Posted on Monday, December 12, 2011 • Category: Sensors
Presented schematic shows how to build simple PIR motion detector sensor. 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 (which you can see above 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. PIR Motion Detector Thermostat Controller with Relay using LM35 and TL431 MCP9700, MCP9700A, MCP9701 and MCP9701A Temperature Sensors Homemade Metal Detector Light / Dark Relay Switch Automatic Fan Controller Circuit Water Alarm Temperature Control using a DS1621 Sensor and a ATtiny 2313 Micrcontroller Digital Thermostat with LED Temperature Display Temperature Controlled Fan
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