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Sagebrush posted:step (5) is doing a lot of heavy lifting there lol Not as much as (4) is. Many fitbit-knockoffs are smashed among the perilous rocks of (4)
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Feb 22, 2021 08:47
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A little suggestion/tweak: if you use the root of the sum of squares of your acceleration components instead of absolute values (sqrt(x*x + y*y + z*z) instead of abs(x) + abs(y) + abs(z)) your threshold is the same in any direction. If you don't do that, it's fine but more sensitive along the diagonals than the axes. 1.7x more sensitive at most, I think. E: easier to keep a running average if you just do the square root. That'll eat some cycles though. Stack Machine fucked around with this message at 16:54 on Feb 22, 2021 |
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Feb 22, 2021 14:56
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And speaking of ars-duino, does anybody have a line on these kinds of ribbon cable jumpers with reasonableish quality: I just dug those out of the trash to take that photo because more of them failed a continuity check than passed. The crimps were all hover-handsing the copper.
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Feb 22, 2021 15:23
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I think any that you buy are going to be of questionable quality. I don't know if any that you make would be any better. You can always try though. Get some ribbon cable, dupont connectors and a crimp tool.
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Feb 22, 2021 16:41
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Stack Machine posted:And speaking of ars-duino, does anybody have a line on these kinds of ribbon cable jumpers with reasonableish quality: Yeah, couple points on that: It's not actually copper. Check them with a magnet. They're steel. Adafruit has good quality, actual copper ones. They are like, a couple orders of magnitude more expensive, though.
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Feb 22, 2021 17:16
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Solid wire is my preference for sticking into female connectors or breadboards. Skip the hassle of dealing with crimps entirely. If you need the flexibility, then I'd solder and heat shrink a single (or however many) header pin from a breakaway connector.
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Feb 22, 2021 17:25
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Stack Machine posted:And speaking of ars-duino, does anybody have a line on these kinds of ribbon cable jumpers with reasonableish quality: It’s weird how universally-shoddy these are, esp for something so essential to prototyping circuits. Half the circuits i’ve ever worked up on a breadboard that didn’t work when powered up were because of some bad connection in either the jumper wire itself or in a bad jumper pin-breadboard socket contact.
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Feb 22, 2021 17:29
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Oh, I meant the copper strands in the ribbon cable were being hover-handsed by the crimp-on connector bit. I'm sure the connectors are steel. They're also obviously stamped into a U shape from thin sheet metal and very easy to bend. Just real cheap all around. Nothing like you get in crimp-on pin kits. I hate to think beginners might get a bunch of these, use them to breadboard up their first circuit, have it not work, and give up on electronics. Anyway thanks, I'll get the adafruit ones, maybe weigh the cost of crimping my own. I already spent a while this weekend replacing alligator clips with micrograbbers on some other random jumpers I had floating around since I needed something I could hit 0.1" headers with and these ribbon cable things were a bust.
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Feb 22, 2021 17:40
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I also suggest just buying a couple of spools of 22ga solid copper wire and using that for breadboard stuff. When Radio Shack was still around they sold a three pack with 25ft each of black, red, and green for a few bucks that was perfect.
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Feb 22, 2021 17:41
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Stack Machine posted:Oh, I meant the copper strands in the ribbon cable were being hover-handsed by the crimp-on connector bit. I'm sure the connectors are steel. They're also obviously stamped into a U shape from thin sheet metal and very easy to bend. Just real cheap all around. Nothing like you get in crimp-on pin kits. I hate to think beginners might get a bunch of these, use them to breadboard up their first circuit, have it not work, and give up on electronics.
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Feb 22, 2021 18:13
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Stack Machine posted:I already spent a while this weekend replacing alligator clips with micrograbbers oooh these are rad, I wondered how you'd swing test connections at a sufficiently-small scale. Also looks like something I can knock out myself... Ambrose Burnside fucked around with this message at 18:38 on Feb 22, 2021 |
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Feb 22, 2021 18:29
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ante posted:No really. Check! The wire itself is steel. It's bananas Huh, how about that. I tested some of mine and the marginally higher-quality ones with square crimped headers are non-magnetic (presumably stranded copper), but the cheap ones with the round molded-on headers are indeed steel. Whaddaya know.
