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scholzie posted:God, I need an oscilloscope. I found one on ebay being sold as-is. It powered on but didn't have a probe so it couldn't be tested. But, it was a newish HP 4-channel scope, and it was $10. I was top bidder until FOUR SECONDS before the end of the auction when someone bid-sniped me. I hope that fucker just bought a broken oscilloscope. Story of my life. I've had that happen probably fifty times, and still don't have a working oscilloscope*. I'm not even all that into electronics (I had a soldering iron once, but lost it), I just want one as a toy. *I have an ancient boat-anchor Tektronix 561A that I pulled out of the bin behind the science building at school, but it's one of the modular ones and missing the modules -- All I've got is the outer case with the CRT and calibration knobs. It powers up, but all it can do without the modules is make a dot, and change the size and position of the dot. I'd look for the modules on eBay, but I don't know which ones I need -- Tektronix made several modular 'scopes, all incompatible with each other, and the modules don't say which one they're for. Edit: It never occurred to me to find a picture of a complete one and get the module numbers off it, until I found an auction for one with good pictures. 
Chillbro Baggins fucked around with this message at 12:31 on Jan 18, 2008 |
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Jan 18, 2008 12:20
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Bad Angus! Bad!
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Skycks posted:Not that I would try this, but can they easily figure out that you are the one transmitting? A guy I might know (i.e., if this were to have come up, I didn't know him) used to have a massively illegal CB amp. He claims he was heard in Nova Scotia once (I certainly wasn't standing beside him at the time), with the reply (something along the lines of "what the hell was that?") passed back down to Texas via the chain of closer-to-legal transmitters. (Before you go calling the FCC, he sold it several years ago to buy a Harley.) That reminds me, what's the average  power rating of CBs on the road? The CB-slang-dictionary sites seem to imply that drat near everybody's running more than the legal 4 watts.
Chillbro Baggins fucked around with this message at 05:51 on Jan 26, 2008 |
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Jan 26, 2008 05:49
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Not sure if this deserves its own thread, but it's an electronics question, so I'm trying it here first. After having two CD head units stolen out of my car, I have decided to add an AUX input jack to my why-the-gently caress-would-anybody-even-want-one stock AM/FM radio. It's an ancient brick, and all the tutorials I can find either are for newer ones with a certain microprocessor, or patching into a tape player. Some of them mention in passing that "you could just connect it to the volume pot," but my volume pot has a lot of pins and no labels, so I don't know what would go where. So the question is, what's the best way to go about attaching a headphone plug to this thing? Oh, and to make it interesting, I can't get to the back of the (rather primitive-looking) circuit board -- it's heavily soldered to the case at six different points, with bent-over pins under the solder. That poo poo is not coming apart. I've got the plug all made up on a length of wire, a partially-disassembled Ford E4AF radio out of an '84 Crown Vic, and a soldering iron (and some solder, of course). What do I do? Edit: Here's what I've got to work with, electronics-wise. Maybe the place to connect the thing will jump right out at you. If not, enjoy the old-school electronics porn. (Click for huge.)  This one is vertical, attached to the back of the faceplate. Those little hooks at the bottom go into a row of holes on the other board to connect the two, and that white wire coming off the top left corner solders to the case. That's the tuner wheel on the left.  The main board. Front at bottom of picture. Shafts, each normally holding two nested knobs, are: volume/power switch (volume down 'til it clicks)/something else on the left, and tuner(not shown: little hot-pink splined shaft that interfaces with the gear in the above pic)/something else on the right. As for level of electronics expertise, I have a multimeter and (mostly) know how to use it, and I just got a cheap soldering iron and spent all day yesterday sticking bits of wire together just because I can, and can name most of the components in those pictures, though taken as a whole they confuse and terrify me. I'm fairly good at working on electrical systems that don't have all those little fiddly bits (e.g. house wiring, or under the hood of an old car). Chillbro Baggins fucked around with this message at 14:21 on Mar 19, 2008 |
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Mar 19, 2008 13:32
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Delta-Wye posted:How many is a lot? UserNotFound posted:Here's how the volume pot most likely is set up: Edit: poked at it with the meter. First pin is ground, second pin is the output to amp, third pin is open, fourth pin is the input. Now what do I do with them? Chillbro Baggins fucked around with this message at 04:58 on Mar 20, 2008 |
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Mar 20, 2008 04:27
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Delta-Wye posted:Might want to clip/unsolder the connection eventually so that your radio doesn't get mixed in. You could mount a switch (which would be pimp) to select between radio and aux. Now, to figure out which is left and which is right.
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Mar 20, 2008 12:22
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And now for something completely different: I have an old Tektronix oscilloscope that uses plug-in units for the timebase and the other thing. It's missing the plug-ins, so it's basically a bigass case around a tiny CRT that can only show a dot. Is there anything fun I can do with it, or should I just start stripping it for parts?
