MC81 Holiday Lights ASIC

The 220V AC power is bridge-rectified by VDI~VD4. One channel supplies power to the colored lights Hl and H2. The other channel goes through Rl and R2 secondary
resistors to step down, current limit and capacitors CI and C2 filter to supply power to the integrated block A (due to the internal power of MC81 There is already a voltage regulator, so
there is no need to install a voltage regulator tube in the external circuit, but a voltage-reducing current-limiting resistor needs to be added). Pins 1 and 2 of the integrated block directly drive the thyristor VSI and vsz to
control the flashing of the colored light strings Hl and H2. The music signal output from pin 5 is amplified by the external transistor VT to drive the piezoelectric ceramic piece B to produce
sound. In order to increase the sound volume of the piezoelectric ceramic chip, the triode power supply only uses the first-level resistor R1 to reduce the voltage supply. SB is an unlocked key
switch. Each press can change the light jump mode and the volume of the music sound, allowing the sound to be selected between loud, medium, small and none.