The (not really) official electronics workbench thread


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Do you have any use for ESD mats? We're going to be changing out some here at my work and if you don't mind older ones that are a little beat up or might need to be cut down to fit you would be more than welcome to them?
Nah, part of the motivation of this is to purge a lot of the electronics shit I know I'll never use, break down a bunch of appliances etc. I have into parts and actually put some solder to stuff.

Have been goofing around making (some) progress. I ended up wiring this project twice after spending a few hours troubleshooting to figure out I had the damn socket wired backwards; ICs are certainly easier, you just rotate it 180 and keep plodding along.


I used the 0D3 voltage regulation tube, but substituted a 6LU8 Compactron tube in for the triode/pentode just because it's self contained. Still doing some research and trying to determine if I want to go to beefier tubes.

http://www.youtube.com/watch?v=https://www.youtube.com/watch?time_continue=347&v=OP-_CBydYuA

Bit windy of a video, skip to 4:40 or so to see it powered up and operational.
 
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Bought some stuff at the hamfest, and made some progress on my PSU.



I'm tying it in to the original power supply, not quite there yet but pretty close. Need to add the voltage divider to feed the grid and I should be good to go. I'm going to use a pair of tubes in parallel to increase current capacity. Up next is a solid state version, we'll see how it works out. Won't be near as pretty but a hell of a lot smaller and more efficient for the current capacity!



The steel rod is part of a chassis punch. These are great for tube sockets among other things. You drill a 3/8ish hole and then stick it through, tighten it down all the way and bam you have a pretty nice large hole



This is the first signal generator I bought. Paid too much for it esp considering the price I got the second one for. It's okay, not spectacular. It also runs to higher frequencies than the second one does though which is a benefit I guess. I can always calibrate against my ham radio if need be.



Here's the second one I got. This goes up to about 240 mhz. It totally fucking rocks. I actually got it cheaper than the one above, which kind of disappoints me. That said it was such a good deal it really makes up for the hit I took on the one above, not to mention with some of the things I want to work on (like mixers) 2 generators isn't terrible at all.

Above that is a function generator. It goes above AF, but not much. It does square, sawtooth and sine. They're handy for certain things like testing AF amplifiers and modulation, plus being used potentially as a clock source for digital in a pinch.



Lastly, this showed up. It is a $10 frequency counter board off ebay. I thought this was going to go to 40mhz or so based on the confusing ratings. Much to my surprise, it's drive sensitive but it seems to be within quantization error even at 240Mhz!!! It definitely needs a capacitor at the power terminals to stabilize the supply voltage, but otherwise it works amazingly well. I'll probably end up with a few of these including one or two that get wired into some ham radio projects.

I also got in my DDS (Direct Digital Synthesis) board, so I'm thrilled to see what that can do. The Ebay Auction said 40mhz on that too, but the oscillator on it's 125mhz and theoretically I think you're supposed to do 50% of that clock input. I'd love to reach into the 6M band at least. I've got my Raspberry Pi finally installed with an OS, so I can figure out the wiring of this beastie and connect it up. It should just be doable via SPI which is a 3 wire serial connection; The other big thing I need to do is get a PC PSU hacked up so I have 3.3V to feed it with.
 
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Took a break from the RF stuff I was goofing around with and did some AF stuff instead.



The circuit is half a 12at7 and a 6aq5 which is pretty well a 6v6. Coupling between stages is RC, and voltage gain is around 25 in the first stage. It is biased cold currently at 1.12 megaohm on the grid, so I need to tweak that some. I am probably going to toss a pot in and use that to tweak things then measure to finalize values.



Please note R2 is in the wrong spot and needs to go after the capacitor as it is a grid leak for biasing.

I also want to get an ammeter in line with the plate on the 6aq5 and see what the current to ensure I am getting full power from it.

RF wise I am playing with toroids and LC circuits trying to get a good setup for my IF. Still ongoing and haven't settled on everything yet. Found out the green toroids I was trying to salvage and use were pretty well good from DC to 50khz when I needed 455khz or so.
 
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Spent probably two weeks troubleshooting this tube amp I was working on building, trying multiple designs etc. I've got a ways to go but am a hell of a lot closer at this point.



The tube with the blue corona is a 6AQ5 (pretty well a mini 6V6 for those of you who do the Guitar thing) and that's normal depending on the tube. Maybe I'll scale this up into a 6L6GC I have that I remember as doing it heavily, it sure looks cool. That said the driver was originally going to be a 12AX7 (may still be, haven't quite gotten there yet) but I stripped the circuit down to its bare essentials to test. I ran a function generator and some Perfect Circle through it, and it can be pretty damn loud for a single baby tube. Sounds good too.

The culprit that caused me to spend a week building, rebuilding and troubleshooting the circuit?





Two of these. They were what I had so I figured what the hell while I had more coming in the mail. They were originally for Classic Macintosh computer monitors and I'd salvaged them likely 15+ years ago but never put them to use. After looking inside the holes for the pins, it certainly seems as if the plate pin had flat out melted away on the inside. It certainly doesn't inspire confidence when you're talking 60mA at 250ish volts.

Now then, it makes me want to go back and try my original circuit and see if it works.
 
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Found this neat trick on the web, you can freehand a PCB using a Dremel with an engraving bit (105) that's kind of like a round ball. It works really well in actuality, I jammed this out in probably 15 minutes.



Here's a neat trick for getting hole spacing right. Get an old device with spacing for what you want and then use that to drill holes.



First holes drilled. More to go!



The capacitors snap in perfectly! Some of my calculations and plans on the book in the background. Ignore the holes I drilled in my notes in my haste to start this. :)



More holes, almost done. I'm going to reserve the other half for another part of the power supply I'm building.



Soldering on the first batch of stuff. I'm using some salvaged PC PSU diodes and capacitors. I have a lot of other parts on order to finish stuffing the board. Something interesting to me is that the solder tends to flow across the board probably because there is a lot of area in the "traces" and it takes considerable heat to get it up to temperature. I may play with that a bit by heating the leads first and then the board, but I think it's just the nature of this technique.



Ready for more parts, pending. $100 Digikey order en route and some stuff from Frys on order they didn't have.

 
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Found this neat trick on the web, you can freehand a PCB using a Dremel with an engraving bit (105) that's kind of like a round ball. It works really well in actuality, I jammed this out in probably 15 minutes.



Here's a neat trick for getting hole spacing right. Get an old device with spacing for what you want and then use that to drill holes.



First holes drilled. More to go!



The capacitors snap in perfectly! Some of my calculations and plans on the book in the background. Ignore the holes I drilled in my notes in my haste to start this. :)



More holes, almost done. I'm going to reserve the other half for another part of the power supply I'm building.



Soldering on the first batch of stuff. I'm using some salvaged PC PSU diodes and capacitors. I have a lot of other parts on order to finish stuffing the board. Something interesting to me is that the solder tends to flow across the board probably because there is a lot of area in the "traces" and it takes considerable heat to get it up to temperature. I may play with that a bit by heating the leads first and then the board, but I think it's just the nature of this technique.



Ready for more parts, pending. $100 Digikey order en route and some stuff from Frys on order they didn't have.

 

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Awesome thread, I can't wait to have space for my own home lab setup.



I'll grab some more pics when I get in the lab tomorrow, but here is the setup for testing a project I'm working on (with 3 other people).

 
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Interseting, the 3.3 and 5V makes me guess something digital, but 15V is kind of different. It looks like you've got a dev board with some form of analog output possibly via common rail op amps?
 

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Interseting, the 3.3 and 5V makes me guess something digital, but 15V is kind of different. It looks like you've got a dev board with some form of analog output possibly via common rail op amps?
You're on the right track! Basically, we are working with an industry sponsor to create a flexible battery backup system. Pretty much any battery can be connected, and you will get 120 VAC @ 60 Hz (15 A).

3.3V and 5V are for digital components.

15V is for some of the higher power semiconductor devices, particularly the gate drivers for the MOSFETs.

Small board in previous picture is not a dev board, but a PCB we designed from scratch, and I layed out personally. They actually just got delivered last Thursday, so we're still populating them and verifying/validating the components and sub-systems, but here's the current progress:



And when it's finished, it should look quite similar to this:



The "hockey pucks" at the top are two big-ass inductors, and the pitchfork things to the right of them is a heatsink for the MOSFETs for the buck-boost converter.



Those small boards are attached to a controller board (again, designed by us, layed out myself), which we didn't receive until yesterday morning, so we've only just begun populating it. Should be functional by tomorrow evening, Thursday at the latest.



When finished:



Microcontroller will sit on the pin headers in the center of the board. on the left side is the H-Bridge rectifier and its heatsinks, as well as the output LC filter (more hockey-puck inductors in the back).
 
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It's kind of awesome to see someone designing the exact OPPOSITE design philosophy than I am for a PSU; You're doing a high precision switch mode DC to AC while I'm doing a brute force linear AC to DC.

What freq are you using for the switching, and where are you sourcing your inductors from? I'll be curious to see what they look like in the end, even with a switcher I'd think they'd have a bit more 'iron" on them by looks alone. I would love to do something like this for an HV tube PSU eventually but probably not in the near future. That said, if I ever get to salvage a microwave with a switcher in it for the HV I may change my mind!