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Mar 20, 2008 15:24
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Dammit. Finally got around to soldering the mp3 player cord onto the radio, left/right be damned. Alas, I didn't get to test it because I hooked it up the the car wrong -- switched the always-on and ignition-switched 12v lines, which are orange and yellow on the radio side but both yellow on the car side, and I'm working without a plug because the thieves cut it off to get the CD head unit out -- and didn't have time to redo it before InediblePenguin left for work. It does work in radio mode, at least, so I didn't kill it. Also, I didn't pay enough attention when putting the front panel back on, and forgot to line up the balance slider, so it's all the way to one side and the slider doesn't move the switch-thing. I'll fix it while she's home for lunch and try it with the mp3 player plugged in. Next project, assuming that works: build a car charger for the mp3 player. I'm pretty sure I've already got a car-lighter-plug transformer that outputs 5vDC; all I'd have to do is wire it up to the correct pins on a USB cable, right? Chillbro Baggins fucked around with this message at 14:15 on Mar 26, 2008 |
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Mar 26, 2008 14:13
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Random question: I have a couple (well, one, the other one seems to be dead) piezo buzzers that seem to change their sound at different voltages. The working one goes "deedleedleeedle" at 4.5v (i.e., three C-cells) and plays "London Bridge" at ?v (9v battery with small red LED and the resistor that came with it in the circuit. Yeah, I was just randomly stringing things together*) How does it do that? It has a tiny little PCB with a resistor and a 1/4"-wide lump of black stuff on it. I'm pretty sure that whatever is under the lump of black stuff is what does the sounds, but I haven't the slightest idea what it might be. *actually I was working on a "ring bell for service" type thing so InediblePenguin can call me from the bedroom, and thinking of putting the LED in the button-handle for confirmation of annoying the crap out of me. I ended up going with just the deedleeedle and no light. Also, how do you tell which end of the resistor to start from when reading the code? None of the ones I've ripped out of various broken devices seem to have any way of telling -- all the stripes are the same distance apart and from the ends.
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Apr 6, 2008 15:35
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Penfold posted:Ok, I have a bunch of disposable camera flashes I want to discharge at the same time. On ring flashes, we have an even more ghetto solution kicking around the office: a black matboard box with a cardboard tube in the middle, with the space between lined with tinfoil in a decent approximation of a sliced-bagel shape, and a rectangular cutout in one edge for the speedlite. Judging from the fading of the matboard and the size of the tube, it's left over from the film days. quote:By the way, one of those capacitors hurts like gently caress all when they blow on the back of your hand (and they make a sound like a screaming woman, that might have been me though) I shorted a one-use-camera flash with a Swiss Army knife once, just for the hell of it. There's a notch in the blade where it arced and melted the steel. Don't gently caress around with capacitors, kids. And now for something completely different: I have a Big Red Button with a covered arming switch (a friend that works at the electronics version of an army surplus store abuses the employee discount for my benefit). What should I use it for? Thermite on the HDDs? "gently caress you" hard-reset switch on my computer? Toss a couple of high-amp batteries in the box and make a general-purpose detonator (and dig out my old model rockets)? The first option is a no-go, because of the temptation to push it. What's a good battery for the all-purpose detonator? I'm thinking a pair of 6v lantern batteries -- it's currently installed in the lid of a Radio Shack project box, so they should fit, though there is the comedy option of a 20-pack of dollar-store carbon-zinc AAs. If I do go the detonator route (with a few big batteries), I'm planning on wiring up a switch to pick between series and parallel on the batteries; is this possible?
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Dec 27, 2008 08:50
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Mill Town posted:Absolutely. Here you go: Looks good to me, but I'm no EE. I think I have one of those switches kicking around somewhere. Actually, I think I've already got it in the box, along with a single-thingy switch (like I said, I'm not an EE) to select between one/both batteries. Now I just need to work out the actual installing the batteries part. Edit: Edit again: following lines is hard. Chillbro Baggins fucked around with this message at 12:20 on Dec 27, 2008 |
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Dec 27, 2008 09:55
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BattleMaster posted:Holy poo poo, I want one of those. I wouldn't even know where to start looking for a store like that in Canada though. Like ante said, any decent-sized city should have some kind of hole in the wall, or at least an electrician's supply house. Flip up the cover, flip the switch under it, and the big button lights up, then press it to fire ze missiles/release the hounds/destroy the evidence/etc. Total cost of all parts shown (it's empty inside for now): $15 or so. The big button alone costs that much on the internet. 
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Dec 30, 2008 00:09
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BattleMaster posted:Awesome, I thought it was going to be hopeless to find something like that because Delivery McGee said his was military surplus. No, I meant the shop has the same sort of business model as an army surplus store -- they get random salvaged/overstock electronics stuff from everywhere.
