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DUAL TRANSISTOR MULTIVIBRATOR CIRCUIT

EXAM QUESTION

V. Ryan © 2004 - 2009

 

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A local garage has started selling a small electronic device. The device has two LEDs that flash alternately and the entire circuit is housed in a small moulded case. It is to be placed on the ‘dashboard of a car so that it looks as if an expensive alarm has been fitted.

The circuit diagram is shown below.

   

   

Three of the important components have been labelled A, B and C. Name each component and explain the function of each in the circuit.

   
COMPONENT A:
 
FUNCTION IN CIRCUIT:
 
 
 
   
COMPONENT B:
 
FUNCTION IN CIRCUIT:
 
 
 
 
COMPONENT C:
 
FUNCTION IN CIRCUIT:
 
 
 
 

Ring the names of two components that work together to produce the flashing of the LEDs.

   

TRANSISTOR

CAPACITOR

RESISTOR

   

 

   

The Printed Circuit Board (PCB) for the dual transistor, multivibrator circuit is shown below. All the components and their position on the PCB can be seen. The garage owners have decided to manufacture a small moulded case for the circuit to fit inside. The LEDs and the switch must protrude through the moulded box so that they can be seen.

   
   

Name a suitable material for producing the moulded case.

 
Name a suitable manufacturing process for producing the moulded case.
 
   
Sketch a suitable design for the moulded case, include detailed notes.
   
 

 

 

 

 

 

 

 

   

Using the boxes below, draw a sketch in each that represents a stage of manufacturing the moulded case, using the process you have named. You do not need to use all the boxes below.

   
STAGE ONE   STAGE TWO
     

 

 

 

 

 

     
STAGE THREE   STAGE FOUR
     

 

 

 

 

 

 
STAGE FIVE   STAGE SIX
     

 

 

 

 

 

 
   
 
   

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