Motion Sensor. PIR_Motion_Sensor Datasheet
PIR Motion Sensor
Created by lady ada
Last updated on 2020-01-25 05:57:43 PM UTC
PIR sensors allow you to sense motion, almost always used to detect whether a human has moved in or out of the
sensors range. They are small, inexpensive, low-power, easy to use and don't wear out. For that reason they are
commonly found in appliances and gadgets used in homes or businesses. They are often referred to as PIR, "Passive
Infrared", "Pyroelectric", or "IR motion" sensors.
PIRs are basically made of a pyroelectric sensor (https://adafru.it/aKh) (which you can see below as the round metal can
with a rectangular crystal in the center), which can detect levels of infrared radiation. Everything emits some low level
radiation, and the hotter something is, the more radiation is emitted. The sensor in a motion detector is actually split in
two halves. The reason for that is that we are looking to detect motion (change) not average IR levels. The two halves
are wired up so that they cancel each other out. If one half sees more or less IR radiation than the other, the output will
swing high or low.
Along with the pyroelectic sensor is a bunch of supporting circuitry, resistors and capacitors. It seems that most small
hobbyist sensors use the BISS0001 ("Micro Power PIR Motion Detector IC") (https://adafru.it/clR), undoubtedly a very
inexpensive chip. This chip takes the output of the sensor and does some minor processing on it to emit a digital
output pulse from the analog sensor.
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