Automatic Bike Headlight Switch
Improved bike headlight switch circuit presented here has been designed to switch bike headlight on (or similar loads) at a presettable ambient light level. The circuit is based on the renowned timer chip LM555 (IC1), here triggered by a decrement in ambient light level. Here is a 220V automatic light switch, just in case you need one. how does the automatic headlight switch works? When 12VDC supply is applied to the circuit, the voltage at pin 2 of IC1 is set by the voltage divider built around the Light Dependent Resistor (LDR) and trimpot P1 (100K). If the ambient light level (presetted by P1) is sufficient, pin 2 of IC1 is at a high potential and as a result IC1 is disabled. Capacitor C1 (100uF/25V) added across the LDR eliminates possible unwanted circuit functioning which may caused by sudden fluctuations in the light level. However, when ambient light level drops, the resistance of LDR increases and the voltage level at pin 2 of IC1 drops to trigger the monostable circuit. Simu...