Schema work. When you clap your hands or click, the charcoal powder in the microphone moves and changes its resistance. At the same time, at the junction point of the limiting resistor R1 and the microphone, an alternating component appears, which, through an isolation capacitor C 1, enters the base of the transistor T 1. Transistor T1 is both an AC and DC voltage amplifier. With the help of the resistor R2, the transistor T1 is in the ajar state. The variable component received by the base is amplified by the transistor and, from the collector through the capacitor C2, is fed to the rectifier-doubler, assembled on the elements DD1, DD2, C3. Doubled DC voltage accumulates on capacitor C3, which is discharged through the circuit: minus the capacitor, resistor R1, base-emitter T1, plus capacitor. At the same time, the transistor opens like an avalanche, relay P1 is activated, its contacts close for the duration of the action sound signal. When setting up the operation of the circuit, sometimes it turns out that its sensitivity is too high, it is triggered by cars passing along the street or by waving a hand near the microphone. It all depends on the type of relay used. You can roughen up the circuit by connecting a variable resistor in series with the capacitor C1. In order to switch the load (light bulbs) using claps, it is necessary to supplement the circuit with a trigger. The scheme of such a trigger on a polarized relay is shown in Figure 2 - it has not been printed anywhere before either.
When an audible signal is given (clap, click), the relay contacts KR1 are temporarily closed. An alternating voltage of 220 V through the light bulb L1 diode D1 is applied with a positive half-cycle to the end of the second winding of the relay RP-4 pin 8, the beginning of the winding pin 7, current limiter resistor R1, capacitor C1, closed relay contacts KR1, pin 220V. The charging current of the capacitor C1 switches the relay armature to the left position according to the diagram, the L1 light turns on, and the L2 light goes out, the D1 diode is blocked by the relay contacts, and the D2 diode is unlocked and ready for use. When the next sound signal arrives, the relay contacts P1 KR1 close. A voltage of 220 V through the bulb L2 and diode D2 is applied positively to the beginning of the first winding, contact 5, from the output of the winding, contact 6 goes to the resistor R1 and recharges the capacitor C1. The polarized relay switches the armature to the right contact according to the scheme. Diode D2 is blocked and diode D1 is ready for the next cycle. Lamp L1 goes out, and lamp L2 lights up. Thus, when sound signals are received, the load is switched in turn. In order for the trigger to perform the function of turning on and off only one light bulb, you need to exclude one of the light bulbs from the circuit, and instead turn on a series circuit of a 0.33 microfarad x 300 V capacitor and a 5–10 kOhm resistor, 2 W. When setting up the trigger operation, it is necessary to adjust the armature of the polarized relay so that it switches well and is securely fixed in the right or left position.
Correctly determine the beginning and end of the relay windings or change the polarity of turning on one of the diodes. Of course, this design of an acoustic relay on a carbon microphone is more suitable for beginners, so in the next article it will be described on a single chip, and a piezoelectric element is used as a sensor.
Discuss the article SIMPLE ACOUSTIC RELAY
In recent years, systems have become popular remote control lighting. Sound commands are received by a cotton switch. With sufficient cotton strength, the light turns on or off. The device can be purchased at the store or, with sufficient knowledge of the basics of electrical engineering, you can make it yourself.
Application
The clap light switch turns on and off as a result of a reaction to the emitted noise. The algorithm of work is as follows: the first clap is on, the second is off.
Devices of this type are recommended to be installed only in quiet rooms. The premises of this type include bedrooms, pantries, utility rooms, basements. It is not rational to install cotton devices in rooms where there are many people (offices, living rooms, production areas), since extraneous noise lead to false device responses.
The most common place to install a cotton light switch is the bedroom. It is very convenient to control the lighting without getting out of bed. Cotton systems are popular in families with young children, as you no longer need to reach for a high-mounted switch to turn the light on or off.
Many people confuse cotton and acoustic devices. The acoustic switch is triggered by any noise, and the cotton one - only by pops.
Principle of operation
The device functions due to the microcontroller installed in it. The controller authorizes the light to be turned on and off by a clap. This device, if desired, can be used to control other household appliances (air conditioners, fans, etc.).
As part of a conventional sound light switch, there is an electronic microphone with a preamplifier. This component amplifies the sound entering the device, which allows you to capture even the quietest pops. The activity of the amplifier is controlled by transistors VT1 and VT2. The circuit is controlled by a pair of resistors R2, and diodes VD1 and VD2 are used to equalize the signal.
