This conventional relay light detector circuit uses a 741 as a voltage comparator. The sensitivity adjustment is made in R1. The supply voltage depends on the relay used.
Found in National Semiconductor documentation from the 1980s, this circuit uses an operational...
This basic voltmeter circuit has an input resistance of 2 M. The instrument is 100 uA and the...
This simple alarm using only transistors was found in a 1990 publication. It can be powered by D...