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.
The circuit shown in the figure below is from the 1993 Linear Technology Applications. The...
In the figure we have the way to implement the E (AND) function with two inputs, in the case of...
This circuit can be used both as a power source and as a battery charger. The resistor R1 serves as...