answer