We need low power consumption (1nA - 1uA) while the circuit is closed, and then wake the microcontroller when the circuit is opened.

A the moment the design includes a custom metal switch which will remain closed in its normal, resting state, which we require have very low power. It will open, and that is when our microcontroller needs to be activated.

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    \$\begingroup\$ No one will hate you for being a noob, we were all noobs once. But you need to give us more information to be able to help you. You can draw a schematic diagram of your circuit using the editor in the answer panel, this will help us understand you problem better. Also, what do you mean by next to no power consumption? 1mA, 1uA, 1nA? An obvious question for you is why you cannot use a button / switch which works the other way around: ie use a normally open switch instead of a normally closed switch,etc. \$\endgroup\$
    – Steve G
    Feb 23, 2016 at 10:45
  • \$\begingroup\$ Sounds like you just need to connect the button to an interrupt input, with appropriate pull up or pull down. Use 'sleep' mode on your processor, CPU will wake on interrupt. \$\endgroup\$
    – Icy
    Feb 23, 2016 at 11:14
  • \$\begingroup\$ i guess 1uA would be acceptable i 1nA would be even better. I cannot use a button/switch because device because it takes to much space, and it doesnt fit nicely into design. Basically what i have is some metal which when pressed could open circle and when not pressed could close circuit but as the only electrical enginner between us said he could check on microcontroller is it open or closed but it would spend a lot of electricity. i will ask him to put some schematics here tomorrow \$\endgroup\$ Feb 23, 2016 at 11:19
  • \$\begingroup\$ @icy atm we are doing it with button but it uses more space than needed and it aint reliable thanks to device construction, ayway we want to sortof create our own button \$\endgroup\$ Feb 23, 2016 at 11:22
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    \$\begingroup\$ Since you're making a custom switch anyway, you should consider redesigning the switch: i.sstatic.net/kob5P.png \$\endgroup\$
    – Adam Davis
    Feb 23, 2016 at 13:07

1 Answer 1


How about something like this?


simulate this circuit – Schematic created using CircuitLab

When switch is normally closed darlington will be off, and the micro will be un-powered. When switch is opened, the bias current through the darlington will turn micro on.

Will need careful choice of darlington and R1 to minimise power consumption.


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