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what diodes do i need?

i made a litle schematic (picture is in paint) as an extra for my binary clock, since the wart is a litle bit to handy (i can reverse polarity) and i dont want to destroy my precious attiny2313, so i thought of of some diodes and made a plan. but, i had 4 zenerdiodes lying around, and i tried it, but nothing happened, the clock didnt power on. i think the diodes are to heavy, so i was wondering which ones i needed. its all in the scheme and i think its pretty obvious (i made it in paint, so the quality isnt good, as wel as my english :P)

Picture of what diodes do i need?
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Re-design5 years ago
Get a small full wave rect. from Radio Shack. Connect the pos to the pos of your clock and the neg to neg. Put that inside you clock case. Attach the power socket, that you wall wart plugs into, to the a/c connections. That way no mater which way the polarity is set you get the right polarity to the clock. You can even plug in an a/c wall wart (of the correct voltage) and you still get the correct dc to the clock. This is very similar to what is used as a protection circuit in expensive electronics that have external power sources. Good luck.
jeff-o5 years ago
Use a 1n4001 diode. It is rated for 50V and 1.0A. That should be plenty for this application. They are pretty easy to find. However, you must be aware that there will be a 1.4V voltage drop at the output (standard for a bridge rectifier setup like this), so if you feed in 4.5V you'll only get about 3.1V. Don't forget a filter capacitor (47uF-100uF) across the output, too. Come to think of it, insufficient voltage may be the reason the clock didn't power on in the first place...
frollard5 years ago
What you're thinking of is a bridge rectifier.

http://commons.wikimedia.org/wiki/File:4_diodes_bridge_rectifier.jpg

The diodes themselves have to be rated for the voltage and amperage you're working with - as with capacitors, a safety margin of 1.5-2x bigger than you need should be a safe bet. Look for diodes with a low voltage drop.

You can also get bridge rectifiers sold as a single unit.
your diagram is basically the same, just drawn a little differently.
godofal (author)  frollard5 years ago
k, i saw that diagram a couple of times, but i never associated (no idea if thats right) it with mine, didnt really look at it anyway :P but i see that it works the same way.