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SENSORS, DIGITAL INPUTS AND OUTPUTS

V. Ryan © 2002-04

Sensors are usually ‘analog’ devices. For example, a temperature sensor. This type of sensor usually ‘warms’ up slowly and cools down slowly. The change is constantly increasing or decreasing. A digital input or output is either ‘on’ or ‘off’. For example, a switch is either pressed or not pressed, an LED is either emitting light or not emitting light. (See previous notes on digital and analog signals).

   
 

 

The LED is a good example of a digital output because it is either ‘on’ or ‘off’

   

THE USER ADAPTER

The ‘user’ adaptor is plugged into the side of the smart box. This device allows analog sensors, such as home-made sensors, to be connected to the interface.
The example opposite is a dark sensor. When it is connected to the smart box a number appears on the screen. As a hand is placed over the sensor the number increases in value on the screen.
If the two outer connections are reversed the number decreases in value as the sensor now detects light
 

A HOME-MADE SENSOR CONNECTED TO THE
USER ADAPTOR

 
   

 

   

HOME-MADE SENSORS

A simple light sensor can be made from two components. The first is a light dependent resistor (LDR) and the second is a fixed resistor. When completed, it can be connected to the user adaptor and used as a proper sensor. A range of other sensors can be made in the same way.

   
Name some other sensors that you think could be made in the workshop.

 

   

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