Make a multifunctional dimming desk lamp with BA5173

In the figure, the 220V AC power is stepped down by R3, rectified by VDI, stabilized by VD2 and filtered by C3 to output about 3.9V DC power for the integrated
block BA5173. Rl is the zero-crossing detection current-limiting resistor of the integrated block, R4 is the external oscillation resistor of the integrated block, R7 and C2
are used for power-on reset, and the phase modulation trigger pulse output by BA5173 is added to the gate of the thyristor vs through R6 and CI to control Its conduction
angle.
    VTI and VT2 form a Schmidt circuit, which together with the photoresistor RG and other components form a photometry display circuit. When the light
illumination is greater than 100lx (lux), the resistance of the photoresistor RG is small, VT1 is turned on, and VT2 is turned off. , the LED does not emit
light. When the light illumination is less than 100lx, the RG resistance value increases, causing the Schmidt circuit to flip. VTI cuts off and VT2 is turned on, and
the LED emits light, indicating that the light is too weak. The LED does not go out until the dimming desk lamp is adjusted to make the illumination greater than 100lx. This
circuit can prevent students from reading and writing under low illumination conditions, thereby protecting their eyesight.
    This circuit is equipped with 4 control key switches SB1~SB4. The functions of each key switch are as follows:
    SBI: stepless dimming control key. Use this key to adjust the light to any brightness. When this key is pressed, the light will gradually change from dark to bright,
and then from the brightest to the darkest, repeating the stepless change. When the light brightness reaches the extreme position (brightest or darkest), The piezoelectric ceramic piece
B will make a "crack" sound as a reminder. When the appropriate brightness is adjusted, the brightness will be retained in memory after letting go.
    SB2: Graded dimming control key. Press the chain once, the light
brightness changes by one level, and cycle through four levels of low light, medium light, brightest and off .
    SB3: Delay extinguishing control key. Press the button once and the light will turn on. After about half a minute, the light will automatically turn off. It is suitable for sleeping at night
or when leaving the house.
    SB4: Timing automatic on/off control key. Press this button once, the light will turn on, and then it will automatically turn off after about 20 minutes, and then after 5nun,
the light will turn on again for 20rrun, and the cycle will repeat. It is mainly used to remind students not to read for a long time to protect their eyesight. It can also be used to
confuse the outside world at night when there is no one at home, so that thieves will not dare to visit easily.
    One thing to note is that no matter what dimming state the light is in, when the light is on, if you want to turn off the light, you only need to briefly
touch any button among SB1~SB4, and the light will go out. Readers can choose one or
several of the above dimming modes according to actual needs.