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Dec 30, 2008 05:00
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babyeatingpsychopath posted:The electrical supply house has those buttons, too. I know because we had to get 8-10 of them for the current job. Red 2.5" Round Mushroom-head Momentary Contact switches labelled "emergency stop." They're stocked parts. Same way with Red Guard SPDT Toggle. The guard for the toggle switch is usually sold separately. ($7 on the internet, $1.50 at the surplus store.) My electronics-store friend got me one of these for Christmas. Unfortunately, I'm up to my ears in stopwatches, so I don't really need an egg timer. She says the alarm on it is really annoying, though. I'm thinking of adding it to the BRB box -- press button, lights count down, and then SKREE SKREE SKREE. It'd make the button a functional toy even if it doesn't do anything else! And I can use the extra switch I've already got in the box to select between the countdown/SKREE SKREE SKREE and the actually doing something as soon as the button is pressed! (Shameless plug: my friend/supplier/fellow goon is at Electronic Parts Outlet in Houston, if you're in the area.)
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Jan 2, 2009 06:48
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Karma Guard posted:This doesn't mean you're going to get a goon discout, though. Yeah, that's just for me  (seriously, don't annoy her. She has a mean left hook).
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Jan 2, 2009 06:56
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InediblePenguin got a proper bass amp today (she had been using a tiny guitar amp), so the first order of business, of course, was to build an overdrive box to make it sound like it did on the lovely guitar amp. Er, wait . . . oh well, any excuse to tear apart a lovely amp and tinker with the guts! I found a nice simple overdrive circuit with a breadboard layout provided and set to work, with some rearranging to make it fit my particular breadboard and substitution of a few resistors because I didn't have the exact ones. Long story short, it didn't work. I tried moving things around, swapped out the diodes for a different kind, tried three different op-amps because I had all but the one specced, and eventually got it to work for exactly one note before it went back to a quiet hum and nothing else. And then the 100uF cap blew. The magic smoke stinks. Here's a picture of the two amps, shortly before the tiny one was gutted, desoldered, and reassembled:  Click here for the full 620x800 image.
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Feb 14, 2009 10:53
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Dug out the soldering iron for the first time in quite awhile today. My partner's Fender Bassman 60 has been having problems for quite some time, requiring pressure to be put in the input cable just so for it to work, so I finally decided to take it apart and try to fix it. I knew it was either that the springs in the jack were bent out of alignment or the thing had come loose from the board, since the plug wiggled in the faceplate like the proverbial hot dog in a hallway. Got it open enough to see the part, it looked like it made contact with the plug just fine, and the whole thing moved. I took out some more screws to get the PCB off its sled and see under it, and:  Yep, there's your problem. (My fingers on the input jack, slightly pressing it to and fro, respectively. I don't know why a guitar amp has a stereo jack, but note the third pair of pins). I resoldered all six pins (only the farthest pair were actually completely broken off, but as you can see the others' joints weren't in the best shape either), and it seems to be working properly now. I tested it by using a 1/4" to 3.5mm adapter to plug it into the headphone jack of my computer and playing the main theme from Pacific Rim: https://www.youtube.com/watch?v=1vU7XqToZso  And now I can never listen to that track again, even in the cinema and especially not through headphones, without feeling disappointed.  (if that foghorn note at the end doesn't shake things off shelves and give you a sense of visceral terror, you don't have enough bass.)
Chillbro Baggins fucked around with this message at 20:38 on Oct 11, 2015 |
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Oct 11, 2015 20:34
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Partially crossposted (a lot of the minutiae is added just for y'all) from the TFR DIY thread, the person AWOG was replying to was talking about having designed a PCB for a grid of small LEDs as an all-purpose portable light: Well, now I have a project. I have one of these:  (Sadly, in similarly rough shape.) It uses two of the big 6V lantern batteries to power a couple of old-school automotive bulbs -- I'm fairly sure the main one is a taillight, and the little one for less light/longer battery life is a dome light). Unfortunately the case is pretty form-fitted to the batteries, so I'm not sure where I'd put the driver, but random Google results from flashlight forums suggest I should get decent life out of the batteries (opinions vary between "10-25" and "50+" hours, but either way is a hell of a lot better than the incandescents for the light output -- the LED is as bright as a 70W incandescent, as opposed to whatever relative drip in the underpants the brake light puts out (I got bored before I found an answer relevant answer from [brake light lumens], most of the results are talking about LED conversions). Maybe make the head/leads removable so I can swap the light part to a magnetic base and it can double as a hell of a work light for poking at the car.  Do they make rechargeable 6V lantern batteries? I can't find any. But I know they're four F cells, and I found this that should fit in the can. And at 13 amp/hours per cell and eight of them wired in series, that gives 9.6V, which the rig AWOG linked should handle, and 104 hours run time, if I'm doing the math right (calling it 1A instead of .9A draw to simplify things and make the numbers nice and round). Or maybe this R/C car 4-D pack that I think has more amp-hours in a pair, and maybe even have enough space to put the driver in the battery case (which puts the kibosh on the detachable-head-to-plug-into-the-car-battery-as-a-magnetic-worklight thing; otoh I could just buy a second driver module to mount in the car, it's cheap enough).
