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Right say you stacked them on top of each other they don't discharge because they are essentially both full? Creating one larger voltage/tank of water.
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Sep 25, 2010 02:28
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Popete posted:Right say you stacked them on top of each other they don't discharge because they are essentially both full? Creating one larger voltage/tank of water. They don't discharge because there's nowhere for the water to go. Two tanks, sitting on top of each other. Nothing connected to the outlet. No current.
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Sep 25, 2010 02:46
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It seems like what I need is a XDS100 flash emulator. Unfortunately they are $80 
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Sep 25, 2010 07:43
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Delta-Wye posted:It seems like what I need is a XDS100 flash emulator. Unfortunately they are $80 Are you a student or anything? If so, you might be able to get one for free by asking TI nicely. Otherwise you'll have to bite the bullet or figure out another way. I wasn't sure if you were still in the process of building the board, or if you were using the one you linked earlier? If you're still in the design phase, you could put header pins with jumpers on the flash lines, so you could connect an external cable to the SPI lines.
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Sep 25, 2010 16:40
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Delta-Wye posted:You basically need something with a stand and a fine enough tip for SMD work (which really doesn't require /that/ fine of a tip anyways). The ZD-99 looks fine, I have a similar Weller WLC100, either will probably do the job (although $17 is cheap enough to make me start wondering about the real value). At the local hackerspace, we use these to teach all our soldering workshops. They definitely feel cheap, but they've held up to some abuse. They are absolutely, assuredly more well put together than the $15 irons at Radioshack. For $50, this is the iron I use everyday: http://www.mpja.com/prodinfo.asp?number=15141+TL It's a champ. With a steady hand, it's no problem soldering some pretty tiny surface mount parts.
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Sep 25, 2010 16:52
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I'm planning on controlling a 120v 6A resistive load using a moc3042 optoisolator and a bta139 triac. I haven't done anything with AC voltages so before I start putting anything together I'm trying to figure out why everything is valued as it is and how to calculate it. Here is the datasheet for the optoisolator. I'm observing figure 12: http://www.fairchildsemi.com/ds/MO/MOC3042-M.pdf I believe I have figured everything out except the wattage ratings for the resistors. When turned off, the moc leaks 500uA.. so that would mean the resistor just needs to be able to carry 0.00005W and a standard 1/4 watt carbon resistor should be able to handle that as long as it's rated for the voltage. When the moc is turned on is a different story. I have seen other projects using 1/4 and 1/2 watt resistors ok, but I can't explain why, especially due to the 1K resistor that helps turn everything back off. It seems to me you would need at least a 3W resistor (because the unit can turn on up to 20V.. so 20v^2/180ohms = ~2.22_W). Furthermore, for a non zero-crossing optoisolator it seems you would need resistors able to handle huge wattage loads.The datasheet says the unit is only capable of dissipating 250mW so clearly that can't be possible. What am I missing? Can someone explain what wattage the resistors (180, 39, and 1K) need to be rated at and more importantly, why?
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Sep 25, 2010 18:35
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The 1K is a pulldown resistor for the triac gate. It is only exposed to the triac gate voltage, and will no be dissipating power. The RC network is to limit the rate of voltage change. At 60 Hz, the impedance of the 0.01 uF cap is 265K, which is why the series resistor there is not rated for power. http://www.google.co.nz/search?hl=en&q=1/(2*pi*60*0.01E-6)&aq=f&aqi=&aql=&oq=&gs_rfai= The 180 ohm resistor is connected to a high-impedance voltage measurement circuit, so will not dissipate power either.
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Sep 26, 2010 00:51
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 Click here to view the full image It's a bit of a sloppy design, but it works. Two channels, drives a 19.2 V p-p sinusoid at 50 kHz quite happily with no distortion. Now for the transducer board and transformers...
