DIY motion sensor: step-by-step guide. Schemes of motion sensors and the principle of their operation, connection diagrams Do-it-yourself linear position sensor

Today, presence sensors have become very fashionable to detect movement when a person moves around the room.

When you connect such a device to lighting fixtures, you will receive an automatic system for turning on the lights. Almost anyone can assemble a presence sensor to detect a person on their own. And here the assembly diagram will be the main one. You will learn everything about the assembly process from this article.

Operating principle

The first thing you need to know when assembling such a device yourself is the principle of its operation.
Pay attention! Many people confuse such devices with motion sensors. But these are different models.
The operating principle of the device is based on the sensor’s response to the location of a person or large animal. The operation of the device is based on the Doppler effect - a change in wavelength and frequency. These changes are recorded by the sensor and transmitted to the device to further turn on the lighting or sound signal. Moreover, the signal arrives at the sensor regardless of whether the object moves or remains motionless. The device is equipped with an antenna and a generator. Without the presence of a reflective antenna signal, the device is in sleep mode. The operating diagram is shown below.

When the device is connected to a light source, in the event of the appearance of any object in the work area, the light is activated. At the same time, to turn on the lighting as such, there is no need for movement (even a slight one).

Where is it used?

Presence sensors are now actively used in the following areas:

“smart home” system for turning on the lights automatically (the connection diagram is shown below). In this situation, it allows you to save electricity consumption significantly;

Connection diagram

security systems;
robotics;
various production lines;
video surveillance systems;
to control electricity consumption, etc.

In addition, interactive toys equipped with similar devices are increasingly appearing. But in most cases, when the device reacts, there is no need to turn on the light. Such products can respond to temperature, ultrasound, object weight and many other parameters. The lighting does not turn on here. The device reacts, for example, by turning on the sound or transmitting a signal to a portable mobile device (for modern models).
Such developments are especially indispensable in the security system. But not every person can afford to purchase such a device. They are quite expensive and may not be affordable. Therefore, some people make such devices with their own hands.

Let's start assembling

In order to assemble the sensor, you will need the diagram below.

In addition to this you will need:

microwave generator;
transistor KT371 (KT368), which must be pre-amplified by KT3102;
comparator;
microcircuit K554CA3.

All the necessary components for assembly can be found on the radio market or in specialized electronics stores.
According to this diagram, it is necessary to assemble and solder the above elements.
According to the given diagram, the sensor will work like this:

the generator produces a microwave signal;
then it is transmitted to the whip antenna;
then the signal is reflected from an object moving in the controlled area;
the result is a frequency shift;
then it is returned to the antenna and microwave generator.

At this stage it will operate as a direct conversion receiver. This is due to the fact that the received signal is converted into infrasonic (low frequency).
After signal conversion, the following happens:

now the low-frequency vibrations already received, reaching the pre-amplifier, are amplified;
they are then transmitted to the comparator and converted into pulses (rectangular).

If the signal is not reflected, then a high level voltage is obtained at the output of the comparator.
A trimmer capacitor is needed to set the frequency. It must be equal to the resonant frequency of the antenna.

Pay attention! This parameter should be selected according to the maximum sensitivity of the sensor.

From a constructive point of view, the device must be made on a printed circuit made of fiberglass. The board must be placed on a plastic case.

Printed circuit (example)

You can use a piece of rigid wire as an antenna. For its manufacture, it is better to choose copper wire. We solder it to the contact pad of the resulting board. The antenna output is carried out through the output on the housing. Experts recommend placing the antenna vertically.
Remember that any shielding objects should not be placed in the immediate vicinity of a self-assembled sensor. In addition, you should know that for the normal functioning of a soldered product, its common wire must have a capacitive connection to the ground.

Final stage

After you have installed the compact device, it should be hung on the inside of the door, as close as possible to the door handle and door lock. The product can also be placed in other places. The main thing is that the controlled area is sufficient.
During installation, it is necessary to ensure that the length of the conductors and leads of the elements is minimal. This will avoid interference, as a result of which the device may not work properly.
Following the instructions and diagram provided, it is relatively easy to assemble a presence sensor with your own hands. The main thing is to mount all the components in the right order.

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What are pyromodules? How to enable and use them correctly? This article will answer all these questions.

