Homemade touch light switches - scheme and principle of operation

"Smart home" has long become a reality and is gaining popularity. Useful gadgets and programmable electrical appliances make life easier for a person. The touch switch can be part of the complex or used separately. Mechanical pressing is no longer the only closing signal. The operation of the device is based on the electrical conductivity of the human body or the reflection of infrared rays. The sensor reacts to light touch or movement.

Smart switch design

The concept of "sensory" is interpreted differently depending on the source. In a broad sense, it is an analogue of a key or power button that responds to voice, movement, room illumination, etc. It does not require mechanical action. In a narrow sense, it is a device that operates due to the energy intensity of a person. The limb of a person, approaching the sensitive plate, becomes part of the electrical circuit, closes it. Due to the action of a special element of the circuit (trigger), there is no opening after the stimulus is removed, the stable state of the system is maintained. The absence of moving parts eliminates their breakage and facilitates wet cleaning of the surface.

Components:

Outside - front glass or plastic panel and fireproof casing. Square, rectangular models are more common than round ones. The size is the same as a conventional rocker switch, allowing a standard socket to be used for mounting. The function of the cover is protective and decorative.

The sensing element is a plate with capacitive sensors or a pair of infrared emitter + receiver, additional sensors may be present. The task of the sensor is to pick up a signal from the outside.

Power component - printed circuit board with SMD components: power supply, amplifiers, microcontroller, radio channel board, key, volatile memory.

Sometimes an additional capacitor is included to prevent the background glow of the discharge lamps when off.

Switch classification

To choose the right communicator, one should proceed from the purpose of the room, the number and characteristics of the luminaires. According to the voltage parameter, the devices are:

• 220 V is a standard indicator for most devices;
• 12V - suitable for LED strips and some other types of lighting fixtures.

By the number of connected light sources, single, double, triple switches are used. A larger quantity is more convenient to control with a remote control.

By the type of key, you can distinguish:

• with an electromagnetic relay - the closure occurs mechanically, so the contacts burn out over time;
• equipped with a triac - a semiconductor device.

Sensing element types in household switches:

• capacitive - requires a light touch;
• optical - reacts to movement or light level;
• high-frequency - tuned for presence, room (volume) occupancy, movement.

Additional functions:

• motion, volume, sound sensors;
• wireless control;
• smooth decrease in brightness when turned off;
• timer.

Touch switches expand lighting options, simplify control, and save time and energy costs. They can be self-contained or mounted in luminaire bodies: floor lamps, table lamps, LED profiles.

Self-assembly of touchscreen communicators

The main disadvantage of smart switches is the price.Having a basic knowledge of electrical engineering will help you assemble a homemade product. DIYers use 3 basic build options.

The circuit of the touch button on transistors is the simplest. For its implementation, a breadboard is required, on which the series-connected KT315 transistors and an electromechanical relay are mounted, in parallel with which a protective diode must be installed. The sensor will be a wire from the base of the transistor connected to the network. The circuit can be complicated by adding an optocoupler and a trigger (NE555 timer or K561TM2 microcircuit) in front of the relay. This modification will allow the network to commit the command.

You can assemble an infrared touch switch with your own hands by adding a square-wave generator to the circuit. An infrared flashing LED will help to increase the current from the generator. The time interval is set on the microcircuit. It determines how long after the signal is stopped, the light will turn off. When the reflection of the beam hits the photodetector, the K561IE20 or CD4040 counter will give one, the circuit will close. In the absence of a signal at all pins, a logical zero, no voltage is supplied, the control transistor does not pass current.

Industrial touch switches can be modified to expand the sensitivity area. Under the cover, you need to find a capacitive element and solder a thin wire to it. Then lay the conductor in increasing rings until the entire perimeter is filled. Replace the protective panel.

Switches adapt not only to lamps, but also as a doorbell, curtain opener, and more. All parts can be purchased from radio markets or Chinese internet platforms at a budget price.

Installation safety

Before installation, be sure to de-energize the network by lowering the circuit breaker switch in the switchboard. Touch communicators are mounted without a front panel. The pole rule is observed. If there is a ground wire in the line, it is connected to the marked pin. The ends of the multicore cable are crimped or deserve to be clamped tightly and to avoid overheating.

Do not use devices with obvious damage or not designed for the specified network load. Homemade touch-sensitive light switches of 220 V do not always withstand - most home circuits are designed for low-voltage consumers.

Do not start installation before reading the manufacturer's instructions.