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Topic: How IR sensors work (Read 420 times) previous topic - next topic


New to forum,

School Project -  I am looking to use an IR sensor and I am looking for information on how it works. I understand is has something to do with Infra Red being sent out from the sensor but I don't understand how the information is gathered back by the sensor.


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Lots of different types of IR sensors. Which exact one do you have?

PIR, ToF, brightness, modulated transmission, break beam... just to name a few things you can do with IR.
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IR sensors work because they have a filter that stops ALL light, except the IR range they were designed for. Behind the filter is a standard light sensor.


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PIR - Passive InfraRed sensors - standard burglar alarm and motion sensing light sensors - have a lens that performs like a flies eye. smooth outside. rows of Fresnel ( Frah - nell ) lenses inside. when an IR heat source moves past, the lenses generate a series of pulses. enough pulses in a short interval causes the sensor to flip a switch momentarily. if they did not incorporate the lenses and pulse counter, the sensor would trip continuously when it saw your neighbors car radiator

PIRs are useless at this time of year in the American southwest. the outside air temperature is body heat temperature. moving past the lenses does not generate pulses

if the lens is yellowed and crumbling, it can't transfer enough IR. the sensor is electronically active but optically inert.
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The sensor that I am using is a PIR sensor

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