WTB for friend: Cheap 12V 20A supply

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chessman
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WTB for friend: Cheap 12V 20A supply

Post by chessman » Fri Jul 11, 2003 1:50 pm

Exactly what the title says...been trying to find one for him to buy, and he doesn't want to pay for the ratshack units.<p>Anyway, somebody have a spare one to sell?<p>lmk, thanks

IRONMAN
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Re: WTB for friend: Cheap 12V 20A supply

Post by IRONMAN » Fri Jul 11, 2003 9:22 pm

Go to E-BAY do a search for "12 volt power supply"
I saw several reasonable units.

rshayes
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Re: WTB for friend: Cheap 12V 20A supply

Post by rshayes » Sun Jul 13, 2003 5:18 pm

If you don't need a regulated power supply, look at battery chargers in an auto parts store. The huskier models may be capable of 20 amps. If you look on eBay, also check the shipping costs. A transformer-rectifier type of power supply capable of 240 watts output may weigh 30 or 40 pounds, and shipping won't be cheap.

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frhrwa
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Re: WTB for friend: Cheap 12V 20A supply

Post by frhrwa » Mon Jul 14, 2003 7:45 am

what exactly do you need? I have plenty of 12vdc supplies...
JESUS”…… don’t leave EARTH without HIM!

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Re: WTB for friend: Cheap 12V 20A supply

Post by fsdenis » Fri Jul 18, 2003 1:15 pm

I just use a 12v car battery about 80 amp-hours
capacity as a 12v dc power supply.<p>It supplies 20 amps easily for 2 hours or more.
Then I just put it on a charger for a while.<p>It is also good for 30 to 90 amps for shorter times and is very quiet -no ripple- compared to
electronic supplies operated at high currents.<p>I've made up a selection of cables for my bench to
make battery use convenient.

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frhrwa
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Re: WTB for friend: Cheap 12V 20A supply

Post by frhrwa » Wed Jul 30, 2003 7:16 am

Kyle... have you received the power supply yet..? haven't heard from you...
JESUS”…… don’t leave EARTH without HIM!

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Re: WTB for friend: Cheap 12V 20A supply

Post by i_myself_matthew » Wed Jul 30, 2003 8:02 pm

I am in the process of making a power supply for a ham radio, and I am stringing 3 computer switching supplies in series and using the 5vdc supply. You can set the calibration pots in each supply to add up to around 12 volts instead of 15. I just made sure that each supply was rated for 20 amps on 5 volts. Some newer computer supplies are even rated for around 20 amps on the 12 volt line, but loads are needed on the 3.3 and 5 volt line for the regulator to function properly. If you use supplies in series, it is very important to isolate the ground on 2 of the supplies in order to avoid shorting them out to ground.
My current design was able to pump out about 25 amps into a 275 foot roll of 12 gauge wire without any trouble. :D
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Re: WTB for friend: Cheap 12V 20A supply

Post by Larry Woods » Wed Jul 30, 2003 8:10 pm

Just curious as I read these posts to try get a feeling of the process. Your statement of isolating 2 of the grounds to avoid shorting out to ground puzzled me somewhat. <p>Is there more than one common ground and a relativity thing?<p>Thanks

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Re: WTB for friend: Cheap 12V 20A supply

Post by i_myself_matthew » Thu Jul 31, 2003 12:53 am

Each individual supply that I have worked with has tied the chassis to ground, as well as the 0 volt line (black output wire). Assuming that the supplies are run off of grounded outlets, they will be at the same potential. <p>If you connect the +5 volt line in one supply to the 0 volt line in another, it will be a short because the 0 volt lines are tied to the same ground.<p>However, if you disconnect the earth ground, the output of the power supply is isolated (because of transformer), and can be added to other power supplies much like a 5 volt battery (or whichever output you select).<p>Also, it would be a good idea to keep the fans in each individual supply to prevent overheating, although using just the 5 volt line isn't straining the supplies very much.<p>I hope that explained what I meant better.
Madness has a toll. Please have exact change ready.

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frhrwa
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Re: WTB for friend: Cheap 12V 20A supply

Post by frhrwa » Mon Aug 18, 2003 11:55 am

well, sent you the power supply and still haven't heard a word, so.... thank you very much... your welcome.... adios
JESUS”…… don’t leave EARTH without HIM!

chessman
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Re: WTB for friend: Cheap 12V 20A supply

Post by chessman » Tue Aug 19, 2003 1:57 pm

I've been banned from the net for a while. Sorry.<p>Wayne: yes, I received it. Thanks a bunch, works great! Sorry I wasn't able to let you know earlier :( <p>
I was thinking about chaining two of my 10amp comp supplies together. Would I just be able to parallel the outputs? It doesn't seem like it would work...just parallel the two +12VDC and the GNDs...

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