Circuit Cellar P5

Although there is a variety of commercially available solid-state sensors, a little-known option is using a common silicon diode like the Fairchild Semiconductor 1N914. They are small and quite rugged as sensors go. And, since they cost only pennies apiece, they are definitely the cheapest option. We’re all aware that a common silicon diode has about a 0.5-V junction potential at room temperature.