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Sep 27, 2010 12:04
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SnoPuppy posted:Are you a student or anything? I think I will be going with plan B on this one - it's a great excuse to order a Bus Pirate! Which sounds totally gay but looks pretty useful. It looks like it will make it easy to program the SPI flash, and so I just have to wire the DSP to boot off of it. I can use my ezDSP board for most all of the development (so I can use a debugger and stuff) and then just write the final/near final revisions onto the final board. Thanks for the info so far! I'm still at the development phase. I'm using an Olimex MSP430-4619LCD board for a development environment for the MSP/user io portion (good portion of the way done with this), and the ezDSP board for the DSP portion (still working this part out, got a long uphill climb ahead of me yet) but in theory I should be able to set the ezDSP up as a SPI slave and start feeding configuration values (volume, clipping levels, what have you) once I get that far with the ezDSP. I think I'm going to start the board layout next couple days as I work out my requirements. I'm thinking about moving from Eagle to KiCAD because Eagle has been kind of annoying me with its 'light' requirements. Doing a largish design with lots of high-pin count CPUs and only having one sheet for the schematic is a HUGE pain in the rear end.
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Sep 27, 2010 20:39
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I brought a picoscope. It seems to work great. Just one question, I have a circuit which beeps when I was using it. I did some testing and the circuit would beep even if I use a single wire by it's self to touch the circuit. 1. Whats the reason the circuit beeps like this? 2. How does it work? How does it know a wire is touching it? 3. The beeping scares me, am I breaking stuff. Also it's limited to 20V I want to measure stuff up to 100V what's the best way to do that? (It's a pic 2104) FSMC fucked around with this message at 22:36 on Sep 27, 2010 |
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Sep 27, 2010 22:29
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Unparagoned posted:I brought a picoscope. It seems to work great. Just one question, I have a circuit which beeps when I was using it. I did some testing and the circuit would beep even if I use a single wire by it's self to touch the circuit. I've never used a picoscope, but maybe I can offer some suggestions. What is the circuit you're measuring? Does it have the beeper? Or is the scope beeping? You're probably able to get a measurement without a real ground because whatever you're measuring isn't isolated from earth ground so you're forming a large ground loop through the AC plug. Don't actually take any measurements like this because you'll measure all sorts of noise that isn't really present. If you need to make measurements of a higher voltage, just use a resistor divider to scale the voltage down. As far as the beeping, you should read the manual if it's from the scope. It could be over voltage or something bad like that.
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Sep 28, 2010 05:57
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SnoPuppy posted:I've never used a picoscope, but maybe I can offer some suggestions. The beeping is definitely the circuit not the scope. The circuit is a tens machine, It basically outputs a frequency through a transformer to ramp up the voltage up to 60V. Regarding the beeping I wanted to know about is how if instead of using the oscilloscope I use a piece of wire the circuit knows and beeps if I touch parts of it. I tried out using a simple resistor divider and it works great. Just one question it's easier and seems to work by having the resister divider on the ground side rather than probe part, is there anything wrong with that? Most things I've read seem to imply that the ground part should be the actual ground and not something else otherwise bad things might happen. Another question. From what I've worked out the transformer takes 6V-60V or something like that, so is that a 1:10 winding? I went online to buy a transformer and got completely lost, I ended up going through all the different types. I ended up getting something in the pulse transformer section, FLYBACK TRANSFORMER, 10UH. I only got that one since it was pretty much the only one I could find with a 1:10 winding. Can anyone give me advise on how to find transformers and what the different types are. In this case I would have pulses with a max width of 500usec & max freq of 40Hz. It would want to take with input voltage spike from 0-6V and output a voltage difference of 60V. FSMC fucked around with this message at 08:47 on Sep 28, 2010 |
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Sep 28, 2010 08:16
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So, for a class project, I'm trying to hack a microcontroller into my car to do remote start/turnoff/whatever else I can get control of with an app on my phone, and I'm trying to get a feel for the car's electrical system. None of it's CAN: it's all just straight voltages, which is really nice for my ability level. I was probing around one of the electrical connectors this past weekend with a multimeter, and instead of getting a read-out on the multimeter of the voltage across the two terminals, touching the two terminals together caused my car to start. This is really nice, since I was afraid that hacking in a remote start was going to be difficult, but I didn't think that what I was doing should even have been able to do this. Shouldn't I have just gotten a voltage readout? Does my multimeter suck and is it just shorting whatever two things I touch with its probes? Also, if I want to control this behavior with a microcontroller, would I be safe connecting those two terminals (I'm guessing they amount to 12v and ground) with a transistor that I switch between fully open and fully closed, or will I need a relay here?
