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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

Etienne Lepage-Lepitre
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  • Yes, it's possible. The 555 always draws power when it's powered. – Ignacio Vazquez-Abrams Apr 22 '14 at 01:41
  • @Ignacio Vazquez-Abrams That's nice, do you have an exemple of this? – Etienne Lepage-Lepitre Apr 22 '14 at 01:43
  • Nothing I couldn't pull off the Internet. Try "monostable multivibrator". – Ignacio Vazquez-Abrams Apr 22 '14 at 01:44
  • 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. – KyranF Apr 22 '14 at 01:45
  • 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. – The Photon Apr 22 '14 at 01:46
  • What about two 5 minute timers in a row @ThePhoton ? – KyranF Apr 22 '14 at 01:48
  • @KyranF, The usual advice is use a very small uC. Like a PIC in a 6-pin package. Not my area...still searching for the old question. – The Photon Apr 22 '14 at 01:49
  • In fact, my needs are flexible, 5 minutes would be ok – Etienne Lepage-Lepitre Apr 22 '14 at 01:51
  • I would think that with very high resistances the capacitor and comparator leakage would swamp the charge current, leading to very low accuracy. – Ignacio Vazquez-Abrams Apr 22 '14 at 02:06
  • @EtienneLepage-Lepitre, the datasheet for these parts typically shows how to get pulses up to 1 ms or 100 ms or so...getting up to 1 s or 10 s means stretching their capabilities. The NE555 datasheet shows components giving up to 10 s pulses. – The Photon Apr 22 '14 at 02:12
  • Here's a similar earlier question: http://electronics.stackexchange.com/questions/22343/how-can-i-make-a-15-minute-egg-timer-circuit – The Photon Apr 22 '14 at 02:17
  • And another: http://electronics.stackexchange.com/questions/63906/i-need-help-designing-a-very-simple-timer – The Photon Apr 22 '14 at 02:21

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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.

Jon Watte
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  • 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? – Etienne Lepage-Lepitre Apr 22 '14 at 02:58
  • 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. – Jon Watte Apr 23 '14 at 15:32