/ohm/ - electronics general, fug edition

[Anonymous No.1281748]

bump limit reached on old thread >>1277831 (Cross-thread)


>I'm new to electronics, where to get started?
There are several good books and YouTube channels that are commonly recommended for beginners and those wanting to learn more, many with advanced techniques. The best way to get involved in electronics is just to make stuff. Don't be afraid to get your hands dirty.

>What books are there?
Beginner:
Getting Started in Electronics Forrest Mims III
Make: Electronics Charles Platt
How to Diagnose & Fix Everything Electronic Michael Jay Greier

Intermediate:
All New Electronics Self-Teaching Guide: Kybett, Boysen
Practical Electronics for Inventors: Paul Scherz and Simon Monk

Advanced:
The Art of Electronics by Paul Horowitz and Winfield Hill

>What YouTube channels are there?
mjlorton
paceworldwide
eevblog
EcProjects
greatscottlab
AfroTechMods
Photonvids
sdgelectronics
TheSignalPathBlog

>What websites feature electronics projects or ideas?
http://adafruit.com
http://instructables.com/tag/type-id/category-technology/
http://makezine.com/category/electronics/

>Where do I get components and lab equipment from?
ladyada.net/library/procure/hobbyist.html
Search the web for "hobbyist electronics sources" to find plenty.
In the US and elsewhere, mouser.com, digikey.com, arrow.com, newark.com are full-line distributors that entertain small orders.

>What circuit sim software do you use?
This mostly comes down to personal preference. These are the most common ones though:
NI Multisim
LTSpice
CircuitLab
iCircuit for Macs
CircuitJS (quick, dirty, interactive)

>What software should I use to layout boards?
Altium
CircuitMaker
Circuit Wizard
ExpressPCB
EAGLE
KiCad

>My circuit doesn't work. Halp?
Check wiring, soldering, part pinouts, and board artwork if applicable, then post schematic. Supply ALL relevant info and component values.when asking a question.

[Anonymous No.1281762]

>>1281748
keked, thanks OP
this bread's digits brought to you in part by the LTC1748 80Msps 14-bit ADC.

[Anonymous No.1281769]

in case anyone hasn't heard the story of the fug, >>/diy/thread/686690

[Anonymous No.1281796]

>>1281769
Thanks, I was wondering.

I hope that anon eventually got it wired into three phase or sold it to get cash for a suitable one.

[Anonymous No.1281800]

>>1281796
nvm I kept reading, good for him DDDDDDD

[Anonymous No.1281832]

>>1281769
fuggin ay ::DDDD

[Anonymous No.1281857]

>>1281769
i love big fat mains transformers

[Anonymous No.1281864]

>>1281769
I remember that one.

[Anonymous No.1281911]

Does anyone know a site where the bulk prices of various screens are listed?

I am trying design a product that needs a touch screen, but I'm having difficulty getting an idea of price. I want to see what you would expect to pay per unit.

[Anonymous No.1281913]

>>1281911
Aliexpress, Alibaba if you're serious.

No fgt, everything is made in China, deal with it.

[Anonymous No.1281914]

>>1281911
I was looking at one of those several months ago. Gimme a sec...
Try panelook.com

[Anonymous No.1281922]

>>1281914
>>1281913

Thanks

[Anonymous No.1281925]

Has anyone got experience with super bright LED life? Pic related is for a Sparkfun red led. 2328 hours is about 3 months, and the blue led has lost about 25%. How bad would it be after a year or so?

And these cost 95 cents apiece. I just got 100 from Amazon for about 7 cents apiece, and they're awesome at the moment, but if I run them continuously at 18 mA what should I expect in a year or two?

the led:

https://www.sparkfun.com/products/528

the spec:

https://www.sparkfun.com/datasheets/Components/YSL-R531R3C-A13.pdf

[Anonymous No.1281979]

>>1281925
>what should I expect in a year or two?
Maybe 5 cents apiece?
The degradation you will not notice unless premature failure.

[Anonymous No.1281984]

>>1281979
>Maybe 5 cents apiece?

ah. good one. I don't write very well..

For those LEDs, I have this in mind: I bought some of those DC-DC step-up converters as seen in the upper circuit. I'm using one to power some LEDs as discussed here >>1281925

The problem is that the LED current drifts a lot, like if I set the voltage so that a string of 10 LEDs has a current of 14 mA, 20 minutes later it might be 12 mA.

If I modify the circuit as seen below, should it work as long as the resistor is sized to give a voltage of 1.25 volts at the desired LED current (the XL6003 feedback threshold is 1.25 volts)?

the chip: https://www.pollin.de/productdownloads/D351434D.PDF

In the chip function block, is OVP what limits the output to 60 volts? In the case where an LED fails open, the output will go to 60 V and stop, correct? The output capacitor is rated at 50 volts. What would you expect to happen if it were subjected to 60 volts for a few hours?

[Anonymous No.1281987]

>>1281925
>Has anyone got experience with super bright LED life?
Yes. Depends entirely on the LED and thermal dissipation. Heat is what kills LEDs, and life will be roughly proportional to the inverse of the current squared for any given cooling setup. They lose brightness on an exponential decay.

So if it lost 25% in three months, it will lose ~ another 25% in three more.

You can make an LED last ten seconds. You can make it last 100 years. It's all up to you, Godpseed!

[Anonymous No.1281989]

>>1281984
>The problem is that the LED current drifts a lot, like if I set the voltage so that a string of 10 LEDs has a current of 14 mA, 20 minutes later it might be 12 mA.
Yes. Never power LEDs from a constant voltage. They are constant *CURRENT* devices. The forward voltage drops as they warm up, and they generally have enough of a positive thermal coefficient to enter runaway when near their rated power.

[Anonymous No.1281994]

>>1281987
>>1281989

Thanks. They are pretty bright at about 15 mA, so hopefully they'll have a long and happy life.

[Anonymous No.1281996]

>>1281984
>>1281989
Oh, OK, looked at the circuit, that is a current-regulated boost converter. That's what you want, (so long as you want an output voltage > than the input). And yes, you choose the resistor to give whatever the sense voltage is at the desired LED current.

OVP is overvolatge protect, yes, otherwise a boost circuit will keep boosting the voltage across an open circuit until it fails. Don't overvolt an output cap. It can arc internally and explode.

[Anonymous No.1281997]

>>1281996
>Don't overvolt an output cap.

Yes, I'm using it to boost the voltage, and I'll switch the cap as well.

[Anonymous No.1281998]

>>1281984
>>1281989
furthering this, your converter chip isn't well suited to constant current applications (it's still possible but inconvenient) so if you want to update your circuit you'll want a new switcher ic. the most convenient way to make a constant current converter is to average and amplify the voltage across a current sensing resistor between the fet's source and ground, and then present that to the feedback pin. because the chip already ties source to its ground any external current sense like that will impose its sense voltage onto the feedback network which is bad. you can still do high side current sensing but that's expensive circuitry.

>>1281996
this kind of current control isn't what he wants. it controls peak switch current only as a method of controlling whatever is provided to the feedback pin. in this case he's providing the output voltage as feedback so it's a constant voltage output. hence why the current changes, because the forward led voltage changes with temperature. it's the wrong way to do this but it seems like the current regulation is close enough with his trimming.

also because of all this the output on led short won't actually rise until OVP if you add a minimum load resistor. 27k should do if you won't miss a quarter watt.

[Anonymous No.1282004]

>>1281998
>this kind of current control isn't what he wants. it controls peak switch current only as a method of controlling whatever is provided to the feedback pin. in this case he's providing the output voltage as feedback so it's a constant voltage output.
No, look again. The voltage feedback is connected to a ground-based current sense in the lower diagram. Peak boost current is internally regulated.

OP, your IC choice is fine.

[Anonymous No.1282007]

what am I supposed to have as the input to the first carry in on the adder?

[Anonymous No.1282008]

>>1282004
you're right i'm retarded. i'd be interested to know why he's seeing current drift unless his tempcos are that bad.

[Anonymous No.1282010]

>>1282007
Unless you're using it to do rounding, logic 0.

[Anonymous No.1282011]

>>1282008
>you're right i'm retarded. i'd be interested to know why he's seeing current drift unless his tempcos are that bad.
Maybe he was previously feeding it constant voltage? Or he's close to the resistor power limit, and it's got a large thermal coefficient (eg, it's carbon).
Also, contradicting what I just said, some boost controller ICs are pretty bad. Especially Chinese-designed ones. I've not personally used this one.

[Anonymous No.1282012]

>>1282008
>i'd be interested to know why he's seeing current drift unless his tempcos are that bad.

It's about 60 F where I'm working so maybe they are warming up? And I put 2 multimeters in series to be sure and they agree pretty well.

[Anonymous No.1282013]

>>1282011
(or his component choices are right at the edge of the regulation range and it's running deep into discontinuous mode)

[Anonymous No.1282015]

>>1282013
let's see, that should be about 83 ohms, .018 watts, nah, that isn't it unless the ambient temp is swinging wildly.

[Anonymous No.1282017]

>>1282011
>Maybe he was previously feeding it constant voltage?

Yes. The upper circuit is what I have, one of those cheap as dirt DC-DC step up converters that Amazon has for about a dollar.

>>1282013

I have a regulated 4.5 volt supply and was boosting to about 25 volts across a single string of LEDs at 12 to 14 mA.

it's a bit nippy in here, about 60 F so maybe the LEDs were warming up; they definitely do not feel warm.

[Anonymous No.1282018]

>>1282017
>Yes. The upper circuit is what I have
Oh. Yeah. Don't do that. You need the lower circuit.

[Anonymous No.1282020]

>>1282018
>You need the lower circuit.

excellent. thanks to everyone for all the advice.

[Anonymous No.1282025]

>>1281984
>capacitor is rated at 50 volts
You could limit the max output voltage this way and still have a constant LED current.

[Anonymous No.1282029]

>>1282025

Thank you sir.

[Anonymous No.1282031]

>>1282025
...yeah, at the price of the thing running full tilt and dumping 100% of its power into the zener and a 1K resistor if the LED output opens. At which point the Zener fails, the resistor fails, or more likely, it still hits 60V because 60V/1000ohms is only 60mA. And now you have multiple things on fire.

C'mon guys.

[Anonymous No.1282033]

>>1282031
> And now you have multiple things on fire.

I DON'T WANT THAT.

[Anonymous No.1282036]

>>1282029
It's even easier, you could use the built-in voltage pot to set the max voltage.

[Anonymous No.1282037]

>>1282031
what will actually happen is
>the led opens
>the switcher sees 0v on fb and hits its duty cycle cap, charging the capacitor to 33+1.25v
>the first discharge cycle to charge the cap above that value causes the zener to conduct, presenting a high voltage on the feedback pin
>the converter floors the inner loop's feedback voltage as fast as the compensation allows, almost or completely shutting the switch off while the ~0.5mJ of extra energy added to the cap discharges through the zener until it's back at 33+1.25v
i have no idea where you got your doomsday scenario from. the zener will sink 1.25mA steady state dissipating 42mW.

[Anonymous No.1282039]

>>1282037
or what would be much funnier
>the led opens
>the shitty chinese switcher hits its duty cycle cap which just so happens to be 100%
>the switcher explodes
this reminds me that the circuit might benefit from a fuse

[Anonymous No.1282043]

>>1282036
Ah yes, my turn to be a moron. The 1k is between the sense resistor and the FB pin. OK, you're right.

