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um excuse me posted:The rule I put in place is easy to follow. If I'm working on anything plugged into a wall, one hand is placed physically behind my back. Luckily, or unluckily depending on how you look at it, I know from experience that I don't lose motor control in similar situations. That's a good one. Fence with your electronics!
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Jan 5, 2020 21:41
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Oh yeah I was gonna say, I always make sure that if anything's even suspected of having exposed deadly power in it (via wall outlet or capacitor or whatever) one of my hands is always in my pocket, since it makes it harder to reflexively try to grab something with it. Anyway I'm real glad you weren't killed, person with forums user name Stabby McDamage. That sounded sarcastic but it wasn't 
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Jan 5, 2020 23:26
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Oh also if you work on stuff like this often and you don't have a Cliff QuickTest, get one. It makes it very easy to cut power to something in a verifiable, obvious way, it comes with built-in fuse socket, and it's designed so it doesn't accidentally turn on if you bump it like a switch would. For a while they were a little hard to get in US colors, but ever since BigClive has been talking them up they've gotten a lot more widely available, you can even get em' on Newark now: https://www.newark.com/cliff-electronic-components/cl1857/qt1-usa-canada-13a-fuse-quicktest/dp/08AC2593 That one doesn't come with a cable but it's easy enough to install your own, or I'm sure you can find one that comes with the cable.
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Jan 5, 2020 23:34
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Splode posted:That's a good one. Fence with your electronics! "Keep one hand in your pocket" has been an electronics safety practice for a century now it seems.
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Jan 5, 2020 23:50
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Shame Boy posted:Oh also if you work on stuff like this often and you don't have a Cliff QuickTest, get one. It makes it very easy to cut power to something in a verifiable, obvious way, it comes with built-in fuse socket, and it's designed so it doesn't accidentally turn on if you bump it like a switch would. For a while they were a little hard to get in US colors, but ever since BigClive has been talking them up they've gotten a lot more widely available, you can even get em' on Newark now: I keep wondering if they'll eventually make one with black/white/green connectors instead of the euro style. e: nevermind! https://www.newark.com/cliff-electronic-components/cl1857/qt1-usa-canada-13a-fuse-quicktest/dp/08AC2593
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Jan 5, 2020 23:57
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Hypnolobster posted:I keep wondering if they'll eventually make one with black/white/green connectors instead of the euro style. So... the one I linked?  They've actually offered it for a long time, it's just they didn't have any suppliers that stocked it until BigClive started talking it up and someone bought a bunch direct from Cliff to sell on eBay (which is how I got mine). Then other places took note and now you can get em' pretty easily.
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Jan 6, 2020 00:13
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Shame Boy posted:So... the one I linked? In my defense, I bought one 6 or 7 years ago and mine is the european color code because at the time it was all I could find. I didn't even click because I had no idea they made US/CA color coded ones.
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Jan 6, 2020 00:16
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um excuse me posted:The rule I put in place is easy to follow. If I'm working on anything plugged into a wall, one hand is placed physically behind my back. Luckily, or unluckily depending on how you look at it, I know from experience that I don't lose motor control in similar situations. Same except my other hand is holding a beer.
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Jan 6, 2020 09:31
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um excuse me posted:The rule I put in place is easy to follow. If I'm working on anything plugged into a wall, one hand is placed physically behind my back. Luckily, or unluckily depending on how you look at it, I know from experience that I don't lose motor control in similar situations. I'm sorry for your paraplegacy because your muscles don't respond to biological rules
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Jan 7, 2020 00:38
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loving solder bridges!!!! That is all.
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Jan 7, 2020 00:46
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ante posted:I'm sorry for your paraplegacy because your muscles don't respond to biological rules It just tingles. I don't know what to tell you, man. I also have enough experience to tell you my muscles do respond somewhere between 800 and 2000 volts. Those were luckily not across my chest.
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Jan 7, 2020 00:58
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kid sinister posted:loving solder bridges!!!! i
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Jan 7, 2020 01:01
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taqueso posted:i My all time (least) favorite was a slight solder tendril on the side of a 1005 capacitor. Took loving forever to find that one.
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Jan 7, 2020 01:26
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taqueso posted:i I like the ones that hide in the glare from your light.
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Jan 7, 2020 03:26
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Thanks for the support. The one-hand tip is wise and something I'll adopt. I installed a timer-switched GFCI on my lab bench and wired it also to a big spinny red light whenever it's powered  That, plus not being an idiot and picking up live AC-powered PCBs, will hopefully make me not die.
