/ohm/

Is an Arduino Uno clone off of aliexpress going to give me a megavirus? Seems way cheaper to buy one of those instead of paying the other costs.

>>1094641

wtf is a megavirus plz

usually the only problems you're gonna have with clones is configuration oncompatibilities that should sort themselves out easily enough. look for forums where people discuss clones if it doesn't work out of the box.

>>1094641
Some of the cheaper ones don't come with an USB serial chip and need an extra USB TTL adapter to flash it.
Though you might want such an adapter anyway, they often come in handy.

>>1094668

if that's the case you might as well just buy the atmega chip for 1.75 or something.

>>1094641
you can get fully functional arduino nanos for $2 which work exactly the same but need a (((chinese))) usb driver. it's a known driver though so you're not at risk.

>>1094641
Mine works fine. Also have a legit one for comparison.

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Pic related, I bought one of these microcontrollers during TI's free shipping offer. I'd like to make an LED blinker program. What kind of device would I need to start making programs for it?

With AVR chips I can use the PC serial port, cable and avrdude to transfer the program code into the chip's memory. Is there anything similar for TI chips?

>>1094951
>surface mount
Have fun!

>>1095011
I bought some surface mount stuff that I want to solder too
EEVblog convinced me that ill be able to do it with a regular iron

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>>1094602
bought something similar like pic related (same brand) and Im using for a setup:
> arduino output with external 6v power source (mobile charger)
> switching 230V

The relais gets stuck now and then. I already increased the power/voltage by using an external power source instead of only the arduino. But it still gets stuck sometimes.

Im ready to buy a better relais but I cant find any.
Do you guys have any tips?
Maybe just buy the same thing and hope the new one works correctly?

>>1095023
You could try a solid-state relay instead.

>>1095027
thx for the tip, I'm still not 100% convinced tho since I will be using almost the max. power the relay is capable of running.

Do you know if those solid state relays run efficiently and safe at their max. power for longer amounts of time (few hours)?

>>1095034
Might wanna watch how much it heats up

>>1095023
Measure the voltage across the relay's coil when it is "stuck", whatever it means. In other words, verify that the relay's coil is powered (unpowered) as expected.
Certainly relays can break, but I haven't seen so shitty relays that they won't work even as new.

>>1095034
250VAC 10A SSRs usually need cooling when run at or near the maximum current rating.

>>1095011
It has little feet on it, it's not really that hard under a microscope

>>1094602
I want to set up a PCB printing station. Is is better to buy presensitized copper boards or just do the regular method with silkscreening the patterns onto regular boards then ferric chloride?

I ask because I've never used presensitized boards before so I'm unsure of the quality

>>1095099
I'm not too sure what is your idea of the regular method. Generally speaking, hobbyists do not make PCBs using silkscreen printing. Only the cheapest mass produced boards are made by that method.
Presensitized boards produce good results if your films are good and you find out the correct exposure time and use suitable developing solution. With less-than-perfect films, random developer and random exposure the results are naturally worse and particularly shitty films ruin everything quickly.
You can sensitize the boards by yourself, but this brings in another variable to the mix and every speck of dust produces a hole. Personally, I haven't bothered for years.

A popular alternative to the photographic method is the toner transfer method. Google it, if you aren't familiar with it.

Let's talk storage. I have a fairly large Plano tackle box with some removable drawers. Will it build up static and kill things?

>>1095099

Presensitized boards are just regular copperclad with photomask prelaminated on there as etch resist. If you have the gear to make silkscreens (for, say, shirts) it's probably just as easy to use that process to deposit resist than it is to buy presensitized boards and UV bake then.

>>1095052
"Stuck" means that when I power it (not measured, but a led is on) it does not switch the 230V. Then when I tap on the relais a few times, it switches. After that it will work again for a while, but it is unreliable.

>>1095262
That would suggest that the relay coil isn't getting the full voltage. Measure the voltage across the coil and compare that to the value printed on the relays themselves (the ones in your pic say 5V, but verify that your own relays are for 5V too). The measured voltage should be reasonably close to the nominal value, for example around 4.5V with 5V supply.

>>1094602
>mikeselectricstuff
that mofo posts a video like once every other month, but whenever he does its always very interesting stuff (filled with teardown/details and explanations) that you wont find anywhere else. great stuff

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>Beginner question

Simple led circuit related.
So I need to meet the forward voltage of the led, let's say 3v and I need to limit the current flowing through the led let's say 20ma. And you can resist the voltage to get the right current flowing with ohms law and I understand how to calculate ohms law but I don't really get voltage drop.

If you have a 9v source and power a 3v led the voltage drops by 3v, leaving 6v left and you use that 6v to calculate the resistor you need to get the right amount of current. But what if the source is 3v, then it drops to 0v? how do you calculate that? What resistor would you use?

https://www.youtube.com/watch?v=NfcgA1axPLo&index=4&list=PLzqS33DOPhJkRn6e9_OTdQwRojO8qlusI

>>1095300
If the source voltage is below the forward voltage then the led will not turn on. If the voltage difference is very small then you will need a very small resistance.
The trouble is if its exactly the same. In practice its not ever exactly the same and you should make a sensible estimate as to the actual difference in voltage, maybe millivolts or microvolts, the resistor will be tiny value and actually in practice the resistance of the battery and wires and omg even the led itself? will be sufficient to save led from burning itself out.
When an led is on its trying to drop whatever extra voltage is there which means its fiddling is resistance to allow whatever current will drop the voltage.
So in theory I guess if the voltage were perfectly matched it would work ok..ish..?

>>1095305
Thank you anon. So basically it scales which makes perfect sense.

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>>1095307

yep, what the other dude said makes a lot of sense, however it's completely wrong.

when the datasheet says 3.0V, that actually refers to a bell curve with a peak at 3.0V. so if you use a tiny resistor based on a 3V breakdown, and your unit's actual breakdown is 2.9V, then you get a massive current and your LED dies.

so, you never use tiny resistors in series with an LED because the breakdown voltages and, often, the supply voltages, are not absolute values, but are ranges of values.

>>1095300
As a rule of thumb, at least 1/4 of the total voltage should be across the resistor. So if you're driving a 3V LED, you need at least 4V.

This ensures that small variations in either the supply voltage or the LED forward voltage don't result in large variations in current.

For long chains of LEDs at higher currents, consider using a constant-current regulator rather than a resistor.

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>>1094602
hello everyone, I have a vacuum motor that I would like to repurpose, but I have no idea where to go with figuring this out. From researching for about an hour or so I found some info. I want to attach a fan blade sort of deal to it to make a shop blower, and I would like to control the speed on it. Any ideas?

>>1095686
Household vacuum cleaners are much less powerful than a standard shop-vac or dust collector, so you won't be building a big blower. I'd check out Matthias Wandel's youtube channel, he's made quite a few wooden dust collectors over the years, and wooden shop tools and such too.
https://youtu.be/LBxFNUWD2GQ

I need some advice.

I'm doing a personal project with Arduino Uno + Sparkfun Mp3 Shield, and I need use something like 64 buttons but I only have 6 Analog Pins and 4 Digital Pins avaliable, so I don't think I can do something like 8x8 keyboard matrix. It's designed to the user not press more than one button at same time, so I'm trying to cascade 8x IC 74LS348 (8 to 3 line priority encoder) to use on my six free analog pins to read the info like binary. But I think that I'm doing something too trouble and dumb. There's any advice /diy/ can give me?

>>1095695
That's not gonna work. You need 3 pins to operate each encoder to access 8 buttons. You have a maximum of 10 pins analog and digital. So even with the encoders you would only be able to 25 buttons total. Besides which, this is an 8 MHz device that would have to scan, do the A/D conversion and interrupts, and processing and it would be quite slow.

Get an arduino Mega, it has 54 digital pins where this scheme would work much better. Or there might be an STM32 board that has >64 digital inputs so you wouldn't have to fugg with all the multiplexing

>>1095695
Could you tell us what the project is so we can tell you that using an Arduino is objectively worse than using a 2c IC?

>>1095712
>>1095695
Juuuuust kidding. I reread that you said "cascaded" its totally possible. It would require 12, 8 to 3 encoders to give a total of 66 inputs. I have the schematic drawn, i might simulate it for you if i have time tomorrow.

>>1095715
He's probably building a synth keyboard of somekind

>>1095695
Use 3 of the digital pins to drive a 3-to-8 line decoder to drive the rows, connect the columns to a 8-to-3 line priority encoder, connect that to 3 analog inputs.

>>1095695
>It's designed to the user not press more than one button at same time
One shift register to drive the matrix inputs, another for reading the outputs. 74HC164 and 74HC165 would require 5 pins if you tie the clocks together and 6 if you don't. If those analog pins are Arduino's, you can use them as digital inputs too.
Or you could drop the second shift register, connect suitably weighted resistors to the matrix outputs (like 1k, 2k2, 4k7...), connect their other ends together and load them with a 1k resistor to ground. You'd need 2 pins for driving the matrix and one analog input to see what button is pressed. This is pretty awful, though.

