auto restart function

[ramoneb]

Hi,

I would like to design a circuit. Its role will be to turn off the supply power of my entire system whenever it receive a 0V in it input. and turn on the supply power after a while (delta T). the diagram block will be like :



I tried with this circuit:
(i simulated the input with the switch S1)



but 'delta T = 0' whatever C1 and R6

can you suggest me another circuit or the solution to have a controlled delta T based on C1 and R6 ?

Thank you very much.

 

[chuckey]

You don't need R3 and R4, either will do. Q2 is not switching on with 4V, try increasing R2 to 10K.
Frank

 

[ramoneb]

Thank you Chuckey for your replay.

Actually I am trying to control it with a Pcduino3 GPIO (3.3 Volt). The circuit is working and switching perfectly with 3.3 volt but in simulation it's need 4 volt to switch :/ ( anyway I am used to this differences between simulation and reality). this is the results of my simulations:



Now my problem is (and still) to maintain this 0 volt, when I switch, for a while... I tried different configuration but not one is workin

configuration 1:

configuration 2:

configuration 3:


Thank you for replaying, and if you think that I am posting my question in the wrong room in this forum pleas tell me.