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Shame Boy posted:Are you looking to build this with stuff you have lying around? Because they make optos that have totem pole outputs and ones that are specifically designed to drive MOSFETs, if you don't mind ordering a few. I'm okay ordering new parts if that's by far the best way, but I have a bunch of normal ones laying around - I have a bunch scavenged from power supplies - so if there's a decent way to do it with a normal one then that's the way I'd want to go. BattleMaster fucked around with this message at 21:33 on Apr 15, 2021 |
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Apr 15, 2021 21:30
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babyeatingpsychopath posted:DS18B120 are 1-wire sensors. I've got some, too. There's some jiggery pokery with resistors and stuff to get them connected. I never managed to have them "bus powered" where you can just use two of the three wires. It was always +5V connected, Gnd Connected, and a resistor between +5V and sensor, and the sensor wire connected to the monitoring device.  check the colour code
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Apr 15, 2021 22:03
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ante posted:
Oh. That didn't even faze me. I got six in a bag. Each one had a sticky tag with the color code for the wires on it. When I was lucky enough to have both red and black in the harness, it was still a 50/50 shot whether red was + or not. Black was always - when available.
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Apr 15, 2021 22:33
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Re DS18b20: Most on Ali and resold on Amazon etc are fakes, but should still work. Expanding on BEP's post: they nominally work with 3.3v, but in practice often need more. So, power it off the 5v line if you have one, and use a voltage divider to keep the signal line from overvolting 3.3v pins A/R. And make sure your driver can do the 1 wire protocol.
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Apr 15, 2021 22:57
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Yeah I had the pullup resistors and everything, I just looked at the wires and assumed well duh, black is ground and red is power and yellow is signal. Naturally.  Works fine now with the wires swapped. Dominoes posted:Re DS18b20: Most on Ali and resold on Amazon etc are fakes um no the seller assures me they are not 
Sagebrush fucked around with this message at 00:50 on Apr 16, 2021 |
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Apr 16, 2021 00:45
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BattleMaster posted:So I have a 24 volt power supply and I want to drive a DC motor with an optically-isolated logic-level PWM signal. So Shame Boy is on to something with gate-driver output optoisolators and along that "do it all in fewer parts" line of reasoning I'll add that you can also consider solid state relays, which are just optoisolators with built-in power FETs. The main trade-off is how long it takes to switch the gate on and off, which directly impacts how hot your FET will get. For that the isolated gate driver is faster than the BJT optocoupler and both of those are much faster than the solid-state relays. In a lot of applications, though, thanks to mechanical inertia you can run PWM frequencies of tens of Hz, so you can get away with even hundreds of microseconds of switching time without dissipating more than a watt or 2 in your FET (each time you switch on or off you burn the same amount of energy in the FET, so if you can do it at a lower frequency you burn less total power). If for whatever reason you want to use BJT-style optocouplers (it won't require a separate supply for your gate drive voltage, it might give you the cheapest total BOM cost I guess), you want to have the opto set up in common collector, like this:  If you only have 24V and can't get 5V for the MOSFET gate (or whatever your gate likes) and 24V is too much gate voltage for that FET, no problem, you can use a divider like this: 
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Apr 16, 2021 02:15
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Thankfully before I wasted money on brushes I discovered the windings on my treadmill motor had a couple open circuits... and a new one is $360. Time to see if this warranty is worth anything.
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Apr 16, 2021 03:23
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Stack Machine posted:So Shame Boy is on to something with gate-driver output optoisolators and along that "do it all in fewer parts" line of reasoning I'll add that you can also consider solid state relays, which are just optoisolators with built-in power FETs. The main trade-off is how long it takes to switch the gate on and off, which directly impacts how hot your FET will get. For that the isolated gate driver is faster than the BJT optocoupler and both of those are much faster than the solid-state relays. In a lot of applications, though, thanks to mechanical inertia you can run PWM frequencies of tens of Hz, so you can get away with even hundreds of microseconds of switching time without dissipating more than a watt or 2 in your FET (each time you switch on or off you burn the same amount of energy in the FET, so if you can do it at a lower frequency you burn less total power). Thanks! I have no problem getting new parts eventually, when I put in a larger order of other stuff I need, but I can whack one of those circuits together with what I have right here. The second one especially is something I didn't think of; I was going to add a linear regulator for the gate voltage but even better if I can just add a single resistor instead. Regarding SSRs, I was under the impression that they were just for AC, which I've used TRIAC-based ones for, but I went and looked and found DC ones. So that's great to know, that may open up a whole world for me. Some are able to drive high enough currents to switch the loads I'm interested in by themselves, too. So I'll go and give that circuit a try and eventually get around to replacing it with something better if needed.
