battery/wall xfmr switching
Mark Willis email (remove spam text)
> I'm finishing up my first (?real?) PIC project. A chess clock. I'd like
> to power it with either a 9V battery or a little wall transformer.
> I'm guessing there is an IC out there to switch between supplies. Or
> maybe there is some other trivial way to do this.
> Any help would be much appreciated.
One way would be to use diode "Or"-ing (use a power supply that has
over 9V output - which would include most 9V wall warts!) - Common
cathodes, an anode to +9V and +WallWartIn, and the system picks the
higher voltage automagically. Cheap, too. (Do lose a diode drop's
worth of power - an FET or BJT circuit might be better if switching
between 2 battery sources.) One project used this with a bridge
rectifier they had scads of, as a reverse voltage protection/spike
protector (connect the common anodes to ground, though Battery & Wall
Wart then need to share grounds.) "Think Devious" <G>
See also: www.piclist.com/techref/power/batterys.htm?key=battery
You must be a member of the
piclist mailing list
(not only a www.piclist.com member) to post to the