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Zero VGS posted:Huh, I had no idea about that before. This is rad: https://www.americandetentionsupplies.com/collections/electronics Before you get too excited, like everything else about our prison system it's horribly exploitative and sad in its own special way, but it does look cool at least. Especially that CRT TV in that Techmoan video I linked.
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Apr 17, 2023 16:03
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Shame Boy posted:Re: plastics, I recently figured out that PVC plasticizers are used in enormous amounts (it can be something like 60% of the entire mass!) and constantly leak out as vapor, and will react with seemingly every other kind of polymer (especially platinum-cure silicones) to turn them into molten puddles. Try and guess how I became intimately familiar with this fact. I got a free beanbag couch off Craigslist one time, made from shreded memory foam. It was in perfect condition, but a whole bunch of other plastic/foam things I left on top of it wound up either discolored or disintegrated.
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Apr 17, 2023 16:07
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Shame Boy posted:Re: plastics, I recently figured out that PVC plasticizers are used in enormous amounts (it can be something like 60% of the entire mass!) and constantly leak out as vapor, and will react with seemingly every other kind of polymer (especially platinum-cure silicones) to turn them into molten puddles. Try and guess how I became intimately familiar with this fact. Oh. Oooooooh. Now i know why my silicone things get attacked by something even when not actually in contact with other silicone things, when they're in a drawer together with PVC things (not sketchy chinese import, just real european stuff).
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Apr 17, 2023 16:15
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PDP-1 posted:I have always wanted to find an excuse to throw my bosses money at a chip scale atomic clock. Mouser has one in stock for just $6,894.23. Only $2700 per if you order over 250+! Lol, that datasheet doesn’t even have the pinout. I wonder if I can get them by the reel
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Apr 17, 2023 16:46
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LimaBiker posted:Oh. Oooooooh. Now i know why my silicone things get attacked by something even when not actually in contact with other silicone things, when they're in a drawer together with PVC things (not sketchy chinese import, just real european stuff). Yyyyep. Silicone with silicone tends to be completely fine in my experience, never had a problem with two silicone things reacting, but PVC plasticizer gets anywhere near silicone and it's a puddle within like a couple days. Took me years to figure that out through trial and error (and eventually having it directly confirmed via a note from my silicone object supplier) but since then I haven't lost a single, uh, important silicone object. Whatever plasticizer polyethylene bags use (ziploc freezer bags, etc) seems to be benign to silicone, so if you wanna be extra careful you can put stuff in those to provide a barrier. Not sure if this is universally true so maybe put a cheap thing in first to test it but I've never had a freezer bag melt anything. Shame Boy fucked around with this message at 17:16 on Apr 17, 2023 |
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Apr 17, 2023 17:13
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Shame Boy posted:
TIL what a Darlington transistor array is. e: it's from a few pages back so to refresh, I'm trying to build a big panel of relays to make clacky noises as part of, well, let's say it's for an escape room, which is close enough to the truth. In researching the right kind of relay, I found this thing somebody had made with automotive relays and a 7-segment display: https://www.youtube.com/watch?v=7hHfkJLniqI Another Edit: the TI TPL9201 appears to be made for exactly what I'm doing... right? It looks like it might be a 5V voltage regulator for your microcontroller, plus a shift register possibly hooked up to a little circuit to deal with inductive load switching (or maybe not: for this application it doesn't matter if the relays bounce a little). So I would just hook 1 voltage output, and 3 data pins, of this puppy to my microcontroller, then wire a bunch of relays directly to it, and I have an art project? Edit 3: I reread replies: the diodes protect the IC. I can't not have the diodes. Edit 4: Oh, snap, I didn't understand what a Darlington transistor away was at all! This is the only thing I need! cruft fucked around with this message at 22:04 on Apr 17, 2023 |
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Apr 17, 2023 19:55
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Well, I spent all day learning about kickback voltage, Darlington transistor arrays, shift registers, and drafting up how I'd set all this stuff up, with 6 relays per SN74HC/ULN2003 pair, and daisy chain them with some sort of connector to send the 4 wires needed for the shift registers to cascade. Then I found this thing:  $16 on Amazon. So I guess I'll hook that up to an I2C I/O expander and call it a day, then.
