Light Dark Sensor With Relay Circuit Using LM741

Above is a schematic diagram of an LM741 light/dark sensor circuit (from the excellent 741 Op-Amp Tutorial by Tony van Roon).The ECG128/NTE128 transistor stipulated can be substituted with any NPN transistor rated at sufficient gain and current for the chosen relay coil.1st Nov 2007 Update - We have modified the schematic diagram above with the addition of a 220uF smoothing capacitor between the