Elenco Circuit Maker Skill Builder 125 - Manual (Page 18)

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Project #13 Clippy the Conductor
Project #14 Nifty Noises
This detector can be used to see if a material like plastic is a
good conductor or a poor conductor. Materials that make the
LED bright pass electricity easily, and are called conductors.
Most metals are good conductors, and copper is used in
most house wiring. Materials that block the flow of electricity
are called insulators. Plastic, paper and air are insulators.
A photoresistor is a light-controlled variable
resistor. The resistance of the photoresistor
decreases with increasing light intensity.
Rebuild the circuit from Project #11 but leave the slide switch (S1) out
as shown on the left.
When you place a paper clip across the terminals as shown in the
picture on the left, current flows from the batteries (B1) through the
100W resistor (R1), through the LED (D1), and back to the battery. The
paper clip completes the circuit and current flows through the LED.
Place your fingers across the terminals and the LED does not light.
Your body is too high of a resistance to allow enough current to flow to
light the LED. If the voltage, which is electrical pressure, was higher,
current could be pushed through your fingers and the LED would light.
Build the circuit shown. Turn it on, press the press switch (S2) several
times, and wave your hand over the photoresistor (RP) to hear all the
sound combinations. You can make the sound from the alarm IC (U2)
louder by replacing the 100W resistor (R1) with the 2.5V lamp (L1).
CM-125_Manual_031514.qxp_CM-125_Manual_031514 4/2/14 12:19 PM Page 18