From: John Popelish
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Subject: Re: Inductor used in 110v to 15v
Date: Fri, 29 Nov 2002 04:54:23 GMT
NNTP-Posting-Date: Thu, 28 Nov 2002 23:54:23 EST
> Hi :
> I'm creating a power supply to drive car audio equipment in order to design and test outside of the auto environ. Car audio amps
> have their own regulators so I do not see that I will need a regulated PS. Any tips you can provide are much appreciated.
In addition to the bridge rectifier, you will need a really big
capacitor bank, to keep the DC reasonable ripple free while dozens of
amps are drawn from the supply. Something like 10,000 uf per amp
total something like 3/4 farad total. You might be tempted to get one
of those 1 farad, 20 volt electrolytics, but I doubt they have a 30
amp ripple current rating. A bank of several 100,000 uf caps in
parallel mounted on copper buss bars would be more conservative. You
might also put a fuse in series with one side of each, so that one
won't explode if it develops a short circuit, and dumps all that
capacitance. These big caps with screw terminals are often referred
to as computer grade caps (for searching suppliers web sites). They
are also expensive.
For instance, a 68,000 uf 25 volt computer grade cap from Digikey
(EEG-AA1E683FHE if you want to look it up on the Digikey site) sells
for about $25 and has a 17 amp ripple current rating. A circuit board
mounted 120,000 UF 25 volt (ECE-T1CP124FA) goes for $15, and has a 12
amp ripple current rating.
Expect your lights to dim momentarily when you charge these up. Don't
forget to add a bleeder resistor to drain these when the power is
off. A couple 12 volt brake light bulbs in series make a self
indicating load that has a high enough voltage rating to last longer
than you do.