Elenco Green Projects - Manual (Page 75)

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Project #124 Gas Pedal
Filling Station
The 470 μF capacitor (C5) is a storage
device, so it would be nice to know when
it is filled to capacity. With the slide switch
(S5) in position C, turn the hand crank
(HC) until the red LED (D1) no longer
produces light. When the capacitor is fully
charged, the current is blocked and the
light cannot turn on.
Flip the switch to the left to show the
voltage across the capacitor, but at the
same time it will use current to move the
meter and the charge will drop as you
read it.
Modify the circuit to include the press switch
(S2), as shown. With the slide switch (S5) in
position C, turn the hand crank until the red
LED (D1) no longer produces light. When the
capacitor is fully charged, the current is
blocked and the light cannot turn on.
Flip the slide switch to the left and notice that
the meter does not move. The press switch is
open and stops current from flowing until it is
pressed, just like a gas peddle stops gasoline
from flowing when the car is stopped.
Press S2 on and off a few times to send
current to the meter.
Project #123
Did you ever wonder
how long capacitor C5
could hold its charge?
Try filling it up and
waiting a while before
taking a reading.
I sure would not get very far if my electric car used a capacitor to store
energy. I guess this is why they all use batteries and carry a gas driven
charger to charge the batteries up when they get low.
5V
5V
See projects 1 & 3 if you need to recharge the battery (B4).