Telephone controlled automatic light circuit (1)

The automatic light introduced is turned on by the telephone. When the phone rings at night or the owner picks up the receiver and pulls the L button,
the light will turn on. After the phone stops ringing (when no one answers the call) or hangs up, the light will turn on after a delay of 10-40 seconds. It will go out in vain
. With this automatic light ur, it is convenient for people to make phone calls at night. In addition, the dredging lamp is also equipped with a touch
button. When the owner gets up at night, he only needs to press the answer button. Chan will also light up handsome s around.
    Telephone automatic light circuit lhl~ 23-1, the right part of the dotted line in the middle is the ordinary lighting circuit, S is the light switch, combined with
1. After s, the light turns on - this El}U pedal is controlled by ILi words; open S. When the lights go out, the lights are controlled by the phone. The left part of the dotted
line is the telephone control part.
    The diode VD7~VD10 and the thyristor VT2 form the main circuit of the control switch. The isolation diode VD6,
the voltage regulator tube VS, and the capacitor (; form a simple resistance-reducing circuit to output a current of about 2-IV Supply
power to the control circuit. Optocoupler 4N25, photoresistor RI. and transistor VT1 form a telephone and light control circuit
.
    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 in series. When not talking,
no current flows during the period. The built-in light-emitting diode of 1N25 emits small light, which corresponds to the photosensitive tube cutoff, that is, the ④ and
⑤ pins of 4N20 are kept rising.
VT1 is cut off and the
pin VT2 is turned off . , the
light E is small and bright. At this time,
the circuit is in a static state
, and the consumption is very small.
It is less than imA after actual measurement,
so it is considered that no power is consumed
. When there is a phone call
or the phone is off-hook and
dialed, there is current flow. The internal stack of 4N2j light-emitting diodes emits light, and the corresponding photosensitive tube is turned on, and the 4
pin outputs a high level. If it is during the day, the resistance is low when exposed to light, and the voltage on it is lower
(compared to the product) Occupied), it is not enough to make VT] conduct, so even if you make a phone call during the day, the light will not light up. Only
at night, RI. shows high resistance, and the voltage distributed on the top of C is higher, so VT1 is turned on, and C , the stored charge is
quickly charged to f_ through v ri and VD5, so that cz is charged to a voltage of about 20V. At the same time, f; is also
discharged between the cathode of VT2 and J through R, so that VT2 is quickly charged External communication, electric lamp E lights up,
hang up the phone after finishing the call, al, no current flows. VT1 resumes cutoff but south of C. The stored charge can continue to pass through the month.
Provide f J pole current to VT2. Therefore, VT2 still Maintain the up-on state, the lamp still lights up and shines until the power supply is completed
. VI, loses the trigger current and turns off when the no-current current crosses zero, and the lamp goes out.
    SB is the automatic light-on button. When SB is pressed, ( The charge stored in j is charged to c through SB and R.
When VI 2¨ is turned on, the electric lamp E lights up and emits light. Its principle is similar to that of an ordinary delay lamp, and it is not controlled by the intensity of
indoor light and can be used at any time. Connect the key to turn on the light.
    VT2 should use 21/6i 6 50% M (_RiOO-S) and other unidirectional thyristors with small trigger current. RI. For the
MG45 photoresistor, the larger the difference between the light resistance and the dark resistance, the better. When installing, be careful to allow it to receive
indoor natural light, but not to be directly illuminated by its own light, otherwise it will flicker on and off when making a phone call.
Changing the R resistance can save light sensitivity. C in the picture, capacity The purpose of obtaining a larger (】..U~"eF)
is to make it have both filtering and energy storage functions, because when making and receiving calls, VT2 rises and
the voltage at both ends of VT2 drops, that is, the power grid can no longer To control the power supply of the circuit, it is necessary to rely on f. Slowly releasing the charge
to maintain the normal operation of the circuit .