The creation and installation of pyromodules in this article will be discussed using the example of modernizing the EK-0.3 coffee maker.

As you know, this type of coffee maker does not have the function of turning off after making coffee. Very often such devices suffer a sad fate, because they can explode because they lack automation. Therefore, in order for the operation of the device to be safe and its “life” to be long, it is necessary to take certain measures.

One option is to use a special thermal switch that will turn off the coffee maker. The disadvantage of this method is that the switch will only operate when the case temperature is above 120 degrees. And at this temperature, there is usually no water in the coffee maker’s reservoir completely. As a result, all this will lead to the body of the coffee maker overheating, and the amount of energy required will increase several times. The best option is to use a motion sensor; it will independently monitor the moment coffee is supplied to the coffee pot.

PIR (motion) Sensor (pyromodule) - what is it?

This abbreviation stands for as follows:

– PIR– Passive Infra-Red;

– FEAST– Passive Infrared.

So what is it? This device converts infrared radiation (more precisely, a change in its intensity) into electric current. In certain crystalline rock materials, if the temperature is changed, a pyrostatic effect occurs. It is on this effect that the operation of the pyromodule is based. The temperature in materials changes precisely due to infrared radiation.

The electric field needs to be registered, but to do this it needs to change. And when changing, the crystalline dielectrics will be compensated by free electric charges. All sensors built using pyroelectrics have this property. This means that they will all be able to track even the slightest change in radiation intensity. In this case, the pyromodule itself (its temperature) will not have any effect on the measurement results.

To protect the pyro-sensor from various negative influences and various interferences, it is necessary to enclose it in a sealed metal case. The housing must have a window that allows light to pass through (narrow radiation range). In order for light to pass through in this range, the window must be covered with an infrared cut-off filter. The spectral characteristic of the filter is 10 µm (1*104 nm).

Design of an imported pyromodule:

– in addition to the pyro-sensor itself, a special amplifier is also located behind the infrared filter. It operates on a unipolar low-noise transistor. The diagram above shows how to turn on the “PIR D203S” pyromodule (foreign production), as well as its pinout.

In order to connect Soviet pyromodules, you will need to install a field-effect transistor. The diagram above shows how to turn on “PM-4” (Soviet production), as well as its pinout.

Previously, pyromodules were secretly developed in military-industrial complexes. They were installed in missiles and other similar devices, and were part of Thermal Homing Heads or THS.

Today, the use of modules in civil engineering is widespread. The most common area is motion detectors in alarm systems and lighting control systems. The picture above shows an example, a Feron LX20/SEN5 sensor, which is intended for a lighting control system.

What results should be achieved when improving a coffee maker?

The coffee maker should turn off the power as soon as coffee starts flowing into the pot. The process will be completed without electricity; the thermal energy accumulated by the housing will be sufficient to complete it.
The coffee maker should switch off abnormally when the temperature exceeds 120 degrees. Otherwise, it will burn out due to lack of water.

This figure shows a block diagram. The motion sensor sends signals to the control unit. The control unit, in turn, can turn off the electromagnetic relay at the right time. And thanks to an electromagnetic relay, the entire coffee maker turns off at the right moment.

This diagram shows the control unit in its electrical version. Elements of the circuit and their purpose:

PM-4– this is a pyromodule without a built-in amplifier;
VT1– with its help, the pyromodule signal is amplified;
DA1-1-DA1-2– adjusts the amplification of the pyromodule signal;
VD1– a temperature sensor based on a germanium diode;
DA1-3– amplifies the signal from the temperature sensor;
DA1-4– stabilizes the virtual earth;
VS1– blocks relay P1 and its power supply. Is a threshold element;
VT2– this relay performs a delay at certain moments. For example, it prevents the coffee maker from switching off during transition processes while power is already supplied;
Z1– stabilizes the voltage at 12 Volts;
Z2– stabilizes the voltage at 8 Volts.

Construction and its details.

The picture shows a printed circuit board on which all the parts are assembled, with the exception of the temperature sensor. Board dimensions – 45x85mm.

Here is the board directly assembled.

As already mentioned, the temperature sensor is made using a germanium diode. The sensor mount is made of tin can.

