We found this circuit in the October 1996 Electronics Now magazine. The circuit uses LDRs as sensors and drives relays. The relays must have voltages according to the power supply.
This circuit allows you to read temperatures with a common digital voltmeter. We found it in the...
This circuit for the 1.5 to 15 V scaled ranges was found in a 1982 documentation, but uses current...
The integrated circuit of this 1976 configuration is the 7400 and the type crystal in televisions of the...