PIC Inputs

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PIC Inputs

 


Many input devices work by some physical change altering the resistance of a component.  For example,

 

¡the resistance of an LDR decreases when the intensity of incident light on it increases
¡the resistance of a negative temperature coefficient thermistor decreases as temperature increases
¡the resistance of a positive temperature coefficient thermistor increases as temperature increases
¡the resistance across the contacts of a normally open push button changes from very high to very low when the button is pressed
¡the resistance across the contacts of a normally open switch changes from very high to very low when the switch his closed
¡the resistance of a pressure mat changes from very high to very low when someone steps onto it
¡the resistance across the contacts of a tilt switch changes from very high to very low when the switch is tilted
¡the resistance of a shock sensor momentarily changes form very high to very low when receiving a sudden mechanical shock
¡the resistance of a moisture sensor decreases with increasing moisture

 

Resistive sensors can be used as inputs to digital systems e.g.PICs by incorporating them into a potential divider.

 

Switch type sensors


Non-switch type sensors

Analogue sensing