Fire emergency light circuit

The battery uses three AA 1800m A. h nickel metal hydride battery can be charged in a bright place without direct sunlight on the solar panel in summer.
AC charging provides 4.3V charging voltage and approximately 350mA charging current. If three AA nickel-cadmium batteries are used, the current limiting resistor Ri should be changed to 8~
iori to reduce the charging current and avoid damaging the battery.
    Fire emergency lights are widely installed in corridors and fire passages in public places and are special equipment for fire protection. Many fire
emergency lighting fixtures on the market are products produced under the supervision of the fire protection police department. They come in many varieties, but their functions are basically the same. When the mains power fails, the emergency light
will light up automatically and turn off automatically when the power comes. Fire emergency lights are a kind of backup lighting equipment. The lamps are equipped with batteries that provide power during power outages.
The batteries are charged when there is mains power supply. Because it works in parallel with the 220V AC power supply for a long time, it is prone to failure. Since
they are specialized products, most do not provide circuit schematics. This picture is the Qihui GF-066 fully automatic fire emergency light
circuit based on the actual drawing.
    (1) Circuit composition The circuit is shown in Figure 16-65. It consists of battery charging circuit, light control circuit, power supply circuit and fault indication circuit.
The lighting bulbs are EL1 and EL2 (2+5W/3.6V spiral bulbs). The battery is 3.6V/1800mA. h nickel-cadmium rechargeable battery,
which can provide a power of 2×2.5W during a power outage, and the lighting time is not less than 100min. There are three light-touch self-restoring buttons in the circuit: S3 (OFF),
S2 (ON), Sl (TEST) test. Three status indicators of different colors. LED 3 (H red) indicates charging, LED2 (W orange
) indicates circuit failure, and LED1 (L green) indicates external power supply. When external power is supplied, the main power supply indicator LED1 lights up, and
when charging the battery, LED3 lights up.
  (2) Working principle
  ① Lighting control circuit: composed of VT3, VT4, VT5, VT7 and keys S2 and S3. When there is no mains power, press the S2 (on) key.
VT5 is saturated and turned on, and the collector current of VT5 passes through Rt. Keep VT7 on; VD11 reverse breakdown works in a stable voltage state. The collector voltage of VT5
provides bias to VT3 and VT4, causing them to conduct. Light up EL1 and EL2. When the S3 (off) key is pressed, VT7 is cut off,
the conduction condition of VT5 is removed, and the light is turned off.
    When there is mains power supply, the external power source through VD9 causes VD7 to reversely cut off, VT5 cannot be turned on, and keys S2 and S3 cannot control the
on and off of lights El, l and EL2. After a power outage, the negative electrode potential of diode VD7 becomes zero. Make it conduct forward instantaneously, VT5 conducts in saturation, forming the lighting circuit
conditions, and EL1 and EL2 light up. After the call comes, the negative electrode potential of VD7 becomes high and the cross is reversely cut off, VT5 is cut off, and the light goes out (playing the role of automatic control).
In the lighting control circuit: VD7 and VT7 work in a critical state through the wind. The switch keys S2 and S3 only play a triggering role.
    ②Electric charging circuit: The external power supply performs constant current charging on the battery through vr2, VT6, wind, and VD10. When there is external power supply, the charging
current charges the battery through RB and VDIO, and the charging indicator LED3 lights up.
    ③Power supply circuit: 220V AC is transformed, rectified and filtered, and the VT1 collector outputs 4.6V DC voltage, which is mainly provided to the charging
circuit to charge the battery, and makes LED1 light up.
    ④ Test circuit: When the test button Sl is pressed and held, VT1 is cut off, the negative potential of VD7 becomes low and the positive bias is turned on, causing VT5 to be turned on,
meeting the lighting conditions, and making LED1 and LED2 light up. Release the Sl key and the light will turn off. The function of the test circuit is to test whether the lighting circuit is
normal.
    ⑤Fault indication circuit: The fault indication circuit is composed of VD13, VT8, R7 and VD11 . If the external power supply voltage is too high and VT8 is turned
on, LED Z will light up. Indicates an overvoltage fault.