wallwarts and regulation..

media at mail1.nai.net media at mail1.nai.net
Thu Mar 5 20:09:06 CET 1998

>But, i have never had to use a wallwart to power anything before that
>needed 13v supply...I dont even know how to go about regulating it to
>13v.. Maybe if i just build a low-pass passive filter just to filter out
>the 120hz ripple..Im really in a quandry, since i never had to do this..
>anyone know of maybe a one chip solution to this, such as perhaps a
>programmable 7805 type regulator?? I need something ultra low power, so
>i can get it into the Oddy once its working properly..

I don't know about low power (you'll have to ask someone skating around
Australia :) but 317 and 723 are very popular adjustable regulators.  A 723
has 14 pins, requires quite a few extra parts and is usually used to build
more elaborate power supplies -- switching, high current, regulated
current, etc.  I've used the 3-legged 317 to ape 9-volt batteries -- all it
requires is two resistors.  It has a 65db (??) ripple rejection that can be
increased if you throw in an extra cap or two (one bybassing the resistors
and an .1uF as an LPF at the output).

There are dozens and dozens of voltage regulator chips available.  Still,
no one will tell me why a 7815/7915 isn't good enough for a modular . . .


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