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I'm a proud subscriber of both Geekcrate and Nerdcoffin https://www.youtube.com/watch?v=sTqSkEbY_N8&t=46s
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Apr 27, 2017 12:58
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remember when they were just called bags of crap? #truthinadvertising
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Apr 27, 2017 18:09
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Last night I realized the folly of my design in which I had connected the ground shield of an all-metal connector to the ground of a device that had high voltage in it and found out that "oh, actually the positive rail pin makes contact before the ground is all the way in and energizes the connector's casing to 400V while it's still in my hand"  At least I was able to use my new power supply to confirm that that geiger tube I had works fine under more controlled conditions, thanks for the help as always guys!
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Apr 28, 2017 14:08
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I need a little advice. There's a few ifs and buts to this however it's just one aspect I'm not sure about. What I want to do is connect the DTR line of an FLT232 to the reset line of my Orange Pi PC. This is assuming it has one exposed. I haven't looked yet. We're working with 3v3 here so no conversion needed anywhere. What I want to know is whether I need any passive components inline? What I'm doing is messing with loading binaries via U-Boot using the FLT232 connected to the debug UART. Being able to do a hands off reboot would be really useful instead of power cycling. Plus with that setup it's location is unimportant. e: Never mind. There's no exposed reset. I suppose I could use a relay to control the power but that seems like a bit of a pain for the moment. General_Failure fucked around with this message at 00:12 on Apr 30, 2017 |
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Apr 29, 2017 23:55
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Connect it to a GPIO to trigger an ISR that turns on the watchdog and spins until that resets it?
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Apr 30, 2017 01:09
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I'm looking to buy a cheap oscilloscope (Rigol 1054Z or Siglent SDS1202X-E) to diagnose and debug various issues with my RC stuff. On the BNC ports they usually mention 400V peak, does that mean I could stick the leads into 230V mains power and check the waveform? Mostly interested in that, since one thing I'm looking for is to check voltage spikes in power systems, that might go up to 40V, and frying a scope wouldn't be nice.
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Apr 30, 2017 16:39
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The Rigol 1000Z's say they are 100Vrms for CAT II, the Siglent says 400V pk-pk. Either will probably work when paired with an appropriate attenuating probe, but both would be damaged by a 1:1 probe, and the selectable attenuation probes that come with them are almost certainly not rated for that much voltage either. You should not be working with mains by jabbing probes into wall sockets.
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Apr 30, 2017 20:17
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Foxfire_ posted:The Rigol 1000Z's say they are 100Vrms for CAT II, the Siglent says 400V pk-pk. To add to this: Don't jab your scope into the mains or mains-powered equipment if it's using a grounded plug. Either cover the ground pin with Kapton, use an isolation transformer, or a plug adapter. Just remember that it won't be protected... https://www.youtube.com/watch?v=xaELqAo4kkQ
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Apr 30, 2017 20:22
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Also buy a X100 probe, they don't cost too much and they're very useful for not destroying your scope when probing high voltages
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Apr 30, 2017 21:53
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Foxfire_ posted:The Rigol 1000Z's say they are 100Vrms for CAT II, the Siglent says 400V pk-pk. As said, I'll be scoping my RC gear, which is DC (or low voltage AC on the triple-phase motors). sharkytm posted:To add to this: Don't jab your scope into the mains or mains-powered equipment if it's using a grounded plug. Either cover the ground pin with Kapton, use an isolation transformer, or a plug adapter. Just remember that it won't be protected... Combat Pretzel fucked around with this message at 22:10 on Apr 30, 2017 |
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Apr 30, 2017 22:07
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I have a 1054z with all the stuff unlocked and it's fantastic for the intermediate-to-advanced-hobbyist level that I'm at. Here I am earlier today measuring the elapsed time (BX-AX) between a signal transition (blue trace) and a microcontroller's response to that signal (yellow trace). The microcontroller is responding by transmitting a string of bytes over RS232, which the scope is also decoding (green hex code, though you can only see the first byte at this resolution).  It's an awesome tool and absolutely worth the $400.
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May 1, 2017 08:51
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Nice. However for that sort of stuff, I have a Saleae Logic (the new ones also do 5V analog). Right now I'm more tending towards the SDS1202X-E, which seems to have a decent resolution FFT function for the price. Not sure if I really need the 4 channels, the idea behind owning this thing is to identify stuff making GBS threads up the power circuit and generally which components are actually broken (instead of going with the Hail Mary approach up until now, so this 400€ scope will hopefully save me money on the long-run).
