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Reducing Sleep Current in ATTiny Digispark

The ATTiny85 is a nice cheap micro-controller useful for standalone applications with a small amount of I/O and not needing connectivity like wifi.
A convenient way of using these is with the Digispark type modules as they incorporate a very convenient way of uploading sketches from an Arduino IDE using the USB bootloader.
When using these modules in battery powered applications one often wants to reduce power consumption by using the sleep capabilities of the ATTiny85. The processor itself has low sleep current which can be further reduced by turning off functional pieces of the micro-controller.
On these boards, however, there is a extra current drain which impacts on the utility of sleep.
This instructable shows how to modify the boards so that current draw during sleep is primarily that of the micro-controller itself.
Before the modifications the current drawn with the micro controller in sleep was 7.3mA. After the modifications it was 24 microAmp; a reduction of 300 times. This allows many months of operation on modest batteries.”

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