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His Divine Shadow posted:That sounds good, I bought a bunch of them as well as rear indicators and brake lights and so on. This car is so old (1990) it doesn't have any of that fancy stuff like PWM dimming. I meant PWM dimming inside of the bulbs themselves. Some of them, especially the ones that replace 2-filament bulbs use 100Hz or so PWM dimming. It's one of those things most folks don't mind but you can definitely learn to see it. His Divine Shadow posted:Unrelated question, I asked it before but the project never took off and I am looking to reboot it. I have an old 4A variac from east germany that I want to build an enclosure for. I need to varnish the windings in places but all my local electronics store carries is an expensive spray can that's 2x the cost of a regular spray can of lacquer. Is there any reason for me to buy the more expensive stuff? If it's already going to be in a box and there's nothing near the windings for them to arc to, I wouldn't worry too much about insulating coatings. There's already a big area of exposed windings on the top of it for the wiper to contact so if your box is safe for that it should be safe for scuffs, etc on other parts of the coil. Unless those are in contact with mounting hardware or something, in which case I'd cut a piece of vulcanized fiber or other insulating sheet to glue to the mounting hardware to insulate it.
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Oct 11, 2023 13:56
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I am working on a project for a client where we will make some interactive challenges for a bicycle course intended to teach kids better bike control. Each obstacle will have some ledstrips or lights, a microcontroller and some sensors and things, maybe a loud buzzer if you do it wrong etc. Challenges like riding a piece of the course as slow as possible, or looking over your shoulder to see a random color, and then pressing the right colored button as you bike past, or a stoplight that sends you in a random direction on an intersection as you approach it. So it will be a bunch of fun and pretty simple little projects that just need to be sturdy and easy to use and set-up.  Anyway, these challenges need to work on battery power, and I was wondering if any of you guys know of any pre-existing easy to use systems, where it would be simple to charge the batteries at the end of the day, and to bring a couple extras if needed and swap them if one of them is drained or whatever. First thing that came to mind was maybe using 18v power tool battery systems, but I thought I'd check if anyone already did similar things.
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Oct 12, 2023 15:54
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Whenever I need simple, easy to use prepackaged battery power, I just make the thing run on 5V USB, cuz you can get USB battery packs for phones basically everywhere for cheap, some with enormous capacities, and they're designed to be used and charged by the general public so they're pretty darn safe as far as batteries go. e: It also makes powering the thing while you're debugging it or programming it or whatever trivial too since you can just... plug it into any available USB thingy, which the modern house has thousands of. Shame Boy fucked around with this message at 16:01 on Oct 12, 2023 |
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Oct 12, 2023 15:58
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All my addressable leds and such would be 5v anyway, so that does seem like a real good idea. should have thought of that  thanks
ekuNNN fucked around with this message at 16:26 on Oct 12, 2023 |
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Oct 12, 2023 16:17
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Pham Nuwen posted:
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Oct 12, 2023 17:57
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Captain Cool posted:I'm not sure what you mean by this. Can you find an example? They probably mean these things: 
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Oct 12, 2023 17:58
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I have a PCB I want to design which is 15x10cm, has mounting holes spaced 81mm on X and 122mm on Y based on measurements I took of the destination existing mounting standoffs. I'm struggling to figure out the best way to precisely position these on my PCB. I have leeway for exactly where on the PCB these are positioned, but with reference to each other, the four screw holes have to be at (X,Y), (X+81,Y), (X, Y-122), (X+81, Y-122). If this were a trad CAD program I could probably do this fairly easily just offsetting the first screw hole from board edge 0,0 then offsetting the next +81mm from first's midpoint, etc. Here I'm sort of struggling to figure out what my workflow should be, or if those kinds of tools work I just haven't managed to find them. At first I tried the "place origin point" tool on the (0,0) of my edge cuts rectangle but footprint placement doesn't seem to reference from that origin unless I'm doing something wrong. Then I moved my board to 0,0 and just started adding footprints and manually editing their x,y but I'm sort of getting lost in the math after the first trying to keep them fairly centered on the board (which is a solvable problem, if this is the way to go) and to making sure the holes are exactly where I need them. I think I may have articulated the problem horribly but hopefully you can gleam what I'm trying to do. e: For the record I've played around with both just creating circles on my edge cuts layer and adding a specific mounting hole footprint which is probably the way to go. So I guess the question that REALLY brings up is, can I place a footprint with specific x,y reference to another? e2: Literally 30 seconds after I posted this I found "right click -> positioning tools -> position relative to" some kinda jackal fucked around with this message at 18:08 on Oct 12, 2023 |
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Oct 12, 2023 18:00
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You sure you're placing the grid origin and not the drill origin or something else? Cuz placing the grid origin always works for me exactly like you'd expect...