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May 1, 2017 12:53
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I've been doing a lot of home circuit board makin' lately and it's pretty tedious and wastes a lot of toner / toner transfer paper / transparency paper so it's got me thinking of other ideas. I remember someone in this thread mentioned that if you have a laser cutter / etcher, you could spraypaint your board black and then burn off the areas you want etched. I don't think I have a laser powerful enough to do that in a reasonable amount of time, but I do have a violet laser and in my experiments 405nm "violet" LED's are close enough to UV to work on UV-sensitive etch resist. My other idea was to get a ~12" LCD screen and shine UV light through it, then use a lens to scale it down. I figure after being scaled down the diffraction around the pixels will be enough to not wind up with a grid of unexposed resist in any large areas but I'm not sure. Anyone tried anything like this? e: I'd only need a feature size down to like half a mm for what I do, though if I can get better than that great 
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May 1, 2017 14:23
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I've attempted the spraypaint etch mask thing, might have been me that mentioned it. Couldn't really get it to work, and then I gave up and just order boards now. I still think it could work, just not really worth it, considering the price and quality of boardhouses now. My time is worth more. Either of those UV methods are liable to be really fuzzy imo. Let me know if you get anywhere with any of that, I'll live vicariously through you
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May 2, 2017 01:31
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sharkytm posted:To add to this: Don't jab your scope into the mains or mains-powered equipment if it's using a grounded plug. Either cover the ground pin with Kapton, use an isolation transformer, or a plug adapter. Just remember that it won't be protected... I don't totally agree...it's true that a grounded scope could pose a problem but only the ground lead here is an issue and you don't necessarily need to connect the ground lead if you're measuring a grounded circuit. Meanwhile a floating scope is particularly hazardous if you're touching mains. You could start with a grounded scope and jam the probe into the socket (assuming its rated for that) and see. If neutral is pretty clean and line is a sin wave then it's probably a good measurement. Floating the scope would only be helpful if there was a lot of ground noise.
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May 2, 2017 03:39
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ate all the Oreos posted:I've been doing a lot of home circuit board makin' lately and it's pretty tedious and wastes a lot of toner / toner transfer paper / transparency paper so it's got me thinking of other ideas. I remember someone in this thread mentioned that if you have a laser cutter / etcher, you could spraypaint your board black and then burn off the areas you want etched. I don't think I have a laser powerful enough to do that in a reasonable amount of time, but I do have a violet laser and in my experiments 405nm "violet" LED's are close enough to UV to work on UV-sensitive etch resist. My other idea was to get a ~12" LCD screen and shine UV light through it, then use a lens to scale it down. I figure after being scaled down the diffraction around the pixels will be enough to not wind up with a grid of unexposed resist in any large areas but I'm not sure. Anyone tried anything like this? Embrace the lovely chinese boards! http://dirtypcbs.com/store/pcbs
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May 2, 2017 04:25
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asdf32 posted:I don't totally agree...it's true that a grounded scope could pose a problem but only the ground lead here is an issue and you don't necessarily need to connect the ground lead if you're measuring a grounded circuit. Meanwhile a floating scope is particularly hazardous if you're touching mains. If you're going to do this note that you can generally completely remove the grounding clip from the probe, I didn't know this for a while and the first live circuit I tried probing the loose clip fell on some live node and part of the circuit instantly vaporized 
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May 2, 2017 13:05
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ate all the Oreos posted:I've been doing a lot of home circuit board makin' lately and it's pretty tedious and wastes a lot of toner / toner transfer paper / transparency paper so it's got me thinking of other ideas. I remember someone in this thread mentioned that if you have a laser cutter / etcher, you could spraypaint your board black and then burn off the areas you want etched. I don't think I have a laser powerful enough to do that in a reasonable amount of time, but I do have a violet laser and in my experiments 405nm "violet" LED's are close enough to UV to work on UV-sensitive etch resist. My other idea was to get a ~12" LCD screen and shine UV light through it, then use a lens to scale it down. I figure after being scaled down the diffraction around the pixels will be enough to not wind up with a grid of unexposed resist in any large areas but I'm not sure. Anyone tried anything like this? It's not clear to me, at least, whether the optics in an LCD screen would work for ultra-violet light. Maybe it would? I don't know. A lot of types of materials absorb UV light. Do you know the exposure dose for the photo-resist/photo-film, and how long it would take to expose the resist with your violet laser/LED versus fluorescent lighting/sunlight in your garage? Quite often, people who do photography & photolithography develop their resist & film in red/yellow rooms to avoid unwanted exposure. This may or may not be necessary, depending on the sensitivity of your resist/film. silence_kit fucked around with this message at 17:45 on May 2, 2017 |
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May 2, 2017 17:38
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silence_kit posted:It's not clear to me, at least, whether the optics in an LCD screen would work for ultra-violet light. Maybe it would? I don't know. A lot of types of materials absorb UV light. I've used the resist with laser-printer transparencies and a lovely little UV flashlight before and it worked alright (though the single layer of crappy $30 laser printer toner let through enough light to gently caress up the end product, it at least worked as in the resist... resisted). It does recommend that you do it under red or yellow light, though I did it by turning off all my lights but a LED desk lamp pointed at the wall for a splash of light and that seemed to be fine. I don't know much specifics about the film because it's cheapo anonymous chinese stuff I got off amazon that just came in unmarked black plastic wrap. I was thinking when I get a chance I'll set my laser to different output powers and shine it on different parts of a panel for ~5 seconds at a time and see where it starts to work.
