Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 253

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.
Fig. 3.32: Circuit 32: Simple peak VU meter with
LED
Fig. 3.31: Circuit
31: Automatic
bicycle light with
phototransistor
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