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MAKING A LIGHT / DARK SENSOR

V. Ryan 2005 - 2009

 

PDF FILE - CLICK HERE FOR PRINTABLE WORKSHEET BASED ON EXERCISE BELOW
   

Opposite is a simple light/ dark sensor. This can be connected as an input or switch to another circuit. The sensors has three green wires (1, 2 and 3). Wire 2 should always be connected to one of the inputs. If wire 1 is also connected then the sensor acts as a dark sensor. If wires 2 and 3 are connected to the inputs then sensor operates as a light sensor.

The preset resistor allows the person using the circuit to alter its sensitivity to light/dark.

1. When are light sensors used?
 
 
 
   
CONSTRUCTING A CIRCUIT USING SIMULATION SOFTWARE
   

All circuits are drawn on software such as Crocodile Clips. Using this software the individual components can be joined together on the screen. Once the circuit is drawn its operation can be simulated to see if it works. If it fails it can be corrected on the computer screen and tested again.
Using software to test circuit designs saves time as there is no need to physically solder together components. It also saves money as components and materials are not wasted on failed circuits

The circuit is then made into a PCB (Printed Circuit Board). Components are added and soldered in position (See PCB Section of this website). Two views of the same circuit are shown below. How do they differ?

   
 

 

 
3. Complete the table below by writing some details about the components used in the light/dark sensor circuit.
 

 
 
   
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