As shown is a very attractive Christmas lights circuit. When the power is turned on, lights HL will gradually become brighter; when it reaches the brightest, it will automatica
lly gradually darken; et brightness of the darkest time, will automatically brighten gradually, so repeated. Smooth the entire change process. Brightness change process depends on the charger lights HL capacitor C3 discharges. When IC1 (NE555) 3-pin output is high, the capacitor C3 begins to discharge through the IC2 (CN25) optical isolation, lantern HL brightness began to decline. IC1 here set no stable oscillator whose frequency is determined by R1, R2 and C1.