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Jan 7, 2020 17:26
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Stabby McDamage posted:Thanks for the support. The one-hand tip is wise and something I'll adopt. I installed a timer-switched GFCI on my lab bench and wired it also to a big spinny red light whenever it's powered Do you have an isolation transformer?
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Jan 9, 2020 18:18
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kid sinister posted:Do you have an isolation transformer? I mean in this case it sounds like an isolation transformer wouldn't have helped, but yeah you should probably have one. Keep in mind though that it renders GFCI's useless.
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Jan 9, 2020 18:23
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Am I an idiot and/or do Mouser / Digikey not sell CdS photocells anymore?
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Jan 10, 2020 17:41
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There's a whole category for them on DigiKey  https://www.digikey.com/products/en/sensors-transducers/optical-sensors-photo-detectors-cds-cells/540 e: I'm not seeing anything on Mouser so maybe they got rid of them?
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Jan 10, 2020 18:22
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Hey guys, I posted this in a programming and they said I might have more luck here. Are there any ball joints that can be hooked up to a computer so that I can read their position?
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Jan 11, 2020 10:06
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Nothing off the shelf on a hobbyist budget. Perhaps on an industrial system. There are ways you could hack something together, too. Couple encoders, or maybe an old ball mouse
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Jan 11, 2020 10:25
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ante posted:Nothing off the shelf on a hobbyist budget. Perhaps on an industrial system. There are ways you could hack something together, too. Couple encoders, or maybe an old ball mouse Hmmm, I was afraid of that. Would it be possible to use something like an analog stick from a joystick and use that in conjunction with the joint? Create a housing with the same electronics as an analog joystick but mount the ball joint in there.
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Jan 11, 2020 10:41
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Look at the way a cable actuated manual transmission car is shifted. The stick is more or less a ball joint that translates it's motions into two linear motions for X and Y. A similar linkage to potentiometers would serve your need. But I can't think of anything off the shelf, especially if it's a load bearing joint.
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Jan 11, 2020 14:44
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um excuse me posted:Look at the way a cable actuated manual transmission car is shifted. The stick is more or less a ball joint that translates it's motions into two linear motions for X and Y. A similar linkage to potentiometers would serve your need. But I can't think of anything off the shelf, especially if it's a load bearing joint. I was thinking along those lines, maybe have electronics inside the joint itself if there is space. I'll have a look thanks.
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Jan 11, 2020 17:32
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How much motion range and strength do you need? Replacement analog joystick parts (e.g. replacements for the PS3 thumbsticks) are very cheap and easy to get but have a limited motion range (about +/- 30deg on both axes). They won't hold much but could probably be embedded in a larger, tougher joint. Also, of course, they won't track rotation of the shaft if that's important. There are also older style analog joysticks (like the ones used in RC controllers) that usually have a bigger movement range (~+/- 50 deg) and I've seen 3-axis ones (that will handle shaft rotation) for about $25 or so.
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Jan 11, 2020 18:12
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You need an Ikari Warriors joystick.
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Jan 11, 2020 18:22
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Hobnob posted:How much motion range and strength do you need? Replacement analog joystick parts (e.g. replacements for the PS3 thumbsticks) are very cheap and easy to get but have a limited motion range (about +/- 30deg on both axes). They won't hold much but could probably be embedded in a larger, tougher joint. Also, of course, they won't track rotation of the shaft if that's important. I need something that will work on a human skeleton. Like a mannequin that you use for drawing.