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Apr 16, 2021 03:58
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TL;DR How do I map the buttons on the left and right of this board so as to interface them with an arduino? https://imgur.com/gallery/DupL12j So, I've decided to replace the internals of an older PC racing wheel controller with an arduino. There are various components I need to interface - 3 potentiometers, and 17 buttons. There are also 5 LEDs and a motor if I'm feeling up to it but they are not essential. The pots are under control, I have them wired up and reading on software. The buttons, well some of them are simple. But the others are in a keyboard matrix configuration I think as there are diodes and stuff in the circuits. In the linked gallery we have 5 golden pads across the top, and these are not matrixed - they have a common ground, and one pin (and wire going back to the mainboard) each. These buttons are not a problem. But the rest of the pads - the rectangle black ones do seem to be matrixed. I am not sure how to map these so as I can plug them into an arduino and write the decoding software. I've kinda probed around a bunch to no avail. There are no microcrontrollers on the board in the image, just resisters and diodes maybe and some headers and wires that go back to the main board. The problematic buttons correspond to a dpad, A B X Y L2 R2 buttons on the front. The ones across the top that are not matrixed are L3, R3, Start, Select, and a custom MODE buttons. I'm not really 100% sure what my next step is here. Edit: are my continuity probes unsuccessful because maybe I need to be driving one pin with 5v to overcome the resistance or something and my multimeter continuity probe isn't giving it 5v? Edit 2: So if I plug it all back together to the original circuit and turn it on, I should be able to find which pins are held high and which are held low with a voltmeter! klen dool fucked around with this message at 03:13 on Apr 18, 2021 |
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Apr 18, 2021 02:34
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I don't know how familiar you are with key matrix so maybe this is redundant info, but I found this page is helpful and complete with diagrams and code examples. Hmmm, also not sure what the next step is but that circuit board looks tricky to understand. Just from looking at it for a couple minutes, I keep getting lost in the through holes in the middle. Not sure how those might be connected without a picture of the backside. Maybe a good next step would be to map out how the key matrix is laid out by recreating that portion of the schematic on a separate piece of paper. If the matrix consists of the dpad, ABXY, L2, and R2, then I guess there are also at least 7 (4x3 or 3x4 = 12 buttons, the smallest rectangular number >10) wires coming out of that board that are intended to go to some microcontroller on another component in the wheel. If that's the case, then if you can identify those wires and hook them up to the Arduino instead, you can basically copy and paste the code snippet from the link and be able to read the input. If I'm not remembering things wrong, the good news is that you don't have to map out all 10 buttons before you can test if things are working. You can start with one button and try to figure out which wire connected to it is acting as col and which is acting as row and then drive those two wire with the Arduino and short the button of interest to test things out while ignoring all the other buttons. I tried a little here:  It appears the leftmost 4 buttons are wired together on the same row (highlighted in red/orange). Past the black rectangle things, are what I think are 4 column wires coming out (highlighted in dark blue, light blue, yellow, and purple). I put ??? where I completely lost where the traces were going. Cory Parsnipson fucked around with this message at 03:33 on Apr 18, 2021 |
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Apr 18, 2021 03:14
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Hey i figured you guys might be able to help me with this. Couple of years ago my surround system crapped out and its been sitting in my attic ever since. I figured i might be able to revive it so i took it apart. I found a couple of loose solder spots (thats the danger of putting all the electronics in the subwoofer i guess) that i fixed and one MOSFET that seemed to have a bad day: Can anyone help me identify what kind of MOSFET this is? I only have a rough understanding of this stuff so i only know that the manufacturer seems to bee Fairchild? I took a photo of the only markings i can find on this thing:  Anyone got an idea what i can replace this thing with?