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>Capacitor question

So they build up an amount of charge at a rate dependent of voltage and current, then when it's full it has a fixed amount of capacity and a voltage that is the voltage you charged it at. So if it was charged with 10v it's essentially a 10v battery now. But what if you applied 20v to it? The capacity is already full so that won't change, but is it essentially a 20v battery now?

https://www.youtube.com/watch?v=e8dTOjrQGg8&index=93&list=PL774BE597B77BF3C5

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>>1095781
The capacitor charges exponentially, so it follows a negative exponential curve, if you apply 10 volts it would charge following that curve, since it's like cramming electrons in a box, the more you've got inside the harder it is to put more, until you reach those 10 volts.

Fun fact: An ideal capacitor is never charged, since it has an asymptotic line at 10 volts, therefore it will take infinite time to reach 10 volts for example. That can be a trick question.

If you now apply 20 volts the same will occur, but now starting from 10 volts, the curve will be repeated.
It's like filling a pressure container, the volume (capacity of the capacitor) is limited, so to get more air in you need to increase the pressure, as long as the pressure is increased the air will flow inside, increasing the "charge" of the container.

The charge can always be increased, but the capacitance not, learn the difference.

Charge=Capacitance*Voltage
------------------------------------------------------------------------------------------------------------------
Question in the same post:
I want to create a microphone in the cheapest way possible with materials I've already got without sounding like shit.
Could I combine the signals of different devices (electret mics, piezos, 8 ohm speakers...) with an OP amp (also using proper filters) in order to have the best dynamic range possible?
Is this a stupid idea?

>>1095787
>Could I combine the signals of different devices (electret mics, piezos, 8 ohm speakers...)

yes, its a stupid idea. if you add three frequency response curves, you dont anything close to a flat line, you get a 3-humped camel, with a huge hump where all 3 curves add up.

>>1095860
There could also be phasing problems, depending on how far apart the transducers are.

>>1095787
the thing about fully charged capacitors is kinda pissing me off.
>say 'technically never'
get
>hurr 5τ in practice durr
back

>>1095781
> So they build up an amount of charge at a rate dependent of voltage and current
The total charge depends upon voltage (Q=C*V), the rate of change of charge is equal to the current (I=dQ/dt, that's what current is).

> then when it's full it has a fixed amount of capacity and a voltage that is the voltage you charged it at.
It's not that capacitors become "full", but that they have a breakdown voltage (above which they'll be destroyed). So there's a limit to the voltage which in turn limits the charge.

I have a ton of printers i get to dismantle and decommision at work. I've saved a few motors and interface panels and displays. I want to eventually make a large interface with buttons and lights that does basically nothing but looks like it's from a 70s-80s scifi movie. First off, how do i control small lcd displays? I'm talking calculator style. There's an 8 pin connector on the small board it connected to, what's the best way of reverse engineering how it works?

>>1095875
At 5T, the capacitor voltage will be at >99% of the input voltage and the charging current will be at <1% of the input current.

At that point, you can either consider it "charged" or you have to start considering deviations from the theoretical ideal, such as leakage current, variation in the input voltage, etc.

>>1095908
>implying who people bitch about 5τ take other factors into account let alone even know about them sufficiently
literally less than 30 minutes later you hear them wondering why the output peak voltage of a 12V transformer (without load) is over 20V
i swear these people have qualifications on paper only
>tfw less qualified on paper

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>>1095860
Well, that's disappointing, I'm still going to give it a try and play with different gains just because I'm curious about the sound it will produce. Even if it's horrible.

>>1095875
Yeah, they "technically never" reach full charge, but for most practical applications you assume they're charged at 5τ (or 99.3%) because nobody cares about the other 0.7%. It's just an annoying fact.

>>1095904
They're just LCD displays, apply a small voltage with a power supply around the pins until you find the positives and common, you can't damage them with reverse polarity or anything like that.
http://www.goldenviewdisplay.com/images/200491713376941.gif
I would say an arduino and some shift registers will suffice to drive as many as you want.
Also, printer rods are top tier to make 3d printers and cnc stuff, or just for shafts.

>>1095694
thanks!

>>1095923
>because nobody cares about the other 0.7%.
Practically every single time I actually need to consider the time a capacitor takes to "fully" charge, 5T isn't enough. 99.3% isn't enough even for a 8b ADC.

>you can't damage them with reverse polarity
If there's only 8 pins, they have some built-in intelligence and reverse polarity can damage them.
>>1095904
What he said is true in many cases, though. If it's a dumb display with no built-in driver, you can simply feed power to random pins until you've figured out how it works. In addition to basic digit-segment multiplexing, triplex displays are pretty common.
If you aren't totally strapped for cash, you might want to consider buying the displays, though. They aren't particularly expensive and you'll get your stuff working faster.

>>1095923
Cool ive also been holding on to those as well so maybe something will come of all my hoarding

>>1095931
> 5T isn't enough. 99.3% isn't enough even for a 8b ADC.
If 5T isn't enough, what is? Are you ever going to get "full" charge? How do you even define "full"? When the capacitor voltage starts to decrease because the difference is less than the fluctuation in the input voltage?

Even if the input is perfect DC, you'll never get above Vin minus parasitic resistance times leakage current.

>>1095941
>If 5T isn't enough, what is?
Depends on application. I don't know about you, but when I need to consider the time to fill a capacitor, I generally know how full is full enough. For example in that 8b ADC's case, one might consider 1/2LSb error acceptable and go with 6.2T.
>you'll never get above Vin minus parasitic resistance times leakage current.
With decent (non-electrolytic) capacitors that tends to be a non-issue. When it is, you typically have plenty of other error sources to consider, too.

>>1095936

dont listen to the dude above, he's completely wrong. you cant just go sticking voltages on an LCD display and expect it to light up. the way you light a segment is to put a square wave on the backplane, and a inverse square wave on the segment. the duty cycle has to be exactly 50% or else the segment becomes permanently dark after a while.

however, when an LCD has few pins, it's because it has multiple backplanes, and the timing becomes much trickier to manage. i cant even explain it without a timing diagram.

>>1095957
8 pins could also mean it has a controller.
He was talking about some "board" not a bare glass lcd

>>1095957
It takes time to ruin an LCD with DC. The seconds or minutes required for testing won't have any noticeable effect and if it's just a film prop which needs to last couple of hours, it's not a big deal either.
Certainly, if you want the display to last, you should use AC drive.

>>1094641
90% of the cheap home 3d printers you see are running on clone Arduino 2560s
They work perfectly fine

>>1095957
>>1095962
Good to know, I'm not incredibly worried about wrecking it if i can gain some knowledge out of it. And like second anon said it looks like there's some sort of driver on the board it's attached to, however i think it also passes inputs through that connector so I'm not sure where to start. I may just desolder the display though and play with that

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Can /ohm/ help me out with a power supply problem I'm having?

The situation:
I have a simple PSU consisting of a 9V battery as a source and three adjustable linear voltage regulators (LM317). I want the regulators to output: 2.5V, 5V, and 7.5V respectively. The 5V acts as circuit ground, so I have +2.5V and -2.5V respectively.

The problem:
Not enough juice. I am able to obtain the 2.5V and 5V outputs with no real issues, but not the 7.5V. I suppose this was a lot to ask of a 9V battery, although I don't need to draw much current (I'm guessing significantly less than 500 mA although I should measure what my circuit is actually drawing).

Proposed solution:
Throw in a boost converter after the voltage source, before the regulators. I've never worked with such a circuit, so I'm unsure how to proceed, or if this is even a good solution. If it is a good solution, is it better to make my own, or use an out-of-the box solution like pic (its only $3.00)?

>>1094602
Doing a """"Robot""" (Its remote controlled) Arm for my senior year of HS for SOINC.
Arduino (which one) or another microprocessor?

It doesn't need to have any wireless capabilities because wires are allowed.

>>1096020

you don't have enough voltage differential for the lm317 to work properly

you shouldn't be using the lm317 as a current sink (5V) though

you should do a

9V -> voltage inverter -> LM337 (-2.5V)
9V -> LM317 (+2.5V)
-> LM317 (+5V)

>>1094602
Has anybody ever used or heard of basic stamp? This book I bought to get myself into electronics (electronics for dummies) requires it for a project but it doesn't seem to compare to arduino. The arduino is also cheaper.

>>1096026
depends what exactly you want to accomplish. How many axes will your arm have?

The arduino uno is the standard (and quite cheap). This shield also looks like it could be helpful too, though I've never used it myself.

https://www.adafruit.com/product/1438

>>1096047
I've skimmed through the for dummies book and I might pick it up myself. Arduino basically killed that board as far as I know. It is a lot cheaper, and I'm certain its capable of performing any task described in the book.

Its a different programming language (C++), but the concepts would be the same. Go for arduino.

>>1096055
Thanks. That's what I was thinking. The arduino just seems better all around. It's a decent book though. A good beginner book and I've learned a lot. It does has quite a few typos. I'm going to contact someone about that because it's bad..lol.

>>1096047
It's much older and yes, it costs more and provides less than Arduino. No-one uses it anymore.

>>1096031
Ok, thanks for the input. Wouldn't the 317 still be acting as a current sink in your suggested configuration?

