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power on/off circuit

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i2c2k

New Member
hi!

does anybody know a very simple circuit which can turn on the power supply by a short signal and turn off by an other signal.
the aim is to let a microcontroller let itself turn off (without sleep) and turn on by an external signal.
thanks!
 

Nigel Goodwin

Super Moderator
Most Helpful Member
i2c2k said:
hi!

does anybody know a very simple circuit which can turn on the power supply by a short signal and turn off by an other signal.
the aim is to let a microcontroller let itself turn off (without sleep) and turn on by an external signal.
thanks!
Anything is likely to either use some power all the time, or use much higher power when on (like a relay). Why not just use sleep mode, that's what it's designed for!.
 

i2c2k

New Member
well... a relay can't be taken into concideration because my device is a battery-driven application.
the reason, why i don't want to use "only" sleep mode is, that there are various other devices which have no sleep mode.
 

bmcculla

New Member
You just need a pass transistor. A button turns the transistor on supplying power to the micro. The micro immediatlely holds the transistor on keeping the power on after the button press. To shutdown the micro stops holding the transistor on which cuts off power.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
i2c2k said:
well... a relay can't be taken into concideration because my device is a battery-driven application.
the reason, why i don't want to use "only" sleep mode is, that there are various other devices which have no sleep mode.
It depends entirely on the application, you have been too vague so far to determine what can and can't be done. Many (if not most?) battery applications without an ON/OFF switch probably use some kind of 'sleep mode' - what devices were you thinking of?.
 

pittuck

New Member
December issue of elektor electronics has a push on push off circuit in it using a 555 chip. It activates a relay. Could this be of help? (Not sure if we allowed to scan / copy circuit and post in here, so best to see if u can find it, if not i will gave it a go....)
 

panic mode

Well-Known Member
pittuck, that would draw more current than MCU in sleep mode.
although i don't see why not use MCU to ocntrol power of devices
i like transistor idea by bmcculla.
 

i2c2k

New Member
hey, thanks for your help!
i think, it's a good idea to let the MCU supply the current for the transistor. i'll try this. i hope the volatge is enough.
 
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