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Jan 11, 2020 22:34
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Anybody know of any DIY-accessible/budget-friendly approaches to underwater active sonar that isn't just the guts of an old fish-finder? alternately, any free/open-source software that can do basic short-range (~10-15m), low-resolution imaging with said fish-finder or a scratch-built ping-echo piezo-hydrophone mic setup? commercial offerings are all absurdly out of budget ($1000+) and also do a lot more than I'd ever need, while more economical fish-finders don't capture the topographic data I'm interested in. from the research I've done, the general sentiment is that a rudimentary active sonar unit is simple to construct, but doing anything interesting with the data (aside from find fish in realtime) is all on the software end. (this would be for underwater topography + large submerged object mapping of small ponds and waterways, for the record) e: Mr Shiny Pants posted:Hey guys, someone already said 'ball mouse', but yeah, that's what i'd focus on, given the significant range of motion you require ruling out any joysticks i've ever encountered. you could probably salvage the contact wheels and X-Y optical encoders from an actual ball mouse and save yourself reinventing the wheel. the position data would be relative, though, not absolute, and would stand a good chance of drifting every time the joint hits its rotation limits or are otherwise reefed on aggressively enough to make the wheels lose contact or skip. you could always implement some sort of homing functionality, though, sth like a limit switch that's only tripped when the ball part of the joint is fully-rotated and in the 12-oclock position, or what have you. kinda fucky to do mechanically but a noncontact reed switch detecting a little neodymium magnet installed in the ball joint shaft would prolly work well b/c you can tweak the sensitivity with enough precision to change detection distances by am incremental thousandth of an inch or two alternately, if you don't specifically need a literal ball joint and can accept a close substitute, a Cardan coupling will offer mostly-comparable mobility but hugely simplify position sensing by breaking the joint up into two single-rotation-plane joints. Ambrose Burnside fucked around with this message at 00:02 on Jan 12, 2020 |
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Jan 11, 2020 23:47
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Mr Shiny Pants posted:I need something that will work on a human skeleton. Like a mannequin that you use for drawing. If you're going to connect any such joint to another, as in a human skeleton, and try to calculate the position of the extremities, be aware that the propagation of error will be a major challenge and continual source of frustration. This is a non-trivial problem even with single-degree-of-freedom joints. A ball joint has three degrees of freedom. I'm sorry if it sounds like I'm trying to scare you off. But the way you describe it has my brain screaming out for a different implementation.
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Jan 12, 2020 00:29
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This definitely seems like one of those projects where if you don't already know how to do it, it's never going to work the way you want it to.
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Jan 12, 2020 01:00
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The example of a drawing mannequin reminded me of this paper I read where they created this modular system for building skeletal joints that would be mapped to 3D models so you could make animations easily by just manipulating the physical skeleton you have in your hands. They were measuring angles using 2D Hall-effect sensors fixed to one side of the joint and and magnets on the other side. e: This one https://cims.nyu.edu/gcl/papers/Rig-Animation-Input-Device-2016.pdf 
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Jan 12, 2020 01:21
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Thanks for the replies guys, the idea is just something I've been thinking about, it isn't really a project. The ball mouse idea is kinda neat I have to say and I can see how that would work. The accuracy does not need to be millimeter scale, just that the overal pose works out. Shame Boy posted:The example of a drawing mannequin reminded me of this paper I read where they created this modular system for building skeletal joints that would be mapped to 3D models so you could make animations easily by just manipulating the physical skeleton you have in your hands. They were measuring angles using 2D Hall-effect sensors fixed to one side of the joint and and magnets on the other side. Something like this looks really promising. Thanks. Mr Shiny Pants fucked around with this message at 09:21 on Jan 12, 2020 |
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Jan 12, 2020 09:17
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Does anyone know if its possible to buy cooling fans (like the generic 80-120mm form factors) without an integrated driver? I'm looking to use a custom BLDC driver, so I would just want the motor windings wired out (plus a hall sensor or encoder output, if available). But all my searching has returned nothing, except for very high power levels (like >20W).
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Jan 12, 2020 22:18
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PC fans? The cheap ones are just motors.
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Jan 12, 2020 23:24
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kid sinister posted:PC fans? The cheap ones are just motors. True, but they're generally brushless motors, which means they have a Hall sensor and a small driver/controller to pick which phase coil to power at any given time. I'm betting he could probably just buy any old PC cooling fan and desolder the controller, although he might want to poke at it with an oscilloscope first to try and figure out the torque and speed constants.
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Jan 12, 2020 23:46
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kid sinister posted:PC fans? The cheap ones are just motors. He wants to use custom BLDC so a brushed can won't help him. I think you can rip out the "integrated" driver, it's usually this coin-shaped thing on the back of the PC fan and can come off preserving the windings. Check some YouTubes on oiling the fans and you might see what I'm talking about.
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Jan 12, 2020 23:46
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You could just buy an existing brushless fan, take it apart, and remove the controller and put in what you want. I had one that was stuck so I ripped it apart. I removed the sticker on the back, pried out a piece of rubber and then there was a retaining ring holding the fan into the housing. It was broken, so I removed it and the fan blade part came out the front.
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Jan 13, 2020 01:30
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This is for a product, so manually hacking the driver out of a normal one isn't an option.
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Jan 13, 2020 02:29
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A project being a commercial product hasn't stopped people from slapping gross hacky bullshit into a box and slamming a price tag on it before.
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Jan 13, 2020 02:34
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Well it should, if it has to be UL certified
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Jan 13, 2020 07:08
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