This circuit was found in the July 1994 issue of Electronics Now magazine. The relay can be rated at up to 12 V and 100 mA. The transistor is a general purpose transistor.
This circuit uses an LDR as a sensor to trigger an LED indicator at a preset lighting level. The...
We found this circuit in an American publication from the 80's translated into Portuguese. The...
We found this circuit in an old French documentation from the 70s, but it can be assembled using...