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Apr 18, 2021 12:02
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That's a D880, which is an NPN bipolar junction transistor. There are a few equivalents out there with various part numbers. The KSD880O is readily available on Mouser (and probably a bunch of other places, that's just the first place I looked) for 97 cents. It'll probably cost 10x that in shipping these days to get one, but such is the way of things. https://www.mouser.com/ProductDetail/ON-Semiconductor-Fairchild/KSD880O?qs=ljbEvF4DwOOZPPpKFWQm1g%3D%3D
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Apr 18, 2021 13:15
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Acid Reflux posted:That's a D880, which is an NPN bipolar junction transistor. There are a few equivalents out there with various part numbers. The KSD880O is readily available on Mouser (and probably a bunch of other places, that's just the first place I looked) for 97 cents. It'll probably cost 10x that in shipping these days to get one, but such is the way of things. Thanks a lot. Sadly it looks like no one in europe ist selling the KSD880O so my only way to get it would be to pay 20€ in shipping to get it from the US which...is not fun. I'm guessing there are several types of D880 transistors? I've been seeing D880-y for example. Would it be fine to find any D880 with comparable specs (voltage, current, etc) and use that? Does the other number on it (the 203) signify anything important? Shai-Hulud fucked around with this message at 14:06 on Apr 18, 2021 |
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Apr 18, 2021 14:04
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Mouser and Digi-Key have fairly low free shipping limits, I'd just find random other poo poo to buy (Digi-Key has a not terrible selection of hand tools, for example).
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Apr 18, 2021 14:23
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... do they though? I don't think I've seen free shipping on any order I've placed in the past 10 years, some small some pretty large. I think digikey used to have a fee if the order was below some threshold back in the catalog days, but I don't recall the shipping being free.
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Apr 18, 2021 15:09
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They do $100 orders free shipping to Canada.
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Apr 18, 2021 15:16
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It's 50€ for free shipping as far as is can tell. Don't really feel like doing that for a 0,80€ part though.
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Apr 18, 2021 15:31
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AliExpress will have loads of BJTs too, or Amazon. Maybe those exact ones, but more likely some decent equivalents if you compare datasheets
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Apr 18, 2021 15:51
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FML the rumors about MCU shortages are now pointing at 2023. I redesigned part of a board to use a diff footprint that came into stock on JLC, but it's now out of stock too*. ** Digikey still has some stuff available if you're willing to be flexible about footprints and variant, for STM32. I'm glad I embarked on that multi-family HAL project; may get to test this functionality soon! Want to try L5 as the new hotness (despite U5 being poised to supercede it), and G0 for the new cheapness on simple projects. The new families are sometimes no longer pin compatible even if you keep footprints though. * Switched from QFP to QFN. TBH I find QFN better/easier since the pins don't bend, and solder bridges can't form high on the pins. The adv of using JLC for the parts over Digikey etc is you don't have to hand-solder MCUs, and it's cheaper. Dominoes fucked around with this message at 16:22 on Apr 18, 2021 |
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Apr 18, 2021 16:17
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Shai-Hulud posted:Thanks a lot. Sadly it looks like no one in europe ist selling the KSD880O so my only way to get it would be to pay 20€ in shipping to get it from the US which...is not fun. I'm honestly not sure what the 203 signifies, maybe a batch number or manufacturer ID or something. But as far as a substitute goes, as others have mentioned, anything with similar specs would be just fine. After doing a little reading up, that seems to be an really generic amplifier transistor and there are a shitload of compatible part numbers. https://www.el-component.com/bipolar-transistors/2sd880
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Apr 18, 2021 16:28
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The silkscreen number seems to be referencing 2SC3421 https://alltransistors.com/adv/pdfdatasheet_toshiba/2sc3421.pdf Quick search of Mouser leads to 2N4922G as a somewhat close match to 2SC3421. Didn't check the datasheets thoroughly. If you end up buying 2N4922G be careful of the orientation as the pin order seems to be reversed compared to the D880. Not sure why the silkscreen reference is so vastly different to the D880 that is installed; they may have up-sized during manufacture? better power dissipation? Closest equivalent I could find to KSD880O is TIP29A, but it's not a great match (VEBO is 5v not 7v, and the DC current gain maxes out at 75). For low quantity orders I try to use RS Components; the individual part cost is relatively high, but shipping is free and total cost usually comes out cheaper in relative terms. For example https://au.rs-online.com/web/p/bipolar-transistors/1844962/ 20 units total cost $16.30 which is relatively expensive but I would avoid $30 to $40 dollars shipping to the land of snakes and spiders.
