I need to create a timer (approx 2 minutes timeout) which will switch on a lamp and alarm if the 2 minutes elapses (no control signals will be given).
This lamp should remain on until a hard reset is performed.
I had the idea of using a 555 timer feeding into an SCR with a push switch in series with the SCR to break the current as a reset.
Not sure though how I can use the 555 as a timer since it would appear to need a trigger but I am sure it can be done.
Any clever people out there have any ideas - maybe you can tell me of any easier ways (so long as they are cheap)
This lamp should remain on until a hard reset is performed.
I had the idea of using a 555 timer feeding into an SCR with a push switch in series with the SCR to break the current as a reset.
Not sure though how I can use the 555 as a timer since it would appear to need a trigger but I am sure it can be done.
Any clever people out there have any ideas - maybe you can tell me of any easier ways (so long as they are cheap)