I came across this tutorial in pyroelectro. I wanted to try it out myself without completing the tutorial. I used a few hints from the tutorial and came up with a working system. This is pretty much the same as the one in tutorial, just that I don’t have the 7-segment display.

I implemented using an Arduino UNO and some discrete components. I have a breadboard solution working now and am planning to make a protoboard version as well.  My Arduino code is available on github.