Manual

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E
ver thought you could use a capacitor to dim a
light? Try this project. After you finish the wiring, set
the switch to A. Then the LED segments will light up
slowly and show an L. Once the LED reaches its
brightest point it will stay on. Move the switch to B
and watch as the L fades away.
Look at the schematic. When the switch is on, the
current flows from the battery to the 100mF
capacitor to charge. Once the capacitor reaches full
charge, electricity flows to the transistor base and
turns it on gradually, which turns the LED on.
Eventually the capacitor will be completely charged
and then the current flows continuingly to the base
of the transistor and the LED stays on.
When the switch is turned off and you remove the
battery from the circuit, then the capacitor starts to
discharge through the transistor and the LED. The L
dims until the discharge of the 100mF is finished.
If you want a slower dimmer circuit, all you have to
do is replace the 100mF capacitor with the 470mF
capacitor. Replace connections 25-116-124 with
connections 25-118-124. Be patient because the
LED does eventually come on.
Go back to project 2 (the police siren) and see if you
can figure out why the siren goes from high to low
as you press and then release the key.
H
int: the 10mF capacitor charges when you close
the key.
Notes:
EXPERIMENT #15: LIGHT DIMMER
Wiring Sequence:
o 18-19-20-48
o 25-116-124
o 46-115-90
o 119-47-131
o 89-132
o 121-122
Schematic
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