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Feb 26, 2016 06:35
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Parts Kit posted:It's important to remember that wiring batteries in parallel will add to your capacity and that in series it will not. So you'd still be at 13 amp-hours with them in series. Dang, forgot about that. Still, it'll be tons brighter for the same battery life at worst -- I can't imagine that little taillight bulb drawing more than an amp. It just occurred to me that a single flat LED like that doesn't really need a reflector, or at least not a parabolic one like a bulb, does it? Removing the parabolic reflector and putting it right near the lens would give me plenty of space to mount the electronics in the head. I like the idea you mentioned in the TFR thread about using a three-position switch for a lower-current/longer battery life option. Could probably use the stock switch, it had a similar functionality originally. Although it might need to be a special switch for what you were talking about. On the other hand, gently caress it, I'll use the stock switch and have a secondary array of low-power LEDs like the ones in a normal flashlight. Edit: alternate option, I could mount enough lesser LED(s) and all the batteries to run them to far outshine a normal flashlight just in the head (like, at least three or four of those little 3xAAA flashlights would probably fit in there using a shared set of AAs) and use the battery can to hold first aid kit/survival supplies/emergency toolbox. OTOH, go big or go home, right? Hell, I'm pretty sure the guts of two 18v cordless power tool batteries would just about fit in the battery box with room to spare, and the lens is 6" wide ... maybe I'm not thinking big enough. Edit again: what kind of heatsink does this thing need? I'm about to start ordering parts. I think I'll go with the slightly different one linked here, it's ~6000K, like sunlight in the shade; the other one's ~3500K like a tungsten bulb, and as a photographer, I loving hate yellow lights. Do I need a resistor, or does the constant-current 900mA driver linked in the earlier post cover that function itself? I'm new to LEDs, I learned on kits with tiny lil' incandescent bulbs. Chillbro Baggins fucked around with this message at 04:37 on Feb 27, 2016 |
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Feb 27, 2016 02:51
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Parts Kit posted:From what I've seen people have been using CPU coolers of various types to keep those 100W modules from burning up. You might also be able to get away with cramming a small case fan in there to help keep it cool if you're okay with say putting a few holes in the back of the housing to let air in and out. I do have a couple of dead desktop CPUs that I could loot the coolers from if it needs to be that big. I was hoping for something closer to the 1" cube onboard-GPU heatsink. I could do the fan thing, but I'd also kinda like to waterproof at least the head (ideally the whole thing, but not sure how to work that with my wish to be able to pull the head off and run it off the car battery, and putting a gasket in the battery case will be difficult at best). The switch is a standard SPDT (one wire in, two out, off detent in the middle) and probably should be replaced anyway because it's 50 years old, but it's a standard toggle switch, IDK what I was thinking wanting to keep it. I momentarily forgot they still make them to fit the same hole, I guess. Here's the innards:   I love the clever (but expensive, you don't see that these days) way they made it so it doesn't matter which way you put the batteries in (well, they have to be right-side-up, but you don't have to put the + terminal on any specific corner; nowadays I'd assume you have to orient the battery perfectly and maybe the fancy ones have a dot at each corner with the bare minimum of wire connecting them, back then they just put a bigass brass ring as the + contact.) Any comment on the resistor vs. driver question I edited into my previous post? If it's either/or, which is better for this application? Edit: holy poo poo, the company still exists and is still making the things. Pretty sure the H266M is an updated version of my Model 211 from God knows when (though when you click, it's the page for the one-battery model). I wonder how flexible they are with the lifetime warranty, mine's a bit rusted. (Sadly they don't have email and I hate making phone calls.)
Chillbro Baggins fucked around with this message at 06:15 on Feb 27, 2016 |
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Feb 27, 2016 05:24
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Having been too lazy to order parts for the giant LED in the old Big Beam flashlight I talked about a while ago, I'm now considering a simpler project with parts on hand: Put two/three of those cheap/free Harbor Freight multi-LED lights in it. I have one (there's another one around here somewhere, but idk where), and they're running this coupon again: So there's two more. Two of the boards will fit side-by-side, and I could cut the third in half to fill in the other sides, in the head of the new body,  Which originally had an automotive taillight and dome light bulbs (two positions on the switch, one for the dimmer but lower-amperage dome light and one for the big bulb) and two 6v lantern batteries. I could even move around the secondary LEDs on the end to keep the spirit of the original (or just use one set and wire the others into the main array). Questions: if I gang up two or three of these on a common switch, will I need to replace the current-limiting resistors? Also they seem to want 4.5v (3 AAAs), but from researching the giant LED, voltage seems to be more a range -- would they run on an old 3.7v cellphone battery?
