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I want to know if it's possible to have a push button so that when it's activated, it turns on my 9 volts circuit for 10 minutes and then turn it off. Also, I don't want this circuit to consume electricity when it is close.

Thanks you

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  • \$\begingroup\$ Yes, it's possible. The 555 always draws power when it's powered. \$\endgroup\$ Commented Apr 22, 2014 at 1:41
  • \$\begingroup\$ @Ignacio Vazquez-Abrams That's nice, do you have an exemple of this? \$\endgroup\$ Commented Apr 22, 2014 at 1:43
  • \$\begingroup\$ Nothing I couldn't pull off the Internet. Try "monostable multivibrator". \$\endgroup\$ Commented Apr 22, 2014 at 1:44
  • \$\begingroup\$ Wow.. surely you have googled using a 555 timer as a one-shot style pulse, whose duration is 600 seconds using T= 1.1*R*C ... The output of the 555 timer should turn on a MOSET used as a high or low side power switch (Google that) and you WILL use a few microamps while the circuits are off because nothing is perfect. Read the quiescent current usage of any IC you use. \$\endgroup\$
    – KyranF
    Commented Apr 22, 2014 at 1:45
  • \$\begingroup\$ There's a limit to how long a pulse you can accurately generate from a 555 (or the modern cousin '123 chip) and 10 minutes is a potential issue. We've discussed this before, but I'm having trouble finding the prior question. \$\endgroup\$
    – The Photon
    Commented Apr 22, 2014 at 1:46

1 Answer 1

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If you use a P-channel MOSFET to switch power, and use a button to turn on a timer, which, when done, releases the gate of the P-channel (pull it up to power-in with a resistor,) you will have a circuit that draws no current when off (well, maybe a microamp or two.)

I'd solve this by a small MCU like an ATTINY-85, but it could likely also be done with a 555 in one-shot mode.

schematic

simulate this circuit – Schematic created using CircuitLab

For a small-current circuit, a cheaper P-channel MOSFET than the SUP75P03 can be used -- something like a BS250 might even be sufficient if current draw is < 100 mA or so.

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  • \$\begingroup\$ That look very nice to me, but since I don't have a lot of knowledge in electronic I juste want to be sure, is this circuit usable in this current state? \$\endgroup\$ Commented Apr 22, 2014 at 2:58
  • \$\begingroup\$ Yes, this circuit is usable in current state. Just add your 555 or MCU or whatever to the output, in one-shot mode, where it pulls the given gate low when the time's up. There are alternative placements of SW1 that may be safer if the gate is driven straight by a 555 output -- I updated the diagram to consider this. \$\endgroup\$
    – Jon Watte
    Commented Apr 23, 2014 at 15:32

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