+/-15v........ easiest way??

[patchell]

    No reason why it shouldn't work....just:

    Make sure the Wall Wart is 18 V AC.
    Remember that you will be using half wave rectifiers, so you will need to
make sure you have enough filtering.  After you have it all hooked up, check the
inputs to the regulators and make sure the ripple is allways greater than the
regulator voltage + 3 volts.  For the 18 volts AC transformer, this will mean
about 7 volts max of ripple.  If you know what the current draw is, it is posible
to calculate the size of the capacitor.  Here is an appoximation:

    C (in Farads) = (Ripple Voltage) * 60 / (Current in Amps)

    For 7 volts of ripple, and 0.5 amps of current draw, I get 1190 uF.  Just
double it and use a 2200uF.

RevTor at aol.com wrote:

> All,
>   I am building a dual filter/LFO type of box and it needs +/-15v.  I will be
> building this into a portable case, so I was wondering what the easiest and
> cheapest way of getting these voltages would be.  I was thinking of a 18v
> wallwart and two voltage regulator chips?  maybe some filter caps..  any
> reasons why this won't work?  Current draw vs wallwart/Regulator chips?
> All I need is a "Sounds good proceed on" and I'm on my way.
> Thanks,
> ~Steve M

--
 -Jim
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