555 telephone desk lamp circuit diagram

555 telephone desk lamp circuit

As shown in Figure IC2 and R3, CI forms a monostable delay circuit with a delay time of T = 1.1R3C1 = 110s. Telephone function: When a call comes in, the telephone ring tone signal transmitted by the outside line of the telephone passes through VDI~VD4. After the bridge rectifier circuit is rectified, it becomes a DC signal voltage. This DC signal turns VT through a photocoupler ICI. After VT is turned on, the collector voltage is lowered. This low voltage triggers the monostable circuit to be flipped by the 2-pin. The monostable circuit outputs a high level. The triac VS is triggered to turn on through R4 and the LED, and the light is on. After the lamp is turned on, the monostable circuit enters the delay process, and the delay time is 110s. After 110s, the monostable circuit delays to return to the steady state, and the lamp is extinguished.