Re: 7824

You need to have a higher input voltage when your equipment is on
for good regulation. When you turn it off, it's not a problem.
Don't worry about it.

Do worry about putting enough heat sink on those regulators if you're
dropping a lot of voltage (e.g. 30 -> 12) with any signicant current.
You can fry them pretty quick that way.

Paul

>
> From: Al Schoepp <a_schoep@...>
>
> Hope somebody here can help with an electronics question. I need to
> step down 30vdc to 12vdc and 24 vdc for a the stepper driver I'm working
> on. I believe a 7812 and a 7824 chip will work for me. However the
> specs say that Vin must exceed Vout by 3 volts. When the system is
> operating that is not a problem. When I turn it off it will take a
> while for the power supply cap to drop to 0 so at some point in time Vin
> won't exceed Vout by 3v. Will this damage anything? If so how do I
> prevent this from happening. The stepped down voltage will be used to
> power small cooling fans, if that makes a difference.
>
> Thanks,
> Al
>
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--
Paul Amaranth | Rochester MI, USA
Aurora Group, Inc. | Systems & Software
paul@... | Unix / Windows / NT