Switch with motion sensor: how to choose and install a light switch with a sensor

Amir Gumarov
Checked by a specialist: Amir Gumarov
Author: Maxim Fomin
Last update: May 2019

To simplify their lives and reduce electricity costs, owners often install different automatic light control systems in their homes. One of such electronic devices is a switch with a motion sensor (DD), which turns on lighting without human intervention when one enters the room.

And when there is nobody in the room, this device itself also turns off the bulbs. Installing such a device is not difficult, but there are a lot of benefits from it. We will talk about how to correctly choose an intelligent device, in what order and where to fix it.

How does the switch with DD work?

By a circuit breaker with a non-contact motion sensor is meant a combined electrical device that responds to the movement of someone in a certain control zone. It is suitable for indoor and outdoor installation. It is only necessary to correctly choose the degree of its protection by IP.

It can be both a control unit with a sensor only, and a device supplemented by a key switch. However, in the first case, turning on the lighting with your own hand, slamming a key on the wall, will fail. You should not forget about this feature of contactless automation.

Sensor plus key switch
Ideally, the motion sensor is best complemented by a conventional key switch, absolute automation of everything and everything in case of failures in the electronics can cause a lot of trouble

The range of devices under consideration is huge. In electrical stores, there are options with different types of detectors and different layouts. When choosing such a switch, the most important thing is to determine in advance the place of its installation.

In some cases, a combined model in one case is more suitable, and in others it will be necessary to take several independent devices and connect them together with wires.

The light switch with the motion sensor operates as follows:

  • when there are no moving objects in the observation zone, the device opens the power circuit;
  • when entering the human zone, a sensor is triggered, which closes the power supply circuit of the bulbs;
  • while someone moves within the sensor’s range, the circuit remains closed;
  • after everyone leaves the controlled room (or site on the street), the circuit opens back with the light turned off.

In order not to burn electricity in the daytime, such a switch is often supplemented with a light level control photosensor. In this case, as long as there is enough sunlight, the device will not operate and turn on the light bulbs.

Photo relay circuit
If, in addition to the motion sensor, the selected switch is equipped with a photo relay, then in the daytime the lighting will not turn on even when a person appears in the room

Switches with a motion sensor are installed to control the light in the following areas:

  • on stairwells and in the corridors of apartment buildings;
  • in basements, pantries and garages, where there is no natural light at all, and it is difficult to find the button of a conventional switch in the dark;
  • in toilets and toilets to increase the comfort of using plumbing sleepers at night;
  • in private cottages built on the technology of "smart home".

Often such a device is part of a security system. In this case, with a non-functioning alarm, the sensor works to turn on / off the light, and when activated, it monitors the penetration of unauthorized persons into the guarded room.

Varieties of motion sensors

To classify devices, we define two main factors: the presence and type of sensor device, as well as installation features.

The main element in this circuit breaker is the motion sensor. There are several varieties of it, based on different physical laws.

Moreover, the result is the same in all cases: when an object appears in the controlled area, the sensor is triggered and the contacts of the supply circuit lighting devices are closed.

IR motion sensor
The most common motion sensor is infrared - it emits nothing, is relatively cheap and can be mounted not only indoors but also outdoors

Motion sensors for automatically turning on and off the light are:

  1. Acoustic.
  2. Infrared
  3. Ultrasonic
  4. Microwave

The first two categories of sensors are passive devices, they do not emit anything. Detectors of the two remaining varieties - active devices. These options send waves of various lengths to the room, and by the nature of their reflection, they determine the presence or absence of new objects in their coverage area.

Equipment of the "active" class with a transmitter and receiver is more expensive than "passive" models. Devices are more complex structurally, but have a low level of false positives. Passive devices in this respect are much inferior to active analogues, but cheaper than competitors.

Acoustic sensors are triggered by the sounds of opening doors, the sound of heels and simply sharp pops. This option is best taken for corridors of public buildings.

It is optimally suitable as an addition to other sensors, so that the light can be turned on by clapping your hands. It is not recommended to put it alone in a private house. There will be too many false responses to various sharp sounds.

Infrared sensors are designed to respond to human heat. But they also respond to animals and to heated radiators. They must be carefully configured, and the coverage area must be set so that heating batteries do not fall into it. This is the simplest, most durable and cheapest touch sensor for automatic light control.