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Feb 22, 2021 19:17
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ante posted:No really. Check! The wire itself is steel. It's bananas Yikes! These seem to be copper, or at least some copper plated nonmagnetic thing, but it's also super-fine gague so the connectors don't have much material to crimp to. Ambrose Burnside posted:oooh these are rad, I wondered how you'd swing test connections at a sufficiently-small scale. Also looks like something I can knock out myself... Yeah they're good. I think good clip leads are a big part of why the other jumpers are all so bad. You stock up your lab with leads that have mini-grabbers and banana plugs in every combination and maybe a couple of USB-to-whatever-digital-thing-you-want-to-talk-to adapters and that has you covered on temporary wiring for basically every contingency. That said, I still want some good pin header style jumpers, because all those mini grabber heads do eventually start to get bulky.
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Feb 22, 2021 19:20
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Stack Machine posted:A little suggestion/tweak: if you use the root of the sum of squares of your acceleration components instead of absolute values (sqrt(x*x + y*y + z*z) instead of abs(x) + abs(y) + abs(z)) your threshold is the same in any direction. If you don't do that, it's fine but more sensitive along the diagonals than the axes. 1.7x more sensitive at most, I think. If all you are doing is just comparing to a threshold, you can skip the sqrt and just do everything in square magnitude. sqrt is monotonic, so every magnitude threshold has a corresponding square magnitude threshold where all the above or below threshold decisions are the same Also if you are triggering of magnitude of acceleration exceeding a threshold, you'll probably want to convert from proper acceleration to coordinate acceleration if you haven't already. Subtract 1 from z so it indicates (0,0,0) when sitting on a table instead of (0,0,1). 1g acceleration down and 1g acceleration up are pretty different situations but both have magnitude 1
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Feb 22, 2021 20:12
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Thanks to the thread I've made good headway with it, and this is the reward: https://www.youtube.com/watch?v=9Yg679t6Nzs
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Feb 23, 2021 04:00
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Harvey Baldman posted:Thanks to the thread I've made good headway with it, and this is the reward: Ooooh man, this is electronics at it's best. Great job!
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Feb 23, 2021 06:33
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This is probably too low-tech for this thread, but maybe you all know where to point me: Looking to build some battery boxes for work gear (packable, waterproof, light). 12V and 30Ah. There's tons of pre-built on the internet (kayak fishing looks closest to what I am aiming at) but I'd like to do it myself. Mostly I am looking for sounding board "is this stupid?" advice when I try to do things like put the charger in the case, or can't find parts to fit the equipment I am trying to integrate.
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Feb 23, 2021 17:07
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pumped up for school posted:This is probably too low-tech for this thread, but maybe you all know where to point me: Looking to build some battery boxes for work gear (packable, waterproof, light). 12V and 30Ah. There's tons of pre-built on the internet (kayak fishing looks closest to what I am aiming at) but I'd like to do it myself. Maybe I'm a coward, but "waterproof" is a tall ask for DIY. If I'm misunderstanding, that's fine, but it sounds like you're either: - packing a whole bunch of stuff into a preexisting waterproof box with no electricity in or out, in which case I'm not sure what the charger is supposed to be doing - modifying or building a waterproof box to allow electricity in or out, which makes the waterproofing exponentially more challenging to be confident in its effectiveness and safety
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Feb 23, 2021 19:15
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Yeah are we talking waterproof as in you can throw it in your pool and leave it there all day and it'll be fine, or waterproof as in you can splash it and as long as you dry it off right after it'll be fine? Also does it actually need to be waterproof simultaneously with the charging/discharging? Because you could always just put it in a sealed, waterproof box and only open it when you need to use it.
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Feb 23, 2021 19:44
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KnifeWrench posted:- packing a whole bunch of stuff into a preexisting waterproof box with no electricity in or out, in which case I'm not sure what the charger is supposed to be doing My guess was that they meant something like this, where you've got a battery backup pack and your devices in a waterproof box, and can remove everything after your adventure to recharge before putting back?
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Feb 23, 2021 20:51
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If that's the situation, just get a small knockoff Pelican case from Harbor Freight and call it a day.
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Feb 23, 2021 21:21
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pumped up for school posted:This is probably too low-tech for this thread, IMO, don't worry about this. My last few posts here have been about literal wires. There's a ton of nuance in simple things.
