![]() If it does detect a frequency shift, the motion detector is activated. It sends out high radio frequency and measures the reflection off an object by sensing for a frequency shift. View Microwave Motion Sensors: How Microwave Sensors WorkĪs the name implies, Microwave sensors uses continuous waves of microwave radiation to detect motion, similar to how a radar speed gun works. (Source: Adafruit/Lady Ada) See related product Figure 2 shows the inside of the Fresnel lens, where you can see the “sections” on it.įigure 2: Inside a Fresnel lens. The optic physics behind the Fresnel lens is a whole other interesting area to look into if you have time, but in this case, it gives the PIR sensor a much larger detection area making it more efficient. The white plastic that you see on the PIR is called a Fresnel lens. ![]() Figure 1 from Adafruit shows a great example of how it works.įigure 1: PIR sensing heat source movement and outputting pulses. ![]() When the sensor senses a differential change between the two slots, this causes a pulse, which is what it detects as “movement”. The PIR has two slots made of a special material that is sensitive to infrared. PIRs have a pyroelectric sensor that detects levels of infrared radiation – everything emits some low-level radiation, but a human body emits a good amount of heat. The way it senses movement is by sensing the change in temperature between the background and a warm body. They are small, low power, easy to use, and inexpensive. The PIR is a motion sensor that you might have seen when you enter a restroom or an office space, usually having a white cover. Passive Infrared Sensors: What is a PIR Sensor? There are three types of motion sensors that are used frequently: Passive Infrared (PIR), Microwave, and Dual Tech/Hybrid. It can be an energy saver by shutting off lights in a building when it senses no motion anymore, which is used regularly in office buildings or restrooms. They can be used for burglary alarms or security cameras, activating these devices when it senses motion in the vicinity. Animals, insects, and foliage can also trigger them under the right circumstances.Motion sensors are popular when it comes to security and energy efficiency. False alarms are usually caused by electrical failures, user error, poor application engineering, power surges, lightning, and faulty equipment. Keep in mind that motion sensors aren’t error-proof, and there are instances in which there could be false alarms. Some DIY systems also give you electronic prompts, video tutorials, or have you call a representative to walk you through the setup process. However, you are responsible for setting up your sensors if you go with a DIY home security system.īefore you install motion sensors, make sure to read the installation instructions, since they will likely include placement recommendations. If you choose a security system that requires professional installation, the installer will know how to set up your sensors. Correct installation gives you optimal coverage for motion detection and helps avoid false alarms. If you know how to use a screwdriver, you can install a motion sensor. With wireless motion sensors becoming standard, DIYers have it easier than ever when it comes to installation.
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