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 aperiodic circuit was found in an old English documentation. The transistor can be any JFET...
The values of R1, R2, R3 and C1 depend on the signal to be integrated. The circuit is from Radio...
This circuit triggers an LM380 oscillator, producing an audio tone with light falling on the LDR....