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Feb 23, 2021 21:55
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If you do want to modify an existing box with a connector pass-through, the thing to filter for on digikey is IP67 or IP68 and panel/bulkhead mount. But plan for needing multiple iterations to get it to seal (+ to see if seal holds for weeks/months). The easiest ones to use without a CNC or template to cut an outline/screw holes in a box will be ones that want a circular hole the connector goes through, then a nut clamps an o-ring between the connector and the case for the seal. i.e. 
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Feb 23, 2021 22:18
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Oh wow thanks for the responses! Nothing has to be submerged, but common to be actively be discharging in the wet. I'd be powering something like a small portable seismograph, which is itself water-resistant. If it is really coming down I throw a tarp over it. But this stuff rides in the back of pickups, gets the stray unexpected weather. Typical work-outside stuff. If all I do is run power, then the seismograph power cable is a 3-pin Brad Harrison 16g (like this, I think) from the seismograph, to mueller-style battery clips. They get charged every night or two. I've done the easy "throw a small SLA battery in a pelican and open when needed" for remote work in Alaska and it is fine. I don't like trying to charge by connecting a charger to little blades, but it works. This is more a DIY fun project. Maybe add a voltmeter display and car-adapter and USB outputs for charging a phone/radio/repeater. I was hoping for no exposed terminals, but still easy to charge. Figure I'll be making 5 of these. I have inherited some Storm iM2075 cases that are bigger than I'd like, but they're handy and they'd hold a larger battery. There is already a 1" hole drilled. I was looking for more stoppers/rings/o-ring set ups as Foxfire_ mentioned, but I did find a few of these in my stash of abandoned field gear:  My main goal here is smaller, lighter, easier to pack into sites. The boxes I have now would be bigger than ideal but would work. Honestly anything would be better than my last trip: hauling 3 optima yellow tops 2 miles in terrain. And those are overkill. Was looking into a lithium iron phosphate solution. 20 amp hr should cover a field day, 30 would give me breathing room. Oh! And the charger in the box was just for fun because the boxes are oversized. My crew guys are always forgetting chargers back at the shop, so we get to a hotel at night w/ no chargers. I was thinking if everything was self-contained and just needed an extension cord to jumper between the wall and the charger, that'd be neat. But 100% unnecessary. pumped up for school fucked around with this message at 22:46 on Feb 23, 2021 |
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Feb 23, 2021 22:43
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Ok new question: is this thing failing going to cost you or your employer a bunch of money if you get to whatever worksite you need to use it on only to find that water somehow got in and killed it, and you have to go get a new battery while everyone just sits around and waits? Because if so you probably don't want to be building it yourself, as fun as that is.
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Feb 23, 2021 23:05
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Shame Boy posted:Ok new question: is this thing failing going to cost you or your employer a bunch of money if you get to whatever worksite you need to use it on only to find that water somehow got in and killed it, and you have to go get a new battery while everyone just sits around and waits? Because if so you probably don't want to be building it yourself, as fun as that is. Fair question! If we eat a day because I've hosed it up, then that's a massive fuckup. But there's always backup batteries in a truck. Realistically all I need is a smaller battery. The other stuff is bells and whistles. I can put a small batt in a toolbag with some padding and be done. It sits in the rain then it is no different than running an exposed 12V battery in the rain. What I am trying to do foremost is to eliminate that particular issue - no exposed terminals at all. The other bells and whistles are just because I am bored and staring at these oversized boxes.
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Feb 23, 2021 23:12
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In general I would say that if your employer is going to use it, your employer needs to pay for it. Just get something purpose-built that yeah will cost ten times what it would if you did it yourself, but it will probably be more reliable and your rear end isn't on the line. If you wanna build something for your own personal use, the knockoff pelican case with the IP68 passthroughs is a good strategy, I think.
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Feb 23, 2021 23:41
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Thanks for letting me type through that after reading all the responses. Gave me space to see it was dumb for lots of reasons. The example battery boxes I see people use for camping and fishing and what have you - they are meant to be stationary and shielded from weather. We're very rough on gear. Items gets thrown in the truck, it gets dropped and rolls down hills, etc. It will all get wet. poo poo breaks in the field and I need to be able to fix it w/ minimal tools and e-tape and lots of cursing. If an integrated charger can't take field abuse from being knocked around all day it is a waste. Also the external votage monitor and added USB/cig adapter out are just an accident waiting to happen. So none of that! I'll put in some lightweight lithium batteries and build some power cables. Here's one of the boxes that was donated, with the old lead-acids still installed. I'll recycle those, have to cut that connector (different, outdated piece of kit) and put a new power cable in. Boring but effective and a good use of my slack time. 
