Michael said:
Hi,
I would like to build a *very simple* "sleep timer" circuit to incorporate
into a stereo system. It should switch the mains, and could even be in a
separate small box. The idea is to press a button to give me power for
one hour only.
Anybody built/seen anything like this?
Thanks,
Michael
I would think that a simple 555 timer circuit would do this - set up as a
one shot timer. Plenty of circuits on the internet, just Google for 555
timer, and all parts available from Dick Smith/Tandy/Jaycar, etc, etc....
The timer circuit can drive a relay - if you use a relay with suitably rated
contacts then you could switch the AC....
I built a 24v timer to turn the light in the back of a rescue truck off
after 10 minutes - press a button and the timer starts, 10 minutes later it
turns the relay off and the light goes off. Ran the circuit straight off
the 24VDC power using a 12 volt regulator to run the IC and relay... You
could do similar for 240VAC as the curcuit doesn't use much power so a very
simple regulated power supply could be built to run the thing, if absolute
precise timing isn't needed (i.e. 1 hour +/- 1 - 2 minutes..)
To save some trouble I actually used the Jaycar timer kit and modified the
circuit a little to suit my needs. Probably have the schematic here of the
changed circuit, but try the Google trick first because 555 timer circuits
aren't very difficult at all..
Cheers
Martin, VK2UMJ