This proximity relay circuit was found in the July 1990 Radio Electronics magazine. The supply voltage should be according to the relay used.
The operational amplifier of this circuit can be the 741. The circuit has very low consumption and can be...
We found this circuit in documentation from the 1980s. It drives an old cassette or roller type...
Place the lamp on the ignition threshold via R2. Your approach causes it to light up. The secret is...