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Sep 29, 2010 06:12
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Exitlights posted:So, for a class project, I'm trying to hack a microcontroller into my car to do remote start/turnoff/whatever else I can get control of with an app on my phone, and I'm trying to get a feel for the car's electrical system. None of it's CAN: it's all just straight voltages, which is really nice for my ability level. quote:I was probing around one of the electrical connectors this past weekend with a multimeter, and instead of getting a read-out on the multimeter of the voltage across the two terminals, touching the two terminals together caused my car to start. This is really nice, since I was afraid that hacking in a remote start was going to be difficult, but I didn't think that what I was doing should even have been able to do this. Shouldn't I have just gotten a voltage readout? Does my multimeter suck and is it just shorting whatever two things I touch with its probes? quote:Also, if I want to control this behavior with a microcontroller, would I be safe connecting those two terminals (I'm guessing they amount to 12v and ground) with a transistor that I switch between fully open and fully closed,
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Sep 29, 2010 06:38
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Exitlights posted:So, for a class project, I'm trying to hack a microcontroller into my car to do remote start/turnoff/whatever else I can get control of with an app on my phone, and I'm trying to get a feel for the car's electrical system. None of it's CAN: it's all just straight voltages, which is really nice for my ability level. quote:I was probing around one of the electrical connectors this past weekend with a multimeter, and instead of getting a read-out on the multimeter of the voltage across the two terminals, touching the two terminals together caused my car to start. This is really nice, since I was afraid that hacking in a remote start was going to be difficult, but I didn't think that what I was doing should even have been able to do this. Shouldn't I have just gotten a voltage readout? Does my multimeter suck and is it just shorting whatever two things I touch with its probes? quote:Also, if I want to control this behavior with a microcontroller, would I be safe connecting those two terminals (I'm guessing they amount to 12v and ground) with a transistor that I switch between fully open and fully closed, or will I need a relay here?
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Sep 29, 2010 13:39
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You can do direct phone control with a wireless ethernet module and ad-hoc networks, then sending the data through tcp/ip. He said 'app' so I assume it's a wifi-capable phone. Lantronix makes some modules that does this IIRC. It's a lot of work though.
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Sep 29, 2010 13:46
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Or, if you're near by, bluetooth or something? Also, if the inputs to a multimeter set up as a voltmeter (as opposed to ammeter) is enough to set off the starter, a transistor might have enough leakage current to start it while the transistor is off. The whole thing sounds kind of weird. If it doesn't have CAN, what does it have? Do you have a wiring diagram (something like a chilton manual). What kind of car?
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Sep 29, 2010 17:19
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ante posted:Voltmeters have a few megaohms between the probes, but they are connected. Why are you measuring the voltage level between two terminals that (presumably) aren't ground? Specifically, the one that's to the battery was labeled '30' and the one that started the car was labeled 'H'. The one I think turns the engine off is 'L', which is why it didn't do anything when I connected it to '30' when the car was off. Delta-Wye posted:Or, if you're near by, bluetooth or something? That's a good point about the transistor... I'm going to mess around with the settings on my multimeter to see if it was just something stupid I was doing and see if I can get a real voltage reading. If not, I might as well spend a buck or whatever it costs on testing a transistor out. The car is a '98 VW Golf, so it seems to predate most technical... things. The locks are pneumatic, even, which is ridiculous. Here's the wiring diagram I just found at the very tail end of my last poking around my car, so I haven't had a lot of time to pore over it yet: http://www.mediafire.com/file/ok24x5r8mwxt7rj/VW_Golf_IV%20_98_Electric.pdf Password is wiringdiagrams21.com (I just picked the first file uploader I found on Google, no idea if this one's any good) From the little that I've looked it, it doesn't seem like there's any data running through the car.
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Sep 29, 2010 19:45
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Any ideas on an easy way to make roughly 170VDC? I'm starting to work on a design for something that incorporates the 4 B7971 Nixies I have laying around, and they require at least that much voltage. I could just use a diode and a cap off of a 120VAC supply, but that won't quite get to 170VDC and will probably be all kinds of ripply. I may also power the thing with a small DC supply and use a switcher to boost to 170. Suggestions?
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Sep 29, 2010 20:59
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Hillridge posted:Any ideas on an easy way to make roughly 170VDC? I'd use a step transformer and rectifier with some decoupling caps. Yeah it will have ripple, but how clean do you actually need it?
