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SubSystem : P2

Task Title:
Seeing in the Dark

Name:
Darlington Pair


OnTrack
equipment you will need:

IP1, P2, OP1 Modules
Bridge Power Base
Component Card
6 x 2mm White Leads
2 x Crocodile Leads
Multimeter


Connecting Subsystems:

1, Place the IP1, P2 and OP1 modules onto the Bridge Power Base (see Fig 2.). Connect up the OnTrack module to hold these down.

2, Use two white leads (shown black in fig.2.) to connect module OP1 to the L.E.D. Then use four more white leads to join module IP1 to the L.D.R. and 22K Variable Resistor as shown below.

3, Now connect two crocodile leads to IP1 and OP2 and then to the meter.

4, Turn the multimeter switch to the 20v. (D.C.) position.

5, Check your wiring is accurate and then connect the 9 volt power supply.

 

Testing and Investigating:

Don't forget to write up your method and results afterwards.

Testing …..and how to adjust the night light sensitivity

1, Turn the variable resistor until the LED just goes out. Write down the voltage reading on the multimeter.

2, To simulate night time, cover the L.D.R. slowly with your hand. What voltage is now shown on the meter as the L.E.D. starts to light?

3, Readjust the variable resistor to make the L.D.R. not so sensitive to your hand. What voltage is now shown on the meter as the L.E.D. starts to light.

4, Complete the following: The Darlington Pair "switches on" when the voltage at its input (Base) is …….

5, Write down situations where this type of control system would be useful.