New simple 555 illuminance tester circuit

Kaixin micro test

Test - lowercase jpg

Test probe PH-5H

As shown in the figure, the illuminance sensor uses photocell 2CR33. When the illuminance is lower than the minimum illuminance 100 lux for learning, 2CR33 is high impedance, VT1 is near cutoff, 555 is high at 2 feet, and 555 is in reset state. Its 3 feet are low level, and the music IC2 is energized to make a music sound.