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Sep 29, 2010 22:37
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Hillridge posted:Any ideas on an easy way to make roughly 170VDC? http://www.dos4ever.com/flyback/flyback.html That guy shows how to make a boost converter and a flyback converter that he is using specifically for Nixie tubes. Nixies aren't my thing but I found the guide useful nonetheless.
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Sep 29, 2010 23:12
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Thanks for the suggestions. I just thought of something else too - Could I just rectify 120VAC from a standard wall outlet? 120VAC is RMS, so peak should be closer to 170V, which may be enough to drive my tubes.
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Sep 30, 2010 19:33
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Hillridge posted:Thanks for the suggestions. I just thought of something else too - Could I just rectify 120VAC from a standard wall outlet? 120VAC is RMS, so peak should be closer to 170V, which may be enough to drive my tubes. Rectifying it should get you enough voltage, and the tubes should be okay with the unfiltered rectified signal (actually, they should have a longer life than they would on pure DC) so all you need is some high-voltage diodes and you're golden. It's effectively 120Hz so you shouldn't see any blinking or anything. You may want to consider some form of isolation transformer or something. Using AC directly carries some risk (I would be lying if I told you I haven't done it though  ).
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Sep 30, 2010 20:51
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Delta-Wye posted:Rectifying it should get you enough voltage, and the tubes should be okay with the unfiltered rectified signal (actually, they should have a longer life than they would on pure DC) What's the deal with this?
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Sep 30, 2010 22:28
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catbread.jpg posted:What's the deal with this? If it's anything like incandescents, then the ripple means they light up, and the filaments stay hot, yet total power output is lower, so life is longer. Lower RMS power, same effective brightness.
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Sep 30, 2010 23:33
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The 13.8V is a standard DC power supply with more current capacity then the load, and the battery is a lead acid car battery. As I understand it that circuit would do the following things:
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Oct 1, 2010 17:11
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I've never used any kind of battery charging circuit, but wouldn't that put 1.3V across the fuse?
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Oct 1, 2010 17:28
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dv6speed posted:The 13.8V is a standard DC power supply with more current capacity then the load, and the battery is a lead acid car battery. I want to say that over charging a lead acid battery can result in plating, but I'm not sure. I would be most worried about long term damage to the battery from 24/7 trickle charging, but it may just depend on how you limit the current. Also, seems like you may need a diode or something to keep the battery from powering the supply in reverse during a failure, but that depends on the type of power supply you're using I suppose. I think that basic circuit is the common way of setting that up though. quote:I've never used any kind of battery charging circuit, but wouldn't that put 1.3V across the fuse?
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Oct 1, 2010 18:20
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Does anyone have any ideas for cheap LCD displays? I need maybe 20 characters by six lines(more is better). Most of what I can find is $30 or more, which sucks. I've found some $15ish 128x64 pixel displays, but I'm not sure how many characters I can jam on that. I would be ok with writing microcontroller software to manually send characters without IC drivers, if that keeps the cost down.
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Oct 1, 2010 20:01
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ante posted:Does anyone have any ideas for cheap LCD displays? I need maybe 20 characters by six lines(more is better). I have a c header for a 5x8 font that is fairly legible. You can stuff quite a few characters onto a 128x64 screen using something like that; I've been working the 128x128 nokia ripoffs sparkfun sells and it's fairly readable even with the tiny font. Delta-Wye fucked around with this message at 06:38 on Oct 2, 2010 |
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Oct 1, 2010 23:07
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Delta-Wye posted:I want to say that over charging a lead acid battery can result in plating, but I'm not sure. I would be most worried about long term damage to the battery from 24/7 trickle charging, but it may just depend on how you limit the current. From what I've read, it seems like the battery starts drawing less and less current as it nears it's full charge. This almost makes it sounds as if it's self-limiting? I know lead acid batteries can be overcharged, I just don't understand the circumstances in which this happens. I've been google searching on the subject, but I'm suffering from information overload and could use a little direction on the subject. Delta-Wye posted:Also, seems like you may need a diode or something to keep the battery from powering the supply in reverse during a failure, but that depends on the type of power supply you're using I suppose. AbsentMindedWelder fucked around with this message at 23:25 on Oct 1, 2010 |
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Oct 1, 2010 23:20
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I want a dual power supply for when I try out various circuits and it seemed like an OK project for a beginner. This is what I have. Mostly it is an amalgamation of app-notes and what I've seen other people do. I plan on having a few boards made up for distribute to friends as well as embedding in future projects. Are there any obvious flaws with this? I don't plan on drawing more than 250mA from it.  Click here for the full 1193x785 image.
