How Do Motion Sensors Work?

Heather Clouse
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So What Are The Different Types of Motion Sensors?

There are three different types of motion sensors in common use today.

Proximity Sensors: Proximity sensors are the most popular type. These are the sensors that immediately detect the presence of a body, and trigger a reaction once this detection has occurred.

The three most common types of proximity sensors are:

I. Ultrasonic

Ii. Magnetism

Iii. Passive Infrared

Speed and Time Sensors: Speed and Time sensors can be used to control lights and fans.

They are useful when you want lights and fans to operate highly energy efficient.

By setting them to the right times and speeds during the dusk and dawn hours, you can save as much as 30% on your energy bill.

Timers & Motion Detectors: Since you can still use switches to interact with lights, fans, and other outlets, a Motion detector can also work in conjunction with a timer to create a very convenient system.

You can program the timer to turn the lights on at a certain time during the day.

The motion sensor can then trigger the lights to turn off when nobody is in the room.

Active Sensors

Motion sensors that are physically connected to the system being monitored are called active sensors. These sensors are usually hardwired to a control panel. Power is supplied to the sensor from a separate power source. Active sensors are usually located in high risk zones. These may include areas in and around the security system’s monitoring range.

For example, magnetic contact sensors may be placed at the doorway of every room in a house. They are also placed under windows as well as on doors.

Thermal sensors can be placed along windows and walls where movement is likely to occur. This is because they are best at detecting heat over distance.

PIR technology is used in household motion sensors that are using passive infrared technology to detect body heat. You can find these sensors in the store by searching for the term PIR motion sensor.

The problem with PIR technology is that it’s not the best at detecting motion over a distance.

This is because of its reliance on passive infrared (PIR). Thermopile sensors offer a much better range. They are able to detect movement from up to 20 feet.

Upon detecting motion near any of these sensors, an alarm will sound to alert the owner of the security system or the police. This is why they are considered the backbone of an intruder security system.

PIR or Passive Infrared Sensors

Your home has probably gotten quite smart with temperature and humidity sensors. These sensors use technology called the “physical phenomenon of changing infrared radiation to measure the temperature reduction caused by the body.”

These sensors are usually placed at the far edges of doorframes. They use a small isolated magnetic field to measure the change in temperature when something enters the field. This leads the sensor into thinking that something is entering the room and enables the lights, sounds, door locks, etc.

Dual Tech Motion Sensors – Dual Technology Sensors

Motion sensors work by detecting changes in the space around them as they constantly send and receive energy to and from their surroundings to detect a change.

There are two main kinds of motion sensors: passive infrared motion sensors & active ultrasonic motion sensors.

Passive Infrared (PIR) Motion Sensor–PIRs are one of the most common motion sensors. They detect infrared light emitted by all living beings. Since infra-red light travels in straight lines, and it’s very reflective, its easy to determine whether or not there is something/someone moving around in a room using infrared sensors.

Active Ultrasonic(AU) Motion Sensor–AU sensors, on the other hand use ultrasonic tones to detect movement. How effective they are depends on the sound waves and the size of the room.

In a wide open space they are pretty efficient. However, in a room with a lot of objects, such as couches and chairs, they are not very effective and should be used in conjunction with IR sensors.

Vacancy Vs Occupancy

Motion sensors are found in a wide variety of industries, from home automation to industrial automation to traffic control. However, despite all the variety, the core principles are the same.

The basic idea of all motion sensors is to track object movement nearby. This data is used to trigger an action.

To determine whether an object is moving or not, you need a sensor. When an object is moving, electricity is generated through the movement of the electrons.

This electron movement causes a change in the flow of current in an electrical circuit. The sensor detects this change in current flow and sends a signal. That signal can be anything as simple as a change in voltage to a change in polarity to an actual high voltage signal.

A sensor can also be anything as simple as a thermistor based device whose resistance changes in response to changes in temperature.

The sensor is also called a transducer because it converts one form of energy into another. The high voltage signal from the sensor is then sent to a circuit to be interpreted.

The way you interpret the signal depends on the type of sensor you use. For example, a thermistor is straightforward in that it produces a voltage that is linearly proportional to temperature. To interpret this, therefore, all you would need is a voltage divider.