[Anonymous No.1282095]

I am trying to get a sine wave that changes frequency over time in ltspice apparantly I am supposed to use this modulate part but I get this Missing mark frequency, I can't find anything about this online exept for the people that have the text mark=number somewhere near this part but I can't find anywhere how I am supposed to add this

[Anonymous No.1282102]

>>1282095
I finally found the awnser in a french piece of documentation. wtf

[Anonymous No.1282121]

hello,
I want a piece of info here.
I want to make a bike led light.
I have no idea what leds to use, batteries(welp, prolly those 18650)
so I would like your recommendations on the topic.
I have a lot of components from spare electronics around. My goal is at least two hours of light.
Any feedback is appreciated.

[Anonymous No.1282123]

>>1282007
Low for adding, to make it subtract, XOR all inputs for the subtrahend and set it high.
Alternatively, just use a half adder for the first bit.

[Anonymous No.1282168]

>>1281748
where is the best place to get components like ICs, resistors, buttons and motors? Im looking at Digikey rn because it looks legit. How is amazon for this kind of thing?

[Anonymous No.1282170]

>>1282168
have you tried checking the OP?

[Anonymous No.1282174]

need to make an adjustable clock in the Mhz range.

its for pitchbending a keyboard.
the xtal I'm replacing is 22MHz, so i dont suppose the regular RC-schmitt trigger oscillator is gonna cut it...?

the go to solution seems to be ltc1799.
anything more of the self, so to speak?
what do you propose?

[Anonymous No.1282175]

if you switch a classic lightbulb with one of those LED bulbs (pic related) without any AC/DC conversion inbetween, the light will flicker right. but would it also decrease the lifespan of the LED?

i would assume so, since it would constantly be switched on/off, no?

[Anonymous No.1282176]

>>1282175
ofc i forget the pic, but you know what i am talking about anyway i guess

[Anonymous No.1282178]

>>1282168
>where is the best place to get components like ICs, resistors, buttons and motors? Im looking at Digikey rn because it looks legit. How is amazon for this kind of thing?

you want to order ICs, resistors, buttons and motors?

what about cheese. where do you get your cheese.

[Anonymous No.1282179]

>>1282121
>no idea what batteries to use
>welp, prolly those 18650
You are not to fool around with Li+ batteries yet, young samurai. Those can explode if not treated with respect.
>components from spare electronics
No.
There are plenty of DIY bike light projects around out there. I'm not going to ask what happened, but you have to read ALL the projects.

>>1282168
>amazon
About as legit as eBay or aliexpress.

>>1282175
Those are usually built with circuits to rectify and regulate the current through the LEDs, unless you bought really, really, really shite.

[Anonymous No.1282182]

>>1282178
>>>/b/

[Anonymous No.1282185]

>>1282168
aliexpress
any non-chinese site will charge you between 10 and 100 times more

[Anonymous No.1282192]

>>1282121
>>1282168
>>1282174
>>1282175
Stop playing dumb!

[Anonymous No.1282193]

>>1282185
It's not so bad if you buy in bulk. There are certain things I'd never buy from chinese sites, namely anything safety oriented or delicate.

[Anonymous No.1282194]

>>1282178
grocery store
>>1282170
>>1282185
thx

[Anonymous No.1282195]

>>1282192
whats dumb about high frequency oscillators?
sorry, but all my experience is in the audible range.

geez

[Anonymous No.1282196]

>>1282195
don't worry, this is /ohm/

people will call you dumb no matter what you say

[Anonymous No.1282207]

Hey /ohm/.

How do I remotely control the on-off switches and the temperature knob on my radiator heater?

Should try to put something on the knobs and switches that twiddles/presses them or should I open the radiator up and replace the control system with something else?

[Anonymous No.1282209]

>>1282207
is the knob smooth, notched with limits, or notched without limits? you can likely accomplish this with an esp8266 and some jellybean components.

[Anonymous No.1282213]

>>1282209
smooth

[Anonymous No.1282225]

>>1282213
ok. i don't know what electrical background you have but you'll want to buy a multimeter (<$20). you'll need to open the case and measure the voltages (both AC and DC settings on the meter) across the switch terminals in both switch states, and between the three pins on the knob. you can report back with that or alternatively open it up and see if you can get good pictures.

remote controlling your switches is as simple as connecting an electronic switch in parallel with them. that electronic switch can be a cheap bjt transistor, a triac, or a relay board (in order of preference) depending on whether your switches are just sending signals to the control board or actually delivering power. in any of those cases your esp8266 can receive a wifi signal telling it to turn on or off those electronic switches, which will work just the same as if you'd used the mechanical switch. the knob is probably a potentiometer which is annoying and has lots of solutions but i'm not sure which is the most retard proofed for you. if nobody else chimes in just get a meter, measure it like i said, and come back.

i'm not sure if you've got any programming knowledge but if you don't then i'd drop the project because interfacing your esp8266 with your phone or some other interface will probably be even more obnoxious than anything i've mentioned here. i've never done it.

[Anonymous No.1282227]

>>1282213
on and off would be easy using a relay.
simple regulation is possible.

but if you want to control it like the step less knob does, you'll need to interface with the triac.
control it with an optoisolating triac.
problem is that you need to sync it to the mains frequency or you'll have all sorts of trouble.
i feel like if this question is asked, you dont have the know how to pull it off safely.

Turn it off and on with a relay you've put in a plug or a cable. dont mess with the oven it self.
easier and safer.

[Anonymous No.1282229]

>>1282227
if the pot goes to a control board (this thing looks reasonably smart, who knows) and it only has ~5v or so across it then he can just get one of those U/D control digital pots and cut the knob out of the equation entirely. circuitry depending of course.

[Anonymous No.1282233]

>>1282193
Casual anglo-exceptionalism or actual experience?

[Anonymous No.1282234]

>>1282233
not him but if you want to see how much the chinese care about your safety (not at all) then watch some of bigclive's teardowns

[Anonymous No.1282236]

>>1282234
Oh, caveat emptor, for sure. I agree anything mains-connected with an enclosure needs to be scrutinized carefully and checked for BoM-reasonableness. If they don't think it's worth getting UL or equivalent listing, or the price is just that cheap, there might be a reason for that.

[Anonymous No.1282246]

>>1282233
Well I've bought a fair bit of electronics from china and the build quality and attention to detail is always pretty low. Perfectly fine for a MOSFET or two, tentatively passible for things with soldered PCBs, but I wouldn't trust it for the safety stuff, not to mention the falsified or non-existent certification.

[Anonymous No.1282252]

Question about the 741 op-amp

The Cc capacitor hanging off the base of transistor Q16. Does that introduce a dominant high frequency pole or a dominant low frequency pole? The textbook says low frequency but my professor said high frequency

[Anonymous No.1282271]

hello, I am extremely retarded. can I use a bunch of schmitt triggers (specifically a CMOS chip) as a crude six-bit ADC, as shown? the idea here is that as the voltage increases it becomes high enough to trigger each node in sequence. not sure what would happen with negative voltages but i guess it could just be rectified before going in. the idea is that it's sort of like an r-2r DAC but in reverse

[Anonymous No.1282275]

>>1282271
no, you'll have a 6-value flash ADC, maybe, if all on the same chip, and if combined with a priority encoder to translate the flash comparisons to binary
look up ADC architectures

[Anonymous No.1282278]

>>1282275
thanks, i couldn't seem to google the right things! I'll try building that example on the wikipedia page around an LM339 and go from there.

[Anonymous No.1282314]

>>1282252
usually opamps are compensated by setting a pole at a pretty low frequency. your professor is wrong.

[Anonymous No.1282330]

>>1282102
what was the solution?

[Anonymous No.1282342]

is it posible to turn 1 or many individual specific leds from a led light strip?

for example, the first and the last

or the first the 20th and the 40th

I was told to do this by some idiot that doesnt know shit about electronics (he pays people on freelancer.com to do shit for him) I told him I can turn them in a row but not individually and he actualy told me he has already done it several times which I do not believe him shit since he names the voltage as "energy"

[Anonymous No.1282344]

Is the current in this resistor 19 microamps?

[Anonymous No.1282347]

>>1282344
only if there's nothing else going on outside the image t b h

[Anonymous No.1282350]

>>1282347
Actually there is some outside the image. the top of the current sourceis connected to 5V and the bottom is connected to 3.1 v. so the curren should be (5-3.1)/1M
Can you eplain why it's not 19 microamps?

[Anonymous No.1282353]

>>1282350
i can tell you with confidence that 1.9 microamps does not equal 19 microamps. i have a degree so i'm citing myself.

[Anonymous No.1282356]

>>1282342
lol you want someone to solve a problem for you so you can get paid for it? i can think of at least two ways it's possible

[Mr.T !LeoPard6uk No.1282360]

>>1282350
>Can you eplain why it's not 19 microamps?

[Mr.T !LeoPard6uk No.1282361]

>>1282342
>is it posible to turn 1 or many individual specific leds from a led light strip?
Sure it is

>>1282356
>i can think of at least two ways it's possible
I can think of four possible ways

[Anonymous No.1282363]

>>1282344
Nice diagram. Shame they don’t understand the difference between a ‘u’ and a ‘µ’

[Anonymous No.1282369]

>>1282363
where are all of you pedants in reality? i work in a stuffy, formal industry and none of my coworkers have ever voiced concern about grammar or unit precision except in externally facing documents.

[Anonymous No.1282376]

>>1282271
Your A/D is roughly 2.6 bits. If you're making a VU meter or something, that's probably fine. You'd need 64 of those Schmitt triggers to make a 6-bit A/D converter.

[Anonymous No.1282379]

Can anyone tell me why I can't drive these fucking BLDC motors? I built three half bridges out of 2n3904s and tried driving the half bridges with the normal commutation sequence (6-step), but the fucking thing won't spin up, it just vibrates. If I give it a flick with my finger just right, it will keep spinning sometimes, but most often not. I tried the normal "blind startup" method of just slowly increasing the frequency of the commutation sequence but the thing just glitches back and forwards like pic related.

Then I read that for slow speeds you need to feed the thing 3-phase sinusoidal signals instead so I drove the half-bridges with 3 phase sine-pwm at 200kHz but got the same result. I know that 2n3904s are pissweak transistors but they can shit out 200mA, which at 5V (the power rail) is still a whole fucking watt and the thing is kicking like a motherfucker while doing this weird vibrating thing so it must have plenty of power. Also the transistors haven't popped yet... Any ides?

I checked the output waveforms by plugging in 3 LEDs instead of the motor and it looks fine, I also plotted the output of the sine-PWM to make sure it's just right.

Each half bridge has 2x 2n3904, 2x 1n4148, 100 R base resistor, driven by output ports of an arduino and powered by a separate USB power pack (so 500 mA at 5 V I assume).

[Mr.T !LeoPard6uk No.1282380]

>>1282379
Increase current / voltage to overcome cogging torque or use smaller BLDC motor.

[Mr.T !LeoPard6uk No.1282382]

>>1282330

>The MODULATE device is a voltage controlled oscillator. See the example schematic .\examples\Educational\PLL.asc. The instantaneous oscillation frequency is set by the voltage on the FM input. The conversion from voltage to frequency is linear and set by the two instance parameters, mark and space. Mark is the frequency when the FM input is at 1V and space is the frequency when the input is at 0V. The amplitude is set by the voltage on the AM input and defaults to 1V if that input is unused(connected to the MODULATE common).

That's built-in help. How fucking hard that could be

[Anonymous No.1282383]

>>1282369

I literally just grabbed my 1984 TI Linear Circuits Data Book opened it to a random page and it had the proper ‘µ’ symbol in it. It was hard for them to do that in 1984, I still got lots of typewritten stuff back then.

Yes, it's externally facing — but hasn’t technology come far enough where it’s just as easy to use the proper symbol nowadays?

It's not like we’re using literal typewriters, if we were, that would be excusable.

[Anonymous No.1282384]

>>1282383
alt+230 is 3 keys longer than u.

