Using an LDR, this Philips circuit directly activates a relay when light strikes the sensor. The relay is 45 V with 20k coil resistance. The 220 nF capacitor must be polyester for 400 V.
In this circuit, which uses only diodes, we have both simultaneous functions. The diodes are...
This logic tester circuit was published in the November 1980 issue of Radio Electronics magazine. The...
This circuit was found in a 90s Popular Electronics. The circuit uses 4 bicolor LEDs to indicate...