The 10 Best Motion Sensors
History Of The Motion Detector
His motion detecting alarm created a grid of ultrasonic waves in a room.
Heinrich Hertz can be considered the pioneer of motion detection technology. He conducted experiments in the late 1900s that proved the existence of electromagnetic waves, including radio waves. In his experiments, he learned that these waves bounced of metal surfaces, dielectrics, and conductors and transmitted through other materials. Without these experiments, humans may never have developed radar technology, which is the basis of all early motion sensing systems.
In the early 20th century, German inventor Christian Hülsmeyer created a ship detection system to aid in maritime navigation, by using short bursts of radio waves to locate the metal makeup of ships. By using an oscilloscope to time the radio wave pulses, a ship's distance could be determined and, when coupled with an antenna that showed the ship's angular location, its location could be precisely positioned. This was the first true motion detection system.
Until the mid 1940s, when Samuel Bagno developed the first ultrasonic motion detector for use in home alarm systems, all motion detectors were radar-based and were used exclusively for military applications. Bagno's device was similar to radar-based motion detectors, except it made use of ultrasonic waves instead of radio waves. His motion detecting alarm created a grid of ultrasonic waves in a room. These waves had a standard pattern based on how the waves bounced off the inanimate objects. Any time something moved inside of the room, the pattern was disturbed, which triggered the alarm.
Bagno's ultrasonic alarm increased the demand for additional non-military motion sensor applications, which led to the invention of infrared motion detection, and paved the way for additional developments in other motion sensing technologies.
Types Of Motion Detectors
There are currently five distinct motion detection technologies; ultrasonic, microwave, passive infrared, tomographic, and camera-based.
The main downside to ultrasonic sensors is their ability to detect motion in areas where coverage isn't needed.
Modern ultrasonic motion detectors use wave reflections off of inanimate objects to register movement by reading Doppler shifts in the frequency of said object. This allows it to detect whether an item is moving closer or farther away. Movement creates a heterodyne signal, which is registered by the sensor. The main downside to ultrasonic sensors is their ability to detect motion in areas where coverage isn't needed. Farther range on motion detectors in lights might not be a problem, but when it comes to automatic doors this can result in them opening at random times, even without the presence of a person.
Microwave motion sensors also use the Doppler principal, but make use of microwaves instead of ultrasonic waves. They send out a continuous microwave radiation signal and can measure phase shifts in the reflected waves as an object moves closer or further away. As with ultrasonic motion sensors, the heterodyne signal of the disrupted waves are detected and used to register movement. Microwave motion sensors are less susceptible to false alarms than ultrasonic detectors.
Passive infrared motion detectors work in a very different manner than ultrasonic or microwave sensors. Instead of measuring electromagnetic or sound waves they measure heat, and when it senses this emitted calefaction, it trips the alarm. Passive infrared sensors do not send out any energy, hence the name passive.
Tomographic motion detectors are rarely, if ever found in home motion detection alarm systems. They are better suited to larger applications that may include outside areas as well. Tomographic motion sensing systems perceive radio wave disturbances as they pass between a network's nodes.
Camera-based motion detection systems have the ability to sense motion by using computer software. This is how motion-activated security cameras know when it is time to start recording. They can be used in nighttime applications with the addition of near-infrared illumination.
The Value Of Home Security And Motion Detection
Far too often, people overlook or underestimate what home security measures should be taken to ensure their family and their belongings are safe. Not only can a home invasion or burglary lead to financial loss, it can lead to devastating emotional repercussions as well. It is common for someone who has been the victim of a home burglary to feel insecure in their home for a long period afterwards.
Oftentimes when people go out in the evenings, they may leave the front door light or the driveway light on so it will be easier to see when they return at night.
In 2014, there were over 8 million property crimes. In total, the victims of these crimes suffered over $14 billion in loses. Many of these crimes could have been avoided if the homeowners had a home security system. In fact, a 2009 study by Rutgers found that property crimes in neighborhoods decreased as the number of home security systems increased. Another study by the University of North Carolina found that over 30% of burglars would retreat when faced with a home security system.
In addition to safety, motion-detection systems can help people save money. Oftentimes when people go out in the evenings, they may leave the front door light or the driveway light on so it will be easier to see when they return at night. Installing a motion sensor, means that it will no longer be necessary to leave a light on for hours just to ensure visibility for a few minutes when returning home. Instead, the lights will automatically turn on when needed.
If one cannot afford a home security system, often just having outdoor lighting with motion sensing capabilities will be enough to deter a would-be burglar. If somebody is creeping around the outside of a home looking for an entry point, sudden illumination will usually be enough to scare them off.