ED:awesome you're sponsored. I sure wish we were when I was going to school for EET.
 

Burtonrider10022

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It's kind of awesome to see someone designing the exact OPPOSITE design philosophy than I am for a PSU; You're doing a high precision switch mode DC to AC while I'm doing a brute force linear AC to DC.

What freq are you using for the switching, and where are you sourcing your inductors from? I'll be curious to see what they look like in the end, even with a switcher I'd think they'd have a bit more 'iron" on them by looks alone. I would love to do something like this for an HV tube PSU eventually but probably not in the near future. That said, if I ever get to salvage a microwave with a switcher in it for the HV I may change my mind!

ED:awesome you're sponsored. I sure wish we were when I was going to school for EET.
Agreed lol. The big reasons for the difference in philosophy are, I assume, the level of power we're going for, budget, and time/motivation.

- We need to supply up to 3.6 kW of power... do they even make op-amps that can handle that level of power? Switching was basically our only option.

- We're about $5k deep in this thing. Yay corporate sponsors!

- We've sunk easily over a hundred hours into this thing over the last two semesters, and need to complete it in order to graduate.


We are switching at 25 kHz.

Buck-boost inductors (2 in series): Invalid Request

Inverter filter inductors (2 in series on AC+, 2 in series on AC neutral): https://www.digikey.com/short/3nm4nz


Definitely don't let this deter you from doing a switcher of your own, though. We're just getting into higher voltages/currents (our dc bus is 200 VDC @ up to 15 amps), so shit is starting to get less straight-forward, component prices are skyrocketing, etc.

This is, however, looking like it will be an excellent stepping stone towards my graduate work, which is in power electronics (thesis will be on a 1 MW switching converter).
 
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Agreed lol. The big reasons for the difference in philosophy are, I assume, the level of power we're going for, budget, and time/motivation.

- We need to supply up to 3.6 kW of power... do they even make op-amps that can handle that level of power? Switching was basically our only option.

- We're about $5k deep in this thing. Yay corporate sponsors!

- We've sunk easily over a hundred hours into this thing over the last two semesters, and need to complete it in order to graduate.


We are switching at 25 kHz.

Buck-boost inductors (2 in series): Invalid Request

Inverter filter inductors (2 in series on AC+, 2 in series on AC neutral): https://www.digikey.com/short/3nm4nz


Definitely don't let this deter you from doing a switcher of your own, though. We're just getting into higher voltages/currents (our dc bus is 200 VDC @ up to 15 amps), so shit is starting to get less straight-forward, component prices are skyrocketing, etc.

This is, however, looking like it will be an excellent stepping stone towards my graduate work, which is in power electronics (thesis will be on a 1 MW switching converter).
1 meg of switching? holy shit you're a bad mother fucker. That is some big transistors.


https://www.digikey.com/product-detail/en/apex-microtechnology/PA50/598-1433-ND/1762092

3mhz gain bandwidth product, but 100A 100V input. That's a badass op amp.

It certainly wouldn't deter me from doing it, I'm willing to use my junk box stuff mostly. My thing is I'd be looking more for HV low current power supplies so I can feed my vacuum tube stuff, or perhaps high current LV high current for some filaments. Even that isn't that high, as I'm not running any broadcast station style tubes. If anyone has one or two I'm ears admittedly.
 

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1 meg of switching? holy shit you're a bad mother fucker. That is some big transistors.


https://www.digikey.com/product-detail/en/apex-microtechnology/PA50/598-1433-ND/1762092

3mhz gain bandwidth product, but 100A 100V input. That's a badass op amp.

It certainly wouldn't deter me from doing it, I'm willing to use my junk box stuff mostly. My thing is I'd be looking more for HV low current power supplies so I can feed my vacuum tube stuff, or perhaps high current LV high current for some filaments. Even that isn't that high, as I'm not running any broadcast station style tubes. If anyone has one or two I'm ears admittedly.
1 MW is retardedly huge. BUT, I'd be a fool to decline an offer to work on a project like that.

But just to put 1 MW into perspective, let's say that my converter has a 99% efficiency (which is nuts), that means it's still dissipating 10 KILOWATTS of heat energy. Which, because I decided I needed some way to quantify that, I've decided to calculate what that much energy would do to a swimming pool (avg residential above ground, 10-15,000 gallons) instead of working on what I should be.

10 kW of dissipated energy for 1 hour would increase the temperature of the pool water by 358 degrees Fahrenheit.

Jesus christ...




That is definitely a bad ass op amp (but it had better be for $500)

I'm pretty sure we'll be using Silicon Carbide (SiC) power semiconductors and IGBTs connected in series.