Also, just curious, why wouldn't that be advisable? Because its meant to act as an output/ source?

what are the biggest things to be wary of when working with analog audio signals in a circuit? I've gotten my feet wet with a few basic circuits (square osc, lp/hp RC filters) but I don't know how to go about designing circuits with audio in mind.

>>1096072
I haven't worked with audio too much myself, mostly simple circuits like a headphone amplifier, once I made a (very) short range audio transceiver using infrared LEDs.

My only piece of advice is to keep connecting wires as short as possible. I hate circuits that look like a rat's nest in general, but with audio in particular this can inject unwanted noise into the signal.

When I was playing with a headphone amplifier chip once, I had left an un-trimmed bit of wire on one of the pins and I noticed I was picking up a signal from a nearby radio or something lol.

>>1096048
The least amount of axes (more specifically actuators) the better score. I'm currently sitting at 4.
I'm just supposed to have the arm pick up a stack of pennies and its timed n competitive n shiet.

The Uno seems like a good choice but Ive been meaning to try out a Pi (just for the novelty of it). How disadvantaged would I be considering Pi's are really not meant for this kind of work. What kind of problems could you immediately foresee?:

>>1096081
that must have been a bizarre troubleshooting session, lol. gotta agree about hating circuits that resemble a gordian knot.
thanks for the advice about wire length also, makes sense.

>>1096088
I'll preface by saying I am just a hobbyist too, so take my advice for what it is :P.

You would have to confirm this yourself but I believe that the arduino has a greater number of PWM capable pins than the RPi. This could make a big difference depending on how you want to accomplish motor control (servos need PWM). I'm counting 6 such pins on my uno, as indicated by a squiggle ~ beside the pin number.

Also, the Pi cannot output as much current and has no analog input pins. If you want to include anything like a proximity sensor, arduino would have the advantage here too. Overall, the GPIO of the Pi is just more delicate and finicky to program. To me, this just sounds like an arduino project lol.

Pi is also more expensive and requires more operating voltage. It is, however, fantastic for streaming TV shows and emulating game consoles though.

>>1096100
I have a limit of 14.4 V. I didn't even stop to consider that fact until you reminded me.

Looks like Ill be ordering an Uno. Thanks Anon.

>>1096100
A Pi would be useful if you want to do fancy stuff with a camera and OpenCV, like object tracking.

You can still combine it with a microcontroller for better low-level I/O.

>>1096070
LM337 would be acting as a sink (which is ok) and LM317 wouldn't, as long as you don't try powering stuff by connecting them between the +2.5V and 5V outputs. And you presumably don't have to do that, since you now have a real negative supply.
Using LM317 as a sink is "not advisable", because it's not designed to do so. As in, it can't sink current.

hi ohm/
I have a question about AC and power factor in normal households.
As im studying EL on my own, i don't really have a teacher on the subject.
I'm writing an assignment, calculating the power need, input and circuits for an apartment
My book is says;
finding the right amount of fuses needed, calculate the total power consumption with the power factor.
but my book doesn't tell me where to find the PF.

I get that PF depends on if its an ohm resistance in a circuit, or a inductive resistance.
but what type is there in households and where would i find the PF?

every example in my book is from some sort of ACengine with the PF already given.

thanks in advance for any help!

>>1096207
I don't get why you'd need to mess with the power factor. you don't even pay for it unless you are some sort of industrial consumer and consumer electronics will have PFC built-in.

>>1096220
ok, I might have misunderstood or not explained it well.

After calculating the total wattage needed in an apartment
all floor heating, lighting, and kitchen stuff.
i end up with 46kw
to find the current needed, and to find the right ammount of fuses the book says:

Current= watt/voltage*square root of 3* cos of PF

then i end up with an amount of Amps which i divide on an amount of fuses.

that's what my book says. but it just assumes that i know the PF. but i do not understand where one get it from.
i get that you could calculate it if i know the conductance, Q,S and uF. but thats only if the power were to come from an ACengine. in which these are written down.
Am i doing this right? I have a feeling i might misunderstand the whole problem

>>1096223
you won't be far off if you simply assume 0.95.

>>1096225
thank you, much appreciated,
Out of curiosity; where do you find it in the normal household electrical net?
Do you generally just assume it to be around 1.0-0.90

>>1096226
your power provider will complain and charge you extra if you go below 0.9. EU regulations also require a minimum power factor for consumer electronics (varies with power consumption).

>>1096229
Ok, tnx, i might misunderstand the whole PF thing. is it based on the equipment within once apartment? i thought it was something the provider offered.

>>1096234
PF is the result of your load. lower PF means that the provider's wiring carries more current for nothing. quite obvious why they want you to keep it high

>>1096235
perfect! Now it makes more sense! Thank you

>>1096223
In USA we assume it to be 0.9 iirc

>>1096239
i see. that makes my answer really far off when i try to calculate the books example. double the answer to be exact.

From the books answer of 72 Amps
to mine 149 Amps from the same example.
I think i get where the PF comes from, but i cant get there

>>1096244
Post the example. You can find power factor

>>1095781
If there's no resistance in the circuit with them they charge instantly. That's an idealization since there's always resistance from the battery, wires, and capacitor, but still. The rate of charging and discharging depends on the resistance in series with the capacitor.

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>>1096308
here it is.
the example is with 32kW

P=watt
U=voltage
I=current
phi= Powerfactor
we have 230 V at 50hrz

the example figures out the amount of amps needed into the apartment.

>>1096315

if you power purely resistive elements, like stoves, baseboard heaters, halogen bulbs, then the power factor is gonna be 1.0. but when you have motorized things, like the fridge and air-conditioner, then power factor drops to maybe 0.8 or 0.9. if you use a lot of motorized tools, it drops even further.
so, it all depends on what's currently running. you cant know ahead of time, so you guess, and use a typical value.

>>1096328
tnx, that makes perfect sense. so its basically a sum of my electrical components within the apartments. Thank you for explaining it, but i still don't get the calculation correct.

>>1096315
Are you doing the cos in rad?

>>1096363
both, isnt it supposed to be radians?

>>1096364
Yeah, just making sure.

>>1096367
for a second there i though that was the problem, i get closer to the original answer then i use parenthesis. Apparently the calculator doesn't know calculation priority

>>1096315
Since you know the current, voltage, and power solve for pf and see what it is.

>>1096379
ok, and how do I do that?

>>1096382
How did you get into the electronic class without knowledge of basic algebra?

>>1096397
hehe. no electric class here. studding on my own as there is no work for carpenter and no free room in electrical school.
what part of algebra do i use here? isn't finding the PF more geometry and trigonometry?

>>1096402
but nvm. >>1096397
are you talking about backwards counting in algebra? my whole idea was to get the example explained so i understand where the PF comes from, and how i calculate it

>>1096443
Clearly that isnt working so you need to work backwards to learn

Hint: to solve for power factor get cos(phi) on one side of the equation

Hint 2: dont take the arccos or youre all fucked up

>>1096315
One factor to bear in mind: the sqrt(3) implies "delta" connection to a 3-phase supply (so you're actually getting 415V from a nominal 240V supply).

>>1096511
that is it! I've been counting with norm. voltage and not the three fase voltage factor this whole time

>>1096511
thank you! so much time Ive spent getting around this

How do I make Wi-Fi thermometer that I can put in my bed so that it can tell the home automation server if I'm feeling cold or hot and have it adjust the furnace accordingly?

>>1096551
Arduino with temperature and wifi shields. Better make multiple thermometers in there to stop one reading too cold if it escapes and burning your house down. Even better, constantly monitor your own temperature with a rectal thermometer, you won't even know it's there!

Does anyone have any ideas for some interesting project kits/project ideas that I can do for under $25? I'm thinking of getting a fever 6j1 preamp for $12, and possibly building a guitar pedal from scratch for about $20.

>>1096588

generally one makes projects to fill a need. in your case, i sense your greatest need is a motorized ass-fucking machine made from an old ceiling fan.

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how do i put two 12vdc power supplies in series to get 24vdc? they are internally grounded so you cant just run ones positive to the others negative. what sort of external components can i use to fill in the ? box? also these are high amp units (up to 100 amps each) so how terribly expensive would it be to have components that could handle that sort of current?

>>1096628
> how do i put two 12vdc power supplies in series to get 24vdc? they are internally grounded so
... so you can't get 24V from them.

> what sort of external components can i use to fill in the ? box?
A 24V power supply.

>>1096628
A really big isolation transformer between supply 2 and the wall.

>>1096628

this is quite easy to do, but you gotta be careful.
- break off the ground terminal on one or both power cords. (you can keep the ground on the supply that's gonna be used as 0V.)
- wire them in series as usual.
- ensure the cases do not touch, and can never touch: wrap them in acrylic, wood, cardboard, or just use isolated spacers.

