Motion sensor to turn on the light: principle of operation and connection methods

A motion sensor for switching on light is a device capable of detecting movements of a person or other living objects and, accordingly, controlling lighting.

Motion sensor to turn on the light

With the help of special sensors (thermal, sound, etc.), it captures changes in space and turns on, turns off or adjusts the degree of illumination. The presence sensor to turn on the light, which reacts to heat, may not even "notice" a person walking by in the winter if the latter is very warmly dressed. Nevertheless, he will easily fix any living creature in the warm season.

How it works?

The principle of operation, which has a motion sensor to turn on the light, is to use a sensor (pyroelectric device). It functions very precisely by increasing the voltage at the output, provided that the level of infrared radiation increases in comparison with the general background. The light is switched on using the internal sensor relay.

Regardless of the type of device, the output signals that the presence sensor receives to turn on the light, depending on the need, go directly to the controller, which issues control signals to the control point:

  • alarm system;
  • relay to turn on the light;
  • ventilation system;
  • room air conditioning system.

This helps the smart home to be extremely useful for the hosts.

For example, while you open the door, the house has already begun to ventilate the room, filling it with fresh air. Or, on the contrary, it starts airing or cooling when there is no one in the room.

Types of motion sensors

On the modern market, you can find many devices that somehow determine the presence of someone in the house or on the street. The general concept of "motion sensor to turn on the light" can be divided into 4 types, depending on the main sensor element:

  • IR sensor to turn on the light (infrared).
  • Ultrasonic sensor (ultrasonic).
  • Microwave sensors (microwave).
  • Combined.

In addition, there is a sound sensor for switching on the light and a cotton sensor.

Each of them is installed in a specific place and most well performs its functions with proper, rational installation.

IR sensor

An infrared light sensor for switching on light detects changes in the thermal radiation of living things or other objects (for example, a car) with the help of several lenses that are indicators.

IR sensor to turn on the light


  • Increased accuracy.
  • Wide temperature range of use.
  • Harmless to pets.


  • Excessive sensitivity to household appliances (batteries, air conditioners).
  • Reaction to sunlight.
  • Lack of fixation of objects covered with radiation resistant materials.

Assigning an infrared motion sensor

The main tasks of infrared sensors are:

  • Saving electricity. The light will be on only if you really need it.
  • The effect of presence. When installing the sensor on the street in front of the gate at the site, in the stairwell, on the windows of the lower floors during its operation, it appears as if someone is at home. This, on the one hand, causes a feeling of comfort, and on the other hand, scares off thieves and gangsters.

Despite its usefulness, it happens that people are affected by this light sensor to turn on the light.Not everyone likes his ability to soothe and take care of non-switched lighting.

You can often hear: “What is he clicking there?”, “Do I need to move all the time now so that the light is on?”, “And if I don’t want it to be on?”

The answer to all these questions is one, and it is quite simple: when installing the sensor, it is only necessary to use a few additional switches, which are ideally suited to the requirements of the occupants and create the possibility of comfortable operation of the system.

The circuit itself connecting the sensor to turn on the light will be described a little later in this article.

Ultrasound sensors

Measurement of the surrounding space using sound waves is the prerogative of ultrasonic sensors. They generate sound waves that are reflected from objects during any movement. The frequency of these reflections is continuously measured, and a kind of echo sounder is obtained. The signal arrives at the receiver of the sensor and gives the command to turn on or off the lighting.

Such sensors are most often used in the automotive industry to create parking sensors.

Presence sensor to turn on the light


  • Possibility of installation in large areas.
  • Insensitivity to weather conditions.
  • Resistant to dirt and dust.
  • Compatibility with different materials of the case.
  • Maximum wide temperature range for operation.


  • The sensitivity of domestic animals to ultrasound.
  • With prolonged use may cause headaches.

Microwave sensors

The microwave dark sensor to turn on the light works due to the emission of high-frequency electromagnetic waves, which are reflected when an object hits, and the quality of these reflections is fixed by the sensor. Any changes in the signal trigger the program set by the owner.

Dark sensor to turn on the light


  • The ability to detect objects behind obstacles.
  • Resistant to aggressive environment.


  • Not safe for the human body.

It can be installed only where the permeability of people is minimal.

Combined Sensors

Combined light sensors to turn on the light imply a symbiosis of several object detection technologies at once.


  • The possibility of the most accurate work.
  • Full control of the area required for observation.
  • Wide possibilities of individual settings.


  • Installation can only be done by a specialist.
  • If one of the systems fails, a complete changeover will be required.

Cotton Sensors

Many have seen such a device in the films, but not everyone was lucky enough to experience it personally. How great it is: here you went to bed and forgot to turn off the light. Warm bed does not want to let go. The solution is cotton, and the light is off. Urgently need to turn on the light? Claps - and the room is lit up again.

