Found in an Elektor from the 90s, this circuit is based on components that are still common today. Power is supplied with only two batteries.
We found this circuit in an 80's Radio Electronics. The circuit uses a PTC sensor and an LED...
July 2016 - It can be obtained from Mouser Electronics new trinkets Adafruit. These trinkets are...
This variation of the previous circuit produces a pulsating sound when the sensor is activated. The...