>>1096628
first off, are you actually sure the outputs aren't floating? just having a ground pin doesn't mean they're grounded. measure the resistance from the ground pin to both output pins.

if one of the pins really is grounded, then as an alternative to doing what the other anon suggested (dangerous) is to see if you can modify the supply internally (dangerous). smps readily lend themselves to galvanic isolation so they're only tied to ground as an intentional design choice. the only reasons to internally ground the output are either to really cheap out on the control circuitry (why bother in an already expensive 1.2kw supply) or for specific applications i can't think of. if the latter is the case, which it very well may be, then letting the output float could be as easy as cutting a trace or removing a resistor or jumper. if you open it up post pics.

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Good morning!

I am inheriting a house in the northeast US from a diseased relative within the next few weeks. The house is in great shape other than being 1970 inside. By this, I mean electric heat, split sink, gm fridge (yellow), wood panel walls, etc. There are a few things that need to be done in the house, but other than that it is ready to go!

The BIG project I am tackling before I move in is the installation of 120VAC smoke/CO detectors, since there are none in the house even though there is a wood stove and two fireplaces.

Along with the installation of these interconnected alarms, I would also like to send the signal wire to a RPI or another ucontroller. The reason I would like to do this is so that if the alarms go off and I am not home, the device could either text or email me! Think of it as a home monitoring system! From what I understand, the alarms all sound when a 9V signal is detected on the signal wire.

Does anyone have experience with this kind of thing? I am guessing that it is a 9VDC rather than AC signal. Is it in reference to the neutral wire? I'm not sure how I feel connecting the neutral and signal to the device's gnd pin.

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>>1096663
9vdc relative to neutral. from quick reading some devices also put data on top of that, so add input protection to account for stupid proprietary shit.

if you're running your controller off a two pronged wall wart or battery you can tie its gnd pin to neutral happily. unless chang was having a bad day at the factory and decided to short + and L.

>>1096560
What kind of case do I put it in so that I don't crush it from rolling over while sleeping?

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>>1096663

if you're gonna use a wired connection, you absolutely need to use an opto-isolator to give you 100% isolation from the power line. a better idea would be to use a 433Mhz receiver/transmitter pair. this also gives you 100% isolation, and no wires to run. you'd need a 5V regulator or zener to power the transmitter.

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rate my art

>>1097027
Seen worse, done worse. Made a few circuits on waxed cardboard.

What happened to those wires?

>>1097057
i sharpied them black because i'm prone to building circuits while half awake at 4am when polarity is optional

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>>1097027
the horror

I just need a micro-usb port, maybe two, for a mod I'm planning. I was wondering, if I want to get this done fast, could I just buy some crap adapters from a dollar store and scavenge ports from them? Is that safe?

>>1097027
That is some nasty shit.

In other words, it's beautiful.

Makes me shed a tear, in memory of the days before I had a computer to plan my circuits for me.

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>Found a use for those tiny voltmeters

Inline voltage display for RC cars

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How do I find free e-garbage? Hopefully without illegal dumpster diving.

>>1097027
>>1097125
What is it?

>>1097512
Legal dumpster diving
If you see neighbors throwing junk out go salvage it
Junkyards

>>1097515
it's a trimmer. as-bought it had a rechargeable AA and a 3v3 wall plug. the AA went bad and the plug couldn't manage to run the motor on its own.

the shitty board is a pwm controller to run the motor off a 12v 1a wall plug i had lying around. it works.

>>1097518
>Legal dumpster diving
explicitly forbidden by local gubmint, if it's in a bin you can't touch it, and putting stuff out on the curb aside from specified days of the year is forbidden.

>>1097532
what kind of shithole do you live? just do it in the dead of night and avoid personal garbage bins

>>1097552
Commiefornia.

>>1097584
i live in bay area. cops dont give a fuck if you look homeless with a shopping cart. go in disguise and cover it in trash bags

>>1097602
I live in the bumfuck east of orange county, cops here are bored and looking for a fight.

>>1097027
not bad, i've seen people go more crazy just over my traces

>>1097618
The OC is a conservative bastion of 'personal responsibility'. Too bad you're not in the commie part of California.

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What is a good source of these 100 watt led cobs that are decent quality but cheap? Best I can find is $8-10 on Amazon which is a bit too high considering i want like 10 or $2-3 on eBay which seems kinda suspect.
>Ant picture is for ants

>>1097897
buy like 50 off of ebay, some of them have to be good.

>>1097897
I know BigClive's done a few videos on 100W LED panels from ebay. You might be able to learn something about what to look for from him.

https://www.youtube.com/watch?v=_wR_mFWeI6Y

>>1097937
but its going to be a sealed work light so i dont want to play the "whelp half of the diodes went out on this one so lemme crack it open and resolder all this shit then reseal it" shenanigans every week

>>1097966
thanks

>>1097937
> some of them have to be good.
Not necessarily. It's entirely possible that they're selling either fakes or rejects.

>>1098013
Clive suspects that the cheap ones on ebay are the damaged goods (hence why they light up in a shitty patchwork), and I'm inclined to believe him.

You might try going for one of the ~$6.00 ones and testing it to make sure it works properly.

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im getting into high current cheap as dirt server power supplies being repurposed for bench power (and rc battery charging and coin mining). for example i got a hp dps-1200fb supply for $30 capable of 12 volts and 75 amps at 110v or 100 amps at 220v which is just ridiculous for a power supply weighing about 2 lbs, and $17 for an x adapter rev 4 breakout board with +12/-12 terminals and built in voltmeter. but 12v isnt enough for me, im wanting to do a big dumb dangerous project. i want to make a boost converter capable of taking 100a@12vdc up to 10a@120vdc (minus losses). i know it will be hard and expensive and require a shit ton of cooling (im actually thinking about water cooling the components with nonconductive fluid used in computers). can i get some help designing a circuit for this stupid idea?

>>1098063
just to make it more clear, i want it to be adjustable 12v up to 120v, not just 120v static. 60 volts is ok i guess too since i have 2 i could series them if i need high voltage dc.

Can someone help me out with this?

>>1098053

>>1098064
i thought about your idea and wrote up some ideas in the hope that it'll give you a general idea of the sizes and costs involved.

a design like this would benefit greatly in form factor and bom standardization from doing 5 to 10 boost converters in parallel on staggered clocks. it would benefit way way more from resonant/zvs switching but if you don't already know what that is then you're not going to implement it period. regardless i gave it a quick think for two interleaved 120V/5A converters. the items in question are the switches and boost inductors. the filter caps and control circuitry are too simple and semi-complex respectively to be worth discussing.

converting 12V/100A to 120V/10A will require a 90% duty cycle on each converter meaning 10% of the time the output rectifier will be subject to 100A+ (50A+/ch) and will have to be dragged kicking and screaming back to 0A when the switches close. this kills the switches.

to minimize massive switching losses you'll want a low swiching frequency in the 30-50khz range, just high enough to stay our of audio. i picked 50 because that's what my boost design spreadsheet was already at. at the minimum you'll need something like two of [374-1375-ND] on digi in series for both channels to constitute a worthy boost inductor and you'll have to settle for discontinuous current at lower outputs. a better solution would be a big hand wound ferrite core (ETD59 or whatever).

cont'd

>>1094602
How can I use my old android phone to do cool stuff. Like installing Kali Linux in it or something.

>>1098075
so on to the switches

i overestimated the switching losses and i'd like to revise a good converter frequency to be something like 100khz if you're switching the fets nice and hard. there's limited gain from higher frequencies since the inductor is carrying a large average current no matter what so selections are limited. the frequency can be dialed up at lower output currents to minimize ripple, but that's limited by parasitic D-S capacitance losses. maybe 300khz at lighter loads.

i put an immediately appealing switch, the FDP51N20, into my loss estimator spreadsheet and based on the output you can expect losses to a minimum of about 5W/switch at 2 parallel switches per channel (~20W total losses) at full output which obviously requires heatsinks and a fan but won't need any liquid cooling. on second glance the FDP51N25 is more appropriate but it's about the same.

like i said these numbers don't tell you too much in the big picture but i hope they convey approximately what your project entails. some of the stuff used here is expensive in a commercial sense but cheap to build one-off on a $100 budget, so #justdoit

>>1098063
First, design for discontinuous-conduction mode (i.e. after closing the switch, allow the inductor/diode current to drop to zero before opening it for the next cycle).

The disadvantage is that the peak current needs to be double the average current. The advantage is that DCM boost converters are much easier to design than CCM.

Because of the high current, I'd suggest a polyphase converter (i.e. several boost converters all feeding the same capacitor).

A lower frequency will be more efficient but require larger inductors, particularly as you don't want to push them to the limit (with a boost converter, if you saturate the inductor you're effectively shorting the input to ground, which isn't something you want to do if your supply can source 100A+). Even so, make sure that you can drive the switches hard (use a push-pull driver with a decent current capability; don't try to drive the switch from a bare logic output or with an open-collector/open-emitter and a resistor).

Cooling will be an issue. Remember to ignore any specs which are given at Tj=25C, because you'll be far above that.

>>1097897

It's an unbelievable crapshoot buying those things from China.

I've gotten ones that were superb for the price. Heavy, copper heatsinks on the bottom, decent CRI, (apparently) good efficiency. And I've gotten ones that were _more_ expensive than those, nearly identical in appearance, but had shitty, thin brass heatsinks, awful color, and not only were less efficient than the good ones, there was wild variation within the batch; some were fine at a little over 30V to hold 2.5A, some needed nearly 40V for the same 2.5A.