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Feb 23, 2021 23:47
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It's not fundamentally hard to put a receptacle matching for that cableset on a box so you can plug the seismograph in directly with just an off-the-shelf overmolded cable and it should be waterproof, but you might need a bunch of fiddling to figure out how to get a nice seal. If there's a small chance that the thing you build breaks some equipment or wastes a day of a bunch of people's time, that's something to be aware of and you should get your boss onboard before doing it. How much money are you willing to gamble on the thing working correctly? Especially since a DIY thing is going to be at least a little bit janky since holes won't be perfectly cut/you won't have correct tools for crimps/etc.. Just a lot of finicky details to get right before you can 100% leave it out in a truckbed during a thunderstorm
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Feb 24, 2021 02:01
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So... what does everyone use to get PCBs made? vv yeah. I also see jlcpcb but not sure if they are good. Cory Parsnipson fucked around with this message at 02:46 on Feb 24, 2021 |
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Feb 24, 2021 02:32
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Cory Parsnipson posted:So... what does everyone use to get PCBs made? Like manufactured? I ordered my last few boards from pcbway. For 2-layer 1oz copper in small quantity they were very cheap. (iirc shipping to the u.s. was more than the price of the boards).
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Feb 24, 2021 02:42
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For hobby, https://pcbshopper.com/ then whatever combo of price/lead time is cheapest. (Lots of these are probably actually the same slack-time/spare space in a panel fabs behind various storefronts)
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Feb 24, 2021 02:45
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I stick with OSH Park because (a) they’re US, (b) their tolerances have always been fine for me, (c) I rarely need more than a few boards, (d) dang it I like the purple solder mask 
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Feb 24, 2021 02:58
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csammis posted:I stick with OSH Park because (a) they’re US, (b) their tolerances have always been fine for me, (c) I rarely need more than a few boards, (d) dang it I like the purple solder mask More expensive though. Also, who can resist the siren call of:  Only offered by some expensive Belgian fab
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Feb 24, 2021 03:41
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In my professional life, I've used Sierra Circuits (https://www.protoexpress.com/pcb/) but I'll concede that that's 95% because they're local and do quick turns, and the time is usually more valuable than my employer's money.
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Feb 24, 2021 03:43
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Thanks! This is all good stuff. I'm still reading up on everything, but do all these places accept some standard files (gerber files or something) or do any of them need proprietary software? I just downloaded KiCAD in case that matters.
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Feb 24, 2021 04:25
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Every one I've used takes a zip of gerber (and .drl) files as their default. Advanced Circuits in the u.s. would take plated/non-plated through-holes in .grb too iirc but pcbway only wanted .drl for those for whatever reason. They will contact you by email if they spot any irregularities in the files you give them. For me that's always been stuff like "we only got one silkscreen file. Do you want that on the top or bottom?"
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Feb 24, 2021 04:43
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What's the recommended way of getting embedded 5V rechargeable power into an item? I have used LiPo batteries and chargers in the past for this kind of thing, but I have to wonder if there's a better way. Something like this PowerBoost + Charger thing is my go-to, but I don't know if there are better-suited options that are natively 5V? I've seen some RC batteries that are rechargeable and around that range, but they seem like they need power conditioners or similar? I like the ability to just plug in a MicroUSB or whatever for charging because everyone has those around. I've considered doubling up on 3.7V cells and just letting the voltage regulators on the things they're powering take care of it, but then I run into the extra complication of charging two LiPo batteries in series, which I don't really understand how to do properly.
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Feb 24, 2021 05:00
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It depends but if you want to see the kind of stuff at least one battery powered open source portable thing with a 5V rail is doing this is the circuit the nanoVNA uses: The chip there (U2. U1 is a USB connector) is an all-in-one USB power bank solution so it charges from 5V and outputs 5V. The inductor there is used to buck down to the battery in charging and boost up from the battery when it's discharging. It's not fancy and has absolutely no telemetry but it's a very simple, low-part-count solution. Also if you want the same circuit for very little money with a cheap lipo, you can buy any low-cost usb power bank and put a USB connector on your own board.
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Feb 24, 2021 05:23
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What are your requirements? Like, if the Adafruit thing works for you, that's a perfectly okay solution.
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Feb 24, 2021 05:25
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