You can use motion sensors to automatically turn on a light when someone approaches your home, sound an alarm when movement is detected in your living room, or trigger a motion sensor camera to start recording when someone enters your home.
How do motion detectors work
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An active ultrasonic motion detector emits ultrasonic sound waves that reflect off objects and bounce back to the original emission point. When a moving object disrupts the waves, the sensor triggers and completes the desired action, whether this is switching on a light or sounding an alarm.
Dual-technology detectors are, as their name implies, sensors that rely on two different motion-detecting technologies to watch for movement. These are a bit more impervious to false alarms, as both technologies have to be tripped for the alarm to sound.
When deciding where to place each motion sensor, make sure they are at least 10 feet away from bright windows, radiators, and heating vents, as abrupt changes in temperature or HVAC-related airflow may trigger false alarms.
A motion sensor, or motion detector, is an electronic device that uses a sensor to detect nearby people or objects. Motion sensors are an important component of any security system. When a sensor detects motion, it will send an alert to your security system, and with newer systems, right to your mobile phone. If you have subscribed to an alarm monitoring service, motion sensors can even be configured to send an alert to your monitoring team.
A PIR motion sensor uses these temperature changes to detect the presence of a person or object. Like active ultrasonic sensors, PIR sensors can be set to ignore small changes in IR, so you can walk around your home or business without setting off alarms all day and night.
Tomographic motion sensors are made up of multiple nodes. The nodes link together, forming a mesh network. These sensors detect the presence of a person or object when the link between two nodes is broken.
Microwave motion sensors emit microwave pulses. Much like an active ultrasonic sensor, the microwaves bounce off objects and return to the sensor. They actually cover a larger area than PIR sensors, but are more susceptible to electronic interference.
The lenses on many of these motion detectors are broken into segments. The segments allow you to focus on some areas of a space and ignore others. As a result, you can configure detectors to ignore certain types of motion or motion in specific zones.
Finally, you can purchase detectors that use both kinds of technology, PIR and microwave. The advantage of dual-technology sensors is that they verify one another. Both sensors have to detect movement before the detector registers that movement. This verification method helps prevent false alarms.
THE MORE YOU KNOW: Because they rely on radio waves, tomographic motion detectors work through walls. As a result, such detectors can cover large areas and hide behind objects or within walls.
Asking whether you need a motion detector is a little like asking if you need a home security system. If you want to keep your home safe from intruders, the answer is always going to be yes. Even apartments need security systems!
You can adjust the lenses of a PIR sensor, for example, to pick up movement in specific areas. In addition, most motion detectors have dials that allow you to set their sensitivity levels. With this feature, you can get your detectors to ignore your pets.
Light can set off a motion detector. If the detector uses light-based sensors, such as PIR sensors or area reflective sensors, turning on the light creates a rapid change in the electromagnetic spectrum the sensors are reading. That change can register as a movement.
Bay Alarm. (2020). How Do Motion Sensors Work: A Guide.bayalarm.com/commercial/burglar-alarm-systems-commercial/how-do-motion-sensors-work-a-guide/#::text=Active%20ultrasonic%20sensors%20emit%20ultrasonic,pulse%20and%20receives%20the%20echo
A motion detector is an electrical device that utilizes a sensor to detect nearby motion. Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area. They form a vital component of security, automated lighting control, home control, energy efficiency, and other useful systems.
An active electronic motion detector contains an optical, microwave, or acoustic sensor, as well as a transmitter. However, a passive contains only a sensor and only senses a signature from the moving object via emission or reflection. Changes in the optical, microwave or acoustic field in the device's proximity are interpreted by the electronics based on one of several technologies. Most low-cost motion detectors can detect motion at distances of about 15 feet (4.6 m). Specialized systems are more expensive but have either increased sensitivity or much longer ranges. Tomographic motion detection systems can cover much larger areas because the radio waves it senses are at frequencies which penetrate most walls and obstructions, and are detected in multiple locations.
Motion detectors have found wide use in commercial applications. One common application is activating automatic door openers in businesses and public buildings. Motion sensors are also widely used in lieu of a true occupancy sensor in activating street lights or indoor lights in walkways, such as lobbies and staircases. In such smart lighting systems, energy is conserved by only powering the lights for the duration of a timer, after which the person has presumably left the area. A motion detector may be among the sensors of a burglar alarm that is used to alert the home owner or security service when it detects the motion of a possible intruder. Such a detector may also trigger a security camera to record the possible intrusion.
Passive infrared (PIR) sensors are sensitive to a person's skin temperature through emitted black-body radiation at mid-infrared wavelengths, in contrast to background objects at room temperature. No energy is emitted from the sensor, thus the name passive infrared.[1] This distinguishes it from the electric eye for instance (not usually considered a motion detector), in which the crossing of a person or vehicle interrupts a visible or infrared beam. These devices can detect objects, people, or animals by picking up one's infrared radiation.[2]
These detect motion through the principle of Doppler radar, and are similar to a radar speed gun. A continuous wave of microwave radiation is emitted, and phase shifts in the reflected microwaves due to motion of an object toward (or away from) the receiver result in a heterodyne signal at a low audio frequency.
An ultrasonic transducer emits an ultrasonic wave (sound at a frequency higher than a human ear can hear) and receives reflections from nearby objects.[3] Exactly as in Doppler radar, heterodyne detection of the received field indicates motion. The detected doppler shift is also at low audio frequencies (for walking speeds) since the ultrasonic wavelength of around a centimeter is similar to the wavelengths used in microwave motion detectors. One potential drawback of ultrasonic sensors is that the sensor can be sensitive to motion in areas where coverage is undesired, for instance, due to reflections of sound waves around corners.[4] Such extended coverage may be desirable for lighting control, where the goal is the detection of any occupancy in an area, but for opening an automatic door, for example, a sensor selective to traffic in the path toward the door is superior.
These systems sense disturbances to radio waves as they pass from node to node of a mesh network. They have the ability to detect over large areas completely because they can sense through walls and other obstructions. RF tomographic motion detection systems may use dedicated hardware, other wireless-capable devices or a combination of the two. Other wireless capable devices can act as nodes on the mesh after receiving a software update.[5]
With the proliferation of low-cost digital cameras able to shoot video, it is possible to use the output of such a camera to detect motion in its field of view using software. This solution is particularly attractive when the intent is to record video triggered by motion detection, as no hardware beyond the camera and computer is needed. Since the observed field may be normally illuminated, this may be considered another passive technology. However, it can also be used together with near-infrared illumination to detect motion in the dark, that is, with the illumination at a wavelength undetectable by a human eye.
Many modern motion detectors use combinations of different technologies. While combining multiple sensing technologies into one detector can help reduce false triggering, it does so at the expense of reduced detection probabilities and increased vulnerability.[citation needed] For example, many dual-tech sensors combine both a PIR sensor and a microwave sensor into one unit. For motion to be detected, both sensors must trip together.[citation needed] This lowers the probability of a false alarm since heat and light changes may trip the PIR but not the microwave, or moving tree branches may trigger the microwave but not the PIR. If an intruder is able to fool either the PIR or microwave, however, the sensor will not detect it.[citation needed]
The "motion sensing" feature on most lights (and security systems) is a passive system that detects infrared energy. These sensors are therefore known as PIR (passive infrared) detectors or pyroelectric sensors. In order to make a sensor that can detect a human being, you need to make the sensor sensitive to the temperature of a human body. Humans, having a skin temperature of about 93 degrees F, radiate infrared energy with a wavelength between 9 and 10 micrometers. Therefore, the sensors are typically sensitive in the range of 8 to 12 micrometers. 2ff7e9595c
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