And, unfortunately, the only reliable option is to buy from an actual name brand. You'd be lucky to see them under $40 at that point.

>>1094602
Is the K155ID1 exactly equivalent pin for pin to the SN74141?

It's hard to find datasheets for it and I can't read Russian.

>>1098075
>>1098091
>>1098102
Holy fuck. Apparently I vastly underestimated the scale of this project.

>>1098103
Happen to remember where you got the good ones?

I use a lot of salvaged components. If I have two caps from different companies with different max voltage, but same amount of farads, could they perform differently?

>>1098299
If you exceed the least max rated voltage you bet your ass it will

>>1097224
This is actually a really great idea...

I know that it is generally a good idea to use brand name electrolytic capacitors, but is there a huge difference in quality between brand name and no name for film caps?

>>1098301
well...duh. Assuming I use them properly and at the same voltage, and that they have the same film type, could there be differences? what about for different film types?

>>1098342
Yes, different materials are possible and different construction is possible. This in turn means different performance.
Whether it matters depends on your application, but if you're going to use random junk capacitors, I'd assume your application isn't critical and both are ok.

Was told to ask you guys about this

I'm making a bluetooth speaker out of a broken vintage GE radio (Don't rage, it's one of the common ones that only resells for $10, IF it sells at all.), but I'm looking at using a rechargeable cellphone battery pack to power the thing

Are the power switches on the battery banks commonly a simple SPST?

Asking before I buy, just in case I need to order a switch as well.

>>1098367
You mean a power bank?
They usually have push buttons, connected to an IC - it doesn't cut the power.

>>1098406
So I wouldn't need a switch or disassembly at all? Just make sure it's charged and it's always on?

(Sorry if that's a dumb question, I've never used a power bank.)

>>1098422
It should turn on automatically when it detects a modest load.

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This is a series of rechargable alkaline 1.5v double a batteries. Can someone explain how tabbing them like this makes it only 12 volts

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>>1098474
Adding another photo of the top

>>1098474
4 x (2 x 1.5) volts = 12

>>1098238
differentfag here,
I hate to sound mean spirited, but what were you expecting with a 900W capable, high current, variable power supply?

>>1098367
>I'm making a bluetooth speaker out of a broken vintage GE radio
who would rage at that?

>>1098474

if they were really all in series, then every + would connect to a -, and you'd get 24V, but that's not the case, you can see they've paired every 2 cells in parallel, then put those pairs in series. so, you double the current capacity but half the voltage.

>>1098482
Fuck if I know, really just Hoping for the best. What about rectifying 120vac and the bucking down to whatever I want, would that be any easier?

>>1098500

if your need for regulation isnt too great, then a variac feeding an isolation xformer, feeding a rectifier and capacitor would be as simple as you can get.

>>1098500
Not very informed opinion here, but that might work. downside is having to deal with high voltage DC
if you've ever opened up a computer power supply, i think they rectify mains then do shit with it down the line, so its something that can done

>someone correct me if i'm wrong.

>>1098500
You can do that, but the risk of electrocution or burning your house down is much higher when dealing with high-voltage DC.

A mains PSU isn't really a good choice for a beginner project. Most beginner PSUs use an off-the shelf fixed-voltage PSU to handle the dangerous parts and just tack a low-voltage buck converter on the end. But that limits you to whatever voltage the PSU puts out (usually 12V, because PC PSUs are much cheaper than anything else with comparable power).

And a boost output stage doesn't make much sense from a technical perspective. High-power boost converters are harder than an equivalent buck converter (DCM requires more hefty components, CCM is hard).

>>1098490
Not him, but there are people who collect old radios, even the plastic portable ones that most people would call shitty or disregard. Some can actually fetch a pretty penny.

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Hey /ohm/, I want to build a decent audio mixer with 6 line inputs (stereo jacks). I also want to make it as small as possible.

I've built the old passive altoids tin mixer before, but I find it cuts the volume too much. (I'm plugging in a few synthesizers.)

Anyone have any advice? Op amp selection? I'm wondering if there is any benefit to amplifying each line separately, or should I use a passive summer then amplify all the channels? I would like independent volume adjustment of each line input.

Also, any ideas on how an "effects send/ return" line works?

i need to measure "ac" current on a single supply. has anyone seen a differential amplifier that can provide the absolute value of shunt-measured current off a single rail? there are plenty of single rail precision rectifiers out there but none for differential amplification.

i can do it with 3 op amps but i feel like someone out there has done it with 2.

>>1098959
I'm not 100% sure what you mean, but if you need a precision amplifier, you could look into so-called "instrumentation amplifiers, like AD524. They are essentially 3 combined op amps in a single package.

Most INA's have rail-to-rail output, and all operate on differential gain. The gain value is adjustable using an external resistor, or in the case of AD524, simply by connecting the desired gain pin.

If you're measuring AC current though, are you using a hall effect sensor or something?

>>1098858
Would you consider doing a dsp digital mixer? Then you're doing it all on one chip.

That might ultimately be easier and more compact than doing a summing amplifier.

Might be more difficult circuit than you were planning on.

>>1098971
i tried to be general enough to not introduce unneeded complications, but the actual goal is to measure bipolar current from 1 to -1A off a 50mohm shunt and output the absolute value of the current over 0-1V. it's a non precision calibrable application so i'm just using jellybean amps.

example is pic related but instead of outputting a negative value or hitting the bottom rail when current flows in reverse, i'd like it to just give a positive value for either polarity.

i can generate a negative rail and append a precision rectifier if it really comes to that but i'd rather not because it's much easier just to throw more op amps at something.

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>>1098978
>pic related

>>1098976
That does seem complicated. I just checked out a couple of TI audio DSP chips. I don't need to do anything fancy like equalization or on-board effects.

I think I've found a simple analog solution.

http://www.circuitlib.com/index.php/tutorials/product/39-how-to-build-an-audio-mixer

1 chip per line + 1 for the summer means I would probably be looking at 7 total. At 83 cents a piece that isn't too bad. Even if it isn't the most efficient circuit, it should work

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What kind of shit should I look out for on the roadside/landfill/second hand store that is more likely to have interesting/novel circuits? I like to learn by taking shit apart like any good autistic boy.

>>1099067
Anything in dollar stores. Just do what big clive does (check out his youtube channel), and keep on doing until you're as good as him.

>>1099074
Love big clive, good advice.

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>>1098858

dont waste your time building your own mixer. you can get an Alto zmx52 for $50 at amazon, which is less than what you're gonna pay just for the externals: pots, knobs, connectors, case, power supply.

>>1099067

This >>1099067 but also just whatever. If you find a TV box on your way home, take it apart. You won't understand it, but you'll get comfortable with the parts/general concept. Also try to get really old stuff like a transistor radio.

>>1099067

I like to buy the cheapest available chinese crap on ebay. Shows you "oh damn that all fits on one chip now"

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>>1099103
The problem with those is half the inputs are XLR (mic)/ mono inputs, and the other half are 1/4" separate left and right mono. Not very convenient. It would also be nice to have a mixer capable of running on batteries (even if the gain isn't too large).

Basically, I just want to be able to plug in a bunch of these (pic) coming from my tiny synths.

>>1099136
oh, and for you're 50 dollars, you're lucky to get 3 or 4 inputs, and I'd like 6 ideally

>>1099136

audio people have a justifiable hatred of all 1/8-inch connectors: they're too easily damaged, they become loose, the cables are weak, and worst of all, they tend to get oxidized and give you scratchy sound. the lovely quarter-inch jack, with its muscular springs and plenty of smooth silky contact area is what turns them on best.

>>1099136
if you have the spare parts lying around i'd say go for it, but if not you're better off buying something used

>>1099136
Are your synths outputting balanced signals or stereo? If stereo, there are plenty of stereo line mixers with many channels. Many of the products are targeted for synths.

>>1099136
3.5mm sucks shit, use 1/4" or rca instead like normal people

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Alright so im repairing this old synth i got, I've probed the CPU ALE and the reset and both signals stay at 5 volts, not oscillating. the CPU reset doesn't ramp down on startup like it should as seen in pic related. The ram reset does ramp up like it should however this is a different circuit. the CPU is an 8051 manufactured in 1980, it also seems to get quiet hot even though it is essentially in idle. is it safe to say the CPU is dead?

>>1099280
>is it safe to say the CPU is dead?
No, and processor failure is pretty rare to begin with.
I'd start by checking if the capacitor used to generate the reset pulse has failed. If you keep the processor in reset, obviously it's not going to do much.
>8051 manufactured in 1980, it also seems to get quiet hot
If it an NMOS version, then it is normal that it gets somewhat warm.

>>1099287
Thanks for the reply. the cap itself doesn't look bad but i'm gonna replace it anyhow tomorrow.

>>1099289
Broken solder joints are also relatively common, particularly on single-sided PCBs.

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>>1099160
>>1099274
lol'd, though I know its true. But my cute little japanese synths need cute little jacks!

>>1099273
Some of the volcas like the keys and bass are just balanced, but others are true stereo as they either have a chorus effect (like the FM) or panning (like the sample(r)).

