Based on the CA3140 IC, this circuit was found in the June 1986 issue of Radio Electronics. Sensitivity adjustment is made using a trimpot in series with the sensor.
This application consists of a circuit that trips when the sensor resistance drops below a few...
Another one of the many possible oscillators using tunnel diodes. This has its frequency...
August 2017 - STMicroelectronics' BlueCoin development environment is available at Mouser...