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Oct 12, 2023 18:08
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Shame Boy posted:You sure you're placing the grid origin and not the drill origin or something else? Cuz placing the grid origin always works for me exactly like you'd expect... Probably the drill origin, I honestly just expected the drill origin and grid origin to be the same for some reason. e: Yep "place origin for drill files and component placement files". I didn't realize you could select grid origin off the same icon. That's super useful to know, thanks!! e2: OK something's not working, I'm selecting grid origin and the top of my rect but somehow I'm still not seeing that as 0,0. I'll figure this out though, guessing I'm just doing something wrong. I think I have my workflow to finish set!  e3: Yeah, changed origin from page to grid origin in preferences and I'm good. This is what happens when you learn just enough of a tool to be dangerous to yourself 
some kinda jackal fucked around with this message at 18:52 on Oct 12, 2023 |
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Oct 12, 2023 18:10
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Shame Boy posted:They probably mean these things: Exactly! It looks like I can just get guitar amplifier pilot lights for about $10 each, but they're 6V incandescent bulbs which is less convenient. I'm also just playing with some cheapo LED panel-mount lights from Amazon to see how bad they are.
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Oct 12, 2023 20:55
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some kinda jackal posted:Probably the drill origin, I honestly just expected the drill origin and grid origin to be the same for some reason. Ah right sorry, I was thinking after I posted that "isn't there some setting you have to set too..." but I set that up like well over a year ago and haven't had a reason to change it since so I couldn't remember for sure 
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Oct 12, 2023 21:10
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It's all good! You got me to investigate which led me to the answer. Perfect setup for a dunk.
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Oct 12, 2023 21:15
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Shame Boy posted:Whenever I need simple, easy to use prepackaged battery power, I just make the thing run on 5V USB, cuz you can get USB battery packs for phones basically everywhere for cheap, some with enormous capacities, and they're designed to be used and charged by the general public so they're pretty darn safe as far as batteries go. One gotcha is that most of these portable batteries will turn themselves off if the current draw is too low, which always causes me problems. Make sure you leave a few LEDs always on and you should be fine.
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Oct 13, 2023 00:41
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Splode posted:One gotcha is that most of these portable batteries will turn themselves off if the current draw is too low, which always causes me problems. Make sure you leave a few LEDs always on and you should be fine. Good to know, thanks!
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Oct 13, 2023 22:14
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Well it all went on just fine. Not my finest work on the first few smd components, it’s pretty rough around that bank of caps and the diode, but it passes continuity tests and I can’t find any shorts. The tiny quad resistor array proved to be the easiest, strangely enough. Everything attached:  The brain in place:  I’m a little bummed I didn’t catch the micro sd card clearance, it would have been so easy to throw a couple extra mm in there. Turning the rpi around would have been more of a hassle but also probably the smartest choice. Anyhow, it does fit, but it’s pressing pretty solidly. Hopefully that doesn’t cause any trouble down the road. If it works well enough to get the whole thing running, I probably won’t bother to redo. Next step is to slam 120VAC in there on the left and see if any smoke escapes. e: No smoke and the pi boots! Huge success so far. Bad Munki fucked around with this message at 02:56 on Oct 14, 2023 |
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Oct 14, 2023 02:06
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I'm building out a button box for flight simming utilizing a Teensy 4.0, and I want to use a 4-way switch for one of the inputs. My VKB STECS throttle came with some swappable components, including several 4-way hats with push button functionality. I figure I could just re-use one of those for my button box. The thing is, I'm not really sure how they've set things up on their breakout pcb. The component they're using is an 8-way RKJXM1015004 switch, but I think it can only be configured as a 4-way switch + 1 button in their software. The tricky part is that they connect it up with three wires, and I don't know how they're determining which way the stick is being clicked. There's no other ICs on the PCB, only resistors, so I'm guessing it has something to do with measuring current or voltage on one or two of the pins. I'm pretty sure the bottom pin near R3 is ground? My electronics knowledge is fairly limited, so I'm not really sure how I would go about reverse engineering this thing. I've tried poking around a bit with plotting output on some of the pins of the teensy, but I'm probably not doing the correct thing because it seems to be mostly garbage data. I could order just one of the switches and wire it up without using the PCB, but that's not quite as fun and I wouldn't learn as much.  
