![]() I made this drawing with Fritzing, a great tool to make electronic design! Playing with the “settings” Testing your PIR with a Battery, LED and a Resistor PIR PCBĪ few points on the PCB of the PIR are of importance to us: These tiny lenses help the sensor to look “around” in one swoop, which would have been impossible with just the flat sensor (see figure 2). If you look closer, you’ll see that the “dome” is build out of little segments – each being a small plastic Fresnel Lens. PIR Lens “Dome”Īs you can see in the pictures above, the PIR has some funny dome-like bubble, which is a collection of lenses covering the sensor. This is done in a smart way, to avoid false positives caused for example by a brief flash or an increase in room temperature.Ī chip and some discrete electronics handles all this for you. If the difference is too high then it will trigger – it detects “motion”. PIR’s actually only look at the “difference” between two sensor “halves”. It’s purely based on what the sensor can pick up out of the environment, what’s being emitted by objects. PIRs are called “passive” since they are not assisted by any “helpers” that for example would send some form or shape of “radiation” or “light” to help detect. ![]()
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