Sound wave propagation
The principle of operation of ultrasonic sensors. Ultrasonic and microwave sensors are similar in principle of operation, they only have a different range of emitted waves

It is not recommended to install sensors operating in the living room due to microwave radiation and ultrasound. A person is not able to feel their effect, but it is there, and there is certainly no benefit from it.It is noted that domestic animals often react to this radiation in a sharply negative form.

Such emitters are more suitable for parking or outdoor areas. At the same time, active motion sensors also have a limited range of action.

When organizing control over a large area of ​​ultrasonic devices, you will have to install a lot. Plus, many of them work only with sudden movements. A slowly walking person can completely “fall out” of their field of action.

The ideal option is a combined sensor with several ways to detect people entering the controlled area. It is more reliable and less likely to erroneously work. However, you will have to pay a lot for this error-free operation, since such sensors are obviously more expensive than conventional analogs.

Choosing the optimal installation location

If the key switch comes immediately with the sensor in one housing, then it is designed for wall mounting. However, if the sensors are delivered in a disassembled kit or purchased separately, they can be installed not only on the wall, but also on the ceiling. Moreover, the ceiling option is often preferable, as it covers a large territory.

Motion Sensor Coverage
The installation location directly depends on the viewing angle specified in the data sheet for which the motion sensor is designed for the light switch

Each sensor device has its own viewing angle in the range from 10 to 360 degrees. If it has this parameter less than 360about, then the sensor can only track movement in a narrow surveillance sector. In this case, several tracking devices will have to be installed in the room so that they cover all the necessary space.

Wide-angle and circular detectors are more expensive than those designed for a small angle of coverage. However, the latter may take too much to fully control the room. Here it is important to carefully weigh and calculate everything before going to the store for supplies.

If the switch is installed in a small room with one door, then sensor settings with a narrow sector of the review is enough. It will only be necessary to accurately direct it to the input and set the maximum possible time for turning on the light in the settings.

Another point is the presence of a “dead zone” in the height of the motion detector. During installation, you must carefully study the passport in order to correctly set the direction of operation of the sensor.

Plus, there are still restrictions on the range of the detection zone. For verandas or long corridors, it is recommended to choose long-range devices. However, remember that with a large area of ​​control, they may start to work too often not when necessary.

Technical parameters and settings

Most models of light switches with a motion sensor are designed for direct connection of lighting devices to a 220 Volt network. In fact, this is a standard keyboard light switch, but supplemented by a detector and an automation board.

Connecting power to the sensor
Motion sensors can be powered directly from a 220 V power supply, batteries and through a 12 V power supply - the first option requires more wires, but more reliable and preferable

Each model of the circuit breaker in question has a parameter in its passport - the maximum connected power. It reflects the total power of the connected lamps. If the device is taken on a group of lamps in the fence at the cottage, then this value should be in the region of 1000 watts.

Otherwise, it will burn out the first time it is turned on. For installation in the rooms of a frequent house or apartment in excess there will be enough a device for 300-500 W.

With the rules for connecting a motion sensor to the lighting device it serves will introduce the article, the content of which is devoted to the analysis of this difficult question.

The minimum degree of protection should be IP44. For heated rooms in the cottage, this is quite enough. But for installation on the street or in the bathroom it is better to take with IP “55”, “56” or higher.

As a rule, a switch on the housing equipped with a motion sensor has three control knobs:

  1. “TIME” - response time to turn off the light after a person leaves the room.
  2. “LUX” (“DAY_LIGHT”) - sensitivity to illumination (in the presence of a photo relay).
  3. "SENSE" - sensitivity to movement (temperature in the case of an infrared sensor).

The first parameter can vary from 0 to 10 minutes. If a narrow sensor is aimed only at the door in the pantry, then this adjustment is best set to the maximum. Then when you enter the "dead zone" you can not be afraid that the light will turn off at the most inopportune time. At the same time, 5-10 minutes is enough for taking anything from the shelf in the closet.

The sensitivity to response from movement and the degree of illumination are set by the method of samples. It affects the level of insolation, the presence of animals in the house and heating radiators nearby, and even swinging trees nearby. If there are too many false positives, then gradually this parameter needs to be reduced and brought to optimal values.

Schematic diagrams of installation

There are several schemes for connecting a switch and an external motion sensor to the power circuit of lighting devices. In general: a sensor is inserted into a wire break with a phase. There are three terminals on its case. The corresponding conductors of the power cable are connected to “L” and “N”, and from the third output the wire is sent to the lamp.

