![]() The PIR sensor itself has two slots in it, each slot is made of a special material that is sensitive to IR. To begin explaining how a basic sensor works, we'll use the rather nice diagram below (if anyone knows where it originates plz let me know). ![]() PIR sensors are more complicated than many of the other sensors explained in these tutorials (like photocells, FSRs and tilt switches) because there are multiple variables that affect the sensors input and output. A great page on PIR sensors from GLOLAB.Parallax Datasheet on their version of the sensor.NL11NH datasheet (equivalent lens used).RE200B datasheet (most likely the PIR sensing element used).BIS0001 Datasheet (the decoder chip used).Sensitivity range: up to 20 feet (6 meters) 110 degrees x 70 degrees detection range.Pulse lengths are determined by resistors and capacitors on the PCB and differ from sensor to sensor. Output: Digital pulse high (3V) when triggered (motion detected) digital low when idle (no motion detected).If there's a datasheet, you'll want to refer to it Nearly all PIRs will have slightly different specifications, although they all pretty much work the same. Experimentation is key! Some basic stats These stats are for the PIR sensor in the Adafruit shop which is very much like the Parallax one. Note that PIRs won't tell you how many people are around or how close they are to the sensor, the lens is often fixed to a certain sweep and distance (although it can be hacked somewhere) and they are also sometimes set off by house pets. They are low power and low cost, pretty rugged, have a wide lens range, and are easy to interface with. For many basic projects or products that need to detect when a person has left or entered the area, or has approached, PIR sensors are great. 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. It seems that most small hobbyist sensors use the BISS0001 ("Micro Power PIR Motion Detector IC"), undoubtedly a very inexpensive chip. Along with the pyroelectic sensor is a bunch of supporting circuitry, resistors and capacitors. If one half sees more or less IR radiation than the other, the output will swing high or low. The two halves are wired up so that they cancel each other out. The reason for that is that we are looking to detect motion (change) not average IR levels. The sensor in a motion detector is actually split in two halves. Everything emits some low level radiation, and the hotter something is, the more radiation is emitted. 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. They are often referred to as PIR, "Passive Infrared", "Pyroelectric", or "IR motion" sensors. For that reason they are commonly found in appliances and gadgets used in homes or businesses. They are small, inexpensive, low-power, easy to use and don't wear out. Go Direct sensors can be used wired via USB or wirelessly via Bluetooth ® wireless technology, allowing you to choose the solution best for your classroom or laboratory.Pyroelectric ("Passive") InfraRed sensors: '''What is a PIR 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. ![]() Our Go Direct sensors connect directly to your mobile device, Chromebook ™, or computer using our Vernier Graphical Analysis ® app-no additional equipment or software purchases are necessary. Wireless or Wired-The Flexibility to Choose Should the battery run low, simply connect the sensor to the charging cable and keep on collecting-no interruptions or inconvenience to you or your students. ![]() Monitor battery life directly from our award-winning Vernier Graphical Analysis ® app, as well as LabQuest ® 3. ![]() The robust rechargeable battery offers long battery life and provides always-ready operation when using the sensor wirelessly. Investigate simple harmonic motion by monitoring a mass on a spring.Analyze the effects of air resistance on falling coffee filters.Match position or velocity graphs created in Graphical Analysis app.Study position, velocity, and acceleration of carts when mounted on a track.The Go Direct Motion Detector can be used in a variety of experiments: The compact design and wireless capability of this motion detector eliminate the concern of a dangling cable getting in the way. The Go Direct Motion Detector accurately tracks objects as close as 15 cm and as far away as 3.5 m. ![]()
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