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Jun 18, 2016 17:55
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Did the thing with the three HF worklights and the ancient car-taillight brick, powered by a 5V phone charger. It works, will blind a person if you point it at 'em in diffused sunlight. Off, showing the blu-tack and electrician's tape bodge job:  On, it's fuckin bright:  Could use a reflector and other improvements, but on the whole I proved the concept -- three 3xAAA flashlights paralleled off a 5v phone-booster battery.
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Jun 20, 2016 05:04
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ate all the Oreos posted:$1000 for 2000 watts seems real terrible if you just need a generator for a couple days a year though. At that point, you might as well get a gas-powered arc welder (most of which have 120V AC output to run other power tools). Now I'm wondering how much it would take to attach my 200A car alternator to my (Honda-powered) lawnmower for a homebrew generator in a Mad Max scenario. I guess engine speed determines the frequency of the alternator's alternations, so you'd have to keep the rectifier diode and then convert it back to 60hz AC? Or just make pulleys of the proper size to generate 60hz naturally. Though does frequency really matter for modern CFL lights and laptop power supplies?
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Nov 18, 2016 16:11
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What's a MC14001DCP chip used for? Looking at the ICs that came with an electronics learning kit (the manual long lost) I had years ago, I have a single 555 and six MC14001DCPs.
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Dec 16, 2016 23:20
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I have a 7.2V NiMH* battery pack and have lost the original charger (and it was too dead to work with it anyway). Theoretically I can just use my bench power supply to put <7.2V into the proper contacts to attempt to bring it back to life, right? I've had it plugged into 5V for an hour, and it seems to be working, but how do I get it up to 7.2V? Of course, my power supply only does 5, 12, and 24 volts (well, +12 and -12, same thing, right?. I think this"learning electronics" box may just be an ATX PSU with a bunch of breadboard and switches on top.) Do I need to build a buck converter? If so, does it use the sort of transistor I'm likely to have laying around? (From various "babby's first electronics" kits and desoldering '70s crap.) Wors -case, I cut it open and replace the cells in it with new, possibly better ones. Well, I guess WORST case it burns my house down, but if that hasn't happened yet it probably wont. ...right?  *huh, I thought everything single cell was 1.5V. Are AA NiMH cells different voltage from the six NiMH cells in the battery, or is 1.2V close enough for government work? Edit: It's at very nearly the supply voltage now (that 5V source is more 4.8V, so it's either working and hit the limit of what I was providing, or two of the six 1.2V cells in it are trashed ), so I unplugged it for a bit to see if it'll hold a charge at all.Edit: derp I just realized I have 7V available with the +5V and -12V, or vice versa. Edit again: the battery is now showing 7.4V on the multimeter (don't ask), but the device doesn't light up. Battery is ... charged, if not fixed, and device is hosed? Chillbro Baggins fucked around with this message at 09:03 on Dec 30, 2016 |
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Dec 30, 2016 06:16
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Platystemon posted:The battery is probably thoroughly dead. One of the cells is still at 1.2V, drat. I don't know whether I should find a use for it or nominate it for sainthood. If you're wondering, I'm trying to get a Nikon D1x to run after rather a long time in storage, to use as a backup/secondary/rainy-day body/giant lenscap to go with my D7000. A replacement battery (of the exact same make and model I have, that was never very good) is about half the value of the camera, so I'm trying to do this on the cheap -- it was originally a newspaper camera, so it's been rode hard and put away wet. They go for $60 on eBay for just a bare body in technically-working condition, maybe $150 with working batteries and charger if the buyer's a sucker, but this'n probably wouldn't even sell as an organ donor (unless the buyer's a sucker). So yeah, I might spend  to replace the innards of the battery and play with electronics, but I'm not paying $35 for a new lovely battery, and $50-$100 for a charger if I can't find/fix the one I have. The only reason I'm trying to get the D1x running is nostalgia and to use in the rain when I don't want to risk killing the good/expensive body (and it was the backup to the backup when I got it).quote:And yes, NiMH cells are 1.2 V. This does cause problems in some devices designed for alkaline or carbon–zinc batteries. ... which are exactly as turbofucked as the battery I was hoping to replace with them -- one is at "probably salvageable" voltage (2.6V), and the other five are less than a tenth of a volt.
