Telephone controlled automatic light circuit (2)

It is an automatic telephone light composed of NE555 time base circuit and optical coupler. When making a call at night,
the light will automatically light up and delay imi after hanging up. Left or right, the lights will go out on their own. The circuit is also equipped with r-key
switches. When a light is needed, just press the switch lightly and the light will automatically illuminate.
    Terminals a and b are connected in series to the telephone line. There is no need to distinguish between positive and negative polarity when connecting, and their connection will not affect
the normal operation of the telephone. Normally, when there is no current in the telephone line, the built-in light-emitting diode of the optocoupler Al (4N4,)
will not emit light, and the corresponding photosensitive tube is turned off, that is, the ④ pin of Al outputs low level. VT1 is in the cut-off
state, its collector is at
the commercial level, the steady-state flip-flop
composed of A2 C NF.555) is in the stable state, the output terminal ③ pin outputs low level, the thyristor wr2 is turned off, and the light is on E does not light up.     When a call comes in from the outside line or the owner picks up the phone and dials, current flows through the telephone line, and the luminous tube built in Al lights up, and the corresponding photosensitive tube is turned on, that is, the ④ pin of Al outputs... high level. VT1 obtains base current conduction, and its collector outputs a low level, that is, a negative impulse is input to the ② pin of the monostable flip-flop A2. A2 is triggered to flip and set into temporary state, and the ③ pin outputs a high level. , the VT2 trap gate is opened by triggering the lU current, and fE is turned on. If no one picks up the phone after ringing or hangs up after calling, Al's ① and ② pins will lose the phone current, the built-in light-emitting tube will go out, the corresponding photosensitive tube will return to the cut-off state, and VT1 will also cut off. Stopping the power supply at this time is called passing R. To C. Look for power, and after about imijI, make the level of pin ⑥ of AZ reach 2, +3V. ,. At the end of the transient state, the trigger returns to steady state, pin ③ returns to low level, VT2 loses the trigger current, the AC current crosses zero and is turned off, and the light F goes out.     SB is the light button. When you need to turn on the light, just press SB. Artificially input a low voltage f to the ② pin of A2 , forcing A2 to flip into temporary exhaustion, so the light E point can also be adjusted to imin.     Rl. It forms a light control circuit with RP. The second operation process of J is the same as the above example. It ensures that the circuit does not work during the day, and the automatic lights are only controlled by the phone at night . The thick section RP can "adjust the light control sensitivity of the circuit. This circuit RI. The installation is relatively free, as long as it can be Just feel the natural light in the room. Don't worry about it being disturbed by the light of the lamp itself.