Cotton switches - application and manufacture by own hands

Cotton switches - application and manufacture by own hands


In everyday life, there are often situations where even a simple action - the inclusion of light in a room can be a problem. This is often associated with children, invalids, or bedridden patients, for whom reaching a circuit breaker is associated with greater difficulty or impossible. In such cases, the acoustic device becomes irreplaceable. He works on the cotton principle.


  • 1Application of acoustic (cotton) switches
  • 2Principle of operation
  • 3Specifications
  • 4Components of the device
    • 4.1Package according to option 1
    • 4.2The device of variant 2
  • 5Connection and installation
  • 6Principle of operation and operation of the automatic soft light switch
  • 7Test procedure for cotton switches

Application of acoustic (cotton) switches

Such devices are gaining popularity due to the ease of use and practical utility. It is enough to pay attention to the smudged spots around the traditional switch, appearing on the wall already soon after the repair. A non-contact device eliminates this unpleasant effect.

It is also useful for the younger generation, if the lighting control devices are installed in a traditional place for Russia, and not below, as is customary in Europe. Just by clapping your hands, the child will easily turn on and off the light in the room.

In the same way, an acoustic switch will be useful for wheelchair users and bedridden patients. In addition, it can become a signal system for them to ask for help if necessary. A small alteration of the circuit will give not only light, but also a sound signal.

The popular name of the device "cotton most likely, is random, because the device can trigger other sharp sounds, including whistling, knocking and other signals.

Mounted cotton controller

It can be assumed that devices of this class will become indispensable accessories of the housing management system called "smart house".

Principle of operation

Light switches for cotton are one of the types of devices for remote lighting control. In this case, a signal for changing the lighting status is a sharp sound in the form of a clap of hands. Of course, an indispensable element of such a control scheme is a microphone. When you make a device yourself, it's not necessary to run to the store for such an important detail. You can use devices from old phones, tape recorders, headphones and other devices associated with the use of sensitive to sound vibrations.

The algorithm of work provides for the inclusion of light in cotton and shutdown for the next same signal.


Such devices are recommended to be installed in comparatively quiet rooms, such as bedrooms, pantry, basements and the like. Use in offices, shops or production facilities is irrational.

Light control device for cotton


As an example, consider the data of a standard instrument

  • the device is powered by a standard 220-volt network;
  • the permissible total power of the connected devices is 300 watts;
  • range of adjustment of a sound signal within the limits of 30-150 decibels;
  • Operating temperatures range from 20 degrees below zero to 40 degrees Celsius;
  • IP-30 class enclosure protection.

In the load network, various luminaires can be used:

  1. Serial incandescent or halogen bulbs.
  2. Fluorescent or energy-saving lamps.
  3. Lamps and light-emitting diode lamps.

Such characteristics allow the device to be used within the framework of the requirements of federal law No. 261, concerning the rational use of electricity.

The dimensions of the device are comparable to the size of the match box, which makes it convenient to place it in the immediate vicinity of the lamp. To fix to any surface it is possible using a double-sided adhesive tape or set on self-tapping screws.

Overall dimensions of the device "Ekosvet X-300-L"

Components of the device

Several schemes of device design can be proposed.

Package according to option 1

This is the simplest scheme. It is distinguished by the use of a microphone with a multiple amplification of the audio signal. It will require several transistors KT 315 and one powerful KT 818. From the microphone the signal is transmitted to the KT 315, multiply amplified and passes through the KT 818, which controls the relay for closing and opening the load contacts, be it a light bulb or any other consumer. Sensitivity of the device allows its activation on the inclusion / shutdown at a distance of 4-5 meters, which is quite applicable for use in domestic applications.

Optimal is the choice of an electret microphone, one of the leads of which is connected to the case. Power consumption is small, the voltage is 4-16 volts.

Transistors KT315
Transistors KT818

The device of variant 2


The scheme of the device in this case is more complicated, but it is more reliable than the previous one. To implement it you will need:

  • resistor;
  • capacitor;
  • a zener diode;
  • controlled thyristors.

A transistor trigger needs to be connected to a voltage divider and a resistor. The trigger is powered via a diode and a resistor. The capacitor and the zener diode are designed to equalize the voltage.

Steady operation of the trigger is possible when one of the two controlled thyristors is turned on. Reacting to the sound from the microphone, the voltage divider takes them to another state.

The load on the switch does not exceed 100 watts. If you want to increase this characteristic, you need to use higher power diodes. Transistors are installed using radiators.

Schematic diagram of the simplest cotton switch

Connection and installation

The device is mounted on a one-key or two-key switch so that it receives power from a 220-volt line. You can do this as follows:

Wiring diagram of acoustic switch
  • A typical scheme for connecting a light bulb looks like this: the power to the switch is made from the shield through the junction box. Neutral wire is supplied to the light source and connected in parallel to the switch;
  • It is necessary to break the power circuit to the key switch and install the acoustic device into the gap. The controller is installed in the housing of the luminaire;
  • More often the switch is equipped with two pairs of wires of white and black color. The power supply is supplied in white, the loads are connected by black ones. The connection should be made by terminals or simply by winding. Soldering in such schemes is not applied.

Principle of operation and operation of the automatic soft light switch

The device is designed to increase the life of lighting products. The supply of the maximum voltage in the salvo mode is often the cause of their burnout. As in the case of a cotton switch, a signal to turn on the light is a beep.

It is fed to the microphone, which converts the acoustic signal into an electrical impulse. The signal is amplified in the operational amplifier and fed to the capacitor to charge it. When the charge reaches higher values ​​than the capacitance, the comparator operates and the signal appears at the output instead of the zero value. As a result, a transistor generator directing the pulses is triggered, and a symmetrical triode thyristor is applied, which supplies voltage to the light bulb.

After some time, the voltage on the capacitor decreases, which leads to a decrease in the pulse frequency on a symmetric triac thyristor due to the growth of the phase delay. At the same time, the lamp slowly goes out. By selecting the denominations, it is possible to achieve a light-emitting time of up to three minutes.

Noteworthy and special devices intended for public places of periodic use. These are places like entrances, lift platforms, cellars and other similar places.


During daylight hours, the optical sensor disconnects the device from triggering. With the onset of darkness, the device is switched on in standby mode. When an acoustic effect occurs, the acoustic sensor triggers, including light in the room. The built-in time relay shuts off the light after 40-50 seconds of burning. If during this period the sound signal repeats, the time count starts from the time it was received.

This lighting control system saves up to 50% of the electricity used to illuminate public passageways.


Test procedure for cotton switches

After installation and connection of the device it needs to be checked in real operating conditions. The test consists in simulating the household noise and the reaction of the installed system to them. The following are common for home noise:

  • noise of domestic vacuum cleaner;
  • work of an electric drill;
  • the clatter of plates;
  • sound from work with a hammer;
  • phone calls, etc.

By creating such noise effects, we check which ones the device can trigger. Undesirable reactions of the device can be tried by eliminating the adjustment of the sensitivity of the microphone. This feature is implemented in all models of devices.

The manufacture of such a switch is shown in detail in the video

To manufacture the acoustic switch by one's own hands, undoubtedly, there is a need for firm knowledge in the field of radio electronics and electrical engineering, but the installation of a standard device is quite possible for a performer with minimal skills of wiring. I wish you success!

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