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May 2, 2017 18:05
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Is there any place in the US who will take solar cells I give them and laser cut + encapsulate them to my specs?
Zero VGS fucked around with this message at 19:30 on May 2, 2017 |
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May 2, 2017 18:47
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Zero VGS posted:Is there any place in the US who will take solar cells I give them and laser cut + encapsulate them to my specs? For decent-sized projects you can really get a long way with some basic carpentry and caulking, I saw a guy who'd made a 10'x6' array of pvcs as a custom cover for his trailer, the other day. It powered his TV and fridge and tools so his ford explorer and trailer were a mobile work and camp site. coyo7e fucked around with this message at 17:42 on May 3, 2017 |
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May 3, 2017 17:40
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coyo7e posted:Well I mean, any place that can cut glass, can cut them do this for you, I'd assume that many commercial solar places probably have the ability to make a custom housing. But I'd imagine anyone familiar with framing up glass could probably do it as well. How big are we talking? Pocket sized, page-sized, car-sized? What kind of mount are you going to use? What kind of stresses is it going to be under? Wind? Vibration? Well, it doesn't quite work that way, you take the naked solar cells and laser cut them, which I guess any precise laser cutting place can do, but then you have to have to encapsulate them, usually by using a kind of oversized lamination press to sandwich them between plastic films and glass to form a waterproof barrier. The more I'm looking the more it seems like I'm stuck with Alibaba... Edit: 10'x6' mobile trailer thing is basically what I'm trying to make too, need it to be built to last though. He have pictures of it at all? Zero VGS fucked around with this message at 19:26 on May 3, 2017 |
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May 3, 2017 19:23
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Zero VGS posted:Well, it doesn't quite work that way, you take the naked solar cells and laser cut them, which I guess any precise laser cutting place can do, but then you have to have to encapsulate them, usually by using a kind of oversized lamination press to sandwich them between plastic films and glass to form a waterproof barrier. Solar cells lose efficency with use no matter how well encapsulated and eventually need to be replaced, so if you're looking at something that size, why not just get off the shelf cells and mount them behind polycarobanate for durability or something?
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May 3, 2017 20:35
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Zero VGS posted:Well, it doesn't quite work that way, you take the naked solar cells and laser cut them, which I guess any precise laser cutting place can do, but then you have to have to encapsulate them, usually by using a kind of oversized lamination press to sandwich them between plastic films and glass to form a waterproof barrier.
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May 3, 2017 20:56
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Zero VGS posted:Well, it doesn't quite work that way, you take the naked solar cells and laser cut them, which I guess any precise laser cutting place can do, but then you have to have to encapsulate them, usually by using a kind of oversized lamination press to sandwich them between plastic films and glass to form a waterproof barrier. Can you not rig together modules ? They are much cheaper than loving with solar cells And likely to last decades.
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May 3, 2017 20:59
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What's the best way to get a stable voltage from an input voltage that could be either higher or lower than the target? Basically I want to get a stable, continuous 12 volts from a motorcycle electrical system, where the input could be anywhere from 9.5 volts (cranking the starter) to 14.8 volts (engine running at high RPM), with what is likely to be a high amount of electrical noise, and the possibility of brief spikes to dozens or hundreds of volts.
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May 5, 2017 08:17
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Sagebrush posted:What's the best way to get a stable voltage from an input voltage that could be either higher or lower than the target? SMPS with a lot of filtering on the feedback signal, with some zener diode overvoltage protection?
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May 5, 2017 08:37
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Something based on the LTC3780 may be the way to go. I've used the module below but I wouldn't recommend this exact model if you're using it in a commercial environment or need it for critical systems: http://www.ebay.com/itm/DC-5V-32V-t...QwAAOSwU-pXunel
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May 5, 2017 10:25
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Sagebrush posted:What's the best way to get a stable voltage from an input voltage that could be either higher or lower than the target? Find an automotive 12v voltage regulator module and use that
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May 5, 2017 10:25
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Malcolm XML posted:Find an automotive 12v voltage regulator module and use that Absolutely.
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May 5, 2017 18:44
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Sagebrush posted:What's the best way to get a stable voltage from an input voltage that could be either higher or lower than the target? I used this little guy's brother for a 5v source. Much easier than rolling my own.