I had a brief look at some line mixers. $50> ones are typically mono, with 4 jacks. Others are $100< and still only 4 lines, usually RCA. (The Rolls MX44s is the closest to what I want but still a little to pricey for me.)


I've got most of the parts lying around. I just need the op amp chips (LM833) and either slide pots or rotary pots with 2 gangs. I know knobs can be expensive so I may not even bother lol. Just leave the metal rotary pole thing exposed if I use those.

>>1098429
Aight, so I'll probably just experiment with adding a switch on the cable going from the BT board to the power bank and see if that works.

(Using an old phone, not the BT board, of course.)

>>1099339
go check out goodwill for some old audio equipment to scavage from plenty of knobs, switches, connectors, power supply etc. from old stereos.

Anyone got a good place to source quality speakers?
I want to may some Bluetooth receivers and I don't really know where to get some decent speakers for them. I want them to be high enough quality to listen to stuff like music.

>>1099067
I work at a place that throws out old/broken home appliances (like fridges, washers, stoves etc.). I asked my boss if I can salvage all the electronics from them before we toss them in a dumpster to be taken to the steel recovery joint. He's cool with me taking whatever I want as long as I don't turn around and sell the parts. I've even gotten a microwave that I fixed and gave to my grandparents as a Christmas gift.
Great source of components and surprisingly very unique input components (switches and dials galore).

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Thinking about building the speeduino project.

It's an open source standalone efi computer for your car.

uses an arduino mega 2560 plugged into a custom board.

The creator sells boards and component kits, but I think I'm going to try to have boards printed and try to buy multiples of kits from a supplier so I can get better pricing, as he's basically charging double for what you can buy the stuff for. plus there is a second vr conditioner board that I'll need to smooth the cam& crank signals.

I'm still in the research phase, they don't seem to have very much centralized data on their forums, or github page. I was thinking about using megasquirt, but I really have grown to despise that project as it's closed source and has quadrupled in price over the years.

I'm going to try to get this thing just reading data first, before I run fuel or spark, I'm not really sure if It will work with my stock crankshaft trigger wheel, already got a wideband 02 sensor and controller coming so I can replace my stock one.

and already sourced a mega which is on the way.

the main design hurdle I'm at now is that the newer version of the board (on the right)uses a 40 pin IDE connector so I need to come up with a connector to run a wiring harness from inside the car to the engine bay. I'm thinking of going with the db 37 connector that the ms uses.

I'll still need to leave my stock pcm, it handles a few things like the voltage regulator for the alternator, and some of the main relays to the car and also the evap system. I could delete it, but I think I'd like the option of going back to it quickly by just plugging the injectors/coil/iac in.

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How difficult would it be to make something like Mbient Meta Wear?

It's a small wearable that takes body temperature readings periodically and send it back to data collector using Bluetooth LE.

I need a device that I can wear that is able to upload the temperature readings somehow (over Wi-FI or BLE to a separate collector device), not just store them in logger to be downloaded later.

Can the cold temperature cause inference or noise?
Can your arduino being next to its power supply cause it?

I have a 3d printer running on an arduino and shield
Just finished putting it together. In every test run it connected to my laptop fine and the steppers were controlled and moved fine.

Now that its on the frame and you start a print it stops shortly after starting. Some searching says thats indicative of the wrong baudrate (mines correct) or interference and noise causing the arduino to drop connection.

Now when reconnecting, half of the time it throws an error thats indicative of it not being able to communicate.

Its in a unheated garage with the temps around 10f outside. The small heater im running isnt making it much warmer
There is only 1 outlet, the only thing plugged in is the laptop and the arduino / power supply, and then a small oil heater

What other causes of interference could I be missing?
The arduino is next to the led driver psu, but its not an issue on my other printer.

Im looking into it maybe being a settings issue too, just trying to get insight on the interference possibility

What kind of current is the specification on a non polar capacitor based on? Is it just DC like polarized caps?

>>1099650
I believe you can buy those connectors. Unless you want to do something different

>>1099659

the WV rating is for DC or peak AC, and, of course, that rating should be about 25% above the expected voltage present.

>>1098474

>>1095011
I exclusively use SMD for my projects. easy af, and PCBs are cheap at oshpark etc.

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I downloaded KiCad for the first time last night and got to mapping out my door buzzer project. I need to see if I can get by using a 3.3v battery for the nrf24l01; While I can't find a definite power requirement, online tutorials usually have it plugged into the 5v rail.

Perfboard looks like it's too much hassle compared to pcb etching, so I think I'll skip that part of the learning process.

>>1099658
Have you tied a different Arduino mega board?

>>1099654
Sounds like a project you can spent at least a year on if not more. Am guessing you want it to be small & use bugger all power, two factors that are fun to optimise. Plus assembly is going to be fun as well ;^)

Still go for it, should learn a whole lot m8

>>1099748
Are you sure you want to use a radio chip requiring you to provide antenna and antenna matching and which is kinda finicky for the PCB layout, if you can't even read the datasheet of the said chip?

Consider using some radio module built around it.

>>1099654
All you need is a temp sensor, an attiny, and a bluetooth module, honestly should be super easy

If i wanted to order a printed PCB with my components and shit already on it, is there a place online i can go to order that?
only has passives and op amps on it is there anyone that does something like that online?

Are electronic learning labs worth messing around with to actually learn anything or should I disregard the one I have?

>>1099800

it would cost an arm and a leg unless you were ordering a lot of pieces. takes a lot of effort to set up a pick-and-place machine with all your chosen parts.

>>1099804

with a shitty attitude like that, you'll never anything about anything. all you need to study the entire universe and every topic in it is a magnifying glass and a pencil.

>>1099800
this is pretty much a short manufacturing run of a finished product so pretty $$$

>>1099808
Some Chinese PCB factories offer low volume production as well. I don't remember any names, but Google helps.
If you want a western company do the job, the setup costs, assuming you want them to do everything, are typically some thousands for small runs. Plus materials, of course.

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Hi, I'm new to /diy/, hoping this is the right thread.
I'm looking for a pressure sensor to measure string tension in a guitar string. For a G string it means I need to have measurements from ~40 newton up to ~100 newton. Does anyone have any recommendations? I'm guessing I'd need about 8 bits of precision in the range 40 to 100 newtons, precision is not terribly important but response time is.

>>1099646
good idea!

>>1099800
Have a look at the PCB assembly tab on http://pcbshopper.com/

I'm a relative novice to electronics, I've built a couple simple amplifiers and performed basic repairs on a number of things like motorcycle CDI units and vintage stereos.

How feasible is it for me to build a discreet digital-to-analog converter (R2R) for audio signals? Something with an optical (toslink) input and 2V line output.

I'm not looking to construct a laboratory or audiophile grade piece of equipment, I just think it would be a fun project that I could actually use.

My understanding is that the critical consideration in getting something like this to work is the consistency of the resistors. If I were to buy a pile of cheap resistors, how precisely do they need to be matched for me to build a workable DAC?

>>1099908
That's kinda like asking how feasible it is to make a seat out of a 2x4 plank to your /diy/ motorcycle. In other words, the rest of the shit is much more complicated that your DAC.
The resistors need to be matched (and maintain their match) very well to get even mediocre performance. For example, the least significant bit of an 8b DAC is worth 0.4% of the full scale.

If you like the idea of making your own R2R DAC, maybe some simple noise maker would serve you better. Toy organ, for example.

>>1099910

I've built tone generators and things before, but I was hoping I could build something that actually had a bit of utility.

Thanks for your reality check though. I'm not exactly committed to the idea, I'm just kind of floating through ideas for my next DIY project right now.

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Like my Pepeduino, /diy/?

I made this to radiocontrol a styrofoam boat and I've got it working with two of those SG90 servos (haven't made the actual boat yet), but now I realize it has many uses, ranging from functioning as a wireless keyboard or other HID device to working as a remote detonator.

Anyone else here into Raspberry Pi systems? Just ordered a case for a PiGRRL Zero project, but I'm adding this amp for sound.
https://learn.adafruit.com/adafruit-max98357-i2s-class-d-mono-amp/overview
Also doing a few other tweaks, nothing major.

>>1099917
Well, maybe that was needlessly negative from me. 0.1% resistors aren't prohibitively expensive and they would provide 1/2LSb maximum untrimmed error for an 8b DAC.
With some trimming, careful component selection and some attention to design in general it should be possible to get 2-3 bits better performance with reasonable effort and cost. Beyond that many things start to matter.

>>1099920
There's a frog on it.

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>>1099748
Why not just use one of those tiny regulators?

NRF24L01 uses very little current, it's ok to use a linear regulator for it.

>>1095011
It's not really a problem until you get below 0603 or anything with no leads. It's actually quite fun soldering smt

>>1099920
i was really hoping all the boards circuits and lights actually drew out pepe. cant someone do it with a green board or whatever

>>1094602
is that a fucking transistor based cpu build? i'm kinda turned on

>>1095099

The thing is, it takes a few attempts to get the exposure time just right, and if you don't get it right with a presensitized board you'll have to strip the resist away. If you have even a cheap laminator you can laminate and strip as many times as you need until you find the right exposure time for your uv light bulb/or just the sun. Use cheap dry film off Aliexpress, as it will work well enough.