The sound from the clap passes through the microphone, where the electrical impulse is amplified and transformed. Further, the sound is equalized due to the operation of the rectifying diodes. The sound is under the control of the resistor (if the sound volume level is lower than the set value, the resistor will not allow the device to operate). When the signal on the capacitor equalizes, the voltage increases, the transistor switch VT3 opens.
The light turns off and on after sequential charging and discharging of the capacitors. At the end of a full cycle of activity (one more pop), the resistor and capacitor C10 are discharged in four seconds. This causes the device to turn off.
Specifications
For example, let's analyze the characteristics of a standard device for turning the light on and off by cotton.
Device data:
- Power is supplied from a standard 220 volt network.
- The maximum total power of consumers does not exceed 300 watts.
- Sound regulation spread within 30 - 150 decibels.
- Permissible temperature regime: 20 degrees below zero to 40 degrees above zero.
- Case protection class - IP30.
The network uses a variety of lamps:
- Incandescent and halogen light sources.
- Energy saving or fluorescent light bulbs.
- LED devices.
The specified characteristics comply with the requirements of the law Russian Federation number 261. This act regulates the rules for the rational use of electrical energy.
The size of the equipment is similar to a matchbox, that is, compact. This makes it possible to install it near the lamps. The device is fixed with self-tapping screws or double-sided tape.
Connection diagram and installation
Below is a diagram of a clap light switch. Based on it, you can connect this device.
The white conductors available on the device are connected to the network. Connect the load to the black wires. To connect copper conductors, you need terminals. Black conductors are connected to the lamp bulb. These devices are connected in parallel.
The power supply of the switch is carried out through a single-gang switch. If you need to turn it off, you just need to press the switch.
Sound sensitivity is controlled by the corresponding knob. It is recommended to use the average sound value.
Tests
Before turning on the device, it should be configured to prevent false alarms on extraneous sounds. For example, a cotton appliance should not respond to hammer blows, the sound of dishes, a ringing telephone, or a switched on puncher.
Settings are made experimentally. The device is considered to be set when it only responds to pops.
Manufacturers
The most famous models presented on the Russian market are Ecolight and Claps. Consider their main characteristics.
Ecolight switch
The Ecolight device is designed to work with 220 volt light bulbs.
Main parameters of the device:
"Ekosvet" is fixed with self-tapping screws for mounting paws. The device is not recommended for installation in noisy rooms. Despite the fact that Ecolight is set to claps, false positives are possible.
The figure above shows the device connection diagram. "Ecolight" is connected to a conventional switch to provide the ability to de-energize the circuit and stop its operation.
Claps switch
This model is one of the latest developments, where the sound signal is processed by an advanced microprocessor. The device only responds to pops, so it ignores false information. Required condition for triggering - a certain nature of the transmission of sounds, when the claps should go in a row.
There can be one or more switches in one room. Each of them will be set to a given number of claps. To do this, put a jumper on the board in the desired position. As a result, it becomes possible to control several unrelated devices, for example, an air conditioner and a lamp, a TV and a tape recorder. "Claps" is compact (like a box of matches) and can be mounted anywhere, including the socket.
Claps costs more than Ecolight (2450 rubles versus 350), but its reliability is higher. "Claps" will work with fluorescent bulbs even if smooth start load (“Ekosvet” is not capable of this).
Making a switch with your own hands
You can make a cotton device yourself.
This will require 3 boards:
- Arduino Nano
- sound module;
- power relay board.
In addition, you need a computer, a USB cable, a 5-volt power supply. The Arduino IDE program should be installed on the computer, designed to flash the microcontroller.
After copying the sketch data and pasting the text into the Arduino IDE window, you need to immediately make the controller firmware. When changing some adjustments and rewriting the device, it is possible to fine-tune the sound relay for your own needs.
The diagram shows that the controller has 4 wires. A couple of them go to power, the yellow wire is directed to control the power relay (pin 13), and the green one is the control wire from the microphone connected to the A0 controller.
Note! A condenser-type microphone can be replaced by an electret microphone, in which an electret plate is used as a fixed capacitor plate and a constant voltage source. A distinctive property of the material is the ability to maintain a surface charge over long periods of time.
The chip has 8 analog inputs and 14 digital inputs and outputs. In this example, A0 and D13 are used because they turn on the LED on the Arduino board.
