DIY motion sensor repair: general information and diagram, self-assembly methods

Motion sensors are used everywhere today. They have proven themselves well both in office premises and in private houses or apartments. Due to their relative cheapness, anyone can install them. However, even the most reliable devices will break someday. Do-it-yourself motion sensor repair will help fix the situation.

General information

A motion sensor is a device that detects any movement in a strictly defined area of ​​action. All such devices are divided into three main types: active, passive and mixed. The work of the first of them is based on electromagnetic and ultrasonic radiation, the second - on infrared. The mixed type combines the characteristics of an active and a passive device.

Types of sensors

Before making a motion sensor, you need to decide on its type. The operation of all such devices is based on the reception and transmission of impulses that come from a moving object. In this case, it does not matter whether he will be alive (man, animal) or inanimate (car).

There are only three types of sensors. Their functionality can be selected based on the requirements and personal preferences of the owner of the premises or site.

Variety of devices:

1. Thermal. These devices react to temperature changes in their coverage area. The device has a built-in laser or infrared sensor that will not miss a single movement made by an object or subject emitting heat. This option is very often used in security systems.
2. Sound. The device receives pulses when the air vibrates from various sounds emitted by a person or a car while driving. The device has the simplest design and is easy to assemble with your own hands. It is best to use such a sensor in an open space.
3. Oscillatory. Such devices record all changes in the magnetic field and vibrations of environmental objects in the area of ​​their action. Sensors are widely used in homes or apartments to automatically turn on or off lights.

Advantages and disadvantages

Motion sensors, like any other devices, have their positive and negative sides. They influence the choice of a particular device and help to avoid most of the errors in operation.

The advantages of a homemade sensor include the following:

1. No additional maintenance required. To install a hand-made device, you do not need to invite specialists and spend money on them.
2. The sensor can be adapted to specific terrain conditions. This helps to more reliably disguise it and customize it to your requirements.
3. Doesn't need a lot of money and time. The device is manufactured rather quickly and from the minimum amount of materials available.
4. The ability to upgrade and make any changes to the settings. This positive feature of hand-made sensors is very important with frequent changes in environmental conditions and the need to adapt to them.
5. Ease of repair. If you independently make a device that responds to movement, then you can easily repair it in case of any problems.

In addition to all the positive aspects, there are also negative ones. All of them, in one way or another, are connected with the possibility of making mistakes during self-installation and its greater complexity.

Among the disadvantages are the following:

1. No guarantee of uptime. Even if the device performed well in testing, there is no 100% guarantee that it will also work during daily use. Because of this, there is a risk of non-standard and unpleasant situations for the owner.
2. Less reliability compared to sensors manufactured at the enterprise. The slightest mistake in design or installation can damage the entire device and leave the room unprotected.
3. The need to search for a large number of details. If you make a device yourself, it will take a lot of time to find and buy the necessary materials.
4. Risk of device failure due to moisture ingress or operation in severe frost. A hand-made motion sensor for turning on the light or guarding the room may stop working in bad weather. In this case, you will need to take additional troubleshooting steps that will lead to unforeseen financial costs.

Self-assembly and repair methods

All do-it-yourself motion sensor circuits for lighting provide for simple assembly using a small number of parts. They are all inexpensive and can be purchased at any specialty store.

The simplest option

For beginners in this business, it is better to use the simplest assembly scheme and make an elementary sensor that reacts to movements. With its help, you can learn the basics that will help you to further develop and improve your skills. All this will also help when repairing the device.

The following items will be used in the work:

• voluminous body (suitable from an old camera or any other similar equipment);
• a control base that can be bought in a store or removed from an old device;
• soldering machine;
• wires of different diameters;
• screwdriver;
• screws.

The control base can also be found at a flea market or at people who are professionally involved in the repair of old and new electrical appliances. It is inexpensive, so the purchase will not become an invoice even for the poorest people.