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Apr 18, 2023 00:07
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Heads up, you will likely find a preponderance of older designs and technical info if you specifically search for darlingtons. Modern designs will generally use mosfets instead. (I think? Are darlingtons preferred for anything in 2023?)
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Apr 18, 2023 07:58
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cruft posted:Edit 3: I reread replies: the diodes protect the IC. I can't not have the diodes. The diodes protect anything connected to the relay coil. When the magnetic field in the coil collapses as it switches off, the energy stored in the field needs to go somewhere, and the diode allows it to just short circuit back to the other end of the coil without causing problems. If you didn't have the diode, the energy has nowhere to go and will instead create a huge voltage spike, one that could even get up into the low hundreds of volts if it happens fast enough, more than enough to fry the switching transistor or nearby IC's or all sorts of things. Think of it like water hammer - the coil is a long pipe with water flowing through it, the magnetic field is the water's kinetic energy and the transistor is a valve at the end you shut off really fast. Without anywhere to go, the water in the pipe will slam hard into the valve, try to dump all its kinetic energy, raise the pressure a ton and probably mess up your pipes. cruft posted:Well, I spent all day learning about kickback voltage, Darlington transistor arrays, shift registers, and drafting up how I'd set all this stuff up, with 6 relays per SN74HC/ULN2003 pair, and daisy chain them with some sort of connector to send the 4 wires needed for the shift registers to cascade. Yeah that'l work too 
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Apr 18, 2023 08:10
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cruft posted:
I have zero practical use for this but some part of my brains wants one so I can make it go clickity clack.
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Apr 18, 2023 08:17
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Here's a long article about the SRF-39FP Prison model radio, actually a pretty cool piece of engineering. https://www.newyorker.com/tech/annals-of-technology/the-ipod-of-prison
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Apr 18, 2023 11:42
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Bondematt posted:I have zero practical use for this but some part of my brains wants one so I can make it go clickity clack. Eh, just make yourself a Floppotron.
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Apr 18, 2023 18:19
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kid sinister posted:Eh, just make yourself a Clackotron.
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Apr 18, 2023 18:50
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I would like to take a moment to honor the design of the Nintendo Gamepad, which is nothing more than an 8-bit shift register, eight membrane switches in 4 pieces, two plastic housing pieces, 4 plastic button covers, and 4 screws.  They sold 61 million consoles. So probably over 150 million gamepads. Images lifted from iFixit.
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Apr 18, 2023 20:04
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I always liked how they did the strain relief with the internal posts. I've had a lot of hosed up cables in my life but never one from a Nintendo. Worst strain relief award goes to Apple, I've been dealing with their cables self-destructing for over three decades.
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Apr 18, 2023 20:23
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Hey there's also some carbon film resistors there. I'm a bit amazed by the complete lack of decoupling caps anywhere near the CMOS IC at the end of a long cable.
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Apr 18, 2023 20:39
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Stack Machine posted:Hey there's also some carbon film resistors there. I'm a bit amazed by the complete lack of decoupling caps anywhere near the CMOS IC at the end of a long cable. Yeah, after making that post, I noticed those, and had to do some more investigation about what the heck they were. Pull-up resistors, apparently printed directly onto the board! e: also check out those awesome traces, I didn't realize anyone was doing traces like that in 1983. cruft fucked around with this message at 21:07 on Apr 18, 2023 |
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Apr 18, 2023 21:01
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Zero VGS posted:I've had a lot of hosed up cables in my life but never one from a Nintendo. ...and then there's the Joycon thumb sticks. Absolute garbage.
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Apr 19, 2023 00:04
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Should I put copper fill on the top and bottom layers of my 4 layer pcb? The two inner layers have ground pours. It's a 2.4mm thick PCB with heavy copper (2 oz outer, 1.5 oz inner).    
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Apr 19, 2023 21:56
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You mean like, extra ground fill? No
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Apr 20, 2023 00:42
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OK, cool. Boards are in production! Wow, stencils really get you on shipping cost. $65 for shipping (plain stencils, no framework).
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Apr 20, 2023 07:43
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Where'd you order from=>to? OSH Stencils is $1.50/in^2 for unframed steel with $3 USPS shipping
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Apr 20, 2023 08:37
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Yeah the most I've paid for shipping stencils was like $20 and that was expedited shipping, what the heck.
