Turn on Atmega328P using Force Resistive Sensor (FSR)

Projects General Guidance
1

I'm working on a project that will turn on the Atemga by pressing on an FSR. I currently have the following circuit which works with an LED. When I press the FSR, the LM393 Comparator goes LOW, enabling a path to ground for the PNP transistor to flow current to the load (LED in this case but will be Atemga in the future).

lm393 fsr switch
lm393 fsr switch2023×1637 66.2 KB

Two quick questions.

  1. I'm getting a 700 microamp drain when the LM393 is in the High state (no path to ground so LED is off). I know that the voltage divider is taking about 20 microamps and the FSR voltage divider probably takes some more. But when I disconnect VCC to the LM393 it drops down about 600 microamps. I'm not understanding where all this current is going.

  2. This works fine for an LED. Are there any glaring issues as to why this would be a problem with a microcontroller?

2

That’s not much current.

3

I understand that the µC should stand on even if the force is removed. Finally it should turn off itself.

4

That’s not much current.

I'm planning to run this off of batteries, so it's definitely not ideal. But I actually, I just read the datasheet again for the Lm393 and saw that it has a supply current ranging from 0.4MA to 1mah :man_facepalming: So I guess I have to find one which requires less current.

5

As soon as the force is removed, the LED turns off. I imagine it should be the same for a microcontroller though

6

For battery powered projects, most people use deep sleep modes. It is much simpler to wake a processor than to turn it on by controlling the power supply. Plus, the state of the processor is maintained at all times.

Excellent tutorial here.

7

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