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May 6, 2017 00:08
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Malcolm XML posted:Find an automotive 12v voltage regulator module and use that I agree except it can't do what was asked. To actually do what was asked requires a switching supply. A buck-boost topology handles it. Or you could boost up (charge pump or boost converter) and regulate back down (linear or switching). However it would probably be more practical to either live with the voltage droops or design around lower voltage like 5V.
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May 6, 2017 01:55
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I can't really design around the need for 12v. I have an OLED module that needs up to 1.5A at 10-20v to drive the panel. I could just boost to like 16v I guess but I've got a few other components that can also nominally run on 12 (plus or minus the regular automotive range, not including spikes), and so I liked the idea of having a clean 12v line for all of that instead of having to boost and filter to 16v AND filter the raw 12v into two different rails. It's already complex enough because the microcontroller I'm using runs on 3.3v logic but I've got some LED strips that need 5v and up to 4 amps...and I need to fit all of this into about the space of two altoids tins. (I am not actually using altoids tins.) It sounds like the cleanest way to get everything I need would be to use a powerful buck-boost to get the stable 12v, then another pair of switch-mode converters for the 5v and 3.3v, or maybe just regulate the 3v3 since it's low current draw and clean power for the logic is pretty critical. babyeatingpsychopath posted:I used this little guy's brother for a 5v source. Much easier than rolling my own. I just came across those on Amazon, actually. How reliable are they? They seem like just what I'm looking for, if they'll stand up to the kind of environment you get on a motorcycle (unusual voltage, greatly varying temperatures, potential of water splashing, heavy vibration)
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May 6, 2017 06:05
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I'm kind of curious about the quality of those things too. I was speccing out 12V to 5V DC-DC converters for something we were building at work and I looked at converters from a few manufacturers that used a very similar form factor (if not were exactly the same item). I wasn't satisfied that they were from reputable manufacturers. I didn't do an actual reliability evaluation on them, but I was kind of squeamish because they'd be powering a board worth over $5000. So I'm wondering if I made the right choice or if they really were perfect for the job. BattleMaster fucked around with this message at 06:15 on May 6, 2017 |
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May 6, 2017 06:13
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Figured out why my power supply was clipping, or rather I have fixed the problem and am only vaguely sure why it was clipping: originally the CCFL was wired to AC couple the output through a 10nF capacitor. I rewired it to bypass the capacitor and connect the transformer output directly into the bridge rectifier and it can now go all the way up to the ~800V design voltage I originally wanted, there's no clipping visible on the scope and the whole thing's quiescent current draw fell from ~75-150mA to 35-45mA  So the only thing I can think of is the rest of the circuit was loading the capacitor enough that it couldn't transfer enough current through it and the voltage started to sag, even though the rest of the circuit shouldn't have been adding much load at all when it's just idling? Well whatever. Shame Boy fucked around with this message at 09:23 on May 6, 2017 |
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May 6, 2017 09:20
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BattleMaster posted:I'm kind of curious about the quality of those things too. Can you say which ones you looked at? A few weeks ago I was considering this Recom series of DC-DC converter modules for one of my personal projects. Since I also needed a 48v to 12v conversion I ended up going with a couple of the wider input voltage range versions. At ~12 bucks each from Mouser I would hope they are at least somewhat reliable.
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May 6, 2017 19:39
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asdf32 posted:I agree except it can't do what was asked. Find an automotive grade buck boost vrm and use that then, geez. The point was not to roll your own and just use what the OEMs do
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May 6, 2017 20:15
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http://www.ti.com/lit/sg/slpt042/slpt042.pdf Id use these
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May 6, 2017 20:27
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Sagebrush posted:I just came across those on Amazon, actually. How reliable are they? They seem like just what I'm looking for, if they'll stand up to the kind of environment you get on a motorcycle (unusual voltage, greatly varying temperatures, potential of water splashing, heavy vibration) I am using it, under the tail of my motorcycle, to run an arduino that (through FETs) switches all the lights and the horn. Works like a champ. I can go look at mine and get the model and stuff, but I just picked "the cheap one" a couple of years ago. I think I got a 3A rated one, and my measured current with everything going is ~250mA or less.
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May 6, 2017 23:53
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| # ? May 28, 2024 02:19 |
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DethMarine21 posted:Can you say which ones you looked at? A few weeks ago I was considering this Recom series of DC-DC converter modules for one of my personal projects. Since I also needed a 48v to 12v conversion I ended up going with a couple of the wider input voltage range versions. At ~12 bucks each from Mouser I would hope they are at least somewhat reliable. I was looking at modules like this one posted earlier: https://www.amazon.com/XINY-Waterproof-Stabilizer-Conversion-Efficiency/dp/B01HB9NP0Y/ref=sr_1_4 I didn't look at PCB mount modules but Recom is a company I have at least heard of and is sold through reputable suppliers.
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May 7, 2017 01:36
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