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Apr 20, 2023 13:42
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I want to get a used server PSU to use as a 12v bench supply. The max load would be something around 50 amps which seems easy enough to get since plenty will do 100+ amps. What I want to prioritize is not being obnoxiously loud due to those tiny server fans; don't want to piss off my better half. Does anyone know a particular model that would operate very quietly? Should I replace the 40mm fans these all seem to use with Noctuas? I see 80-Plus Titanium models that look like they have a single fan, or lower-efficiency models that have side-by-side dual fans which maybe would allow a lower overall RPM.
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Apr 20, 2023 14:15
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Finished my headphones project! In a masterstroke, I figured out a way to get the audio from the right earcup over to the left side's input without running extra wiring across the headset. Can you guess how? I ran it through the unused microphone jack on the Astro headset, which goes across the headset to the TRRRS plug as "mic out", then i wired the "- - - RS" to the "-RR--" to loop it around from an output to an input:  I also sanded down the Astro A40 magnetic tags, then with Command Strips I bonded them to some translucent covers I made from a discarded Sterilite shoebox they had in the trash at Home Depot.
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Apr 20, 2023 17:03
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Zero VGS posted:I want to get a used server PSU to use as a 12v bench supply. The max load would be something around 50 amps which seems easy enough to get since plenty will do 100+ amps. What sort of high current / high power work are you doing? IME a 5A lab supply with adjustable voltage and current limit is much more useful (unless you already have that). And why, especially, do you want to use a server supply with 40mm fans? 40mm Noctuas move hardly any air. You can blow more air with your mouth than a 40mm noctua. I feel like you should have some solid requirements leading you this design choice, because these server supplies are not some easy to use, civilized lab supply, only bigger and cheaper. They're kind of a pain in the rear end.
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Apr 20, 2023 17:07
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I’ve used some server power supplies for stuff before, but never as a bench supply. The ones I used relied on the server to pull air through them, so I had to add whatever fans I wanted to the end. If you really want to use it, I’d suggest putting something like this in front of it, maybe? https://www.amazon.com/gp/aw/d/B089ND7PTH?psc=1&ref=ppx_pop_mob_b_asin_title As someone who started their electronics journey this way and with a 12volt battery, you’re gonna want the current limiting capability the linked thing provides.
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Apr 20, 2023 17:15
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ryanrs posted:What sort of high current / high power work are you doing? IME a 5A lab supply with adjustable voltage and current limit is much more useful (unless you already have that). Well, I have a PC that uses a "12V Only" motherboard and the CPU/GPU pull 500 watts, so it is mainly to run that and I need it quiet. But I'm doing work on some other projects at the same desk that also need some stable 12V, such as the laptop panel conversion I'm doing (the panel takes 12v at up to 4 amps to drive the mini-LED at HDR levels). It would be nice to have one item to handle it all, especially since I have to transport this stuff around. ryanrs posted:And why, especially, do you want to use a server supply with 40mm fans? 40mm Noctuas move hardly any air. You can blow more air with your mouth than a 40mm noctua. Server supplies only output huge amps at 12V which is exactly what I need, and they're very cheap to get and efficient (94% efficiency can be had for like $40 or less). If my PC and other electronics are drawing 500 watts, that means 30 watts of waste heat, which maybe a Noctua can manage without the supply overheating?
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Apr 20, 2023 17:28
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Seems like a really bad idea to run your PC motherboard and your electronics experiments off the same 12V supply.
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Apr 20, 2023 18:00
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I wouldn't run experiments off a supply that I can't limit the current.
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Apr 20, 2023 18:11
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I've tried to replace tiny loud fans with big quiet ones on a high current Meanwell supply. I designed some gorgeous 3D printed ducting, and spent tons of time speccing nice, quiet, relatively high CFM fans. It didn't work. Those little fans have like ten times the static pressure of anything else.
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Apr 20, 2023 18:26
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ryanrs posted:Seems like a really bad idea to run your PC motherboard and your electronics experiments off the same 12V supply. I learned a thing about relays disconnecting this week! Would now be a good time to talk about it?
