Auto-cutoff Power to Circuit

[Ser Brynden]

How can I automatically cutoff power to a 12VDC circuit after about a minute, while power is still applied to it? I'm not trying to keep it powered after main power is removed, like a delay-off circuit.

This is in regard to my circuit posted here: Help with Vehicle Audio Sound Board Design
I did a web search and found a few auto-off designs, some with 555 IC timers, but wasn’t sure how to adapt them to my circuit.

 

[Joe G]

using the search at the top I found this; https://www.electro-tech-online.com/threads/power-off-time-delay-circuit.135560/#post-1135745 it may help

 

[Ser Brynden]

using the search at the top I found this; https://www.electro-tech-online.com/threads/power-off-time-delay-circuit.135560/#post-1135745 it may help

Sorry, I should have clarified... I want the circuit to cutoff after a minute even though power is still applied to it. I'm not trying to keep it powered after main power is removed, like a delay-off circuit.

 

[MikeMl]

Check out post #2 in this recent thread. You can play with the RC time-constant to get the delay you want.

 

[Ser Brynden]

Check out post #2 in this recent thread. You can play with the RC time-constant to get the delay you want.

Is the MOSFET required? I just want power to cutoff after a minute and not come back on until source power is reset. It looks like the the circuit you mentioned goes off and on again.

 

[MikeMl]

Is the MOSFET required?

Yes, the PFET is the key to such a simple circuit. The PFET will switch several Amps of current with only a small voltage drop (a few 10s of mV). There are dozens of PFETS that would work in this circuit.

I just want power to cutoff after a minute and not come back on until source power is reset. It looks like the the circuit you mentioned goes off and on again.

The circuit produces an output for a duration of ~R2*C1 each time power is applied. I did it twice in a row in the simulation to show that even a momentary interruption of the input power resets the timing network for a new cycle.

 

[Ser Brynden]

I see. Thank you! I'll test it out in LTspice.