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Apr 18, 2021 16:33
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Acid Reflux posted:I'm honestly not sure what the 203 signifies, maybe a batch number or manufacturer ID or something. But as far as a substitute goes, as others have mentioned, anything with similar specs would be just fine. After doing a little reading up, that seems to be an really generic amplifier transistor and there are a shitload of compatible part numbers. That site is super useful. Thank you! I've found some that have the same specs and are available here. Here's to hoping this actually fixes the thing!
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Apr 18, 2021 16:34
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Acid Reflux posted:I'm honestly not sure what the 203 signifies, maybe a batch number or manufacturer ID or something. Usually manufacture date. Does 2nd quarter of 2003 seem reasonable for this part?
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Apr 18, 2021 16:58
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Dominoes posted:FML the rumors about MCU shortages are now pointing at 2023. I am getting completely hosed, professionally, by the shortages. Just bought up the world's supply of a critical part directly from the MFG, in the hopes that it will tide me over until October.
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Apr 18, 2021 17:02
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ante posted:Just bought up the world's supply of a critical part directly from the MFG, in the hopes that it will tide me over until October. FYI I own stock in STM, TI, AD, and Maxim.
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Apr 18, 2021 17:06
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Dominoes posted:There's also speculation that this sort of speculation is the real cause of the shortage! Yeah, like many things in economics, human psychology matters, and just believing that something is true can often make it true. I wish electrical engineering worked like that too . . . What kinds of components are really getting hit by the shortage? Is it limited to only certain kinds of parts/foundry products, or is the shortage happening all over the industry? silence_kit fucked around with this message at 17:21 on Apr 18, 2021 |
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Apr 18, 2021 17:19
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Dominoes posted:There's also speculation that this sort of speculation is the real cause of the shortage! I bought 16,000, and I've already used 4,000 of those! It's not speculation! silence_kit posted:Yeah, like many things in economics, human psychology matters, and just believing that something is true can often make it true. I wish electrical engineering worked like that too . . . I have a couple (nonmicrocontroller) ST parts that are challenging, and then also just ran into some issues with (also nonmicrocontroller) Microchip parts. The Microchip stuff comes from Thailand, which I don't even think has been hit by a lot of the natural disaster stuff going on, like Texas's libertarian power problems, or Taiwan's drought. I guess the combination of people switching to Microchip stuff due to other shortages, electric car manufacturing ramping up, and the pandemic are also big problems.
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Apr 18, 2021 17:40
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Shai-Hulud posted:Hey i figured you guys might be able to help me with this. Couple of years ago my surround system crapped out and its been sitting in my attic ever since. I figured i might be able to revive it so i took it apart. I found a couple of loose solder spots (thats the danger of putting all the electronics in the subwoofer i guess) that i fixed and one MOSFET that seemed to have a bad day: By the way, if your transformer in this is separate from that main board and it's easy to get a multimeter on it, maybe connect the transformer secondary to the multimeter in AC volts mode, plug it in, and poke/jostle it a bit to make sure the voltage doesn't suddenly jump up to 240. I say this because the last time I encountered some burned-out parts in an amplifier like this and replaced them, they continued to have this odd habit of occasionally burning out when nobody was around*. Years of head-scratching and occasional repairs went by but eventually the event happened while I was watching the supply on a multimeter with the case opened and it was very clearly an isolation failure in the power transformer. It was a dangerous condition that could have shocked somebody and now I’ve added "giant power transformers for audio equipment" to my list of things that can fail in absolutely terrifying ways. * yet another reason to turn things off when not using them.
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Apr 18, 2021 18:14
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silence_kit posted:What kinds of components are really getting hit by the shortage? Is it limited to only certain kinds of parts/foundry products, or is the shortage happening all over the industry? The SMT assembly service I use (JLC) is out of nearly all STM32 variants - this was not the case about a year ago. Western sellers like Digikey and Mouser have a much smaller inventory of these than before, but have enough variants available to get by if you're flexible. Most of the other ICs I use are still in stock at both, with some exceptions.