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Dec 31, 2016 06:04
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I'm bad at this. Trying to build a joule thief to light my keyboard (I have one of those desks with a smaller table above the main part for the monitors to sit on, and my laptop hands over and shadows the external keyboard), and ... welp. Mainly I don't have a ferrite donut. Can I use the inline inductors that look like resistors? Or wrap some wires around a nail? On the other hand, I finally finished out a much simpler project that I posted about before -- three of those Harbor Freight free worklights stuffed whole* into a flashlight that originally had a car taillight bulb and two 6v lantern batteries, powered by a USB phone battery. I call it "the sun." Well, I put the lens on, hot-glued the LED boards in place, and filled the rust holes in the case with epoxy (the latter worked out surprisingly well -- I put masking tape over the outside and painted the resin onto the inside of the tape). *The boards, I mean, obviously I took them out of their cases and hot-snot siamesed the PCBs together, but I just wired them in parallel to a common source, didn't have to gently caress with choosing resistors or anything. I still need to rejigger the wiring and strip the cable right near the plug inside the battery box so I can use the USB data wires with alligator clips for alternate power in an emergency -- last time the power went out, it was out long enough that the USB battery ran out, so I alligator-clipped a 4-AA holder onto the wires on the back of the LED panels (before I finished gluing it together) and ran through four sets or rechargeables and two sets of alkalines.) :"poo poo, power went out in the storm. Which flashlight you want? gently caress, where is a flashlight? I found one, but it's low on batteries." :"Nah, we cool, I got the sun." [flip switch, reenact Genesis 1:3] "loving gently caress of a gently caress, why did I look at it when I turned it on?!"Once the sun goes down I'll take some pictures of it. Seriously, it's damned near as bright as the CFL in the ceiling fixture, just more focused. Also, alligator leads are a drat godsend -- I have car chargers for our phones, but the cigar lighter socket in the car only works with the key on, so during the recent power outage I just clipped the charger nubbins directly to the car battery (after using the last of my phone's battery to Google the pinout, because I never remember) and set the phone being charged on the intake manifold and closed the hood. Chillbro Baggins fucked around with this message at 01:16 on Jun 27, 2017 |
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Jun 27, 2017 01:11
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I have a pair of Bluetooth headphones with poo poo battery life. 3.7v 240 mAh Li-ion, size of your thumbnail, the stock battery is. I can replace it with any other 3.7v Li-ion battery that I can cram into/gaff-tape to the housing, and it'll still charge when I plug it in, right? I have a couple obsolete cellphones lying around with 2000+mAh 3.7v Li-ion batteries... Chillbro Baggins fucked around with this message at 14:35 on Oct 7, 2017 |
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Oct 7, 2017 14:16
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Crosspost from the AI Stupid Questions thread: How much current do modern high-beam car headlight bulbs draw? Mom accidentally bought the wrong ones when a low beam went out (the lookup book was unclear), and I have one of those old steel-cased Big Beam flashlights that take two 6v lantern batteries and a reverse-light bulb, and since my cheapass LED conversion of it was disappointing, I'm thinking of stuffing the case with as many 18650 lithium cells as will fit, ganged up in a way that makes 12v (or strip a couple of cheap 12v power-tool battery packs and wire them in parallel, whichever is cheaper) to make a portable sun. Any idea if it'd run for long enough at a time to be practical?
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Nov 5, 2018 19:55
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Queen Combat posted:Ohm's law, motherfucker.  Checked the package, and 55W, so a little over 4.5A at 12v. Judging from Milwaukee's Fuel line's 12v batteries, I can probably pack in enough juice to run it for at least a couple hours between charges (probably on cheap individual cells from the local battery store or Amazon), so it's feasible. Am I going to have to build my own charger or can I just buy a cheap 12v tool charger for the same chemistry and modify it to plug into my homemade pack, and a cigar lighter plug for charging it in the car on camping trips? Ooh, maybe a charge/run switch on the lighter-plug circuit to run it directly off the car battery, because I like to overcomplicate things like that.*Could be worse, my father bought my now-9-year-old nephew one of those click-together electrical toy sets for Christmas a few years ago, mostly hoping my brother/the kid's dad, who doesn't understand electricity at all, would learn something by playing with it with his son. Like, my brother's 29 years old, and according to Dad has failed to grasp the concept of "it has to be a circuit with one end positive and one end neutral/negative and has to go a certain way in some cases." Dad and I can at least do house wiring (I helped him wire my parents' current house -- with Dad checking my work, of course -- when he built it, and did a fair job of it, when I was 7) and know what all the things on a PCB do, can follow a schematic and put simple things together, but neither of us can design anything electronical from scratch. Li'lbro Baggins' entire knowledge of electricity is "red to red and black to black, and don't let the red touch the black", and that probably only because his pickup has some kind of vampire draw and he has to jump-start it on a lot of mornings when it's cold (by Texas standards -- it's not the electrolyte freezing, Mom's car starts just fine to pull it around and jump the truck). (And yes, Li'lbro still lives in his room in our parents' house because the friends he got an apartment together with went their separate ways. He's saving up to buy enough land to build a shooting range, a nice house, and a cottage for my parents on. And he's making bank being the foreman of the non-technical dudes [i.e., the guys with machetes] survey crew, so he's just waiting until he finds a proper property in his son's school district.)
