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.
Common operational amplifiers like the TL series, CA3140 and others can be used in this circuit...
This high-gain amplifier was found in the March 1994 issue of Electronics Now magazine. The...
We found this timer for times of a few minutes in a 1974 Ferranti transistor manual. The relay is 37...