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Apr 18, 2021 18:24
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Dominoes posted:I offer a rumor: It affects broad ranges of ICs. And an anecdote: It mainly affects MCUs. Soon Ambrose Burnside will rule the world with Baghdad batteries and cat whisker detectors!
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Apr 18, 2021 19:29
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I just wanna throw out in this thread that there are no automatic shower cleaners. Scrubbing bubbles used to make one for $25, it wasnt reliable at all, and it now sells for $200+ on amazon. If anyone in this thread makes one, if you'd like, I volunteer to contribute my knowledge in hardening electronics to humidity (been part of 15+ MIL-STD-810 10 day cyclic humidity tests), mechanical system design and systems engineering for free. I'll be the first person on kickstarter and kick in $1000 for a couple working prototypes if I like the design. I'd make one myself but I am very entrenched in my own startup right now and also starting to have the "maybe we'll have kids soon" chats so its no time for
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Apr 18, 2021 19:39
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That's in my lane, and I like the idea, but need to wrap up 2 other projects first. I work best when not attempting too much at once. e: For a dispensing mechanism, do you think the right approach involves a spherical nozzle with variably-spaced holes around the whole thing? e2: Briefly, do you think complete water and moisture-proofing is the right approach? Maybe O-ring-based? Maybe a user-openable dynamic O-ring for when the device isn't in use so it can dry out should anything get in anyway? Dominoes fucked around with this message at 19:48 on Apr 18, 2021 |
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Apr 18, 2021 19:41
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Dominoes posted:That's in my lane, and I like the idea, but need to wrap up 2 other projects first. I work best when not attempting too much at once. My experience has been that you can never keep moisture out of a sealed enclosure of substantial volume, and that generally drain holes are the right approach. Whether o rings are appropriate is a big it depends. I’d try to find an inexpensive commercial nozzle first and make as few custom parts as possible. Like something on a cleaner spray bottle. My first thought was a small submersible pump where the pressure from the pump both rotated the nozzle 360* and sprays. Trigger it to run on a timer. That said I’m not sure if that’d actually work or if there’s some oversight there. EDIT: On 2nd thought I'd make the smallest PCB I can and then pot the thing, mounting it high with any wires coming out assisted by gravity and having a drip loop. EDIT2: Hmm tempting: https://www.ebay.com/itm/DC5V-USB-L...5.c100010.m2109 CarForumPoster fucked around with this message at 23:02 on Apr 18, 2021 |
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Apr 18, 2021 22:46
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How would you make an automatic shower cleaner that doesn't just get water everywhere all streaky and gross. How would you get it to actually scrub things? So many unanswered questions.
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Apr 19, 2021 02:33
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CarForumPoster posted:My experience has been that you can never keep moisture out of a sealed enclosure of substantial volume, and that generally drain holes are the right approach. Whether o rings are appropriate is a big it depends. M_Gargantua posted:So many unanswered questions. Dominoes fucked around with this message at 02:43 on Apr 19, 2021 |
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Apr 19, 2021 02:37
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I have some experience in industrial tank cleaning and my advice is if you want to automate cleaning you're going to want to design the shower around it vs trying to come up with an appliance. For a self cleaning shower system your customer is going to be contractors renovating bathrooms for nouveau riche types who don't want to hire help. It's a business to business product unless you want to market them directly and then sub out the actual installs. You might be able to tap into institutional new construction too.
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Apr 19, 2021 03:17
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Forseti posted:Soon Ambrose Burnside will rule the world with Baghdad batteries and cat whisker detectors!
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Apr 19, 2021 03:29
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what the gently caress is a self cleaning shower
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Apr 19, 2021 03:32
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In all seriousness, I want to make tiny or small mesh robots. They don't need to self-replicate or anything. They should probably walk on the ground with legs, perhaps according to carcinisation. Maybe have one remote-controlled, and the rest swarm around it within a certain distance. They could have different claws, like cameras operating at various wavelengths, welding torches etc.
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Apr 19, 2021 03:43
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ante posted:what the gently caress is a self cleaning shower It was this thing that used to be advertised on TV (this is a news channel review of it): https://www.youtube.com/watch?v=_S1aOSY1eN0
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Apr 19, 2021 03:45
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