[Mr.T !LeoPard6uk No.1282388]

>>1282384
Compose key, then m, then u and you get µ. Also modern CADs and stuff are smart enough to auto-convert 'u' to 'µ' where needed.

[Anonymous No.1282390]

>>1282380

If the motor isn't getting enough power, it must be because the current is being limited somewhere though right? and AFAIK the 2n3904's are the "weakest link", current wise (max 200mA continuous), so if the motor wants more than 200mA, the transistors should be overheating and popping, since they are in saturation? But they are barely even warm. And my USB supply should be able to provide at least 500mA so it's not getting limited there either. Not saying I don't believe you but now I'm more confused than before. Maybe it's simply a voltage thing? But this is a quadcopter motor which usually runs off LiPo voltages..

[Anonymous No.1282392]

/ohm/, I don't know what class to take next quarter.
Electronic Circuit Design:
>Provides an understanding of modern analog solid-state circuit design techniques what are used for instrumentation purposes. Emphasizes design techniques using integrated circuits, particularly operational amplifiers.
It's not in the course description, but it has a lab.

Intro to Power Electronics:
>Introduction to power electronics. Topics covered include characterization of power semiconductor devices, design of magnetic components and filters, analysis and design of ac-to-dc, dc-to-dc and dc-to-ac power converters. Applications in power supplies are presented. Theoretical concepts and analyses are augmented by simulations and lab projects.

I want to take both, but this is my last year, and both courses are offered at the same time. What would you guys take?

[Anonymous No.1282395]

>>1282392

Notice that everything in your discipline needs power.

[Anonymous No.1282424]

>>1282392

with op-amps you can build a million things. with power electronics, you build one thing: power supplies. boring!

[Anonymous No.1282427]

I ordered some Bluetooth module expansion boards and AliExpress sent me these sensors instead. I can't complain much since they are quiet at least 3 times more than what I paid, but.... now I need to do something with these. I have a bunch of raspberry pis that I use for building small arcade machines. Any cool ideas come to mind? I know I can monitor temp and humidity with these, but, can I make something a little cooler with these?

[Anonymous No.1282431]

>>1282395
>>1282424
These are both my exact thought processes, but I'm still not sure which way to go.

[Anonymous No.1282437]

>>1282379
Show tits and/or schematic. If any if those phases are connected to the emitter of the power driver, so help me I'm going to fug you up.

>>1282424
What is an amplifier but a power supply with a control input?

[Anonymous No.1282438]

>>1282392
go for power electronics so you can compete with all the other power electronics people. leave my specialty sub-field of opamp wizardry and deep magic alone.

[Anonymous No.1282445]

>>1282437

Schematic is extremely basic, just one 2n3904 connected as high side switch and one as low side, each driven by an arduino output. And yeah, I'm using an NPN as a high side switch, it's all I have in the cupboard. Gonna get some joocier transistors and try again I guess

[Anonymous No.1282446]

>>1282392
if you have ANY interest whatsoever in signals and systems, then choose "design techniques what are used for instrumentation purposes".

your odds of designing and building power supplies in any future job are nearly null and void unless you go to work for FuG Elektronik. you'll pick some off-the-shelf supply for most jobs because it is quick and easy and cheap, and you don't redesign the wheel.

your odds of having to interact with a variety of real world signals is infinitely greater.

[Anonymous No.1282448]

What are you driving the high side with?

Show full schematic.

[Anonymous No.1282454]

>>1282448

Here u go anon. On the right is the waveform from the 3 of the 6 AVR GPIOs (other three are just the inverse of these 3 obviously). Also I had to decrease the PWM resolution to record one full cycle in the ATMega's RAM if you're wondering.

[Anonymous No.1282456]

>>1282438
Ha, I don't think I'll be becoming a wizard from one undergrad class. You're safe for now.
>>1282446
Good advice. There's actually a lot of aerospace companies in my area, and they all seem to do power electronics. The capstone project I start next quarter is for one of those companies building a power supply, and I was thinking taking a power electronics class could ease the project process, or I could just say to heck with it, and learn/research it as I go. I think I will take the design class.

Thanks, everybody.

[Mr.T !LeoPard6uk No.1282465]

>>1282392
>Intro to Power Electronics:
>>Introduction to power electronics. Topics covered include characterization of power semiconductor devices, design of magnetic components and filters, analysis and design of ac-to-dc, dc-to-dc and dc-to-ac power converters. Applications in power supplies are presented. Theoretical concepts and analyses are augmented by simulations and lab projects.
>I want to take both, but this is my last year, and both courses are offered at the same time. What would you guys take?

EV's are rising, all of them have chargers and motor drivers. That's what I'd choose.

[Mr.T !LeoPard6uk No.1282469]

>>1282424
>with op-amps you can build a million things
Op amps and analog signal processing is dying, everything is moving towards DSP.

[Mr.T !LeoPard6uk No.1282472]

>>1282390
>If the motor isn't getting enough power, it must be because the current is being limited somewhere though right?
Yes
> and AFAIK the 2n3904's are the "weakest link",
Yes
> current wise (max 200mA continuous),
The fact that you use "200mA transistors" doesn't mean that you will get 200mA (or 5V 200mA)

>so if the motor wants more than 200mA, the transistors should be overheating and popping,
Nope, it's a bit more complicated than: "if 200 mA transistors aren't popping then I must have 200 mA current going to motor"
> since they are in saturation?
Upper transistor isn't saturating.

> But they are barely even warm. And my USB supply should be able to provide at least 500mA so it's not getting limited there either. Not saying I don't believe you but now I'm more confused than before. Maybe it's simply a voltage thing? But this is a quadcopter motor which usually runs off LiPo voltages..
blah-blah-blah what a BS.

A sane person would do this:
1. open 2n3904 datasheet
2. search for h_fe and h_fe vs collector current
3. h_fe is ca. 100, it drops to 15 at 200 mA collector current
4. at 200 mA transistor will have base current of 13 mA and you'll get 1.3V drop on base resitor and like 1v drop on BE junction.

You clearly designed shitty driver for that motor.

[Anonymous No.1282476]

>>1282472

Never said it was a good driver, like I said it's just what I had in the cupboard. Still surprised it doesn't work though.

So the top transistor has Vce ~2V in the worst case, so what? bottom transistor probably has .5V drop as well if I'm reading the datasheet right. There's still 213mA at 2.5V across the motor windings according to those numbers though. 50% efficiency at peak load is shit, yes, but still doesn't explain to me why the motor vibrates violently rather than rotating. Thanks for your advice regardless.

[Mr.T !LeoPard6uk No.1282479]

>>1282476
>but still doesn't explain to me why the motor vibrates violently rather than rotating.
Low voltage / low current -> low torque -> torque is less than cogging torque -> oops

What transistors do you have at hand? don't you have 2n2222

[Mr.T !LeoPard6uk No.1282481]

>>1282476
Also a get a scope. You are basically wasting your time guessing what could be wrong. It's dumb.

Even old CRT 5 MHz scope would help you tremendously.

[Anonymous No.1282482]

>>1282445
>you don't have any PNP in the cupboard
Son, I...
>50% efficiency
But 25% power, no?

[Anonymous No.1282485]

>>1282479

Don't have anything but 2n3904's on me right now, obviously I was a bit too optimistic that I could just chuck em on and hope for the best. I'll have a look at what I can loot from uni tomorrow (and try and use their scope too). Thanks for your help

[Mr.T !LeoPard6uk No.1282488]

>>1282485
You can find smaller BLDC motors in old CD/DVD drivers. They should work with the driver you've built.

[Anonymous No.1282496]

>>1282427
>can I make something a little cooler with these?
A fridge!

[Anonymous No.1282500]

>>1282485
Get some P channel and N channel MOSFETs if you can, much better than trying to use BJTs.

[Anonymous No.1282504]

Is chinkshit air mail running super slow for anyone else?

[Anonymous No.1282507]

>>1282330
right click the part and write "mark=200000 space=10000" in the value field

[Anonymous No.1282509]

>>1281748
how am I supposed to find an rs flip flop, I am searching on digikey and mouser but I can only find T-type JK-type and D-type am I missing something. is one of these types just rs with a different name or are you supposed to use one of these as an rs flip flop in some way.

[Anonymous No.1282511]

>>1282509
Normally you just take two NAND or NOR gates and cross-connect them like so.

[Anonymous No.1282512]

>>1282511
I am pretty sure there should just be an IC that can do this, I need it to be in a small package and most nand gates come in 16 pin packages

[Anonymous No.1282513]

>>1282512
74LVC2G00
available in TSSOP8 down to 1.2mm XSON8

[Anonymous No.1282514]

>>1282513
So you are telling me that SR flip flop IC's just do not exist.

[Anonymous No.1282515]

>>1282512
7474 can do that and it is available in tiny packages too.
Some RS latches were available in the original 7400 series, but afaik those weren't copied to the later incarnations like 74HC.

[Anonymous No.1282518]

>>1282513
but in that case A 555 would take up the same amount of space and could perform the same job without losing speed from capacitance in the signals outside of the package.

[Anonymous No.1282519]

>>1282518
Except that the 555 is slow as fuck to begin with.
Well, if it's fast enough and you like it, no-one is stopping you from using it.

[Anonymous No.1282524]

I’m building a diy kit and like a fucking idiot I’ve put one of the transistors in around the wrong way!
How fucked am I? I’ve already powered it up, can I get away with desoldering and just turning it around or do I need to find a replacement part? Is it likely to have fucked something else in the circuit too?
Part in question is a C945P331 transistor

[Anonymous No.1282528]

>>1282524
its probably fine, just take it out and put it in correctly

...also check any others

[Anonymous No.1282529]

>>1282528
Thank you anon.
I think I’ve checked all of them now. It’s the 4th time I’ve been over the board looking for faults!

[Anonymous No.1282531]

>>1282524

some NPN transistors have the base as the center pin which makes it not so bad to install it wrong.

you might be ok, but unfortunately you have the kind that does not like to be flipped.

[Anonymous No.1282533]

>>1282350
Current goes the path of least resistance, so only a certain percentage of the 19mA go through R11 based on the resistance of whatever is outside of the image.

[Anonymous No.1282538]

>>1282531
Ok I’ll replace it. I have another 2 boards that I’ve managed to fuck up also so will grab a part from one of those boards.

[Anonymous No.1282542]

>>1282538

it might be ok; it all depends on the circuit. I just posted that because I'm autistic that way.

[Anonymous No.1282549]

>>1282542
That’s ok maybe I’ll try it in the other broken board, I’d rather not just turn it around, put it all back together again and then have to replace it anyway after finding out it doesn’t work!
I have no idea what’s going on I’ve built quite a few kits now and never really had any problems but all 3 of these are non working at the moment.
Thanks for your help

[Anonymous No.1282570]

>>1282350

[Anonymous No.1282619]

>>1282524
You can test a transistor with your Ω meter and a (wet) finger. Connect red (+) lead to collector and black (-) to emitter, meter should show open loop. Now bridge base and collector with your finger. If the transistor is ok the meter should show some resistance. Pic shows how to measure and calculate the approximate current gain B. The 2SC945P should be between 200 and 400. Which kit is it?

[Anonymous No.1282626]

>>1282524
You can test a transistor with your Ω meter and a (wet) finger. Connect red (+) lead to collector and black (-) to emitter, meter should show open loop. Now bridge base and collector with your finger. If the transistor is ok the meter should show some resistance. Pic shows how to measure and calculate the approximate current gain B. The 2SC945P should be between 200 and 400. Which diy kit is it?

[Anonymous No.1282670]

>>1282528
>>1282531
>>1282542
>>1282626
Thanks anon/s

I took a transistor from the other board and it’s all working fine now...other than needing an oscilloscope to calibrate it properly, but it’s at least doing what it’s supposed to...sort of.