The sensor is attached to the body of the coffee maker; silicone sealant is suitable for more reliable fastening. You can also apply a drop of KPT-8 thermal paste between the case and the bracket. The MGTF wire is used to connect the sensor (fluoroplastic insulation).

You need to drill two holes in the coffee maker stand.

These holes are needed to carry five wires. Two wires are needed for power, one wire will control the load and two more from the temperature sensor. The control unit is made in such a way that it is suitable for repair at any time.

The pyromodule eye must be protected. A polypropylene plate is perfect for this purpose. Such a plate can be taken in a disposable syringe, cut off from the piston. The pyromodule operates in a rather narrow spectrum of infrared radiation. This spectrum can be blocked by simple glass, but polypropylene will transmit it.

Additional materials.

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Various types of detectors that allow monitoring of communications and security systems in buildings and private homes make it much easier to manage the entire complex as a whole. Due to built-in algorithms, devices operate autonomously, and human intervention becomes minimal. One of the important elements of such circuits are motion sensors. With the help of these devices you can protect the territory from unwanted intrusion and save on electricity. Sensors will automatically turn on and off lighting in the house and on the street, and switch power to other electrical appliances.

Most of these detectors can be made independently; the main thing is to understand the operating principle of these detectors. A DIY motion sensor can be a complex device or, conversely, be assembled from several parts.

Ring switch

The simplest motion sensors include self-return points (ring switches). Such equipment is used when turning on the light in the refrigerator. To operate the circuit, the following is used:

reed switch or sealed contact, is a flask with 2 ferromagnetic contacts sealed inside;
magnet.

When the magnet approaches the reed switch, the contacts close, and when removed, they open. When the contacts are open, voltage is supplied to the lamp in the refrigerator, and the light comes on. When the contacts are closed, the light bulb is de-energized.

This homemade motion sensor can simply be connected to an existing security alarm or sound detector. Due to this, when the contacts open, that is, the door opens, the system will sound a sound signal. The scheme is used on the doors of protected objects, but is not suitable for open areas.

To control large areas, more complex devices are used that can respond to various changes in the environment. Such elements include:

photo, - and sound relays;
field sensors;
pyro receivers.

Light motion sensor

Quite often, a motion sensor is needed to detect an object as it moves across a certain line, for example, at the entrance to a room. To create such a sensor, two devices are needed: a light source and a photodetector. When a person passes in the area of the beams, the connection between the source and the receiver will be lost, the sensor will operate and produce a sound signal.

The entire circuit of this device is based on a photocell - a transistor. Moreover, such a phototransistor can also be made with your own hands. To do this, you need to take a transistor that looks like a hat with a brim on three legs, for example, P417A. You need to saw off the top of the element so that a hole is formed, or simply open the entire crystal. Now, when exposed to light, the element will begin to work like a phototransistor, although its sensitivity will be slightly less than usual. You don’t have to waste time on this operation, but immediately take a ready-made photocell.

First we assemble the photodetector. The device uses the following elements:

VT1 – phototransistor;
R1 – resistor;
C1 – capacitor;
DA1 – operational amplifier with feedback;
R2 – resistor with feedback to the operational amplifier;
R1 – performs the functions of load and collector. Using this element, the operating point is set. The selection of the required value is done empirically.

When choosing the characteristics of R2, it should be remembered that the higher the gain, the less stable the amplifier. On the other hand, the higher the resistor value, the greater the gain. It is optimal to use a nominal value of 100 kOhm.

Homemade products work as follows:

when light hits the transistor, a small operating voltage appears and the element opens;
the capacitor is charged;
if the light goes away, the capacitor begins to discharge;
at point A the voltage decreases, which reduces the voltage at the output;
An operational amplifier is needed to amplify the signal from point A for further transmission to other devices.

A photodiode can be used as a light source at short distances. The red laser will allow you to significantly gain distance. The laser motion sensor can be used over large areas. But if you need to make the sensor invisible, use an infrared diode.

Attention! When selecting a laser diode, check that its characteristics comply with safety regulations. Some of these elements have a detrimental effect on the eyes.

The photosensor itself must be darkened and covered with dark transmitting material. This will reduce the influence of conventional lighting. We place the light source opposite the sensor. Due to this, an optical connection is formed, that is, until the object covers the light source (crosses the line), the voltage in the phototransistor will be constant. When the optical connection is broken, the output voltage is reduced to zero by the operational amplifier.

