This circuit was found in a Popular Electronics from the 90s. It is based on components still common today and an optical coupler for the triac. The sensor is a thermistor.
I found this circuit in a 1979 documentation. The phone must be at least 1k magnetic or crystal...
This simple circuit is designed to charger AA or AAA Nicad batteries. Current can be changed...
This circuit converts voltages from 5 to 12 V at voltages of 100 to 400 V. The transformer has a...