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Implementing sleep mode

A project log for DIY Body Scale

Fixing a broken scale with DIY hardware

BenjaminBenjamin 11/24/2016 at 22:080 Comments

Today I implemented the basic sleep mode of the Atmega8. My basic idea was to periodicly sample the ADC do check if someone stands on the scale. If yes, turn the whole system on and do a "serious" meassurement.

I got it running fine but the current draw is not really at a point where it should be. Currently the whole circuit uses 22mA in running state and 20mA in sleep mode. With a adoption that the AAA Batteries have 600mAh this circuit would only last >30h!

I think the biggest current draw comes from the rather stupid HD44780 display. The next step is to put a Transistor in between to completly cut the power supply of the HD44780 display in standby.

https://kilobyte.ch/scale_sleep.mp4

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