>>1282626
>You can test a transistor with your Ω meter and a (wet) finger. Connect red (+) lead to collector and black (-) to emitter, meter should show open loop. Now bridge base and collector with your finger. If the transistor is ok the meter should show some resistance. Pic shows how to measure and calculate the approximate current gain B. The 2SC945P should be between 200 and 400.
Thanks. That’s really helpful to know. I’m pretty new to all this so any help is much appreciated. I’m trying to build as much as I can at the moment in the hope I’ll eventually be able to make my own modules.

>Which diy kit is it?
It’s a Din Sync VCF303 Filter Module. Pic related is next on the list for trouble shooting. I’m not really having any luck with filters!

[Anonymous No.1282671]

>>1282344

Don't forget, voltage is generally measured in parallel and current is measured in series.

So that 19 µA does not represent what is measured across the resistor.

An ideal current measuring device is 0 Ω (dead short) and an ideal voltage measuring device is ∞ Ω.

In reality, though, many instruments that measure voltage are 1 M Ω (for example). In case you try and build it and take some actual numbers.

Also, you don't necessarily know what the “current thing” is exactly... it could be a measurement or it could be a constant current “source” but whatever it is, there is 19 µA going through there.

[Anonymous No.1282672]

I have a 220v outlet in my kitchen that used to support an electric range, but now I'm getting a gas range and only need 120v. Are step-down converters useful for something like this? I don't want to have to do a full conversion on the outlet...Pic related is the type of thing I'm talking about, but likely something less expensive. Any recommendations on how to get this done?

[Anonymous No.1282685]

>>1282672

Oh god, no. Usually a stove outlet will have two "hot" wires -- a black one and a red one. Between black and red it's 220, but between each hot, and neutral it's gonna be 110.

[Anonymous No.1282699]

>>1282685
Yeah...my own research also turned up the same. I'm scared as fuck of electricity so I'm hiring an electrician, got quoted ~$425 for the job including permits, which is an unexpected hit, but I'm saving a ton on the appliance itself from black friday deals so I guess I'll have to bite the bullet.

[Anonymous No.1282713]

>>1282699

Yeah, code would probably require running new 12/2 right from the box on a 20A circuit (breaker).

That's the other problem: stove outlet might be, say, 50 amps, and if there is a short somewhere it won't break and could cause a fire.

[Anonymous No.1282732]

>>1282713
>change breaker to two 20a if you're scared
>cut tab on outlet, have two different circuits worth of 110, one on top, one on bottom
>if you don't have a neutral in your outlet, tape the red hot to change color code to white. Change wiring appropriately in breaker box
425 is a ripoff. 150-250 more like. Just an hour of work.

[Anonymous No.1282788]

>>1282732
>425 is a ripoff. 150-250 more like. Just an hour of work.
Are you sure anon? I know sparks get a good wage but that obviously $150-$250 p/h?

[Anonymous No.1282798]

>>1282699

They also make these things for, like $30 bucks. Might not be code in your area (and I've never seen one before). It's a Woods Gas Range Adapter.

[Anonymous No.1282806]

>>1282788
+gas + taxes +insurance
Figure he's actually taking home 1/3 of that.

[Anonymous No.1282810]

>>1282806
>+gas + taxes +insurance
Figure he's actually taking home 1/3 of that

Ah ok so it’s a 7 hour round trip to the job, makes more sense now.

[Anonymous No.1282811]

>>1282806
>>1282788
I actually got another quote elsewhere for like $175 from a reputable company, so I think that other guy was just a terrible guesstimator.

>>1282798
Looks neat, but I'd have to look into if it's code. It's going to take a long time until someone can come out and help me though, so in the mean time is it unsafe to plug the gas range into a standard 120V outlet that I have nearby above the counter? I believe they're all grounded together like a GFCI, but internally without the reset buttons on the front. Sorry if I butchered that terminology, I'm no where near capable with electricity.

[Anonymous No.1282821]

>>1282810
You have never run a business or are just a shitlord I guess.

[Anonymous No.1282824]

>>1282811
They could all be feeding off of one gfi but it would still have reset buttons on it. The outlets down stream from it would just look normal, but would trip the upstream gfi.

[Anonymous No.1282825]

>>1282821
fine /pol/, what's your breakdown look like?

[Anonymous No.1282829]

>>1282509
Just use a J-K flip-flop, they're the same thing except the J-K flip-flop toggles when both the set and reset inputs are held high. Though this is assuming you want a synchronous flip-flop, not a latch. If you want a latch then go for >>1282511.

[Anonymous No.1282834]

>>1282825
Anon I can't even

[Anonymous No.1282835]

>>1282811
Yeah, it's safe as long as the cord reaches.

Gas uses bugger all in electricity. 30,000 btu range is equivalent of nearly 10,000 watts (around 45A at 220) that you don't need anymore! You can buy a little tester for $15. It's probably a good idea to have one and check them...

... some of my outlets had the hot/neutral switched around when I moved in. I'm glad I checked mine.

[Anonymous No.1282837]

>>1282514
4043 and 4044 are R/S only.
using the various JK as R/S is trivial.
using NOR and NAND gates as R/S is also trivial.

[Anonymous No.1282838]

>>1282524
>>1282670
hey fellow eurocracker!
what are you working on?

[Anonymous No.1282840]

>>1282837
I guess it's conceivable that using an RS flip-flop could simplify the surrounding logic as long as the flip-flop ignores a R=S=1 condition. But I think you might be confusing latches with flip-flops there.

[Anonymous No.1282844]

>>1282838

[Anonymous No.1282847]

>>1282844
4chan deletes metadata from pictures posted.
image rotation from the standard picture viewer along with it.

how do you not know this?

[Mr.T !LeoPard6uk No.1282848]

>>1282847
if you know this shit then why didn't you rotate the picture? Relying on metadata is dumb as it gets deleted...

[Anonymous No.1282851]

>>1282848
honestly, its a bit of a bitch, and its seemingly random.
hope this works.

[Mr.T !LeoPard6uk No.1282852]

>>1282851
much better

what the hell is this rig??

[Mr.T !LeoPard6uk No.1282853]

>>1282851
also share some tunes

[Anonymous No.1282854]

>>1282811
Why would a gas stove need electricity at all? My wonderful natural gasprom stove has no plug. Also, this climate of electric fear is totally alien to me.

[Anonymous No.1282856]

I made a splitter plug to turn a nema 14-20 into 2 120v outlets by taking 2 extension cords and chopping off the male ends and putting them in a plug. I used pic related as the diagram, both greens to ground, both whites to neutral, and each black to their own hot. I'm getting 108v at each end (220v service divided by 2 minus 50 feet of loss) however I can't get any current from it, I've tried my grinder and drill and neither work. what the fuck, over?

[Anonymous No.1282858]

>>1282854
Electric ignition for burners and oven, timer, oven controls.

[Anonymous No.1282862]

>>1282856
I think you just said it yourself, you're getting 108v, not 240.

You've verified X to N is 120 and Y to N is 120, and XY is 220?
If X N and YN check out, and XY is 0, then both plugs you picked are on the same phase, you have to look for another plug.

[Anonymous No.1282864]

>>1282847
That explains a lot. So what are the good and not good ways of rotating an image?

[Anonymous No.1282868]

>>1282852
modular synthesizer.

all my clips are crap, and more demonstration than musical.
bul ill see what i can dig up.

the rig itself is indisposed atm, due to redecorating.

[Anonymous No.1282875]

>>1282864
open in photoshop, gimp, paint.net, or any other graphic editor
save (without EXIF, if prompted)
done

[Anonymous No.1282880]

>>1282856
check to make sure your 240V outlet actually has a neutral connection and not just two hots. 240 can run without neutral because it's just two 120s that are 180 degrees out of phase.

[Anonymous No.1282881]

>>1282862
I don't think you're understanding, I have a 220v female plug in the wall which I split into a pair of 110v extensions, I'm making two 110v plugs NOT trying to make one 220v plug.

[Anonymous No.1282883]

>>1282880
the plug is 4 prong center tapped, so it has a ground and neutral. if the neutral wasn't hooked up then I would get 0v at each plug not 108v.

[Anonymous No.1282885]

>>1282883
Depends on the impedance of your meter. You could be seeing capacitive coupling. Is there voltage between neutral and ground? If not, is there continuity between neutral and ground?

[Anonymous No.1282887]

Die anyone know the exact chroma sub carrier frequency of the Sony Umatic dub signal (NTSC)? I know it's 6.88MHz, but what exactly? (Example: 3.58MHz=315/88)

[Anonymous No.1282907]

>>1282883
yet you have no current flow, ergo, there is an open somewhere in your circuit.

[Anonymous No.1282926]

>>1282838
Howdy

Nice rack anon

>what are you working on?
I’ve been trying to sort out my Befaco Sallen Key filter, finding it kinda hard to calibrate 2ms peaks by ear...I really need to get a scope.

Next on the list 2 spring reverbs

[Anonymous No.1282938]

>>1282821
>anon gets a quote for $425
>business anon chips in with “that’s an hours worth of work, should be more like $150-$250”
>I do the maths...$150-$250 p/h
>”2/3rd of that is gas and taxes”
I’ve run my own business and yes if I had to travel for 7 hours round trip to do an hours work I’d charge for a days work, but if like you say that’s an hours worth of work then wouldn’t it make sense to get someone local to the job to do the work so they don’t have to charge for 7hours of traveling and petroleum?
That’s probably what I would suggest to a customer of mine if they wanted an hours worth of work done 3 1/2 hours away?
>”you’ve never run a business you shitlord”

[Mr.T !LeoPard6uk No.1282944]

>>1282887
>Die anyone know the exact chroma sub carrier frequency

Did you check patent(s) for umatic? I bet it'll answer your question.

[Anonymous No.1282948]

>>1282944
Good idea, I'm looking at this right now... https://encrypted.google.com/patents/US4323915

[Anonymous No.1282962]

>>1282948
It might just be 688kHz. Best way is to look on a digital scope with a frequency counter...

[Anonymous No.1282963]

>>1282962
Ok, so I have to get a 688KHz oscillator to use with a demodulator to convert the Sony Dub Chrominance?

[Anonymous No.1282969]

>>1282963
You'd need an oscillator with gated control that only tries to sync during the colour burst.

If your deck has S-video out this will be much easier as there are chips available.

[Anonymous No.1282971]

>>1282963

Not exactly sure what you're looking to do but your question reminded me of this i saw a few weeks ago:

http://tubetime.us/index.php/2011/03/29/oscilloscope-video-monitor/

Easy way to get a sync signal from an NTSC source.

[Anonymous No.1282979]

>>1282971
It's not the sync signal they need, that part's relatively easy, it's the chroma carrier that's tricky

[Anonymous No.1282983]

>>1282969
Well I was thinking of recreating a chroma demodulator from scratch so that I can use a custom oscillator (688khz).

I actually haven't bought one yet because I wanted to find one with S video, but I haven't found one yet.

[Anonymous No.1282985]

>>1282979
Right, but why not use the sync signal instead of trying to match the frequency/phase with an outside oscillator?

[Anonymous No.1282988]

>>1282985
Obviously you'll use the sync to gate the color burst through to the PLL or whatever. The sync signal itself has no defined phase relationship to the chroma subcarrier.

[Anonymous No.1282995]

>>1282985
If you don't match frequency/phase you won't get the correct colours out.

[Anonymous No.1283002]

I'm looking to buy an ESR meter, can /ohm/ recommend one?

[Anonymous No.1283003]

>>1282988
>>1282995

I probably just don't know enough about NTSC. I think I know what I misunderstood now.