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Oct 14, 2023 05:20
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Do you have a multimeter? Poke around in continuity mode and draw out a schematic. Things become more obvious when you can see that.
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Oct 14, 2023 05:29
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Poked around and put these together. Gonna stare at it and see if it reveals its secrets to me 
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Oct 14, 2023 06:51
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Ah geez I hate when they do clever analogue voltage stuff with switches to save wires. I get why they do it, but it isn't very elegant or robust, and it's often a real pain to reverse engineer.
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Oct 14, 2023 07:06
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Yeah, that does look like some analog bullshit that you'll have to build a table of, and the corresponding switch closings. One comment is that I'm sure you've missed a connection between switches A and D
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Oct 14, 2023 07:11
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Pham Nuwen posted:Exactly! 6.3V is a common side tap for tube powered equipment, like guitar amps. I restore old radios. Any bulb over 3 volts these days will most likely have a drop in LED replacement. Most will fit in the housings for those old bulbs. Also, bulbs aren't picky about AC or DC. Most of those LED replacements will take a range of input too. You might just be able to drop them in and have them work. edit: Honestly, I'd just google "pilot lamp" and find one that you like. They come in all sorts of shapes and colors. kid sinister fucked around with this message at 22:39 on Oct 14, 2023 |
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Oct 14, 2023 22:31
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Hi, I'm trying to do electronics and have no idea what I'm doing. So my state right now is I have a raspberry pi zero, the pi-blaster thing to control GPIO pins, and a couple of servos. I managed to get one of the servos to whirr one time, but now I can only persuade it to twitch in an annoying fashion where I'm not sure if it's even heading for the angle I'm trying to set it to, or just twitching in place. I was doing the thing that seems to be half and half "this is fine" or "don't do this everything will break"; powering the servo straight off the 5v pin. Maybe that's my problem, maybe the servo sucks, maybe both. It's definitely using the expected GPIO pin, because it stops twitching if I set that output to steady off or steady on. At this point I'm thinking I probably didn't really want to be using servo motors in the first place, they seem finicky and I now gather quite sensitive (a lot of people saying they'll jitter if your signal isn't perfect, and you won't get a perfect signal out of a pi because interrupts etc. - I'm running a low-end pi with also a camera at the same time so I expect my signal quality is not going to be the best). For my use-case I don't really need "point this way" I just need e.g. "turn left this much" which seems like a better fit for a plain old motor with "high torque low speed" gearing, where if the signal update is delayed by a millisecond or two it just turns slightly more than you wanted and that's fine. (I realize it sounds actually like a job for a stepper motor but I think that leans towards the "annoying signal" problems again, and also costs more - I'm fine with software-timing-based imprecision here.) But then it looks like I probably need some extra hardware in the middle because a motor is just "you got this voltage and amps and now you spin" two-wire input, and there's no direct control over that sort of thing from a pi. So I think I'm looking at a TB6612 as a controller for two motors, and maybe these motors, but then I'm lost when it comes to this: "Just make sure they're good for 1.2 Amp or less of current, since that's the limit of this chip"; what controls the amps going to a motor in this situation, and how do you know what amps a motor is "good for"? Is it feasible to power such motors from the pi's 5v pins (perhaps with a capacitor on there to reduce brownouts) or do I have to introduce another power supply brick here? Is there some sort of thing people typically use for this purpose, like something with a USB-out to power a pi *and* some basic "act like a set of batteries" wires? All the example projects I see using motors put actual bundles of batteries into their things, which I'd really rather not. Also, is there a simpler control method for this task, given I don't really need speed controls? I think maybe an L293D can do it (and also has PWM speed controls!) but maybe I'd just be making my life more difficult as that thing seems like it maybe needs me to understand the electronics more. Or maybe it's literally the same thing just with bare spike-things instead of pins that aren't even soldered on anyway? (The totality of the project is a remote-controlled remote-aimed water-pistol turret, essentially.)
