Automatic switching of lighting dependent of ambient condition - uses two threshold trigger stages to provide difference between switch on and off condition

摘要

An automatic switching system is used to control lighting dependent upon ambient conditions. The ambient light intensity (E) is detected by a photoresistor (R1) that operates in series with a supply resistor (R2) to apply a voltage (V) to a voltage divider (R3,R4,R5). Threshold switches (SW1,2) react to set voltage levels and are switched to generate outputs (a1,a2). One switch controls a transistor switching stage (T1). The generated output (6) from a main power amplifier is produced such that a slight difference in switching level is obtained between the switch on and switch off states.