We found this circuit in the May 1996 Electronics Now magazine. The relay must have a voltage according to the circuit power supply and a trigger current of no more than 50 mA.
This switching circuit for analog signals is from a 90’s Electronic Engineering. The components...
This circuit triggers a relay when a pulse of light hits the LDR. The potentiometer serves as a...
This circuit acts as a VU-meter when connected at the output of any audio amplifier, triggering a...