Remote adjustment of light, undoubtedly, is very convenient. But do not confuse the cotton switch and acoustic (it will be discussed below).

Such a device works differently than a light sensor to turn on the light.

With it, you can adjust not only the lighting, but also:

  • ventilation;
  • transformers;
  • any electrical equipment.

Important! Be sure to comply with the requirements for power load limits.

Algorithm of actions:

  • The first clap is turning on the voltage.
  • The second clap is shut off.

Very simple, agree.


The cotton sensor is a kind of noise sensor for switching on the light. So, its installation is advisable only in those rooms where the stationary noise level is not too high. And certainly not where the holiday is planned.Applause guests can arrange a real disco light-music.

Ideal room:

  • utility room;
  • basement;
  • pantry;
  • bedroom;
  • children's room.

Where it is not necessary to install the cotton sensor:

  • crowded rooms;
  • offices;
  • production rooms;
  • workshops, etc.

It is highly recommended to install similar equipment in the nursery. This is not only convenient, but also provides additional security for your child. Ordinary switches are quite high, and children have to either climb up or ask for help from their parents. The frequency of falls from a chair in such a situation is impressive, and injuries are very high. Cotton is a good alternative.

It is also useful for people with disabilities.

Acoustic Sensors

Sound sensor to turn on the light

The difference of this type of switch from the previous one is insignificant, but there is. The acoustic sensor responds absolutely to any sound that exceeds a predetermined threshold in decibels. Its installation is advisable in the hallways in order to save electricity.

As soon as the door bangs, footsteps are heard, the light turns on, and it turns off after a few seconds after everything is quiet.An important difference: cotton reacts only to cotton!

Motion Sensor Parameters

Of course, each sensor automatically turn on the light has its own parameters, but in general there are certain performance standards:

  • Voltage - 220-240 V and 50 Hz.
  • Delay timer (on time) - 2-8 seconds.
  • Voltage supply time - set using the regulator.
  • Sensitivity to light - 2-1000 Lux. Installed on the switch. The minimum number of modes - 2 on the simplest models. To make it clearer: 100 Lux means that the sensor will work only in the dark. At maximum settings, the capabilities of the sensor are not limited by the degree of illumination.
  • The viewing distance is up to 15 meters. When combining different types of sensors, this parameter can be increased.
  • The response rate is 0.5-1.5 milliseconds. If the object moves slowly, and its temperature (clothing) merges with the general heat background, the sensors do not work. Driving too fast also causes detection difficulties.
  • The maximum current - may be different, depending on the area in which the sensor will be used, from the required minimum to 1500 watts.The load power determines the electromagnetic relay.
  • Viewing angle - 360 degrees for ceiling sensors. For wall - from 100 (for corner) to 180 (for a straight wall). Height becomes a decisive factor in the possibilities of the review: the higher, the greater.

IR Sensor Diagrams

volume sensor to turn on the lightThe volume sensor to turn on the light is not installed as difficult as it may seem at first glance. Enough minimal knowledge in electrical engineering.

For example, use the Chinese sensor LX-01 and connect it to a conventional incandescent lamp.

Wiring diagram of the light-on sensor (action algorithm):

  • Choose a sensor model that you like.
  • Determine the room to install.
  • Consider the layout of the room (windows, doors, movement patterns of people, high furniture).

Important! If there are no windows in the room, then this is an advantage, because the sensor will not have to be further adjusted to the degree of illumination - the room is always dark. If the room has a door on each wall - the sensor of the selected type will have to be fixed in the corner, since it has a viewing angle of 120 degrees.Wiring diagram of the light switch sensor

  • Study the connection diagram to the network, which is always attached to the instructions.
  • Do not connect the sensor otherwise, do not confuse the wires, otherwise when you turn on you will hear the clap, and the device will be ruined forever.
  • If necessary, add a control switch to the circuit so that it is possible to adjust the lighting manually.
  • Ring all wires before connecting the device to the network using a tester.
  • Connect the wire from the switch to the lamp with the red contact of the sensor.
  • The wire on the other side of the switch - to the brown contact.
  • To blue contact - a wire that matches the lighting fixture not from the side of the bulb.


Conclusion and advice

Noise sensor to turn on the light

Important! Be sure to follow all safety measures when working with electricity:

  • Wear thick rubber gloves.
  • Turn off the electricity in the apartment.
  • Upon completion of work, insulate the exposed wires.

It remains only to hang the sensor on the wall and check its performance! To do this, leave the room and close the door.

Go to the room. The first time the motion sensor to turn on the light sometimes works with a delay. It's not scary, you will have the opportunity to adjust the parameters later using the controller.

If you installed a cotton or acoustic sensor - make the appropriate sound. Enjoy using!

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