[Anonymous No.1283008]

Well do I just have to get a 688KHz oscillator to connect with a chroma demodulator?

[Anonymous No.1283041]

>>1282938
It costs $100 to get someone to show up at your house that isn't named Pedro amd can do anything besides haul trash, fuck your wife, or trim your grass. I don't know why you're so butt blasted I know what things should cost.

Okay, not just gas, i was attempting brevity but toy tards are too fucking dumb to put it together. The car too, the rent on your office, the cut for the manager and marketing, the cut for the payroll people. All the shit to run the business.

[Anonymous No.1283044]

>>1282938
Also
>250 for 7 hours of work
Did you haul scrap metal for free off of peoples property or something? You need a different line of work tbqhfamalam

[Anonymous No.1283045]

Just stopped by to ask a dumb question. What size solder is typically used in electronics and automo wiring. From what I understand they use the same type of solder but varying sizes.

[Anonymous No.1283060]

>>1283045
It doesn't really matter. If you're really slathering it on to thick wires then go ahead and use a thicker gauge, otherwise thinner might give you more control. Typically everything soldered now-days uses lead-free solder, which is typically worse to solder with compared to lead-tin solder. You'll also probably want flux-core solder unless you're using external flux, which you might if you want to use no-clean flux. No-clean flux is usually used on SMD boards.

[Anonymous No.1283063]

>>1283041
That's a good reason to only hire sole proprietors. Less wastage on crap.

[Anonymous No.1283064]

>>1283008
The color burst "rings" your oscillator like a bell. Divide by the appropriate ratio of course.

[Anonymous No.1283067]

>a new general that actually makes sense
sasuga, /g/

[Anonymous No.1283076]

>>1283064
What do you mean to divide by, the oscillator frequency?

[Anonymous No.1283096]

>>1283067
>new
Now don't you make me question my status of "not a newfag".

[Anonymous No.1283118]

>>1282858
>Electric ignition
Oh, mine has manual piezo, you have to push and wait for the thermo-electric safety valve to kick in. Does that mean you cannot cook without electricity?

[Anonymous No.1283121]

>>1283118
Any flame will usually start the burners, in a pinch. Ovens might or might not be electronically controlled these days depending on model.

[Anonymous No.1283124]

>>1283076
Looks like it's common to use a resonator at a multiple of the chroma carrier and then divide it back down. For PAL it makes generating the 90 degree phase shift easier, not sure why it's useful for NTSC only.

[Anonymous No.1283159]

>>1282851
Very nice

[Anonymous No.1283220]

what's a cheap benchtop power supply that's decent for the money? One that I could find on eBay?

[Anonymous No.1283224]

>>1283220
specifically for a very new electronics hobbyist? It doesn't need to be fancy, in fact the more bare-bones/cheaper the better. It just needs to output power

[Anonymous No.1283231]

>>1283220

You can do a lot of experimentation with any DC adapter, like the $15 ones at Walmart or most laptop chargers. Some of the cheapo ones have a switch for quite a few voltage ranges from about 3 to maybe 15 or so. If you can afford a nice power supply go ahead and buy it, but unless you are driving large motors or other power hungry devices you can do a lot with something cheap, and eventually you might use it in some permanent project so it might not be wasted money.

If you want a lot of power and can settle for 5 and 12 volts you might look at PC supplies which give you a lot of bang for your buck.

[Anonymous No.1283236]

>>1283220

and if you get a fixed voltage power supply since variable voltage supplies are a bit pricey, this >>1282017 costs about $2 on amazon and can boost lower voltages to about 30 or more, and are easily adapted to provide constant current.

[Anonymous No.1283254]

so I wanna give this a try
http://www.instructables.com/id/Synthesizer-using-555/

instead of outputting to a speaker, could I instead solder on a 3.5 mm audio jack to it and hook it up to a MIC IN input on my computer?

[Anonymous No.1283262]

>>1282853
>>1282851
>>1283159

hit the workshop the rig is at and recorded this.
new phone fucked up on me three times so this is not as good.

https://vocaroo.com/i/s01O3Vs2ikC8

recorded on a phone, out of a guitar tube amp i built (as featured on /diy/)
its a bit thin because the bass response isn't great the amp. though i love the overdrive.
all just an analoge sequencer. no midi or keyboard.

[Anonymous No.1283288]

>>1283220
A benchtop power supply should be adjustable, both voltage and current.

[Anonymous No.1283305]

>>1283220
I have one of these, $40 variable power supply
been using it for a couple years, works great
https://www.ebay.com/itm/30V-5A-Digital-DC-Power-Supply-Variable-Adjustable-Lab-Bench-Test-Equipment-Tool/222410060720

[Anonymous No.1283340]

> -20% to +80% tolerance capacitors
what even

[Anonymous No.1283344]

I am still working on my little LED driver circuit.
I plan to power the circuit from a 24 VDC power supply. I did a DC operating point simulation with LTSpice and it shows that the current-limit transistors Q1..4 dissipate about 180 mW of power when operating at 24 V. With an unregulated power supply the voltage may rise above the nominal 24 V, further increasing dissipation.

Do you think the dissipation would be too high for this small signal transistor type (2N3906)? Its datasheet mentions max. dissipation of 250 mW at ambient temp of 60°C.

Are there any ways to improve the efficiency of this kind of constant-current source?

[Anonymous No.1283346]

>>1283340
bad tolerances exist. sometimes it doesn't batter that much. mostly power filtering where they over-dimension anyway.

if you are reacting to the tolerances are way higher on the positive, that is thing for the same reasons.

[Anonymous No.1283347]

>>1283340
I read a really good explanation of this last week but I can't remember it at all.
I think it was basically, nobody gives a fuck if capacitance is too high but it fucks you if its too low so they just lower the value to get the errors more appealing
Low precision is cheap

[Anonymous No.1283350]

>>1283344
>Are there any ways to improve the efficiency of this kind of constant-current source?

some guy has some posts up here that might make your life simpler.

>>1281984
>>1282017

that's a dirt cheap device that will provide constant current easily for a few bucks at pretty good efficiency, and you only have to solder a few lines.

[Anonymous No.1283351]

>>1283344
Well is 180 greater or less than 250?
Why do you have series resistors if its current limited?

[Anonymous No.1283356]

>>1283346
>>1283347
The manufacturing precision has a spread, they dont manufacture 1% or 20% caps specifically. They aim for a value and sort them out in different tolerance bins, the ones with the closest tolerance will be the expensive 1% caps, the shit ones will be sold for 20% caps for cheap. Thats why you dont buy only 20% caps hoping you will find a couple of 1% caps. You wont.

A pretty good short article on tolerances:
http://dangerousprototypes.com/blog/2010/07/01/actual-values-of-10-tolerance-resistors/

[Anonymous No.1283366]

>>1283351
Balance, Daniel-san.

[Anonymous No.1283376]

Does this look right?
The two output pins to the right are ADC that I'm trying to multiplex as the the two pins on top are ON/OFF only.
the IC is an ATmega8, but not on an arduino if that helps at all.
Never attempted multiplexing before and whilst I'm fairly confident about the coding this is my first real circuit designing beyond just putting a bunch of LED's in parallel.

The four photo-transistors sit at the base of a very basic pinhole camera to allow direction sensing, similar to a cup eye or simple compound eye.

[Anonymous No.1283384]

>>1283376
As long as you are confident that you can turn t1/t2 on and off without obliterating the other one? The two 20ks you have a surplus of 20k? One 10k will do the same

[Anonymous No.1283385]

>>1283356
Whether the manufacturer does this or not depends on what exactly is being made. For example, some ceramics have so horrible temperature and voltage coefficients that "making" 5% capacitors by sorting doesn't really work.
Better resistors are also often factory-trimmed to their final value.

[Anonymous No.1283386]

>>1283384
I'm fairly sure, supplied voltage is 4.5V, shouldn't blow up a normal transistor should it?

Basically this is a custom extension plugin board for the asuro robot. I based this circuit off of the standard plugin that normally sits in that slot, but basically I removed an LED and added two more phototransistors. The circuit diagram for that has two 20K resistors so I figured double sensors double resistors.

[Anonymous No.1283390]

>>1283386
If you pull PB3 to V+, T2 will be off while T1 is on.
If you let PB3 float, T1 gets biased via T2 and the both transistors are on.
If you pull PB3 to ground, T2 melts.

[Anonymous No.1283401]

>>1283390
hmm, how should I fix that.
Could I put a couple of diodes in to stop T1&T2 and T3&T4 interfering with each other?

[Anonymous No.1283402]

why is a transistor not an AND gate

[Anonymous No.1283409]

>>1283401
Base resistor on T2's base would prevent it melting when you pull PB3 to ground.
Consider using an analog multiplexer like 4051/4052/4053 or switches like 4066.

[Mr.T !LeoPard6uk No.1283433]

>>1283262
>all just an analoge sequencer. no midi or keyboard.
awesome

[Mr.T !LeoPard6uk No.1283439]

>>1283376
>Does this look right?
wouldn't work at all
try again with p-/n-channels mosfets but don't forget they come with body-diode.

[Anonymous No.1283478]

>>1283366

I think the guy is wondering why there are effectively *two* current limiting resistors for each of the four LED banks (In addition to the other unbalanced series limiting resistor)

If you're going to do that, you might as well get rid of the expensive PNPs altogether, no?

Furthermore, it appears that the banks are all powered at the same time. I've seen more complicated balancing setups (e.g. 7 segment displays) where, if only one segment was powered it was ultra-bright and if all then they were very dim. Looks terrible, eh? But this doesn't seem to be the case here.

[Anonymous No.1283489]

>>1283376

That seems overly complicated: can't you apply a bias voltage on the phototransistors (from Pxx inputs) so they go into saturation when they are simultaneously lit and selected? If that were not detectable as a logic 1 you might be able to pull them up.

If it were me, I'd play around with some 10-turn trimpots, and when I got it working, measure the trimpot values and sub-in fixed resistors.

[Anonymous No.1283496]

>>1283402
in what configuration? you can use a pnp as an and gate with one inverting input but nothing else comes to mind.

[Anonymous No.1283499]

>>1283496
https://en.wikipedia.org/wiki/Transistor%E2%80%93transistor_logic

[Anonymous No.1283500]

>>1283499
pretty sure he's referring to using a single transistor as an and gate, not multiple.

[Anonymous No.1283510]

>>1283496
>>1283500
Yeah, I guess you could somehow use the base and collector as two inputs, but input and output impedances would not be ideal, like pic related.

[Anonymous No.1283554]

>>1283344
The NSPW500BS is specified to about 3.5V at 18mA which is 14V for four in series. With a 24V supply you could drive six LEDs per branch instead of four or increase the value of R8 .. R11 to 330Ω. The current value of 2.7Ω doesn't make sense in any case.

The circuit was originally meant to stabilize the LED current over a wide range of supply voltage. If you have 24V or a bit more this is not needed. With 10V headroom a single 560Ω series resistor per branch of four LEDs would be good enough.

[Anonymous No.1283559]

>>1283376
double ouch

[Anonymous No.1283567]

>>1283376
Don't short the port.

[Anonymous No.1283605]

>>1283433
thanks mang

[Anonymous No.1283608]

>>1283510
yeah, but TTL from the wiki page is using a four-leg transistor with two emitters. omit the output buffer and just use resistors. define logic levels however you want.

[Anonymous No.1283620]

>>1283384
>>1283390
>>1283409
>>1283439
>>1283567
cheers lads.

[Mr.T !LeoPard6uk No.1283624]

>>1283620
Also why wouldn't you bias the photo transistors directly? E.g. wire two phototransistors to one gpio and another two to another gpio.

