PICers,
That thread about battery backup reminded me of something ...

I have a 5V PIC cct and an 8v driver cct. (Coupling is by 4N25
optocouplers). To save power I'd want to switch off the 8V regulator,
say a 7808 in this case.

OK, Let's say I put an NPN transistor (say BD139) in the earth leg of
the 3pin 7808 & switch it on/off with a 4N25. No worries, that kills
the 7812 ... BUT the o/p voltage then floats to supply, 12V in this
case.

So what you need is some simple way to switch off the regulator and
have its o/p volts go to zero when it's OFF = when the npn tarnsistor
is OFF.

Any ideas?

Thanx - Ian


__________________________________________________________________
Get your free Australian email account at http://www.start.com.au

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu