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Voltage Control: 20v DC Answered

I am trying to find an electronic part that will take in anywhere between 12-36v and put out a consistent 20v. What could do this? And how can I get one? If amperage matters, I'll probably be putting between 1 and 4 amps through it.

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tech-king (author)2008-07-27

3.5 amps? sounds like a zener diode might work.

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guyfrom7up (author)tech-king2008-07-27

is that your answer to all electronic regulating questions? I havn't seen you here for a while Glad to have you back Also that won't work when it's below 20 volts

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tech-king (author)guyfrom7up2008-07-27

hmmm..... yes, i suppose a zener diode is my answere to regulating questions. and i dont think an lm317 can add voltage.

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V-Man737 (author)tech-king2008-07-27

I was thinking a 78xx would work, but I don't know which... Or exactly how to get one (or ten, lol).

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guyfrom7up (author)V-Man7372008-07-27

I don't know if it exists, but you'd need a 7820. Also those are only like 50% efficient, so half of your battery will go to waste I look into it tommorow, but it's late here

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V-Man737 (author)guyfrom7up2008-07-30

It exists! It is cheap! I have made a tiny purchase on eBay to see if it works. Thanks a ton!

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tech-king (author)V-Man7372008-07-30

you may need heatsinks for prolonged use....

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guyfrom7up (author)2008-07-26

you could use 2 or 3 (preferably 3 or 4) lm317 regulators in parallel (cause each one can only handle 1.5 amps max) google lm317, radioshack carries them, they are pretty simple to use, you just need 2 resistors to determine the output voltage. If I were you I'd heatsink them.

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guyfrom7up (author)guyfrom7up2008-07-26

woops, my bad, that'd only work if the voltage is above like 22 volts, I'll get back to you on this

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guyfrom7up (author)guyfrom7up2008-07-26

actually, I don't know if there's a practical solution at that voltage and amperage what's the application, maybe there's a work around

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V-Man737 (author)guyfrom7up2008-07-27

;_;
I'm trying to change power source from wall wart to battery pack. It's a project I've been working on since early June (in fact, the thought process is what brought me to Instructables). If I can guarantee 20 volts from these batteries (3 9.6v packs in series, each varying its voltage based on how charged they are), I'll have one of the best Instructables up in a week or less. The load draws a max of 3.5 amps, but the actual current is sporadic and transient. Thank you for taking the time to think about my problems!

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guyfrom7up (author)V-Man7372008-07-27

just out of curiosity, what device takes 20 volts!?! what kind of chemistry are the batteries (NiCad, NiMH, Lithium Polymer, Lithium Ion, etc.)

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V-Man737 (author)guyfrom7up2008-07-27

I'm using NiCd batteries (actually, the very same ones in my first instructable!) to power a laptop... It will be the best instructable ever! Except I thought I wouldn't need any kind of voltage regulation. So it is going to have some unfortunate complication.

I hooked up both batteries in series to the laptop, making sure they were charged to 11 volts each. My laptop ran on that power for four whole minutes! As soon as the batteries' voltage dropped below 19 volts, the laptop cut short. :-( I'm trying to see how I can utilize another battery pack to give me more time, and then maybe have something that will take the lower voltages and make it into the required 20.

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