The purpose of this circuit is to indicate which of the two cars crosses the finish line first on a slot car lane. The circuit is from an 80's Popular Electronics.
This circuit activates a relay when the sensor receives light. The sensor can be any common LDR,...
We found this circuit in a 1980 documentation. With basic changes, including transistors that were...
When a small air current reaches the piezoelectric sensor, a small audio signal is generated and...