To analyze the data coming from the sensor, a relay should be connected to the circuit. We connect the winding to the input, apply 12 V to 1 contact, ground the other end, and connect the third to the radio. If light falls on the photocell, the power circuit is connected to the photodetector, the radio does not work. If the optical link is broken, the voltage drops and the power supply is shorted to the radio. This causes the radio to turn on. Instead of a radio receiver, other detectors can be used.

Motion sensors with capacitive relay

The capacitive relay reacts to the occurrence of objects within a given radius. The main elements of such equipment are an antenna and a microwave generator.

Many of us have noticed that the sound of a radio changes when a person gets very close to it, strange noises appear in operation, or the station’s waveform gets lost. Microwave motion sensors operate on exactly the same principle.

The role of the high-frequency generator of the radio receiver in the circuit is simultaneously performed by transistor VT1. A detector diode is needed to rectify the voltage, which sets the bias at the base of transistor VT2. Transformer T1 has windings tuned to different frequencies. If the antenna is not affected by external objects, there is no voltage on the VD1 detector, since the signal amplitudes cancel each other. If the frequencies change, the amplitudes begin to add up and are detected on the diode. Due to this, VT2 opens. In order to accurately set the value for turning off and turning on, a comparator is used - thyristor VS1. This thyristor is controlled by a 12-volt power relay.

Important! Sensors should not be placed near fans or large household appliances. All this equipment can interfere with the operating mode of any sensor.

Design Platforms

To create more complex and functional devices, you can use ready-made boards for radio design, for example, Arduino. This is the name of a hardware computing platform with its own processor and memory. Arduino performs several important tasks at once:

reads and processes the signal from the infrared sensor;
reacts to movement;
carries out notification.

To create the sensor you will need the platform itself, a PIR sensor, a breadboard and wires. You can connect the sensor directly to the Arduino, but it is more difficult to ensure a tight fit. Therefore, it is more convenient to use a Bradboard.

All infrared sensors have the same structure. The main parameter by which one sensor can be distinguished from another is sensitivity, and, therefore, the optics used. The optimal PIR sensor today is a device with Fresnel lenses. These lenses can concentrate radiation, increasing the threshold of sensitivity.

The main task of the platform is to send data via USB Serial when motion is detected at certain intervals. Hardware debugging is carried out using Python and PySerial software.

Such a motion sensor for turning on the light can be programmed to create a certain level of illumination. This equipment can be used to install an alarm system in the garage, then the detector will be connected to the sound module.

Video

A device called a motion sensor is widely used in everyday life. With its help, lighting is installed in entrances, office premises and even apartments, ensuring that the light is turned on only in the presence of a person, and significantly saving electricity (Smart Home system). These devices are also used to create effective security systems. Unfortunately, their cost is not always affordable, especially if the size of the perimeter requires not one sensor, but several. In this article we will talk about what such a device is, what its types are and how it works, and we will also figure out how to make a motion sensor with your own hands at home.

These devices are divided into external and internal: the former are used outdoors, and the latter are installed indoors.

The functioning of street devices is based on calculating the distance from them to the object. Where it is necessary to trigger at a long distance (extensive local areas near high-rise buildings or large private properties), perimeter alarms are used, the response distance for which can reach 500 meters. Installation and connection of indoor DDs is carried out indoors in any desired location. They cannot be used outdoors due to their high sensitivity to temperature changes.

The following types of motion sensors exist:

· ultrasonic;

Microwave (radio frequency);

· infrared (IR).

Let's figure out what their differences are and how they work.

Ultrasonic devices are the simplest and most durable, and also have the lowest cost. The basis of their work is the emission of ultrasound and its reception when reflected from a moving object.

The operation of microwave (radio frequency) DD is based on the principle of radar. The device automatically triggers only when it detects signals in a certain range. Experts believe that such devices are more practical than ultrasonic ones, but they are also more expensive.

The operating principle of infrared devices resembles the operation of a highly sensitive thermometer. They are tuned to a certain temperature and are triggered when an object with the corresponding indicator enters their field of “vision”. Due to the high sensitivity of the devices to temperature fluctuations, they cannot be placed in the kitchen or near the entrance doors.

