Indicated for activation by microcontrollers, this circuit was found in the Radio Electronics magazine of December 1987. The MOSFET can be of any type according to the buzzer.
In this circuit the output voltage depends on the light that falls on the LDR, increasing when the...
In this version from the 60s, the indicator is a light bulb, but the circuit can be modernized with the...
We found this circuit in an American documentation from the 90s. Through an LED it indicates the...