[Anonymous No.1283632]

>>1283624
like this?
that does look a lot easier, like I said this is my first crack at circuit design.

[Anonymous No.1283636]

>>1283478
I see, the 2R7s are surplus to requirements.
>brightness fail
That happens if you try to save on resistors or current sources by putting only one on each digit line instead of one on each segment line, or if the power supply just can't hang.

>>1283632
No. Look at the bottom. All your emitters are connected together.
You really need something more like a switch for this. If you're tight on input pins, you really need an analog mux, which combines the decoding and the switching in one package. Consider the CD4052 analog DP4T multiplexer, Pic related. It can handle a very modest amount of current without introducing a whole lot of error, about 150 ohms or so, fine for a 10k pulldown. You could connect up to 8 sensors to this, if you use the other half of the mux. You could also move two of the sensors to the other half of the mux if you wanted to compare them at an instant.

>>1283624
Depends on what the reverse Vce on those is. I'd rather just leave them float.

[Anonymous No.1283643]

say I wanted to build a computer from scratch. It would pretty much just be a BASIC interpreter like the zx spectrum or Apple I/II
Assuming my newness isn't causing me to suggest something ridiculously out of anyone's league, let alone mine,

where would I get an IC with a basic interpreter on it? Or is that something where I'd have to flash my own to some EPROM ic

[Anonymous No.1283646]

>>1283643
It's not a trivial task. A lot depends on how you want I/O to happen, how much RAM you want, etc. Have you done any microcontroller projects or digital design?
BASIC interpreters don't really grow on trees. You might end up writing your own or compiling some open source thing from the net.

[Anonymous No.1283647]

>>1283646
I can already tell this is way out of my league. Dunning-Kruger and whatnot.

Oh well I'll just stick to building synthesizers and amplifiers for now

[Anonymous No.1283649]

>>1283647
I/O is the hard part, really. It's pretty easy to make a BASIC system that just talks over the serial port. Just about any microcontroller with a decent amount of flash and RAM can do that. If you want to scan the keyboard, display video, talk to storage devices, etc., it gets complicated.

[Mr.T !LeoPard6uk No.1283655]

>>1283632
>like this?
I'm too lazy to make a symbol for photo transistor so I put BJT's instead.

The idea is the same as you had in your first prototype

[Mr.T !LeoPard6uk No.1283659]

>>1283636
>Depends on what the reverse Vce on those is. I'd rather just leave them float.
I imagine photo transistors would operate akin generic BJT in III quadrant, i.e. have extremely low gain so we can simply ignore them.

[Mr.T !LeoPard6uk No.1283661]

>>1283659
Oops, forgot the pic. Anyways if tests show they still pick up something you can put few small signal diodes to "float" them.

[Anonymous No.1283663]

>>1281748
>>What books are there?

the electronics bible

http://electriciantraining.tpub.com/

[Anonymous No.1283669]

>>1283663
>electricity for NEETs
kek

[Anonymous No.1283677]

>>1283659
>extremely low gain
I tried it, my PT331C phototransistors have a reverse gain of about 10%.

[Anonymous No.1283692]

Looking around a bit it seems DIY synths tend to have 12 or 15 volt. If I could choose, which one would be the best one to go for if I were to make my own synth?

[Anonymous No.1283710]

>>1283677

Geez, the PT331C's data sheet is terrible. Makes me wonder how they managed to make a device in the first place.

[Anonymous No.1283711]

>>1283710
What's so awful in it? It looks pretty normal to me.

[Anonymous No.1283717]

>>1283710
>data sheet is terrible
Why? What are you missing? Which one is better?

[Mr.T !LeoPard6uk No.1283721]

>>1283692
I think there should be virtually no difference, go with either

If you can't decide then choose 15v because 15 > 12 :)

[Anonymous No.1283723]

>>1283692
audio circuits are vastly simplified with split rail power supplies (ie. a + and - supply). The amount of voltage just determines how much dynamic range the signal can have. With lower voltage signals are more prone to clipping and distortion. Of course you can just lower the signal levels, but if you go too low noise can become a problem

[Anonymous No.1283733]

>>1283692

It seems to me that a lot of devices (i.e. op-amps) were run off +/- 15v. Many of them couldn't drive all the way up to +15 and down to -15 though.

I'd go with the 15v.

Also, it's easier to blip the voltage down a cog than it is to boost it.

[Anonymous No.1283737]

>>1283710
>>1283711

Sorry, I just mean the data sheet itself is pretty bad, quality-wise, and the wavelength (and probably others) are hand-drawn rather than actually measured.

Here's hoping they invested all their efforts into the actual device.

There is some TI app notes that I remember seeing (examples of good quality data sheets :-) that biased phototransistors using resistors so they were in the active regions for a micro controller with A/D converter...

...not exactly what you're trying to do but it might help to nose around those.

[Anonymous No.1283755]

>>1283737
>hand-drawn rather than actually measured
Next you will criticize the inconsistent font
and all that triggered by a minor misjudgement..

[Anonymous No.1283841]

>>1281748
Can someone suggest a heat gun for soldering? What specifications I should look for and what do you use?

[Anonymous No.1283845]

>>1283002
pls respond

I live in Germany, so the Anatek Blue ESR meter is not an option. Shipping and import costs are almost more than the ESR meter itself.

[Anonymous No.1283872]

>>1283845
https://m.aliexpress.com/s/item/32615310550.html

[Anonymous No.1283880]

>>1283608
Where do you even find 4 leg transistors?

>>1283872
I prefer this one, it's slightly cheaper and uses a ZIF socket, though it doesn't recognise FETs.
https://www.aliexpress.com/item/Digital-ESR-Meter-Mega328-Transistor-Tester-Diode-Triode-Capacitance-MOS-PNP-NPN-LCR-TESTER-METER/32740536071.html

[Anonymous No.1283882]

>>1283872
>>1283880
I have one of these but I want to do in-circuit testing.

[Anonymous No.1283885]

>>1283882
Solder three alligator clips to it? In-circuit impedance measuring is kinda dodgy because you're putting a voltage, and potentially a current, through other elements in the circuit. Those LCR meters especially use a handful of different waveforms that could couple to a voltage rail through a capacitor and give you wonky readings, so I would stick to a DC ohmmeter/multimeter if anything.

[Anonymous No.1283886]

>>1283880
>Where do you even find 4 leg transistors?
From eBay, as pretty much everyone stopped making and using discrete multi-emitter transistors ages ago.
You can also emulate it with two normal transistors, but I guess that doesn't count.

https://www.ebay.com/itm/3N79-NPN-Dual-Emitter-Transistor-Texas-Instruments-/311488052061

[Anonymous No.1283887]

>>1283721
>>1283723
>>1283733
15v it'll be then, thanks for replies

[Anonymous No.1283892]

>>1283885
Alright, now I'm confused. I've read the book in the OP; "How to fix everything electronic" and they said, buy an ESR meter, it's good for in circuit testing. I obviously read this book because I want to repair some things. Desoldering all of the caps would take too much time so I thought I'd get a way with buying that meter. Now you're saying it's not needed. I've got a multimeter. I'm obviously new to this kind of thing.

[Anonymous No.1283898]

Question: Can I use arduino and I2C to talk with other arduinos over a distance of 10 to 20 meters? Would there be any problems with interference in the wires or whatever? Can I do something to minimize said interference?

>>1283841
I bought link related, it's the standard when it comes to cheap chinesium soldering stations. I've been using it for half a year now and it works quite fine, comes with spare elements in case they go kaput.

If you want something nicer you can look at the Hakko stations, but they're an order of magnitude more expensive.

Aliexpress link: tinyurl com yajulo5q

[Mr.T !LeoPard6uk No.1283925]

>>1283892
>and they said, buy an ESR meter, it's good for in circuit testing. I
What are you going to test? Caps? You can surely get skewed readings, you must understand what are you measuring and have solid understanding of a circuit.

For example trying to measure ESR of a bypass cap on 3v3 rail on a board with lots of 3v3 digital logic would give you skewed result as there are a lot of caps on 3v3 rail spread across the board and they are all connected in parallel.

[Mr.T !LeoPard6uk No.1283933]

>>1283841
>Can someone suggest a heat gun for soldering? What specifications I should look for and what do you use?
stay away from heat guns with built-in centrifugal blowers. Get a generic chinese one with diaphragm pump or something like that.

[Anonymous No.1283934]

>>1283898
Practical I2C distance is limited by how fast the pullup resistors can charge the cable's capacitance, lower value resistors and/or low clock speeds can get decent distances. Interference can be an issue, if so, a shielded cable can help, but will also add capacitance.

If you're looking for reliable communication I2C isn't ideal, particularly because a slave device can lock the bus low forever if you're doing a read and the device misses a clock pulse. Serial can be a better option, especially if you do level conversion to RS485 or RS422 which use differential signalling.

[Anonymous No.1283956]

I need a decent affordable soldering iron for hobby work. Sometimes I need to solder large pads for lipo battery connections and my current iron can't handle it.
I've seen recommendations for the hakko fx888d but I want a simple analog knob
Suggestions?

[Anonymous No.1283959]

>>1283933
>stay away from heat guns with built-in centrifugal blowers.
I'm curious, why? Mine works pretty well. The fan has quite a bit of power, I normally use it on 1/3 of the total speed.

>>1283934
Thanks, I'm trying to create an alarm system with a couple of motion sensors and a central monitoring unit.
I didn't know I2C could fail in such a way, I'll do some more research on serial comunication or write my own rudimentary protocol.
I don't need much speed to refresh the data from the sensors and the capacitance of the cable shouldn't be too high, so that's one problem less.

[Anonymous No.1283961]

>>1283956
i like my weller wlc100 but i really would prefer a temperature readout. it allows the iron to heat faster too.

[Anonymous No.1283962]

>>1283959
i have a hakko 850. i've used it to solder 0201s where even with paste you basically need still air to avoid blowing them off. the pump can provide a very low air speed that i imagine a blower couldn't match.

[Anonymous No.1283967]

>>1283962
You can set the air speed to be quite low. In any case that's the difference between a 50€ station and a 500€ one. If you're doing it on a professional level I'd say it's worth the difference, if you're only going to solder some ICs every now and then I'd go for the chineesium option.

[Anonymous No.1283977]

>>1283959
there is no active high, only pullups.
there fore its extra susceptible to loss from capacitance in cable.

i2c is more about chips and modules in a single unit communicating, not communicating with external hardware.

[Anonymous No.1283980]

So what's up with every electronics website (mouser/element14/etc) being complete dog shit.

[Anonymous No.1283987]

>>1283980
It's a combination of keeping the old school feel and their disdain for software people

[Anonymous No.1283989]

>>1283980
Even Octopart isn't that much better, mainly due to the different sites it features using different parameters. Arrow is a bit better than the others, though it suffers a bit from worse selection.

[Anonymous No.1283993]

>>1283956
define "affordable". Aoyues are bretty gud deals as far as chinkshit goes.

>>1283980
>complete dog shit
Digikey's web site is actually only partial dog shit.

[Anonymous No.1283994]

>>1283993
>Digikey's web site is actually only partial dog shit.
it took those fuckers years to add sort by price

[Anonymous No.1283997]

>>1283994
come on goy, buy that $15 deprecated ic

[Mr.T !LeoPard6uk No.1284001]

>>1283959
>I'm curious, why? Mine works pretty well. The fan has quite a bit of power, I normally use it on 1/3 of the total speed.
Lower air pressure limits air flow if you put some small nozzle.
For some reason they aren't reliable, at least 3 out 2 took crap in less than 6 month (they were used daily though), diaphragm-type based type seems to work for years.

