The presence of all kinds of detectors in the room allows monitoring and control of most modern houses, remotely and automatically, according to a predetermined algorithm, without constant monitoring person. In this article, we will discuss how to make a motion sensor with your own hands at home, and also consider the scope of possible application of these devices.
Content:
- Briefly about sensors
- Assembly diagrams
- Microwave
- Thermal
- Homemade Arduino
Briefly about sensors
A limit switch or self-return button installed at the door and responding to opening and closing is the simplest motion sensor (penetration, opening). With the help of a simple scheme, this device turns on the light in the refrigerator. You can also equip a pantry or a vestibule of the hallway, a door in the entrance, a standby LED lighting using this switch or an alarm that will notify about activation.
Such devices, based on reed switch and magnet, can be seen on the doors and windows of protected objects. Lack of devices in a narrowly specialized application. They are not suitable for monitoring open areas, squares, passages.
For open passages, there are devices that respond to changes in the environment. These include photo relays, capacitive (field sensors), thermal (PIR), sound relays. To fix the intersection of a certain area, control an obstacle, the presence of movement of any object in the overlap zone, use a photo or sound echo of the device.
The principle of operation of such devices is based on the formation of a pulse and its fixation after reflection from the object. When entering such a control zone, the characteristic of the reflected signal changes, and the detector generates a control signal at the output.
For clarity, a schematic diagram of the operation of the photo relay and sound relay is presented:
Obstacle detector
Intersection sensor
Interactive machines, automatic doors, voice detectors, burglar alarms and other automation that reacts to a clear position of an obstacle or object.
For example, it is great to equip an illuminated mirror with a motion detector. The lighting will be turned on only at the moment when a person is directly next to him. Do not want to do this mirror illumination on one's own?
Assembly diagrams
Microwave
To control open spaces and control the presence of objects in the controlled area, a capacitive relay has been developed. The principle of operation of this device is to measure the amount of absorption of radio waves. Everyone probably observed or was a participant in this effect, when approaching a working radio receiver, he begins to change the wave or and make a noise straying from the station. Let's talk about how to make a microwave-type motion sensor. The heart of this detector is a microwave radio generator and a special antenna.
This schematic diagram shows a simple way to make a microwave motion sensor. The VT1 transistor is a high-frequency generator and, in combination, a radio receiver. The detector diode rectifies the voltage by applying a bias to the base of the transistor VT2. The windings of transformer T1 are tuned to different frequencies. In the initial state, when no external capacitance acts on the antenna, the signal amplitudes are mutually compensated and there is no voltage across the VD1 detector. When the frequency changes, their amplitudes are added and detected by a diode. Transistor VT2 starts to open. As a comparator, for a clear working off of the on and off state, a thyristor VS1 is used, which controls a 12 Volt power relay.
Below is a working circuit of the presence relay on the available components, which will help you assemble a motion detector with your own hands or just come in handy for getting to know the device.
Thermal
Thermal DD (PIR) is the most common sensor apparatus in the business sector. This is due to cheap components, a simple assembly scheme, the absence of additional complex settings, and a wide operating temperature range.
The finished device can be bought at any electrical store. Luminaires, alarms and other controllers are often equipped with this sensor. However, now we will tell you how to make a thermal motion sensor at home. A simple outline for repeating looks like this:
A special heat sensor B1 and a photo element VD1 make up an automated lighting control complex. The device begins to work only after the onset of dusk, set by the level of the resistor R2, when a moving person enters the control zone. The built-in timer can be set with the R5 knob.
Homemade Arduino
An inexpensive sensor can be made from special boards for a radio designer. A rather miniature device is assembled from ready-made modules. For assembly, we need a motion sensor module for Arduino microcontrollers and a single-channel relay module.
Each board has a three-pin connector, VCC +5 volts, GND -5 volts, OUT output on the detector and IN input on the relay board. In order to make a working device with your own hands, you need to apply 5 volts to the boards from the power source, and connect out and in together. As a result, it should look like in the diagram below.
The finished detector can be placed in a housing or disguised in a convenient place. Finally, we recommend watching a video that clearly demonstrates instructions for assembling homemade motion sensors at home:
Now you know how to make a motion sensor with your own hands. We hope the provided diagrams and videos helped you in assembling a homemade sensor!
It will be helpful to read:
- How to connect a motion sensor for lighting
- How to make a dimmer
- Do-it-yourself automatic garage doors