Two automatic light circuits for TVs

When watching TV, it is required to have a certain brightness around you, otherwise watching TV for a long time will easily cause eye fatigue and is not conducive to vision
protection. Here is an example of a small background lighting lamp that is controlled by a TV. When the TV is turned on, the small lamp automatically lights up.
After the TV is turned off, the internal energy of the Chiyi Neng is extinguished. When watching TV during the day, the small lamp is automatically blocked. will light up.
    The small circuit controlled by the TV is shown in Figure 23-6(a). The circuit
is composed of a TV on-off signal pickup, a signal amplifier, a signal rectifier, a thyristor switch, an optical circuit and other parts.
    The TV on-off signal pickup and signal amplifier are respectively
composed of electromagnetic coil I., -w tube VT1, VT2, etc. When the TV is operating, the TV power cord will generate a 50Hz electromagnetic field in the surrounding area due to energization. The coil
j picks up this 0OHz alternating magnetic field, thereby generating a corresponding electrical signal from C. The output
is amplified by [. The rectifier composed of VD1, VD2 and ' is sent to the army for voltage doubling rectification.
The corresponding DC voltage is obtained at both ends of彳F(4. This voltage is divided by R. and R. and is added to the base of VT3 to
turn on VT3. The thyristor Vding1 obtains the trigger current and does not pass, and the lamp E lights up. When the TV is turned off,
the AC signal on the power cord is interrupted, and the coil L outputs an alternating signal. (The terminal current L disappears, VT3
is cut off , and VT4 triggers the current when the idle current crosses zero. When the sky breaks, the light F goes out. If it is a color TV, turn it off remotely.
Although there is still AC current flowing in the iLt source line after shutting down, the signal strength is greatly reduced (. The DC voltage at the resistant end
is very low, after Rr . and R. are not enough to maintain the conduction of VT.3, so the light F will also
go out with the remote control Im. The light control circuit should be composed of a photoresistor RI. During the day, RI. shows low resistance. , so that the DC voltage at both ends of c.
is attenuated greatly, so v D 3 will remain cut off, and the lamp E will be lit. Only at night r,
RT. is a high resistance, and its presence has a positive impact, so The circuit function TF works normally.
    The value of G of this machine is very small, only 1pF. The same thing is that after the TV is installed, the light F can light up when it is powered on. If you
increase the capacity to 47 F/F After the TV is turned off, there is a charging process, so there needs to be a delay of tens of seconds before
the light turns on. But after the TV is turned off, there is a discharge process, which also takes tens of seconds. After a delay time of seconds
, the light F will go out. Whether to delay the call time can be decided by the operator.
    VT1 and VT2 can use 90-type silicon NPN threshold tubes, and the p value should be between I (JU-i50; VT3 should use
9 Type 014 and other brick NPN transistors, Lu;::200. V+J, 4-inch 2N6565. WiCR1008 type and other small plastic-packed
unidirectional thyristors and electromagnetic coils L need to be homemade. Find the input or output transformer core in an old radio.
The dimensions are shown in Figure 206 (I,). First cut off one side of the iron core to make the iron core into a "u" shape, use the original
skeleton , and wind 2000-3')00 turns of ≠0 imm enameled wire on it. Yes.
    Cabinet test: Wrap RL with black tape first, and use the light control circuit to make small work. Then place the core U of the cable L
against the power cord J of the TV (only rely on the root of the power cord) , turn on the TV, the light should glow, and
after turning off the TV, the light will go out. Then, remove the black tape on the outside of the RI, and use insulated wires to lead it to a
suitable place outdoors and fix it. To ensure safety, the RL should be installed in the glass The oysters are placed in the vial so that the metal parts cannot
be exposed, and the stomach is kept in a safe place where ordinary people cannot touch or touch it. It can
work normally by just twisting and debugging the parts.