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Oct 2, 2010 16:51
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therunningman posted:I want a dual power supply for when I try out various circuits and it seemed like an OK project for a beginner. Not a bad start. Is AC-IN post transformer? I don't think the regulators are going to like ~170V across them Also, I'm not sure what the 330 resistors (r12 and 13) are for. Not that they are necessarily wrong, just don't recognize their purpose. Noise reduction? Stability? Do you have an app note that recommends them?
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Oct 2, 2010 17:11
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Delta-Wye posted:Also, I'm not sure what the 330 resistors (r12 and 13) are for. Not that they are necessarily wrong, just don't recognize their purpose. Noise reduction? Stability? Do you have an app note that recommends them? Also, an important note on the LM317. In order for its output to regulate correctly, it needs a load of around 10ma or more. Any less and the output will rise to its dropout voltage, possibly wreaking havoc on your load. Those leds on the outputs can help do this, but their currents will change drastically with output voltage. Might want to make them current sourced. ANIME AKBAR fucked around with this message at 18:37 on Oct 2, 2010 |
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Oct 2, 2010 18:34
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Thanks for the input! I plan on running it off of a 16V AC-AC wall wart I have. I'm not touching line AC for a good while yet. The 330R's are 3W resistors to discharge the capacitors when turned off. Good point about the load. My hope was to be able to keep it loaded enough with the LED's, but with it being adjustable what you suggest sounds better and more reliable. Is there an easy to understand way to do that?
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Oct 2, 2010 21:06
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To follow up on my previous question...Delta-Wye posted:Also, seems like you may need a diode or something to keep the battery from powering the supply in reverse during a failure, but that depends on the type of power supply you're using I suppose. What I really need is something like this awesome little box. That is a higher-end battery charger that also has the capability of powering an external load while charging the battery, thus acting as a DC UPS. As far as overcharging a lead acid battery, from what I have been reading, the higher charging voltage, the faster the charge rate, thus the more amps drawn. You should be able to keep a lead acid battery at 13.5v indefinitely without overcharging. AbsentMindedWelder fucked around with this message at 00:20 on Oct 4, 2010 |
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Oct 4, 2010 00:18
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dv6speed posted:To follow up on my previous question... Huh, I'm actually very interested in how you know this, because it seems strange to me. Also, just put a diode in series with your 13.8V supply. 13.2V or whatever you'll have after the drop should be okay. ANIME ACKBAR posted:I'm guessing it's so that when you disconnect the input power the caps discharge in a couple seconds rather than several minutes. Not a bad idea, I suppose. 
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Oct 4, 2010 01:26
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Delta-Wye posted:Huh, I'm actually very interested in how you know this, because it seems strange to me. Can you recommend any part numbers to diodes that will comfortably handle 20-30 amps? I'm curious to see if it is that simple, or if there is something else I may be missing in order to charge a battery and run a load at the same time without blowing poo poo up. Most power supplies allow you to open them up to trim the voltage, so dealing with voltage drop from the diode isn't a big concern of mine. AbsentMindedWelder fucked around with this message at 02:10 on Oct 4, 2010 |
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Oct 4, 2010 02:07
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It works! (still without the actual transducer). Blew a few drivers to get here, I will remember to never again design an output terminal for a chip with zero short-circuit protection with single-pin spacing... I've got some 33R series power resistors in there now to avoid blowing the chips, as they are the last that I have. Outputs up to a 200 V DC bias + 200 V signal, with the input coming from a line level audio jack. The cores are 3C85 RM12s, with 12/240 turns, ungapped.  Click here to view the full image
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Oct 5, 2010 05:38
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Between that manual I posted and some exploration, I figured out how the starter and locks work on my car (voltages only, no CAN). The next step is to figure out how to switch this with a transistor or relay using a microcontroller. I'm concerned about flyback voltage, which looks like it's going to be a problem with my starter. Here's a picture of how I'm thinking this should look: Forgive my diagram if it sucks, it's the first electrical diagram I've made  Is my flyback diode in the right place? How capable of a diode will I need to mitigate the voltage spike from the starter without smoking the diode each time?
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Oct 5, 2010 22:02
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