The presented video describes in detail motion sensors, their types and operating features:

Now let's talk about how to make a motion sensor to turn on the light with your own hands. The technical diagram of this device, shown in the figure, is quite simple, and for a person who has some experience in making homemade devices, it will not be difficult to assemble it.

To assemble the device you will need the following set of tools and electronic parts:

· electric soldering iron;

· plumbing gasket of the required size;

· laser pointer;

· photodiode (can be selected on the page);

· reed switch relay (can be selected);

· power unit.

If everything you need is at hand, we proceed directly to assembling the motion sensor circuit with our own hands.

When assembling this device, you need to proceed in this order:

Prepare the power supply. To do this, you need to cut off the connector from it, and then use a volt-ohmmeter to determine where the “plus” is located;

Solder a resistor to the positive contact;

· also use a soldering iron to connect the cathode of the photodiode to the positive of the resistor;

· then you need to solder the anode of the photodiode, as well as the emitter of transistor VT1, to the minus of the trimming resistor;

· after this, the emitter of VT2 must be soldered to the negative of the resistor, and the collector of VT 2 to one of the contacts of the reed relay. The second relay contact is connected to the power supply;

· A laser pointer is most often used in homemade sensors, so it is easiest to use. To save money, 2 additional wires are connected to the power supply;

· The screw must be inserted into the plumbing gasket. Its cap should be placed inside the pointer so that it rests against the spring;

· one power wire must be connected to the screw, and the second is inserted between the body of the laser pointer and the plumbing gasket.

Before turning on the DD, you need to make sure that the assembly is correct by checking the diagram. After this, you can connect the device and check its operation.

How to assemble a motion sensor with your own hands is shown in this video:

Such devices are widely used not only for automatically turning lights on and off, but also in security systems. For this purpose, infrared sensors that respond to the temperature of the object are used. Since the human body is an active source of infrared rays, the device instantly reacts to it, turning on the alarm.

The advantages of infrared DD include:

· safety for humans and animals;

· reliability;

· ease of setup.

You can assemble a simple motion sensor for an alarm with your own hands. For this you will need:

· housing (suitable for an old household appliance);

· photodiode (you can choose any of those presented on the page);

· bipolar transistor with p-n-p junction (can be selected);

· trimming resistor (can be selected).

Assembly order

The device is assembled in accordance with the presented diagram:

The function of the sensitivity regulator is performed by resistor R11. Zener diodes act as comparators (comparing relays).

There is an antenna on top of the board. To prevent it from oxidizing, it is polished and a thin layer of acetone is applied on top. The coils are wound in 12 turns with thin wire. A sleeve is fixed to the central hole using a 3 mm screw.

The finished device is placed in a housing in which a hole for mounting is made in advance. If necessary, the internal corners of the body part can be bored.

To better see the LEDs, you can also drill special holes for them, but in most cases this is not necessary - their glow is clearly visible through the body material. After this, a fluorescent lamp is connected to the device.

This completes the work. We put together a simple infrared motion sensor with our own hands.

These devices, as mentioned above, are very simple and easy to use. With their help, you can save a lot on electricity bills, as well as create a completely reliable security system. Since now you know how to make a motion sensor with your own hands, you can handle it yourself. All products presented on the pages of the site are certified and of high quality.

DIY motion sensor

Classification of motion sensors

These devices are divided into external and internal: the former are used outdoors, and the latter are installed indoors.

The following types of motion sensors exist:

· ultrasonic;

Microwave (radio frequency);

· infrared (IR).

Let's figure out what their differences are and how they work.

Operating principle of motion sensors

Ultrasonic devices are the simplest and most durable, and also have the lowest cost. The basis of their work is the emission of ultrasound and its reception when reflected from a moving object.

The presented video describes in detail motion sensors, their types and operating features:

Motion sensor to turn on the light

To assemble the device you will need the following set of tools and electronic parts:

· volt-ohmmeter;

· power wires;

· electric soldering iron;

· plumbing gasket of the required size;

· laser pointer;

· screw;

· photodiode (can be matched to a 10 kOhm trimmer resistor);

· transistors;

· reed switch relay (can be selected here);

· power unit.

If everything you need is at hand, we proceed directly to assembling the motion sensor circuit with our own hands.

