Velleman EDU01 User Manual
Page 31
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Pag. 31
Required parts: 9V battery*, 3x1K resistor (brown black red gold), 3x100K resistor
(brown black yellow gold), 3 x red LED, 3x BC547 transistor, 3x10µF electrolytic capaci-
tor, 2x wire jumper
This circuit makes each LED light up shortly in succession. The circuit consists of 3 identical
channels. It is theoretically possible to expand; per LED a similar circuit is needed in series
with the previous. The capacitor of the next channel is charged when the transistor of the
previous channel is not conducting. As long as a certain transistor is not conducting, the rele-
vant LED will light up. Capacitor C4 is added to the circuit to create a certain starting condi-
tion when connecting power and to ensure a good operation.
Time to experiment: What happens when you change the value of R1, R2 and R3 to 10K?