>>1099966

yes

there are transistor level software models as well

>>1099751
Nah thats my next step
Ill swap them and see what happens

>>1094602
I just got about ten Keyence KV-24 dt, DTP, 24AT. from my work (we are moving warehouses so they are tossing random stuff) and I am wondering how do I test ones that are not NIB to see if they work and the outputs and inputs are good? I don't have a power supply at home. Just a 3 prong i am willing to cut and throw lugs on to put into the plc's screw terminals.

>>1099773
It'd need to be sturdy enough that I wouldn't break it while wearing it to sleep.

So, clunky boards haphazardly soldered/glued together probably isn't going to work.

>>1100122
>clunky boards
Small BT modules are available.
>haphazardly soldered/glued together
Build it carefully.

And of course you need a proper case.

>>1100122
Encase it in epoxy

>>1099751
>>1100059
Welp I swapped out the arduino board, and it is responding to commands much faster, connecting to the PC much quicker and the stalling problem went away.

I suppose this means my new ardiuno clone is a lemon?

I'm interested in making flash carts for old game consoles, but I have very little knowledge of the electronics side of things. In the simplest case it just seems to be an eeprom soldered to some pins related to addressing and data transfer and power and a few other things I have no clue about. More complex flash carts involve microcontrollers and FPGAs and storage devices and stuff.

On a scale of beginner to advanced, how hard would this be?

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So i got a question, will soldering iron made for 24V 48W break burn out faster if i power it from 20V laptop adapter??

>>1100474
No, why would it? Less voltage means less current flowing through the same resistor (the heating element)
If anything it will operate at a lower temperature.

Know your Ohm's

>>1100474
it'll be 33% cooler. also can your adapter do 2A?

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>>1100474
There is also a soldering iron that's designed to be powered from a laptop adapter.

>>1099807
saved. this post resonates with me.
especially anything about anything

>>1100562
i thought it was pretty arrogant and faux-intellectual given the post he replied to. it's like browbeating someone for realizing they can't learn to cook with an easy-bake oven.

>>1100448
More advanced than adavanced. You need to figure out the proper timings for everything.

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>>1099920
I've made a second of this board. It turns out having an image of Pepe on the top of the board made me rip two pads while soldering. I've made one without Pepe and everything went smooth and mistake free. One will be the remote control and one the remote controlled thingy. I also bought an ESC and a brushless motor and a fan. If I use a battery made from 3 18650 batteries I get 12.6v when fully charged, and it's enough to drive the brushless motor. Now, should I use a switching voltage regulator for the microcontroller board or can I use the 7805 I've put in it?

>>1099136
http://synthtech.com/motm/830/
Check the user guide for the schematic and go from there. I'd go with TL072's unless you can find their ridiculous OP285's

>>1100589
There's not much point in using a switching regulator if you only need milliwatts.

>>1100640
What if I also have a servo running at the same voltage as the microcontroller? When I'm testing on the USB port and it's moving the power led even gets dimmer

So the Galileo global positioning system is online. Is it possible for mere mortals to buy antennas to utilize it like with GPS yet?

>>1100493
>can your adapter do 2A?
Almost all adapters i saw can do at least 2A, unless they are lying bitch...

>>1100661
Measure the power consumption, estimate the duty cycle.

5V from 12.6V with a linear regulator is 40% efficient, i.e. you're wasting 1.5J for every 1J you consume.

If the average power consumed by the 5V devices is a significant fraction of the total power consumption, then it's worth considering a switching regulator.

Do you guys know where to buy a really small lcd display like 1"? Im playing with the idea of building a digital wrist watch with bluetooth and a stm32F1 controller but i can't find such a small lcd display.

>>1100675
aren't most phones GPS/GLONASS/Galileo compatible?

>>1100719
those cheap tiny oled displays from Ali/ebay are about 1"

>>1100728
Yes i saw them but they are OLED and have a pretty high power consumtion (0.08W). LCD without backlight are far better in that aspect.

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>managed to solder a lcd driver board to ras pi with this soldering iron
>had to kind of melt the solder on the side of it then quickly flick it onto the pcb

I can't bring myself to pay £7.99 for tips in a store when I can get 5 for £1.50 online

>>1100730
you could try buying some shitty sub-1$ watch and reuse the lcd glass + some zebra strips
but driving them directly is tricky

>>1100732
>had to kind of melt the solder on the side of it then quickly flick it onto the pcb
why are you proud of a dogshit soldering job

>>1100767
It is my first time and it actually works, I thought I had fucked it all up.

I have gone out and got some 2 part epoxy to keep any dodgy connections in place.

>>1100768

You need no-clean flux, buddy. It will help fix shorts and "cold" solder joints.

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>>1100732
Better to do things right the first time around.
The moment you spend an hour or two troubleshooting something only to find out it was a bad solder joint you'll regret your method.
Although to be fair to the tip, it seems you aren't keeping it tinned. Here's a shitty $3 ebay special, and it works well enough.

Hey I need some purchasing advice.
Anything a rookie would be missing?
>>>/g/58066776

>>1100498
Bump for TS-100
I have one and it's great.

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any guitar bros in here? quick question, here we have the schematic for a hybrid amp, tube pre ss power. i like the concept as a practice amp, but id like to try it out with a tube power amp from a different amplifier. since there's no transformer on this schematic i have no reason to think that having no load on the speaker out will cause damage. ive done this hundreds of times with other amps using effect loops, effect send from one amp into effect return from another.

my question, since i have only a basic knowledge of electronics, can i add an effect send and return? id assume if i could it would be between c9 and vr4.

also, any of you know a resource explaining the switching they use for things like this? where plugging into the jack disconnects the 2 sections. to me it seems like a relay working in reverse, but i dont know. if i cant figure it out ill just keep a 6 inch jumper in it when im using the power amp stage.

>>1100675
Isn't the whole idea that anyone can use it?

>>1100915
>c9 and vr4.
probably makes sense i guess
>seems like a relay
the socket has 3 pins, when there is nothing in the socket two of the pins are connected, when you plug in one of these pins connects to the tip or whatever and the other pin connects to nothing it just floats about in space.
so by plugging the cable in you cut the output from the switchy pin to the next bit and divert the signal down the cable. same thing going on at the other connector, when you plug in the return it cuts the connection from the pream and the signal from the cable is fed instead. kind of back to back. these things
http://www.ebay.co.uk/itm/Switchcraft-SC-12-mono-1-4-shorting-jack-socket-for-amps-fx-pedals-etc-/282263443251?_trksid=p2141725.m3641.l6368
look at the top there is a bendy strip and a short straight strip. when you plug in the bendy strip is pushed away from the non bendy one. they were connected now they aren't.

>>1100732
Jesus christ guys.

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>>1100915
switching stereo jack
when nothing plugged in amp acts normal
when twin lead cable is plugged in signal goes out on one lead and returns on the other

pic related

i want to make a 120vac to 36vdc buck converter to drive some high power leds that will need at least 2.75 amps at 36vdc each. should i use a linear converter or switch mode (after rectification and smoothing of course)? doesnt need to be super efficient but the more i can limit the need for heatsinking the better of course because i would like this to be handheld.

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could i take 4 of these 250w boost converters, put their outputs in parallel, desolder their v and a adjustment pots and hook them all up to 1 set of pots to adjust them all at the same rate, and have it work semi reasonably well

>>1101118
If you used a standard 36V transformer, a linear PSU would waste around 40W at full power. On the plus side, it would be simple. The extra 40W isn't that much more in comparison to your LED's 100W heat sinking requirement, either.
If you want to go with a switcher (but retain the mains transformer), then for example TI and Linear tech have suitable, quite easy to use switcher ICs.

>>1101122
No. Putting them in parallel without any attempt at load balancing just results in one of them supplying most of the current. Connecting all the trims in parallel only worsens the situation, assuming it works at all.

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Anyone have experience with the HC-SR501 IR PIR Sensor?
Anything else I should look at?

>>1101118
Converting 170V to 36V with a linear regulator is insanely inefficient.

A buck converter is non-isolated, so if the transistor fails short-circuit, you have 170V DC on the output, possibly leading to electrocution or a house fire.

At that power level, you'd normally use a flyback converter.

A bridge (full- or half-bridge) topology would be more expensive, but is simpler. A bridge converter is almost identical to a classic linear PSU except you increase the frequency so that you can use a smaller transformer. You don't even need feedback if you can tolerate the output voltage fluctuating with the input voltage (which is typically +/-10% maximum).

Flyback converters are normally used because they only use a single transistor. But they're conceptually more complex (the transformer isn't actually a transformer, it's a pair of magnetically-coupled inductors). Above ~500W, bridge converters tend to be preferred because they get better utilisation of the transformer, and a smaller transformer eventually beats out the cost of the extra transistors.

Which one should I get?

The GY-80
https://www.amazon.com/dp/B00CD239UG

or the GY-89?
https://www.amazon.com/dp/B01HXDQ3O8

I have seen more videos and such on the GY-80, but does it really matter?