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Nov 5, 2018 21:15
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ante posted:Okay but what about your life story Yeah, I already have modified a drill charger in an attempt to make the cordless tools corded for use in my tiny shed, it didn't quite work because the thing was amperage-limited and shat itself (the smoke is still inside, it just nopes out when you ask too much of it, still charges a battery), and I know how to solder/braze. A battery charger will happily charge any number of series groups of the proper voltage ganged up in parallel if you break out the contacts to alligator clips or a plug, right? Load balancing might be a problem. If so, the cheap/easy solution is to put the cells in holders and randomly swap their positions around every few charging cycles, innit? And yeah, I've seen video of battery fires, that's why I'm asking here. As for my life story, assuming you weren't being sarcastic, I spent a few summers in high school helping Dad install air conditioners while I was driving '70s cars, so I can fix house and car wiring (and I know that if something in a car isn't working, it's most likely a bad ground connection.) I can make an LED work, but I tried to build a tube guitar amp once from plans from the internet, never got it to work.
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Nov 5, 2018 22:06
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I bought a Peltier cooler on a lark with a bunch of other stuff (including a digital microscope as a Christmas present for my lil' nephew) from sciplus.com. Pulled the processor heatsink off a dead computer I had laying around, soldered it to the good end of a broken-at-the-phone-end USB cable, blew my parents' minds. Me: "Plug this into your computer and touch the side labeled 'cold'." Mom: "Wow, it's like an ice cube!" Dad (I'll call him Bilbro Baggins, because that was more or less his CB handle back when he was a trucker, and inspired my current forums name): "How does it work?" Me: "Magic." Bilbro: "Well yeah, but ..." Me: "Weird transistors between two ceramic plates, try not to think about it too much." Bilbro: "Ah, neat." Also, I'm using zinc oxide lifeguard-nose-protection ointment for heat-transfer goo. It expired in 2001, but it's not like it's gonna go bad, it's oxidized metal in Vaseline, the metal is already burnt and the carrier goop is a petroleum byproduct, so ... Edit: Working on figuring out how to clamp the cooler, heatsink, and a big flat piece of copper on the cold side together. Chillbro Baggins fucked around with this message at 01:52 on Nov 12, 2018 |
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Nov 12, 2018 01:48
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I bough an osmelloscope (Rigol 1054z, and I've already hacked it). Any preferred sites to teach me how to use it? I have a "how to oscilloscope" textbook from the 1940s, in a box, somewhere, and I assume it'd be good enough, but would prefer text on the internet. If not, I could always call up my old racist uncle who used to be a TV repairman and get lessons in person.
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Nov 17, 2018 21:55
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I had a mains-locked clock once, for about a day and a half. My ex and I found one of those old punchcard timeclocks (if you've played Team Fortress 2, it's pretty much the same as the one used as set dressing in the interiors) for like $15 at an antiques store. We tried using it as a mantel clock because we were really into the TF2-style midcentury aesthetic at the time, but after the first night the gears noise and clicking when it tripped over ever minute got annoying, so I gutted it and replaced the innards with a quartz movement from one of those cheap wall clocks that takes a pair of AAs (I did keep all the bits for the parts bin, there were some nice terminal blocks and motor and all). Probably more accurate, and certainly more efficient. Edit: I really wish I could've gotten the wall clock from my grandmother's bedroom after she passed away, but my aunt called dibs when divvying up the estate with my mom. That thing must've been mains-timed, it sounded like a drat factory when I'd stay the night at her house on weekends/summers when I was a kid. And aesthetically, it would've fit right in onboard a Soviet submarine in the mess hall. In other news, I used the oscilloscope to actually diagnose a thing for the first time*! I bought a couple of those little solar-powered security lights from SciPlus, finally found the "on" switch (not mentioned on the packaging) and hung the as-yet-unmounted one up right under my desk lamp for a few hours, still no joy, so I opened it up and put the 'scope to it. The solar panel seems to be working, putting out 245mV to the pads where it goes into the PCB. Seems reasonable for being on its side under an old-rear end 20W fluorescent tube. The (*My $25 Harbor Freight multimeter would've done the job in half the time, but when you've just bought a $350 hammer ...) Chillbro Baggins fucked around with this message at 10:31 on Nov 19, 2018 |
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Nov 19, 2018 04:27
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Sagebrush posted:Yes, lithium batteries are generally dead (as in killed) A. Sorry, forgot to clarify since we were talking about batteries. I believe the technical term for the condition I was describing is "turbofucked". B. Opened it back up and popped the cell out (it's clearly the same molds as used for the previous version, just with the wires soldered directly to the battery instead of spring terminals), says "LC 14500 800mAh 3.7v" on the back side. And yes, I realize I vastly overestimated the physical size of it. 14500 means AA-sized, as I confirmed by opening up my wireless mouse and looking at the AAs in there. Derp.. It's gained a quarter of a volt since my last post, leaving it pinned up under the desk lamp. So still certainly drained, but maybe recoverable with enough solar-panel trickle-charging? What chemistry is nominally 3.7v? According to some light Googling, it is Li-ion after all. Welp. I'll leave it up and see what happens, I guess. Edit: If I can't fix it, I'll send it to BigClive, this is the sort of thing he loves.  (to be fair, I could go down to the local battery store and get a replacement cell and still be under the cost of buying the same light that had a better chance of not being DOA, but that's half the fun of buying surplus, innit?)
