Subject:
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RE: power source
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 14 Feb 2002 01:07:35 GMT
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Original-From:
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Kingsley Gifford <kgifford@thezone^spamcake^.net>
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Viewed:
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688 times
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Yeah, I used a multimeter and measured the 11.2V
I'm going to go to my local electronic store and get all the parts (they
have everything in stock) but why the 16v capacitor?
-----Original Message-----
From: Mathias Uhr [mailto:uhr@mathias.net]
Sent: Wednesday, February 13, 2002 7:17 PM
To: Kingsley Gifford
Subject: RE: power source
hi kingsley!
> In reference to http://www.aaroncake.net/circuits/supply6.htm
> I have an old transformer from a tape deck that produces 11.2V AC. (I
> just checked it). Can I build the circuit on the above page and use • this
> transformer? Or do I need to get one that produces DC.
yes, you can use it! the bridge rectifier (labeled "BR1") makes (some
sort of) dc, and the rest of the circuit filters and regulates it.
a bridge rectifier can be made from 4 diodes (1N4007).
for "U1", you need a 7809 regulator as discussed before;
for "C3", a 16v type is enough; you don't need a switch; if you add
the fuse, choose a 1A "slow" type.
for the rest of the parts, take the values listed on the page.
by the way: there are no transformers that produce dc - any transformer
only works with ac. this is why you need rectifiers and so on...
one more question: did you actually measure these 11.2v of your
transformer or does the label say like that?
in the first case: under load or "idle running"?
important note: the voltage applied to the regulator ic will be around
16v! without load, it may rise up to 21v or even more!
so the ic needs to "cook up" 7v (or up to 12v), which produces quite
some heat! i definitely recommend mounting the regulator on a
heatsink!
hope this helps
(and i hope the rest of the list doesn't get pissed with all this
electronic stuff...)
happy soldering
mat
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