Step-by-step assembly instructions:

1. A weak oscillation generator is assembled on the basis of the transistor.
2. Then a low-pass filter and capacitor are attached. Thanks to them, the impulse will go to the alarm contacts.
3. After that, a resistor is placed to help adjust the sensitivity of the device.
4. A stabilizer is connected to the general circuit, increasing the signal.
5. In the next step, a zener diode and a small relay are attached.
6. An antenna is located in the upper part of the board, which is carefully treated with degreasing compounds and polished. In addition, you can additionally cover it with rosin, which will prevent oxidation during operation.
7. A wire of a small cross-section (about 0.2 or 0.23 mm) is taken, and with its help two coils are wrapped.
8. The sleeve is screwed neatly into the hole in the center of the sensor and is securely fixed.
9. Then the body is adjusted to the desired size. For this, all the necessary measurements are made.
10. Then the center is outlined, and a hole is drilled in it.
11. A light or sound source is connected to the detector, which will serve as an alarm.

Laser device

Despite the initial complexity, such a sensor is quite simple to assemble. The work can be done without any problems even at home. The mechanism itself consists of two devices connected to each other: a laser sensor that emits a light beam, and a sensor that receives it. The principle of operation is based on the effect of a light source on a photocell. As soon as the flow is interrupted (a person passes or a car passes), the circuit is closed and a light or alarm is turned on. Such a device is ideal for the protection of especially important objects, the entrance to the territory of which is strictly limited.

To DIY a laser sensor that reacts to movements with your own hands, you need to purchase the following materials and tools:

• a housing that will house the electronic circuit;
• a control unit removed from an old Soviet device, or a set of parts for its assembly;
• wires of various thicknesses;
• fasteners;
• resistors of different ratings;
• soldering iron with solder and fine tip;
• pliers;
• screwdriver;
• cambric;
• insulating tape.

It is best to immediately purchase everything you need for work, so that later you will not be distracted by the search for this or that item. This preliminary preparation will greatly speed up and simplify the sensor manufacturing process.

A laser sensor is made in compliance with the following sequence of actions:

1. The power supply is being assembled. After that, it is configured and the current output by the device is checked.
2. A resistor is connected to the minus of the block, and a diode is connected to the plus.
3. Then the trimming resistor is brought out.
4. In the next step, a transistor emitter is attached to the negative wire of the power supply.
5. At the very end, the resistor is connected to the base circuit.

The finished device is installed in the right place and masked. The scheme of operation is simple, so the device will work as follows:

1. As soon as the light beam hits the phototransistor, it opens and helps charge the capacitor.
2. If someone or something interrupts the luminous flux, then the phototransistor will fix it and provoke the discharge of the capacitor.
3. In this case, the voltage will drop sharply, and the operational amplifier will work.
4. As a result, he will turn on the warning device (alarm or lighting).

The light source for the photocell can be an ordinary laser. He is able to cover an area within a radius of 10 meters around him and respond to even the smallest movements. In addition, an infrared LED can be used. It is good because, unlike a laser, it is practically invisible to the naked eye.

Helpful advice from professionals

A self-made sensor that reacts to movements is good because it can be adjusted to suit your needs. For this, any available materials and tools that can be found and bought in specialized stores are suitable.

Helpful hints:

1. You can use a webcam as a motion indicator. To do this, it must be connected to a signaling device or a computer. In the latter version, you will need a special program that is installed on the PC.
2. When connecting the sensor to the warning system, make sure that there are no large household appliances and fans nearby. By their work, they can affect the device and lead to incorrect or untimely notification.
3. When creating a “smart home”, it is recommended to use touch switches that already have a similar motion sensor.
4. It is best not to use a laser device to guard residential premises. This is because infrared radiation can harm human eyes.
5. In the same way, you can make an alarm for a car. The only difference will be the addition of a dedicated audio signal.

Making and repairing a sensor that responds to various movements is a rather difficult undertaking that, if you have the skills and abilities, you can do it yourself. With the right approach to business and following all the advice of professionals, you can independently make a useful device that will reliably protect the room and simplify the life of the owners.