You can do HV stuff easily, current is the real bitch. Something else besides microwaves is a good source for those types of power supplies... I'll have to try to remember what it is.
 
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Actually if you want a random cool op amp go look up the OPA452s. The problem I ran into was the gain characteristic was different in inverting vs non inverting modes; I'd end up with extreme rolloff one way and not the other. It was really odd. Thoughts?

Here's the almost final rendition of my bias and lower high voltage board. There is a choke external to this, and I'm missing the Zener still.



Then I started on the next board. Some penciling to figure out where I want stuff to go. I drilled the capacitor holes first since they were going to be what I ended up working around.



Then I took the cutter to it.



Afterwards I populated it once again best as I could; I have a few extra holes because things were a bit tighter than I anticipated with the bleeder resistor for the capacitor; I may end up adding a couple to the other PSU as well, don't need to shock the crap out of myself working on this especially with the ability to disconnect the PSU from the radio.

 

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Soooo... Solar Roadways stopped by the other day with a couple of panels






Much larger than I had expected, but it makes sense for stability. The creators (the husband and wife from the video) seemed nice, and overall very enthusiastic about their idea. :dunno:
 

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My Thotcon badge has an ATMega microcontroller on it, so I think I'm going to use it to run a small obstacle-avoiding robot. :D

 

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Do any of you work for a company that manufactures custom boards by any chance, or know any places that do it in the Chicago area?

We just got a job to quote and part of the build is a pcb that needs to get made. We would populate it, we just dont have the ability to make boards here.
 

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Do any of you work for a company that manufactures custom boards by any chance, or know any places that do it in the Chicago area?

We just got a job to quote and part of the build is a pcb that needs to get made. We would populate it, we just dont have the ability to make boards here.
The boards I mentioned above were done by Sierra Circuits (https://www.protoexpress.com/) in CA . Great quality, would recommend.
 
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Soooo... Solar Roadways stopped by the other day with a couple of panels






Much larger than I had expected, but it makes sense for stability. The creators (the husband and wife from the video) seemed nice, and overall very enthusiastic about their idea. :dunno:
Guessing 800w the pair?
 
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My Thotcon badge has an ATMega microcontroller on it, so I think I'm going to use it to run a small obstacle-avoiding robot. :D

Coolest badge ever. Seriously.
 
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Progress on my power supply. My zener diode showed up today so I can finish wiring and hopefully not melt. Load testing to come I have a 225w 3k ohm resistor to load test with.



 
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I've been letting a lot of my stuff go to the way side the last year or so. That said, I was wondering if anyone had ever seen these? They look cool as fuck. I think I could program it using a standard serial port and a MAX232. They have a few flavors and they're about $10 each.

http://www.dorji.com/docs/data/DRA818V.pdf
 

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Do you have any use for ESD mats? We're going to be changing out some here at my work and if you don't mind older ones that are a little beat up or might need to be cut down to fit you would be more than welcome to them?

Definitely worth saving.
I work live all the time, and what I do is not really sensitive, it's still nice to have.

.
 

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Theyre long gone already... That was over a year ago. We replace the mats every so often because they get beat up with all the assemblies we do that we need to be grounded on.
 
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I've been letting a lot of my stuff go to the way side the last year or so. That said, I was wondering if anyone had ever seen these? They look cool as fuck. I think I could program it using a standard serial port and a MAX232. They have a few flavors and they're about $10 each.

http://www.dorji.com/docs/data/DRA818V.pdf
The modules showed up, they're the size of a one of the large postage stamps. (about 1"X3/4") and weigh in about 3.5 grams each. They're also designed to run off 3.3-4.5V which means that an 18650 (about 45 grams) will run one. A small weather balloon will lift about 160 grams. Regulation wise it seems like if it's under 4lbs of payload with weight to size ratio of 3 oz to a square inch your regulatory stuff is very minimal as well as a force of 50lbs max to separate the payload from the balloon.

I'm thinking a basic cross band repeater which could be made for the $30 vicinity would be pretty darn crazy to make up. Output power would be 1W each way. A single 18650 has around 8.88 Watt Hours with the 2400mAH version. If you were running it full bore and assuming you had to power the other RX and poor efficiency you could see 5-6 hours of continuous use being realistic and plausibly more if just beaconing.

The balloon and helium its self would be $40-50, so for well under a hundred dollar bill you could have a mini repeater you shot up. Add a bit of basic micro controller work and you could make it beacon too. I'd probably toss a PIC on it and be done with it.

Anyone do stuff with weather balloons before? Just thinking it may be something interesting to try a couple times.
 

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