Multifunctional dimming desk lamp circuit

It is a multi-functional dimming desk lamp circuit. It adds a photometry
circuit based on the above example. It is very suitable for teenagers to use when reading and writing.
    In the figure, 220V AC power passes through R. Buck, VD rectifier, vs regulator and C. The filtered output is about 3.9V DC
, which is used by the integrated block HT770e3. , is the zero-crossing detection current limiting resistor of the integrated block, R; is the external
oscillation circuit B of the integrated block, and R, and Ct are f. For electrical reset, the phase modulation trigger pulse of HT7706 input m is passed through R. , r. Add it to
the f J pole of the thyristor VTH to control its conduction angle.
    VT1 and VT2 form a Schmidt circuit, which together with the photoresistor RL and other components form a photometry display circuit.
When the light illumination is greater than iOOlx (lux), the resistance of the photoresistor R1 is small, VT1 is turned on, and
VT2 Cut off, the luminous tubes I1:D do not emit light. When the light illumination is less than iOOix, the RL resistance value increases, causing
the Schmidt circuit to flip, VT1 is cut off, VTZ is turned on, and I.FD emits light, which means that the light is not too weak until the thick
light table lamp makes the illumination greater than iOOix. LFD just goes out. This circuit prevents students from
reading and writing in low illumination conditions with insufficient light, thereby protecting their eyesight.
  This circuit is equipped with 4 control key switches SBl-SB4. The functions of the key switches are as follows.
  SBl: Stepless dimming control key. Use this key to adjust the light to any brightness. Press this key and the light will
fade from dark to bright, then from brightest to dark, repeating the stepless change cycle. When the brightness of the light reaches the extreme position (brightest or
darkest), the piezoelectric ceramic piece B will make a "beep" sound as a warning, J_. When the brightness is adjusted to the appropriate brightness,
the brightness will be remembered and maintained after letting go.