This simple three-LED sensor uses an NTC at the input. The circuit is based on an uncommon integrated component today. We found it in documentation from the 80s.
This circuit was found in a 1987 edition of the United States' Hands-On Electronics magazine. The...
This circuit was found in a 1966’s Delco Radio documentation. Transistors are from the era, high...
Found in a 1960s RCA documentation, this circuit applies to most common triacs. The trigger device is a...