How to assemble a motion sensor for lighting

When assembling this device, you need to proceed in this order:

Prepare the power supply. To do this, you need to cut off the connector from it, and then use a volt-ohmmeter to determine where the “plus” is located;

Solder a resistor to the positive contact;

· also use a soldering iron to connect the cathode of the photodiode to the positive of the resistor;

· then you need to solder the anode of the photodiode, as well as the emitter of transistor VT1, to the minus of the trimming resistor;

· A laser pointer is most often used in homemade sensors, so it is easiest to use. To save money, 2 additional wires are connected to the power supply;

· The screw must be inserted into the plumbing gasket. Its cap should be placed inside the pointer so that it rests against the spring;

· one power wire must be connected to the screw, and the second is inserted between the body of the laser pointer and the plumbing gasket.

Before turning on the DD, you need to make sure that the assembly is correct by checking the diagram. After this, you can connect the device and check its operation.

How to assemble a motion sensor with your own hands is shown in this video:

Motion sensor for alarm

The advantages of infrared DD include:

· safety for humans and animals;

· reliability;

· ease of setup.

You can assemble a simple motion sensor for an alarm with your own hands. For this you will need:

· housing (suitable for an old household appliance);

· power wires;

· photodiode (you can choose any of those presented on this page);

· bipolar transistor with p-n-p junction (can be found here);

· Here).

Having prepared all the necessary components of the future device, we proceed directly to installation.

Assembly order

The device is assembled in accordance with the presented diagram:

The function of the sensitivity regulator is performed by resistor R11. Zener diodes act as comparators (comparing relays).

The finished device is placed in a housing in which a hole for mounting is made in advance. If necessary, the internal corners of the body part can be bored.

This completes the work. We put together a simple infrared motion sensor with our own hands.

All kinds of sensors allow you to automate many processes in everyday life.

Some of them you can make yourself.

Today we will learn how to do it ourselves.

Based on their operating principle, factory-made motion sensors are divided into three types:

ultrasonic;
radio frequency;
infrared.

Ultrasonic (US)

The sensor working area consists of two parts:

ultrasound emitter;
reflected signal analyzer (receiver).

When a moving object appears in the sensor's field of view, changes will appear in the reflected signal. The analyzer will register them and send a signal to a semiconductor switch or relay, causing the circuit to close.

Advantages of the ultrasonic sensor:

is cheap;
atmospheric factors do not affect operation;
“sees” objects made of any material.

Flaws:

range is limited;
does not respond to smooth movement;
causes discomfort in animals (they are sensitive to ultrasound).

Radio frequency (RF)

The principle is the same, only instead of ultrasound, radio waves are emitted.

Advantages:

compactness;
significant range;
the ability to capture moving objects located behind glass or a thin opaque partition;
high precision.

Flaws:

are expensive;
are hypersensitive, which is why false positives sometimes occur;
with significant power, they have a negative effect on people and animals who are in the field of view of the sensor for a long time.

Infrared (IR)

They do not emit anything, but only capture infrared radiation, thus determining the temperature of objects. When an object with a given temperature (usually set to 36.6 degrees) appears in the field of view, they are triggered, closing the lamp circuit.

Advantages:

do not have harmful effects on people and animals;
easy to customize;
have an affordable price.

Flaws:

operating temperature range is limited;
do not “see” through materials that do not transmit IR radiation;
react to heating devices.

Ultrasound and RF sensors are called active, IR - passive. The latter are also called pyromodules - from English. PIR, which stands for Passive Infra-Red.

Classification by purpose

Based on their purpose, motion sensors are divided into:

internal (room);
outdoor (street).

The latter are resistant to extreme temperatures and have a significant range of 500 m or more.

Types of homemade sensors

Homemade motion sensors work on different principles:

reed switch. Reed switch is an abbreviated phrase for “sealed contact”. This is a capsule with two contacts made of ferromagnetic steel, sensitive to the magnetic field. When a magnet is brought close to the reed switch, the contacts in it close, and when removed, they open. Such motion sensors are installed on doors and windows: a reed switch is attached to the jamb, a magnet is attached to the sash. When the sash opens, the magnet is removed from the reed switch, the contacts in it open and power is supplied to the lamp or some kind of signaling device. Of course, this device is not a motion sensor in the full sense of the word. It is rather a door opening sensor;
light. The sensor consists of two parts: a light source and a photocell. When a moving object crosses the line between them, light stops flowing to the photocell-transistor, which leads to the closure of the circuit;
microwave. When a person approaches a working radio, it reacts - interference appears in the playback. The action of this sensor is based on this phenomenon. It consists of two main parts, an antenna and a microwave generator.