Chillbro Baggins fucked around with this message at 11:06 on Nov 19, 2018 |
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Nov 19, 2018 10:29
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My seemingly-DOA solar light has made it up to 2.1V since my last post, maybe there's hope for it yet. In other news, I apparently pushed the "hold" button (which is a latching switch) on the cheap meter, and when I turned it on it read 6.66V  Is that just a thing with the HF meter in the red rubber bumpshield (Cen-Tech P37772), or should I contact a priest and/or the store?Also, forgot to reply to this: Sagebrush posted:You do kinda need some signals to probe, though, to practice setting triggers and making measurements and stuff. Have you got an Arduino? Set it up to send serial data and probe the TX pin and play around with that. No, but I have some FRS walkie-talkies that were all the rage in the late '90s and still work, I figure poking around in one of those ought to be interesting. Obviously I won't be able to see the oscillator chip's output, but the bit before the crystal should be within my 'scope's range (now 100MHz, does that count as  ?) Or get out an extension cord and hump the thing out to my other car that's having issues with the ignition system -- i.e., it has eight pistons, runs as a V6 (four working in one bank, two going bang and two pumping air on the other side), and the exhaust smells of raw gasoline. Having replaced the coils-on-plugs, I'm pretty sure it's the engine computer, and now I can find out! Comedy option: Take apart a dead TV laying around, see what's wrong with it. The modern ones are somewhat less likely to kill you than the CRTs my uncle worked on back when 'scopes had CRTs.. quote:Finding analog signals is a little harder but maybe play with a microphone or a piezo cell and see what happens. Anybody got a source for audio files to make Lissajous whatsits? I found all the videos explaining the principle/how to set up the 'scope, but can't find an audio source to do the input end of that thing I now know how to do on the 'scope end. Chillbro Baggins fucked around with this message at 07:58 on Nov 20, 2018 |
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Nov 20, 2018 07:55
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ante posted:Oh yeah, pro tip for the guy with the new scope, don't use it to test mains grounded things unless you have an isolation transformer Oh yeah, I'm only going to be touching the low-voltage side, my TV-fixing uncle has told me enough horror stories about flyback transformers and my HVAC-fixing father about 120V to be sure of that. And I misspoke, I meant "obsolete" more than "dead." I have access to a couple of CRTs and a 13" LCD that work, they're just completely useless.
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Nov 21, 2018 01:35
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ante posted:No, my statement stands. With your scope, it's not the voltage that you have to worry about (although you do). It's the grounding situation that will arc through your scope, even on the low voltage side. Good to know. 4.5V (3xAA) radio it is, then, for the learning process.
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Nov 21, 2018 06:03
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Shame Boy posted:Yeah, this old EEVBlog goes into why if you're interested: Finally watched the video (I somehow missed that post earlier). So if it doesn't have a ground pin on the plug it's safe to poke at with the 'scope? Everything I was planning on poking at has a 2-prong plug. I don't recall ever seeing a TV with a ground pin, now that I think about it. If that's not the case, it should be fairly easy to tell (by looking at the wiring or prodding with the demonic multimeter) that the transformer between mains* and whatever I'm poking at is or isn't isolated, right? (*I'm in the US, if it matters, I just occasionally use Commonwealth terminology.) (Edit: ... I can't actually think of the American word for "mains." Probably because all the "messing with electronics" youtube people I watch have the Queen on their money.) Edit again:  Huh, so that's what the modem and TVs are working with. Neat. (I unscrewed the coax from the TV and clipped the 'scope leads onto the respective parts of the connector.) Chillbro Baggins fucked around with this message at 22:11 on Nov 25, 2018 |
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Nov 25, 2018 20:02
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Shame Boy posted:I didn't notice nobody had replied to you, sorry. Lemme give it a shot since it's important safety stuff we're talking about This is why I need to dig out that "How to oscilliscope" book I mentioned. Thanks for the tips. The AM/FM clock radio I was eyeing does seem to be isolated per your testing regime, but probably not worth the risk. I'll find something battery-powered, and buy that SDR kit because I've been wanting to play with SDR anyway. In related news, the 'scope shows a 60hz sine wave when I connect it to an 18" alligator lead, or touch it to my own body. When I have one thumb on the probe, the amplitude goes up and down depending on how close I put my other hand to the fluorescent desk lamp. I'm an antenna! ... I think I just independently invented the theremin*. Neat! *I've played with one, and know how it works in theory, but seeing the waveform on the 'scope made me actually understand it. Chillbro Baggins fucked around with this message at 21:19 on Nov 30, 2018 |
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Nov 30, 2018 21:07
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I got an RTL-SDR. What do I do with it? Is there a thread for that? It picks up the local country FM station 5x5, but apparently nothimg else.
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Dec 7, 2018 00:37
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