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Oct 14, 2023 22:52
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roomforthetuna posted:Hi, I'm trying to do electronics and have no idea what I'm doing. It sounds like you're trying to solve all of the problems at once. I suspect that servos are the correct choice if your goal is to make a pan and tilt mechanism for a turret, one servo for pan and one for tilt, and then some switch to fire. There's a lot of servos that can handle different amounts of torque and while they get more expensive the more they can move, it sounds like you're still in the hobby grade RC servo realm unless it's a truly massive water gun. Most servos have three wires. Power, ground, and a signal wire. In your implementation I would not try very hard to get power from the raspberry pi's GPIO pins but just worry about signal. If it doesn't work well after trying it out, only then would I look to a controller board for servos or maybe just a microcontroller you can send commands to from the Pi since you're using that for your camera. For power, I'd prototype it using whatever you want to use (if you use two independent power supplies the grounds will need to be tied together or the servos won't work correctly), and then finalize it with a larger power supply and a buck converter for the Pi and tie the PSU directly to the servos. For example, you could use a 12v wall wart that can do enough watts when sent through a buck converter for the Pi plus the current draw for the servos. You can buy little buck converters on amazon/ebay/aliexpress/wherever or even do something like (for a 12V source) crack open a USB car charger to get the 12V to 5V adapter inside for the Pi. The exact power requirements will depend on what raspberry pi you're using (since the newer ones tend to draw more current than a normal USB device) and what servos you use. As an example here are some metal geared servos that take 6-7.2 volts input, typically used for RC stuff. You could still use a 12V power source with them with an appropriate buck converter (I'm not saying to buy these, they were the first result on amazon): https://www.amazon.com/4-Pack-MG996R-Torque-Digital-Helicopter/dp/B07MFK266B/ Here's a pile of buck converters you adjust with the screw head on the potentiometer with a max output of 3A: https://www.amazon.com/LM2596-Converter-3-0-40V-1-5-35V-Supply/dp/B08NV3JCBC/ You'd adjust those by hooking a multimeter (in dc volt meter mode) to the output and adjust until it hits the voltage you want. The same amazon listing has an option for a larger model with a LCD display on it to display the output voltage as well, which can be nice but are slightly larger. I use one of those in my 24V 3D printer to drop voltage to 12V for some quieter fans. Anyway for your first step I'd get to the point where the Pi is controlling your servo. That will be the main thing your program needs to be able to do to make the rest work. You can set that up with just the Pi and one servo to start but you may need an separate power supply for the servo (and tie the grounds together if you do it this way). That's just to get started, though, you can't do everything at once. Rexxed fucked around with this message at 00:38 on Oct 15, 2023 |
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Oct 14, 2023 23:48
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Rexxed posted:Anyway for your first step I'd get to the point where the Pi is controlling your servo. That will be the main thing your program needs to be able to do to make the rest work. You can set that up with just the Pi and one servo to start but you may need an separate power supply for the servo (and tie the grounds together if you do it this way). That's just to get started, though, you can't do everything at once. I did some multimeter tests on the pins to ensure that they have the expected voltage, and the pi doesn't die when the servo starts doing stuff, which I assume means the servo isn't draining so much power that it's causing a problem, but it's also not working. My multimeter doesn't have frequency analysis capabilities so I can't tell if the signal timing is right, but I *can* tell from the command-line (raspi gpio get 14) that it is on/off proportional to the expected amount. I guess I do have three servos so I could try connecting different ones to determine whether it's the pi or the servo that's failing to do what I want. One thing that's maybe making it difficult is that the servos are some generic brand sg90 with no datasheet - I don't know if all sg90 have the same PWM frequency etc. The datasheets I found both say 20ms PWM period (50Hz), 1-2ms duty cycle. I notice pi-blaster seems to have a 10ms PWM period (100Hz), but I don't know if that means it's expected to be straight up incompatible, or if I should be halving the 'on' fraction of the duty cycle, or it's okay using the same fraction, or what? (It is possible to change the period but I assumed from the fact that doing so requires rebuilding the whole library that it's not normal to do so - maybe that assumption is wrong.)
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Oct 15, 2023 05:14
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YES! THIS IS SO COOL. Found a poor-man's oscilloscope sketch using processing, and I have DATA for button presses! I can map this out and then add it to my existing joystick sketch. Ugh, this stuff is so cool when it works out like you might expect it to
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Oct 15, 2023 07:22
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On those various 'laptop/cellphone repair' channels on youtube, people seem to pull off the sketchiest poo poo imaginable when it comes to soldering QFN. But then lots of people are going full blown with custom stencils and paste and such. I'm trying to decide if I want to take a stab at a 36-QFN (or 36-SQFN) with ground pad on my next project. I only need to build one or two and the chips are only about $2.50, so I could buy the standard 5 PCBs and a couple extra chips. Maybe take a stab hand-soldering (by tinning with an iron and then using hot air or a hot plate) one or two first and see how much it would cost to add a stencil as a backup plan. Anyone done a medium size QFN recently and have any trip reports?
