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SYSTEMS PREPARATION QUESTIONS 2008 - 6
 
V. Ryan 2007-2017
 
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7. The student has decided to use a PIC microcontroller to control the motor that raises and lowers the barrier. The student uses outputs 1 and 2 to control the motor. Output 1 will turn the motor on and off. Output 2 changes the direction of the motor.
Complete the circuit below to show how the control of the motor can be achieved.
 
 
 
 
ANSWER
 
 
8. The student decides to use one of the inputs to detect when the barrier has completely opened.
 
Name a suitable sensor:
 
 
ANSWER
 
Name a suitable sensor: Microswitch
 
9. Explain how the sensor would be used.
 
 
 
 
 
ANSWER
 
The microswitch will be positioned so that when the barrier is fully raised it is pressed. The micrositch will be connected to an input of the microcontroller circuit. The microcontoller will detect when the microswitch is pressed and keep the barrier raised until a train is detected.
 
 
 
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