Required tools and materials

To make it you will need only two tools:

The elements and materials needed are:

phototransistor (designated VT1 in the diagram);
(C1);
operational amplifier with feedback (DA1);
feedback resistor to the operational amplifier (R2);
normal (R1);
relay RES 55A;
laser pointer (if the distance between the light source and the photodetector is small, a photodiode can be used instead of a laser);
plumbing gasket;
screw.

You can make a phototransistor yourself from a P417A transistor or any other one that looks like a hat with a brim on 3 legs. The housing cover is dismantled, revealing the semiconductor filling, or a hole is formed in it by cutting off the upper part. When illuminating an open crystal, the device will act like a phototransistor, only with less sensitivity.

The R2 rating is chosen taking into account the fact that as it increases, the gain increases, and this leads to a decrease in the stability of the amplifier. The optimal resistance is 100 kOhm.

Stages of device assembly

The motion sensor is assembled in several steps:

The connector is cut off from the power supply. Next, a multimeter is used to determine the core with a positive charge;
A photodetector is made from the components listed above, connecting them into a circuit.

Photodetector circuit

Then connect the laser pointer to the power supply:

solder two additional wires to the block;
pierce the water gasket with a screw and place this structure in the laser pointer with the head first, so that it rests against the spring contact.

One of the additional wires is connected to the screw, the second is placed in the gap between the gasket and the pointer body.

How to connect a motion sensor: diagram

It is advisable to install a homemade light motion sensor in a doorway - then a person entering the room is guaranteed to cross the line between the light source and the photodetector.

The product will look more elegant if the photodetector circuit is placed in a plastic box with a hole opposite the phototransistor.

Approximate installation of a motion sensor on the street

To exclude the influence of other light sources, the photosensor is darkened and covered with dark light-transmitting material.

Installation height - 1 m from the floor. With this placement, the sensor does not notice pets and the laser completely prevents the laser from entering a person’s eyes (it has a negative effect on the retina). To supply power to the lamp, a RES 55A relay is connected to the sensor.

The connection diagram is as follows:

the winding is connected to the input;
is supplied to one contact;
the second contact is connected to ;
the third is connected to the lamp.

The device works as follows:

under the influence of light, an operating voltage is formed in the photoresistor, causing it to open;
power is supplied to capacitor C1, as a result of which it is charged;
when a light-proof barrier appears between the light source and the photodetector (a person has entered the room), the phototransistor closes and capacitor C1 is discharged;
this leads to a decrease in voltage at point A and, accordingly, at the output to zero. This is facilitated by the operational amplifier DA1;
when the voltage drops, the power source is closed to the lamp via a relay.

The sensor can be made invisible by using an infrared diode instead of a visible light source.

Making a Microwave Sensor

This sensor is assembled according to the diagram below. Here, transistor VT1 simultaneously plays the role of a high-frequency generator of a radio receiver. The voltage set by the bias at the base of transistor VT2 is rectified by the detector diode.

The T1 windings are tuned to different frequencies. In the normal state (there are no moving objects), the amplitudes of the signals cancel each other out and no voltage is applied to the detector VD1.

Schematic diagram of a microwave motion sensor

When moving objects appear that obscure the antenna and distort the radio waves going to it, the amplitudes of the signals are summed up and detected on a diode. This causes VT2 to open.

Settings

In the proposed circuit 1, resistor R1 performs the functions of collector and load. The operating point can be adjusted using it. The optimal resistance is determined by the selection method.

A comparator is required to fine-tune the microwave sensor on and off values (diagram 2). Its role is played by thyristor VS1. It is controlled by a 12 V power relay.

Video on the topic

How to make a lamp with a motion sensor with your own hands:

The process of making a homemade motion sensor for lighting control is not complicated. Even a beginner can cope with this; you just need to carefully study the diagrams and recommendations presented in the article.