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Oct 15, 2023 20:04
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A stencil for a smallish board costs like $5. I would not try to do a QFN without one, it isnt worth the effort
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Oct 15, 2023 20:53
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I wouldn't want to do a QFN without paste, trying to pre-tin with an iron sounds like torture. And yeah a stencil makes it even easier.
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Oct 15, 2023 21:18
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I've done a couple by dropping a string of solder paste across each row of pads and then hotplating the board or using a hot air pencil, it was a slow process and had a decent error rate (mostly shorted pins) but was not really difficult to do. The trick is getting all of the solder liquid at once so the surface tension pulls the chip into place.
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Oct 15, 2023 21:19
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I frequently do those without stencils or paste. But when I have the foresight to get a stencil, it is a lot nicer. Edit: you better have solder braid, though. The nice MG Chemicals stuff, not the cheap stuff
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Oct 15, 2023 21:22
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Perhaps someone can answer the question in this simple form - if you have a servo and the datasheet suggests it expects a signal like the top graph and you give it a signal like the bottom graph, what would you expect to happen?
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Oct 15, 2023 23:50
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 it will depend on how they implemented the thing, may be inconsistent part-to-part, and probably nobody has spent much time thinking about what exactly happens. "Don't do that" and "If you do, it's up to you to figure out what happens" are the likely official answers
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Oct 16, 2023 00:07
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Foxfire_ posted:
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Oct 16, 2023 00:15
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Are you unable to produce the required signal? Servos are usually controlled by an IC reading the PWM you are sending it and it might not be able to read such a narrow pulse.
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Oct 16, 2023 00:20
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Cojawfee posted:Are you unable to produce the required signal? Servos are usually controlled by an IC reading the PWM you are sending it and it might not be able to read such a narrow pulse.
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Oct 16, 2023 00:33
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roomforthetuna posted:Perhaps someone can answer the question in this simple form - if you have a servo and the datasheet suggests it expects a signal like the top graph and you give it a signal like the bottom graph, what would you expect to happen? The servo’s little internal driver expects a 50Hz waveform (top). If you hand it a 100Hz waveform (bottom) that’s definitely going to be out of spec. I’d expect it might twitch, at most. source: currently working on a project with a dozen cheapass sg90 servos which don’t do poo poo if driven out of spec and barely do poo poo when driven in spec
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Oct 16, 2023 00:34
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For a project I worked on, the servos wanted 50 hz but I couldn't get them to do anything with a 50hz signal. I was using a 400hz signal for the DC motor controllers and that worked for most values except the lower ones. So you could probably use the 100hz signal, but you might end up with a lower bound of how far you can move the motor.
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Oct 16, 2023 00:37
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csammis posted:source: currently working on a project with a dozen cheapass sg90 servos which don’t do poo poo if driven out of spec and barely do poo poo when driven in spec
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Oct 16, 2023 00:40
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I'll definitely pick up a stencil while I'm ordering from jlcpcb if I'm going to do this QFN. I still may try one with hand-tinning, mainly so that I don't have to buy a tube of solder paste that will 100% sit in the fridge and go bad in a year without getting used.
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Oct 16, 2023 00:44
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Rescue Toaster posted:I'll definitely pick up a stencil while I'm ordering from jlcpcb if I'm going to do this QFN. I still may try one with hand-tinning, mainly so that I don't have to buy a tube of solder paste that will 100% sit in the fridge and go bad in a year without getting used. If it helps any, I've found that solder paste does not go bad nearly at the rate the manufacturer claims it does. Maybe if you're running a high throughput process line you'd want to use it within the specs to make sure you don't have to re-work a bunch of boards, but for one-off hand assemblies you can always adjust your heat and re-work a spot or two if the paste is old. I've been using the same tub of paste that sits at room temperature and is a few years old now and it seems fine, or at least good enough that I haven't noticed any changes over time. If you're ordering from JLCPCB anyway check out their surface mount assembly service, you have to use parts they have in stock but they have like 50k parts so it isn't a huge restriction and it's really cheap. They also limit you to one sided parts and no thru-hole stuff, but for the low cost I'm happy to let them solder on 90% of my stuff and then hand assemble the relatively large thru-hole bits and then tack on the 2-3 special chips that they didn't have ready to go.
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Oct 16, 2023 02:44
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