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Project Notes

#128 ATtiny TotalSleep

Test a total power shutdown with an ATtiny85 processor on a breadboard.

Here’s a quick video of the circuit in action:

TotalSleep

Notes

The ATtiny SleepMode project showed me that even in CPU sleep mode, an ATtiny85 circuit can still draw something in the order of 238µA.

This project tests a scheme for total power shutdown triggered by the microcontroller itself. The circuit then draws virtually no current (certainly less than 10µA - the resolution of the ammeter I was using in-circuit).

The trade-off is that the circuit requires an external trigger to wake-up again. Here it uses a push-button.

How it works:

  • power is supplied to the ATtiny and other circuit elements through a p-channel MOSFET (I’m using a BS250 here)
  • when power is turned on, the 1MΩ resistor charges the 100nF capacitor with a time constant of 100ms
  • this keeps the FET Vgs negative long enough for the ATtiny to power up and apply a high signal to the base of the NPN transistor
  • the NPN collector-emitter conduction holds the FET Vgs negative, and therefore “powered on”
  • when the ATtiny wants to power-down, it brings the NPN base low, cutting the collector-emitter channel, and sending the FET Vgs to 0V.
  • this turns off the FET and everything is powered down. The current drawn in this state is limited to leakage of the components
  • to powerup, the push-button shorts the capacitor, bringing the FET Vgs down and setting the cycle off again

This all seems to work very reliably.

Construction

Breadboard

The Schematic

The Build

Credits and References

About LEAP#128 ArduinoATmel
Project Source on GitHub Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.