[Mr.T !LeoPard6uk No.1284003]

>>1283980
I genuinely hate element14/farnell interface, the "new" one which was introduced like a year or two ago. Fucking terrible, it requires like 10 times more clicks to setting up filters / search criteria.

Digikey is a lot better.

[Anonymous No.1284004]

Guys, I need some help.

I have a Canon DSLR camera that died and it's out of warranty so I'm stuck with the cost of the repair. Given how Canon would charge me something like 50-60% of the cost of the camera to repair it, I'm not so keen to go down that route. I'd probably sell it as broken/for-parts before paying for the repair.

Anyway, this camera is notorious for overheating when shooting video and then dying. The fix is to replace the whole main board (pic related).

Apparently, they use lead-free solder and solder joints fail when the camera overheats.

I remember from Xbox days that you could stick the mobo into the oven and reflow the joints this way. I'm thinking about trying this. Got some questions...


1) What's the best diy way of trying to reflow the connections? I don't have a reflow oven (have regular oven and a toaster oven too. I don't have a soldering station heat gun but do have a regular heat gun. Would any of these things work?

2) See these little plastic things in pic related (connectors etc)? Would these melt it I placed them in an oven?

Anyway, looking for some ideas I could try. Thanks!

[Anonymous No.1284006]

>>1284004
the plastic connectors are very susceptible to melting if brought outside their fairly narrow soldering range so do your research.

[Mr.T !LeoPard6uk No.1284009]

>>1284004
Find a place that does cell phone repair and can reflow solder BGA's. Bring them the PCB. Done.

[Anonymous No.1284012]

>>1284004
>Apparently, they use lead-free solder and solder joints fail when the camera overheats
SAC305, the most comonly used lead-free solder, melts well above the usual junction temperature limit for silicon devices and about 30°C above leaded solder. They must have used bismuth solder on one side.
>a regular heat gun
is probably the more selective solution, if you know the approximate outlet temperature of the heat gun and can guesstimate about how far to back off to get a reasonable heating profile. As >>1284006 said, research this rework task carefully. You could be the hero of the Canon DSLR community.

[Anonymous No.1284015]

>>1284006
>the plastic connectors are very susceptible to melting if brought outside their fairly narrow soldering range so do your research.
Right. That's what I suspected and why I asked the question. They're so fucking small so there's no chance in hell that I'd be able to desolder them and then solder them back in after the reflow. So oven's a no-go.

>>1284009
>Find a place that does cell phone repair and can reflow solder BGA's. Bring them the PCB. Done.
That is an option. I'll ask around but this type of work isn't cheap. I can buy from China a replacement mobo for $200 that's guaranteed to work. If reflowing is gonna cost me $150, with no guarantee of success, I'd probably pay the extra $50 to be sure.

>>1284012
>They must have used bismuth solder on one side.
Not sure what they used. But after this happened to me, I did a lot of research and reading and it seems to be a common issue.

>if you know the approximate outlet temperature of the heat gun and can guesstimate about how far to back off to get a reasonable heating profile
Heat gun that I have is 1500Watts and has an 1" nozzle. That sounds like an overkill and it seems to be way too powerful and would destroy the board/IC.

I've been searching chinese websites and came across pic related. It's 300W which sounds a lot more reasonable. What do you think I buy one of these, isolate the IC in question with some aluminum foll shroud/cone and heat it?

I have no idea how long I should heat the IC for... any guesstimates, anyone?

Anyway, I truly appreciate you guys reading and throwing in your 2cents!

>You could be the hero of the Canon DSLR community
I hear you. It's a ridiculous situation and the only solutions right now are to pay $200 for a mobo or pay $350+ to Canon. Both of these solutions fucking suck!

[Anonymous No.1284031]

Shopping for LED lights to run vertically in the corners of my air filtration wardrobe.

I like these but they cost too much
>http://archive.is/qiKK0

And here's the really sick looking recessed channels
>http://archive.is/al6wf

Probably going to order these for the prototype
>http://archive.is/8gMuR

Cheapest white LED strips I could find, is this a good deal?
>http://archive.is/rD8P3

What's the favorite LED controller on this board? Preferably I'd be running five strips off one controller because I can re-use one of the 5 pack of light strip channels on the outside of the wardrobe as a night light.

[Anonymous No.1284040]

>>1284015
>ye olde cell phone repair shoppe
I suspect it'll cost far less than that. It's only about ten minutes worth of work.
>heat gun
1500W is probably way too heavy. The little chinkshit one is probably pretty reasonable.
>how long
Ideally the process should take about 3-4 minutes to get from room temp to liquidus temperature, at which point you back off just a little bit, hold for about 30 seconds, and then remove air and allow to cool naturally. For best results you're going to want to squirt some liquid flux under the BGAs, and (if required by the flux formulation) clean it off once it cools. Do not move the board once the solder has reached liquidus until it's cooled to room temp.
Still, if you're not skilled at rework, you should probably let ye olde cell phone shoppe do it, since this is kind of a high-value item.

>>1284031
>Cheapest white LED strips
bretty gud
>favorite LED controller
don't have one, buy on price and power capacity

[Anonymous No.1284042]

>>1283993
>define "affordable"
The fx888 is about $95 which is fine.
I already have a chink shit one and now I need to replace it

[Anonymous No.1284044]

>>1284042
I got an Aoyue 888A a while back from sra-solder for $72 (with hot air) and it's teh secks.

[Anonymous No.1284045]

>>1284044
>teh secks

[Anonymous No.1284048]

>>1284045
that's old man speak for really good

[Anonymous No.1284056]

>>1282168
DigiKey is one of the most reliable vendors.

[Anonymous No.1284062]

>>1284040
>don't have one, buy on price and power capacity
I tried to calculate actual wattage but until I have the strips and can tinker with them, I'm not 100% sure how much my 16-18 feet of strips will actually consume, because Chinese.
I like this power supply, everthing else is in that wattage range is $50-60 and looks overpriced.
https://www.amazon.com/12V-Dimmable-LED-Driver-AC-A60VD12H5-0/dp/B00H7WNQ6Y

also found this in my searching:
>most Chinese LED strip manufacturers use very thin copper film in strip's FCB (Flexible Printed Board). They rate LED strip "theoretical" power without taking in to consideration copper resistance. When 12v applied to the LED strip wire leads, the voltage at the opposite end of the strip will be substantially lower because of the resistance loss in FCB copper.
>In order to get full 72 watt from those strips, run pair of 12 gauge wires parallel to that strip and connect those wires to every FCB stitch pint located 50cm apart.
>Or power each end, or three points (Both ends and center), for practical testing.

https://electronics.stackexchange.com/questions/51778/large-difference-between-specced-values-and-real-values-for-led-strips
There's also a bunch of useful information about why a lot of chinese LED strips are meant to be volted at 14 because automotive current.

[Anonymous No.1284066]

Just found this one in case I need a full 100watt of capacity (doubt it)
https://www.amazon.com/LPV-100-12-Single-Switching-Current-Voltage/dp/B00YF3FIFU

[Anonymous No.1284073]

>>1284062
Look at the type of strip you want and count the *resistors* per meter. Assume each resistor on the tape is set for a 20mA forward current through the LEDs and calculate accordingly. For the 3528 strip, there are 20 resistors per meter, so 400mA/m. For the 5050 strip, there are 60 resistors per meter, so 1.2A/m.
>driver
Any power supply of adequate current capacity at about 12V will handle it. Adjustable is nice, in case you wanted to upvolt them slightly. You could even power it from an otherwise unused ATX power supply.
You might also want a controller to go between the supply and the strips. See a crazy variety of them here for about $15 each, some with remotes, some with wifi, etc. etc. etc. https://www.aliexpress.com/wholesale?SearchText=single+channel+led+controller
If all you need is on/off, there are a bunch of RF/relay remote controls for sale from just about every arduino vendor on ali.
>pair of 12 gauge wires
Wisdom.
>volted at 14
Not without a real heat sink.

>>1284066
You'll need about 75W for those 60 resistor/m strips. It's wise to not operate chinkshit too near maximum capacity. 20-25% is a good derating factor.

[Anonymous No.1284102]

>>1283898
>>1283933
Thank you.

[Mr.T !LeoPard6uk No.1284106]

>>1284015
>I have no idea how long I should heat the IC for... any guesstimates, anyone?
Well heat till solder melts, use decent flux suitable for BGA, i.e. it must not boil and form bubbles. Your main board has PoP DRAM, it kind of makes things harder (I wouldn't try to reflow that w/o preheating).

GOOD LUCK (you need a lot of it esp. if you have never dealt with BGA's and fine/ultra finepitch BGA's particularly).

P.S. if it's the journey that matters and not the destination then go ahead. If you want to repair your DSL - go to cell phone shop or whatever.

[Anonymous No.1284179]

>>1284073

Thank you, now I know where to start on the math. And the computer PSU is so obvious, I don't know why I didn't think of it. All those 12v rails..

[Anonymous No.1284195]

>>1284106
>Well heat till solder melts, use decent flux suitable for BGA, i.e. it must not boil and form bubbles. Your main board has PoP DRAM, it kind of makes things harder (I wouldn't try to reflow that w/o preheating).
>
>GOOD LUCK (you need a lot of it esp. if you have never dealt with BGA's and fine/ultra finepitch BGA's particularly).
Anon, how would the phone repair shop reflow this IC? ZTake a look at the pic... the IC in question is the biggest one on the right side of the board. Would they completely remove the IC and then somehow apply balls to the bottom of it? How does it work?

My idea was to simply heat it up and how the joints reflow...

[Anonymous No.1284197]

>>1284106
Hi there!

You seem to have made a bit of a mistake in your post. Luckily, the users of /diy/ are always willing to help you clear this problem right up! You appear to have used a tripcode when posting, but your identity has nothing at all to do with the conversation! Whoops! You should always remember to stop using your tripcode when the thread it was used for is gone, unless another one is started! Posting with a tripcode when it isn't necessary is poor form. You should always try to post anonymously, unless your identity is absolutely vital to the post that you're making!

Now, there's no need to thank me - I'm just doing my bit to help you get used to the anonymous image-board culture!

[Anonymous No.1284214]

>>1284197
>identity has nothing at all to do with the conversation!
If so, what is your problem, Mr. Lockstep?

[Mr.T !LeoPard6uk No.1284223]

>>1284004
>>1284195
>Anon, how would the phone repair shop reflow this IC?

On your second pic it looks like DRAM and NAND are separate IC's.

They would apply flux to the sides of the IC, preheat the board to 120-150degC or so and then heat the IC till solder balls melt (you can poke it gently to check the balls have melted). If the PCB is "small" you can preheat it with hot air gun, if it's "large" you better use IR preheating station.

I doubt they would re-ball it. However if the issue is related to lead-free solder re-balling with Sn/Pb balls should fix it.

[Anonymous No.1284227]

Any of you use an app for keeping stock and location of your components?

If so please share

[Mr.T !LeoPard6uk No.1284228]

>>1284227
I use few plain text files, I also try to track source as well.

[Anonymous No.1284230]

>>1284228
>I use few plain text files, I also try to track source as well.
isn’t the text file a nightmare once you have lots of components to track though?

[Anonymous No.1284236]

>>1284230

you've heard of CTRL-F? grep? find? windows search? google desktop?

[Anonymous No.1284245]

>>1284236
Not used any of that? Sounds complicated.

[Anonymous No.1284246]

>>1283880
> Where do you even find 4 leg transistors?

Depends on what you mean by “find”

Chip manufacturers use them all over the place (and even crazier configurations with multiple bases & collectors) but their capabilities are way beyond ours unless you have your own epitaxy process line.

[Mr.T !LeoPard6uk No.1284252]

>>1284230
>isn’t the text file a nightmare once you have lots of components to track though?

