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SubSystem : P1

Task Title:
Touch Sensing

Name:
Transistor Switch


OnTrack
equipment you will need:

IP1, P1, OP1 Modules
Bridge Power Base
Component Card
2 x 2mm White Leads
4 x Crocodile Leads
Multimeter


Connecting Subsystems:

1, Place the IP1, P1 and OP1 modules onto the Bridge Power Base see (Fig 1.). Connect up the OnTrack module to hold these down.

2, Use the two white leads (also shown black in fig.1.) to connect module OP1 to the L.E.D.

3, Connect two crocodile leads to IP1 and then to the red and black meter leads (Make sure they are the right way round).

4, Connect two more crocodile leads to IP1 as shown.

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

6, 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 …..what needs to happen for the LED to light

1, Squeeze the two input crocodile clips tightly in your fingers and check to see if the voltage on the meter rises.

2, If you press hard enough the LED should light. What voltage is shown on the meter as the LED just begins to glow?

 

Connecting up Further Circuits

3, Let somebody else try squeezing - Do they find it easier or more difficult to light the LED? Now try it with the buzzer as the output device.

4, Try licking your fingers and then repeat the test - Is this easier now?

5, A small current has flown through your fingers. Do you think it flows more readily when your fingers are wet or when they are dry?