Function Of Adjustable Resistor; Function Of Photoresistor - Elenco Electronics Projects 306-511 Instruction Manual

Project #325
Project #326
-15-
Function of
Adjustable Resistor
OBJECTIVE: To understand the function of the adjustable resistor.
An adjustable resistor is a normal resistor with an additional arm contact.
The arm moves along the resistive material and taps off the desired
resistance.
The slider on the adjustable resistor moves the arm contact and sets the
resistance between the bottom (point C1) pin and the center pin (point
B2). The remaining resistance is between the center and top pin. For
example, when the slider is all the way down, there is minimal resistance
between the bottom and center pins (usually 0Ω) and maximum
resistance between the center and top pins. The resistance between the
top (point A1) and bottom (point A3) pins will always be the total
resistance, (50kΩ for your part).
Set the meter (M2) to the LOW (or 10mA) scale. Adjust the adjustable
resistor (RV) for maximum resistance by setting the slider to the top. The
meter only deflects part of the way. As you move the slider down,
decreasing the resistance, the meter deflects more.
Function of
photoresistor
OBJECTIVE: To understand the function of the photoresistor.
Build the circuit shown. Set the meter (M2) to the LOW (or 10mA)
scale. The photoresistor (RP) is a light-sensitive resistor. Its value
changes from nearly infinite in total darkness to about 1,000Ω when a
bright light shines on it.
The meter reading changes as the resistance changes in the circuit.
When the lights are on, the meter points to a higher number on the
scale. When the lights are OFF, the pointer will point to a lower number
on the scale. This means that the resistance of the photoresistor is
changing according to the amount of light in the room.