I have few files, one with a list of magnetics components (like E ETD, toroids), a list of IGBT and high-voltage MOSFETS, high voltage / high capacity electrolytic caps, a list of MCU's and other digital stuff. And a separate file for HF/VHF/UHF stuff. etc.

I do not track resistors, small caps, small-signal transistors (2n3904/2n2222/2n7001/etc) and stuff like that.

[Anonymous No.1284254]

I want to add BT to this old car cassette radio without losing cassette features.
Do I splice the BT module audio out in between the head and the board directly? Also what BT module would you suggest

[Anonymous No.1284264]

4000 series logic is characterized down to 3v. if i start it at 3v and run it at 2.7v (with a coin cell) could i generally expect it to work?

[Anonymous No.1284269]

>>1284252
>I do not track resistors, small caps, small-signal transistors (2n3904/2n2222/2n7001/etc) and stuff like that.
How come is that just because you always have loads of those?
I’m just starting out and have got one of those file cabinet with the little draws to keep things organised but I’ve recently started buying larger amounts of components for builds so I will acquire lots more components, so I was thinking of taking stock so next time I make a build I don’t double up on components.
Should I just give up on that idea and stockpile a fuck load of everything so I always have the bit I need? I’m guessing it’s going to end up a bit like that anyway?

[Anonymous No.1284286]

>>1284227
I just use a spreadsheet.

Small inventory management program would be a nice programming project, though.

[Anonymous No.1284288]

>>1284004

I've reflowed a few things with this kind of problem. I find the reflow doesn't last long though, but usually I'm just trying to get the data off. Your milage may vary :-)

My suggestion is to practice on some similar boards. I use all my senses: I can smell the flux, I can see the flux smoke, I can feel the heat, and when the solder is melted, you can move the chip (or, sometimes it moves a little by itself because of the tension of the solder it automatically seats). Sometimes you want to use your (very steady hands) and just test it for movement by nudging it a quarter mm.

• I usually lay a temperature probe next to the chip so I know when it gets in the ball-park.
• You should pre-heat the board to prevent cracking due to the temperature difference.
• For huge chips and pre-heat I use a regular heat gun.
• I cover other nearby things (components, plastic standoffs, etc) with 1 or 2 layers of foil.•
• Keep the board *LEVEL* and well-supported.
• Sit comfortably and remove any distractions... prepare.

That's really about it. There's these crazy people out there that "re ball" things and whatnot, but on a big chip that's another plateau altogether. Smaller chips (e.g. with, say, under 16 pads) can be removed, wicked, and the solder replaced with leaded without too much difficulty and a small heat gun.

[Anonymous No.1284301]

>>1284264

TLDR: Try it.

There are too many variables. A 3v coin cell will run at slightly higher voltages when fresh. When driven by a cell, the voltage you get will often depend on the current draw of your application. The process of making CMOS has changed over the years, and different manufacturers do different things in different CMOS lines. You might find *some* gates work, but others do not because of variances in manufacturing.

While I think generally all the designs have lower drop-outs, less power requirements, higher impedance inputs, etc, etc... you'd probably want to "bin" them for your application at the boundaries of their spec.

I can also say that usually components surprise me and beat their min/max specs, but On semi (for example) wouldn't want to guarantee such things if you are ordering a million of them for a mass produced life support system. Would they?

[Anonymous No.1284308]

>>1284254
You could do that, but depending on the design, it might not let audio through unless the heads are engaged (playing a tape). Follow the leads coming from the head and see where they go. Chances are they are going to a control circuit that enables the signal to go to the amp section. Find the output leads on the control circuit and solder your bt outputs to those.... You might have to use a diode or two to stop the bt audio signal going into the tape head (not sure if that would do anything to your tapes) and vice versa.

[Anonymous No.1284341]

>>1284264
>characterized down to 3v
But not specified, that's done for 5, 10 and 15V. If your circuit works at 3V it most likely will at 2.7V, it depends on speed and noise immunity requirement of your design. 74HC is a better choice for low voltage operation.

[Anonymous No.1284352]

>>1284308
Or I could use a gutted cassette tape as a way to mock the cassette in to engaging the head, right?
Also what type of diode are we talking about I hadn't thought about the signal not going to the head

[Anonymous No.1284363]

>>1284352
Tape head and BT output have vastly different audio levels. The right place to inject audio is after the head preamp. Forget the diode, that will not work unless part of a more complicated circuit. Try to get a circuit diagram of a car cassette radio, all else is guesswork.

[Anonymous No.1284365]

>>1284352
I use 1N4007 diodes for general use. They work ok for most situations. I'm not sure if the signal going to the head will actually do anything, so don't worry to much about that. I'd be more worried about the possibility of the tape head signal going into a preamp, so if you just splice your bt unit into that, you might get distortion at higher volume levels from the bt unit. You should give it a try, and learn a few things in the process. You could try a BK8000L unit or an xs3868.

[Anonymous No.1284397]

>>1284363
>after the head preamp

[Anonymous No.1284399]

>>1284341
nothing faster than a watch crystal, no static current consumption other than quiescents and leakage, and no sources of noise in the circuit. my understanding is that all the 74 series logic consumes more current. i don't know if that's true but i'm only using 4000 as a fun retro project so at this point i'd rather just slap a different battery in there if i have to, or stack two.

[Anonymous No.1284437]

>>1284399
CMOS quiescent current is far below self-discharge of a battery. What needs energy is charging and discharging of capacities, like oscillation.

[Anonymous No.1284509]

>>1282445
Not even the juiciest transistor will saturate at high side without a proper high side driver. A MCU digital output will not suffice.

[Anonymous No.1284525]

Can I make a guitar pickup with a single solenoid instead of a magnet? If I run DC through the solenoid and put a DC filtering cap on one side can I just get the AC audio signal out of the solenoid? I can't seem to find a small enough magnet locally.

[Anonymous No.1284537]

>>1284525
Sure. But I wouldn't load it with a voltage source, you want the induced signal after all. Use a current source instead.

[Anonymous No.1284551]

>>1284509
'juicy' in not a valid parameter and half a volt isn't that much.

[Anonymous No.1284566]

Always on top

[Anonymous No.1284569]

>>1284399
>my understanding is that all the 74 series logic consumes more current
7400 is not synonymous with TTL. There are several 7400 series CMOS families for micropower and nanopower applications.

>>1284566
what is this, a power supply for ants?

[Anonymous No.1284575]

>>1284537
Ah, that makes sense. I could also try it with a resistor in series with the coil and take the voltage from between them, but I guess that's just a primitive current source anyways.

[Anonymous No.1284578]

>>1284569
I think 7400 is 5V TTL and 74HC is CMOS for 2V..6V and may run down to 1V. The 5V TTL compatible version is 74HCT.

[Anonymous No.1284581]

How would I go about controlling one of these with an arduino? Like for a mock control panel kind of thing? Any breakout boards or anything good for this?

[Anonymous No.1284583]

>>1284575
You can use a single transistor in common emitter configuration as current source.

[Anonymous No.1284584]

>>1284581
PWM DAC

[Anonymous No.1284587]

>>1284581
PWM
srsly lolduino people search adafruit.com before you even ask

[Anonymous No.1284595]

I just want to know why are these caps swollen like that, found this a while ago.

[Anonymous No.1284603]

>>1284595
overwork, just apply a bandage and let them rest a few years

[Anonymous No.1284608]

>>1284551
Half a volt isn't that much, but when a NPN transistor is on the high side, you may need much more voltage to saturate.

[Anonymous No.1284610]

>>1284595
There's also this, are they kill?

[Anonymous No.1284611]

>>1284610
yeah, that cap's got eternal bleeding
replace all

[Anonymous No.1284613]

>>1284608
>you may need much more voltage to saturate
but you may not need to saturate when you gain only half a volt.

[Anonymous No.1284615]

>>1284611
Too bad, thanks.

[Anonymous No.1284616]

>>1284613
Are you the guy who was trying to drive a BLDC motor with only NPN transistors and an arduino?
Thats who I quoted on my 1st post.

[Anonymous No.1284622]

>>1284610
>>1284595
That's a very old device you're working on. What is it?

[Anonymous No.1284624]

>>1284616
No, I have no such motor. He had a different problem, missing saturation was not the reason.

[Anonymous No.1284625]

>>1284622
Used to be this but I found it with some speakers on the side screwed in. It also says Solid State but there aren't any tubes in it.

[Anonymous No.1284631]

>>1284625
>there aren't any tubes in it
That's why it says solid state.

[Anonymous No.1284641]

>>1284631
I thought it was the other way around, ok.

[Anonymous No.1284662]

why do I have 250v across the hots but 135v and 85v across individual the hots to neutral?

[Anonymous No.1284664]

>>1282926
>spring reverb
sweet!

what sort? post schems if you have.
i have a music thing spring drving an old tank from a marshall. cant say I'm very happy with it.

i tried to make my own first, it sounded great but the noise was unacceptable.
I've been meaning to give it another go though..

[Anonymous No.1284666]

>>1283692
I'd say 12v because almost all diy schems and kits these days are for euro, which is +-12v.
the extra headroom is pretty pointless anyway.

[Anonymous No.1284675]

another pic

[Anonymous No.1284678]

>>1284662
Because something's very, very wrong with your neutral.
I recommend calling a sparky.

[Anonymous No.1284692]

>>1284678
figured as much

[Anonymous No.1284716]

>>1284692

before you commit to paying a professional thief, ask your neighbours if they have similar circumstances. could the the transformer outside.

it happened to me once and it turned out to be one of the 100A fuses before the meter had oxidized contacts. a bit of steel wool fixed it.

[Anonymous No.1284790]

I thought I'd show you guys my finished boombox. I was trying to implement a Bluetooth unit in this early 90s box. I learned a lot in the process. There was insane noise from the bt unit, and I after trying out a few circuits, I ended up just getting a b1203s isolated power module. Once I wired everything up, I almost had a freaking orgasm. I disabled the tape decks while bypassing the preamp, since the rubber bands driving all the gears turned to goo as soon as you touched them, and I got a motor for a future project. The blue and red lights in the tape decks are sound activated. Thanks for all the help, dudes.

[Anonymous No.1284791]

>>1284790
Nice to see someone finishing a project and being satisfied with the result. Looks damn cool.

[Anonymous No.1284793]

>>1284791
Thanks, man! It looks even cooler in action. I had to mess with the mic sensitivity to get the LEDs to act somewhat like a vu meter. The mics I have are really sensitive and the lights were on all the time instead of really reacting to the dynamics of the music being played. Next on the list is maybe using the AM circuit as an auxiliary in along with the headphone jack.

[Anonymous No.1284853]

>>1284716
>the transformer outside
Strange things can happen.

[Anonymous No.1284959]

>>1284853

at my GF's condo, this past summer, all the plugs and lights in all 36 units had 55Vac instead of 120V for several hours. oddly enough, quite a lot of things worked nonetheless, like LED and fluorescent lights. even a Sony LCD TV kinda worked.

[Anonymous No.1284990]

>>1284905
>>1284905
>>1284905
>>1284905
New thread

[Anonymous No.1284998]

>>1284959
Electronic power supplies can have a wide input voltage range to produce a usable output.

[Anonymous No.1285913]

>>1282438
hey anon, what do you recommend me for my opamp function generator?

lm324 based

[Anonymous No.1286155]

Hi /ohm/. I recently got an electric guitar and a small amplifier. I have some technique on classical guitar but I'd like to learn to do some cool stuff with pedals and I'd like to make them myself.

Anyone here who has done it can give me some advice where to start? I'm not a scientist or a technician but I have a background knowledge on math and physics and I'm currently learning about basics of electricity and the Forrest Mims book for electronics.