I wanna build something similar to what this guy did to his telescope, but with a gyroscope.
https://www.youtube.com/watch?v=fRAF6LnHk1A

>>1101118
There are commercial 36vdc psu's, just get one instead

Why doesn't the OP have Fritzing software and these youtube channels?

https://www.youtube.com/user/makemagazine (they have electronics but seems like they have other things as well)

https://www.youtube.com/channel/UClTpDNIOtgfRkyT-AFGNWVw

https://www.youtube.com/user/EugeneKhutoryansky (pretty good animation with explanation)

I'm pretty sure there are more. But wouldn't these be suggested too? Or too much?

>>1101220
Fritzing is garbage unless you want a pretty breadboard diagram.

>>1101223
I guess, can EAGLE simulate the schematics by the way? I've been using EAGLE for all my labs but without seeing if it runs simulations.

>>1101224

It can export to LTSpice or whatever, but Proteus is a more integrated solution. It will even simulate audio.

>>1100944
>>1100965
Perfect, thats just what i needed. I appreciate the link and the modified diagram.

>>1101215
i got a 10d sensor off ebay for $4 last year and it worked great. don't blow $20 for no reason.

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Hello


I am wanting to design a relatively high power boost converter that has the following (simple) specs:
Vin = 13.4V to 14.4V
Vout = 15.5V
Iout = 30A

Would anyone be able to point me to a resource that talks about the advantages/disadvantages of various topologies (SEPIC/CUK/ZETA...) or recommends which topology to use for such a power level?


Cheers

>>1101423
Oh nice, what model? Was it similar to the GY series? I'm just wondering, if it would make a difference if it's the GY-80 or GY-89. Is it an updated version or something?

>>1101547
>http://www.ebay.com/itm/222324066604
>China
O-oh. Well, will it give me similar results thought?

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>>1101487
> advantages/disadvantages of various topologies
If your Vin will be always lower than Vout - go for boost topology. Most of the pwm controllers can work with 99+% duty cycle.
>Iout = 30A
Do you care about space, efficiency, transient response or ripple?
If not, go with uc3843 at 100khz, 0.3uH 70A saturation inductor, 4x1000uF filter, 30v 15mohm mosfet (it wont dissipate more than a watt so it can be in smd package), and get the lowest Vf shottky you can (it will dissipate more than 11w).

Othewise choose some fancy ic and follow the app note. But it wont be easy or cheap.
http://cds.linear.com/docs/en/datasheet/3787fc.pdf

>>1094602
I want to make an simple amplifier for my basic $8 AKG headphones, coz my old LG phone wont turn the volume too much, and in crowded places or on the street I can't hear the music at all.

There is better solutions to that, the whole point is to get some basic DIY stuff going.

Any ideas where to start ? All the amplifiers I find on the net is too huge or for desktop applications I want something cheap and small (pocked size)

I have a lot of 555 timers if that helps, everything else I will buy from the hardware store or aliexpress

>>1101661 http://www.amb.org/audio/mini3/
AD8397 is one of the best single chip headphone opamp. And it is not too expensive.
You can go with original schematic, but i personally do not like 9v batteries and virtual ground. It will be better to use two protected cellphone liion batteries in series and charge them with simple cc/cv charger (ld1117 + tl431) from 12v. Or you can charge them in parallel configuration from micro usb. But on the downside you will not be able to use the device while on charge.
It your headphones are 250+ohm you will need higher voltage, e.g. 4 liion cells in series.

is there any reason i shouldn't use a 250va 12v transformer as a mains isolator? it has two primary windings for 110 or 220v operation. idea is to use those as pri/sec and run a small fault detection circuit on the side off the 12v winding. only reason i'd think this could be a "bad" idea is because the two prims are on the same bobbin half but idgaf about multi kv isolation rating, i just want to be able to poke around more with my scope.

also where do you buy big silicon steel E cores without paying $90 online for shipping?

I have a heater for my car. I'd like to use a ESP01 to control it.
Is there more to this than getting a relay suitable for 230v (I'd like recommendations too) and connecting a gpio pin to that relay?

>>1101686
you need a relay driver circuit. driving the relay off the esp directly will fry it. i'm at work so i can't draw you a diagram but google will have plenty. you can fit that and a 3v3 regulator on a shitty perfboard.

if you want to be clever you can use the esp's adc to disable the heater when your car battery gets low.

>>1101671
/sqg/ how to measure my headphones ohm's ?

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>>1101686 Chink relays are shit so buy a good din rail mounted relay from Finder or similar brand (40.61 series 16a 5v dc relay and 95.05 baseplate). It will cost less than 5$.
Driver circuit is pretty simple.
>>1101693
Just look for manufacturer specs or use damn multimeter. Btw almost all of the cheap <100$ headphones are 32-60ohm.

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Which program should i use for drawing plans and such?

>>1101720
xfig

>>1101547
>>1101552
sorry for vanishing. the actual module was an MPU9150 on a GY-9150 board. that chip is now obsolete and the one all over ebay is now the 9255.

the accelerometer has 3% tolerance on the 2g range out of the box so you won't be able to do astronomical calculations without calibrating it. ideally you could maybe get 0.1 degree resolution. calibrating it might not be tough since there are maps of earth's gravity to compare it to.

Does that guy who restores old radio microphones still lurk?

>>1101643
Thanks for that help, was thinking of making a crude UC3843 tier DC-DC converter but having that much power being lost across the freewheeling diode is not good. So will have a poke around some LT chips, LTC3786 looks to be good so far

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Hey /ohm/, I'm currently moving and kinda tossing stuff as I do. Among the stuff I tossed was a few old Dell server blades. So before I tossed them, I (of course) opened em up and gutted what I could.

Inside one of them was a FPGA daughter board. It had a Xilinx Spartan on it, and a Agilent proc as well. The other blade of the same make/model didn't have this board.

So I was wondering if you guys had any guesses what the board was for? I'm fairly certain it was placed there by Dell, because the guy I (indirectly) got them from is incredibly incompetent. I've taken VHDL in uni, and I guess this is the first time I've seen the fruits of that labor in the wild.

>>1101959
probably some kind of remote access controller

How do you cut holes for ports on a plastic Hammond case?

I'm putting in a C.H.I.P connected to an USB telephony modem, I2C text LCD, and a bunch of sensors.

I need to cut holes for the telephone jack, LCD, and the micro-USB power jack.

I don't think I can cut the holes with just the knife without completely destroying the case in the process.

>>1101969
Drill a hole then use a coping saw and/or small file

>>1101220
>learning about electronics
>from a woman
top kek

>>1101969 https://www.amazon.com/Carbide-Milling-Cutter-CNC-Machine/dp/B00SMDPF4I

>>1101989
Well, not learning, but this video was pretty nice

https://www.youtube.com/watch?v=_kDhpFaf4EY

Unless you're talking about the other channel, that one's decent, used it for my physics classes.

>>1101868
>GY-9255
Well, it's more than $20, but there are these other sellers that are for $4, these what you mean right?

What my main question was that like, let's say there are the GY-80 and the GY-9255, what is the difference? You said it's obsolete, but how different are they? The controlling from Processing / Arduino IDE? Or material used in the ICs?

>>1101968
Yeah, probably this.

>>1101989
EE student here, the few girls at my uni have better grades than most.

>>1102106
She also has some interesting educational videos,
like how to make your own MOSFET:
https://youtu.be/w_znRopGtbE

>>1102136
suckey suckey passey passey
>or you and your classmates are just retarded

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I have this old clamp meter that's completely unresponsive. I opened it up and there's surprisingly little in there, but as you can see nothing that stands out as being faulty. How do I debug this?

>>1102148
Go back to your containment board

>>1102157
>completely unresponsive
check the winding on the clamp core
check the meter movement (carefully!)
check the diode

>>1099650
>db 37 connector

been years, but the mil-type DB connectors are pretty easy to work with. spendy, but you can pull each pin with the extractor tool to connecting wiring.

personally, i'd find a pigtailed IDE connector, then wire the other side up to the DB connector. If you want to do it on the cheap, then look for the solder-cup version of the DB connectors. how fancy you go from there is just a matter of connector housings and braided cable sleeves, etc.

>>1102108
yes, there's no reason not to buy the ebay chinese clone boards for hobby work.

the gy80 and gy9255 have different accelerometer ics full stop. both ics have the same non-calibrable tolerances at a glance though. for both you'll still need to calibrate what you can if you want to do anything more than vaguely point towards a celestial object. both offer i2c communication (at least the chips do, don't care enough to search your breakout), which is what you want.

you should be fine getting either one. just get the cheapest. i don't think greymarket MEMS is a thing so you're getting legit ics regardless.

>>1101720
Eagle or Kicad.

KiCad is totally free and very powerful, but Eagle is little bit more spreaded and user friendly.

Free version of Eagle is limited but sufficient.

>>1101487
Can you explain what device can't work at 13.4V but can on 15.5V? It just like 2V on this kind of voltage should not matter at all.

>>1098474
You have a few cells connected in anti series.

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>>1102621
>>1102621
>>1102621