quantboy
Newbie level 5
For a project, I need to design a circuit that will make sure that a relay (connected to a load) will not get stuck "on" if the computer that controls it freezes (with the input to the circuit being either high or low). I think I recall this being called a dead man switch.
COMPUTER ----> DEAD MAN CIRCUIT W RELAY ------> LOAD
The best thing I could come up with is a pulse generated by the computer that must be present for the deadman circuit to remain active (and the relay turning on the load, closed). If the driving computer freezes with the output high or the output lo, the circuit opens the relay and shuts down after a few seconds.
The responsiveness could be very slow -- Ideally a pulse of once per second would be sufficient and the response time for relay to open could even be as long as 30 seconds.
Attached is a rough "guess" for what is needed... Anyone have any ideas? Any better way of doing this? Do the values look kind of correct in the attached circuit?
ANY help would be greatly appreciated.
Ted
COMPUTER ----> DEAD MAN CIRCUIT W RELAY ------> LOAD
The best thing I could come up with is a pulse generated by the computer that must be present for the deadman circuit to remain active (and the relay turning on the load, closed). If the driving computer freezes with the output high or the output lo, the circuit opens the relay and shuts down after a few seconds.
The responsiveness could be very slow -- Ideally a pulse of once per second would be sufficient and the response time for relay to open could even be as long as 30 seconds.
Attached is a rough "guess" for what is needed... Anyone have any ideas? Any better way of doing this? Do the values look kind of correct in the attached circuit?
ANY help would be greatly appreciated.
Ted