There's an issue with linear regulators when the output voltage
is higher than the input voltage. You might want to look at
adding diodes around the linears to discharge the output caps.


-------Original Message-------
From: Tim ODriscoll <tim@STOKEPOGESWAY.NET>
Sent: 08/15/03 01:37 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE:] 24vdc from a 15vdc psu

>
> On Sat, 16 Aug 2003, Jinx wrote:
> You could use a 7824 or jack up the reference pin (or "ground"
> as it's commonly used) of a 7812 with a 12V zener. Or a 7815
> and a 9V1 zener. The anode of the zd goes to circuit 0V and the
> cathode (band) to the reference pin of the reg. Take a few mA
> from the 781x output back to the zener cathode to keep it steady
>
First off, Thanks for all the replies.

This is the idea I was thinking of. The only similar example I can find is
this: http://www.mitedu.freeserve.co.uk/Circuits/Power/alarm_psu.htm

It's just like you say Jinx, but with a 7805.

And best of all, I've already got the parts for it in my junk drawer :)

Cheers,

Tim

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