Classic circuit breaker
The simplest circuit with a motion sensor, but without a key switch - the light will turn on only from the sensor built into the device

If one automatic detector is not enough and you still need a manual way to turn on the light, then the "key" in the circuit can be included in two ways. In the first, such a switch is inserted into the phase wire going to the sensor from the shield. When it is open, the sensor simply does not work and does not apply voltage to the light bulb.

The second option involves inserting the switch into the line from phase to input to the light bulb. When such a “key” is closed, the light will burn even if the sensor has not tripped.

Key Switch Circuits
Two circuits with different ways of connecting a key switch to a circuit with a load (lighting appliance) and a motion sensor

If you want to install multiple detectors, they are interconnected in parallel. A supply wire goes to the lamp from each of them. Light will appear when any of the sensors is triggered. If this solution seems unnecessarily complicated, it is best to purchase bulbs with integrated motion sensor.

If the lighting device is powerful or there are several of them, then instead of a light bulb, a magnetic starter with an amplifier should be installed in the circuit. And already through it, power a separate lighting circuit. In this case, the detector can be selected low-power and cheaper.

Most energy saving lamps quickly burn out with frequent on and off voltages. Therefore, connecting them through a motion sensor is not always advisable, since they will fail too often. The savings from the use of such light bulbs will result in zero.

To avoid problems with the burning out of expensive lamps, after the motion sensor, it is necessary to put a protection unit in front of them with a soft light on. Due to the absence of sudden voltage drops in the mains, the light bulbs will not “burn” as often as without such a protective device.

Introduces the marking and rules for the selection of smart switches next article, which we strongly recommend reading.

Conclusions and useful video on the topic

To make it easier for you to understand all the features of the selection and installation of the devices in question, we have made a selection of video materials for you. They explained everything in detail and in detail.

Clip # 1. Nuances of connecting a motion sensor and a standard switch with a key:

Clip # 2. Sensor Overview for Combined Auto Lighting Switches:

Clip # 3. Description of connection schemes:

Automatic “switches” incorporating a motion sensor are extremely easy to install. At the same time, energy savings from their use are substantial. In addition, they make the house more comfortable for living.

With the installation of such automatic devices do not hesitate. Everything can be done independently, without involving highly qualified electricians.

Please write comments in the block below, ask questions, publish photos on the topic of the article. Tell us about how you chose a smart switch for your own home / apartment / office. Share useful information with site visitors.

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Visitors Comments
  1. Alexandra

    A few months ago, my husband decided that a motion sensor should be installed in the hallway to save energy. At first, it irritated me very much, because in the morning he went to work, and the light through the door woke me when my husband passed the sensor. The problem was solved. Now this sensor amuses me when the cat comes up, the light turns on, and at first it scared and ran away, but it soon got used to it. After some time, the sensitivity decreased, the light began to turn on at a time when it was already not necessary, as a result, because of which I stumbled more than once. Nevertheless, I want to note that motion sensors are a very necessary and economical thing, especially for people who forget to turn off the lights.

    • Expert
      Amir Gumarov

      Good afternoon, Alexandra. It seems that buying a sensor by a spouse was an impulsive act - he did not study a solid range of devices.

      Let me explain: there are sensors that ignore animals - they “estimate” their mass. Among them - Colt QUAD PI. Positioned by marketers as a passive infrared detector. It does not respond if the pet weighs ≤ 27 pounds. Photos with technical specifications - attached. The market offers other models.

      Attached photos:
  2. Nataliya

    That's what the technique has come to :) In the past, it was impossible to imagine such conveniences. For me, so cool development. Sometimes we forget to turn off the light, but here everything will turn off without the participation of your memory. The only thing is it responding to pets? More convenient, of course, is this option for office buildings. For me, so if you install, then be sure to have a timer.

    • Expert
      Amir Gumarov

      For office buildings, I see no reason to install a light switch with a motion sensor - this is neither advisable nor practical. But with a timer - this is the best option. After all, people come and go to work at the office almost at the same time. If some kind of emergency occurs, then some employees remain late.

      In this case, the light in the main part of the office is turned off and zealous workers switch to individual lighting in the form of table lamps. But in the utility rooms in the office and with \ y it will be more practical to put switches with a motion sensor.

      As for pets and how this same motion sensor will react to them. So that the sensor does not work on the movement of the animal around the house / apartment, you must either mount it in such a way that it is at the level of movement of people, or buy special models (see the comment above, my answer is Alexandra).