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Apr 20, 2023 18:50
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ante posted:I've tried to replace tiny loud fans with big quiet ones on a high current Meanwell supply. I designed some gorgeous 3D printed ducting, and spent tons of time speccing nice, quiet, relatively high CFM fans. Good to know. Funny enough I have the Meanwell that is fanless, the HEP-600-12, but it only hits 40 amps. It has been running my PC for years now with an undervolt on the GPU, but if I try to run the GPU at stock or overclock the PSU will overload. So that's part of the reason I wanna upgrade the PSU, but I'm spoiled but this one being fanless. ryanrs posted:Seems like a really bad idea to run your PC motherboard and your electronics experiments off the same 12V supply. Fair enough, guess I won't try to double-dip.
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Apr 20, 2023 18:51
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a good workman always blames the tool, right? I am ready to blame my Hakko 888D but I need some advice to ensure I'm not an idiot. I am trying to solder an enormous metal shield on an RJ45 connector to a fill plane on my PCB. I can't seem to get enough heat into the connector or the PCB to make it not garbage cold joints. I think the iron is basically not responding fast enough. It seems to get 'cold' enough to no longer melt the solder straight off the roll in some situations after its dumped heat into the RJ45. Originally I was putting the THT into the reflow toaster to preheat the component. This worked in preheating and making it solderable, but sometimes caused SMD parts nearby to not reflow. It was pointed out to me that the enormous thermal sink of the RJ45 shield and the rest of the connector was probably sucking the heat away. I am using ChipQuik TS391 for paste, some sparkfun thing for solder roll, a Hakko 888D, a chisel tip, and I have to set it to an absurd 800F to get it to solder. heres a picture, you can see the hand soldered joints look like crap. USB-C shield, enormous blob next to R5, and RJ45 THT pins  Is dropping a lot of cash on a JCB CD-1BQF ($550) and a few of C245 tips ($150) smart? I am allegedly trying to make money on this and I want to buy a Good Tool and will pay good tool prices if I can resolve this problem and move on to something else.
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Apr 23, 2023 05:42
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Or spend 60 bucks on a hot air rework station to dump heat into it. https://www.amazon.com/gp/product/B08BK3M6YW/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
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Apr 23, 2023 05:56
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Preheating everything (not just locally with hot air) in the toaster oven is what I am doing now, and it helps for sure. I am having problems getting all 6 joints done before it cools off. I suppose I could put it through multiple trips of the toaster oven... I have a hot air station (ST-862) but getting heat into a bottom side component and soldering on the top side at the same time is impossibly awkward. I have also tried preheating the THT component by putting it on one of those USB-C hot plates, but I burned myself trying to get the hot RJ45 into the board, not a great time.
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Apr 23, 2023 06:11
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I use one of these IR ones and it works real well  https://www.amazon.com/Preheater-Rework-Station-Preheating-Infrared/dp/B07QKBQ717/ I don't see my exact one listed anymore but they're all basically the same design of a radiative heater and some way of holding the board over it. e: Also I've never had problems with the Hakko not being able to solder something like that, you sure the solder is properly wetting everything and you're getting good thermal contact?
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Apr 23, 2023 06:20
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Shame Boy posted:I use one of these IR ones and it works real well This preheater is a good idea, a lot cheaper too, this is a good tip and I am going to look into this. No I am not sure about anything. It seems to do fine with lil 0.5mm pitch SMD pads with just the core flux. I've got a wetted tip and using reasonable mechanical pressure to make contact. I could flood it with flux and see if that changes anything. All EING coatings. Back when I was doing leaded assemblies it was just fine, going lead free is what is causing me paaaaaaaiiiiin. I am suspecting the thermal contact between the heater cartage and the tip itself as being the problem horse_ebookmarklet fucked around with this message at 06:36 on Apr 23, 2023 |
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Apr 23, 2023 06:33
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Is this a situation where you are able to use tin-lead solder for those couple of joints? It has a lower melting temp than the non-lead stuff you're using.
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Apr 23, 2023 12:17
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Just as a basic troubleshooting step, are you actually changing the target temperature of the 888D, and not the calibration? Not that I've ever made that mistake. 
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Apr 23, 2023 13:50
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