255
Fig. 3.31: Circuit
31: Automatic
bicycle light with
phototransistor
Fig. 3.32: Circuit 32: Simple peak VU meter with
LED
Circuit 31: When it is dark, the phototransistor PT1 blocks, R1 is switched via T1, LED1 turns on. Bright ambi-
ent light turns the phototransistor on, T1 blocks, LED1 turns off.
