Using a tunnel diode, this circuit was found in a 1966 American publication. The circuit is for signals sampled at a speed of 8,000 sps.
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...