When replacing the AnalogRead indicator, the threshold sensitivity is determined. The highest value is 1024. If you change the Delay value, the time to execute the sketch will be corrected. In this way, the desired switchover time is achieved. The threshold that protects against interference and false positives is also determined. The sensitivity of the microphone is also changed by a variable controller located on the board. Setting up and testing circuits is carried out on the Arduino UNO board.
It is powered by a DC source with a voltage of 5 to 12 volts. Parts are available and not expensive, they can be purchased at any radio shop. Personally, I used parts that I dropped from old boards. The circuit is really simple, and even if you are not familiar with radio electronics, then guided by this article, you will be able to assemble this device.)
Initially, I found this circuit without any description and of course there was no printed circuit board, so I had to make it myself in order to facilitate the assembly process for myself and of course you, so use it. Download PCB
Acoustic switch circuit:
The circuit consists of a microphone amplifier, which is assembled on two KT315 transistors and a power unit, on a KT3107 (BC557) transistor. To increase the sensitivity of the microphone, you can use more powerful transistors, such as KT368 and the like. In the power part is also sufficient wide choose analogues, almost any PNP structure transistors are suitable, for example, KT814 or KT818, here you first need to look at the power of the power source used.
Below are photos of the necessary parts:
Acoustic Switch Parts List:
So, first you need to make printed circuit board. Please note in printed circuit board there are holes for the VD1 diode, since I plan to control room lighting and a 12 volt relay will be used as a load. The diode is needed to protect the transistor VT3 from the EMF of the relay coil. If you are going to connect a light load to the switch, then it can be replaced with a jumper.
After making the board, drill holes and heat it. Open the signet in the sprint-layout 6.0 program and, looking at the location of the parts, solder them in place.
Our acoustic switch is ready! Now I want to talk about a small nuance, the circuit uses a 1.5 kOhm resistor R8, I replaced it and set it to 2 Ohms, since the voltage at the load output dropped sharply and the relay did not work. If you have the same problem, then follow this advice. That's all, share the article below if you liked it.
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Buy an acoustic switch, kit for self-assembly:
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The acoustic switch is a very useful thing in household use. Such a device will add comfort and creativity to your home. With it, you can turn the light on and off, or use it for other appliances, such as an electric kettle or a fan.
Such a switch will find application in a situation where a person needs light, but is limited in opportunities. It will be enough to clap your hands and the lighting will turn on. They are also called cotton sensors.
The principle of operation of acoustic switches is to use a microphone with adjustable sensitivity. The microphone turns on or off when sound is detected.
Disadvantages of acoustic sensors
The disadvantages of these sensors stem directly from what they respond to - sound. The selectivity of the microphone is very high and the development of acoustic light switches is progressing, so that modern sensors respond very accurately to a given sound. But in order to produce this sound, you need to know which one, and this sound will always be a signal to turn on or off.
Second significant disadvantage is the zone of sensitivity. For a room with large sizes you have to clap loudly enough, or get closer.
And if you increase the sensitivity, the sensor can respond to similar signals from an adjacent room.
The simplest acoustic switch circuit
The simplest effective acoustic switch circuit can be assembled by anyone with the desire and time. Such a switch can be used for various purposes, for example, to turn on and off the lighting in the room with the help of cotton, the same principle of operation and control of any equipment. In general, this acoustic switch is a very useful thing in household use.
This sensor makes it possible to turn on and off the power circuits with the help of cotton. Such a device can be used to turn on the light.
It is quite sensitive, due to the presence of a two-fold amplifier on transistors with low power. Responds well to cotton from a distance of five meters from the microphone.
Required parts for assembly
To assemble an acoustic switch with your own hands, you need to take the following parts:
- Resistors (R1-10k, R2-1M, R3-22k, R4-270k, R5-2k, R6-1.8k, R7-330 Ohm, R8-1.5k)
- Transistors (VT1-KT315, VT2-KT315, VT3-3107)
- Capacitors (C1-3200pf, C2-1uF×10v)
- Diodes VD1
- Miscellaneous: M1 - electret microphone, HL1 - LED or relay, terminal block.
Acoustic switch device
The microphone amplifier is assembled on two bipolar transistors of the KT 315 series. In order to increase the sensitivity of the microphone, transistors of the KT 368 type or their imported analogues (SS 9018) can be used.
The power part of the circuit is a powerful transistor KT 818, and it controls the load. If you want to control a large load, you can use a relay, supply voltage from 3.5 to 15 volts.
When controlling loads powered up to 12 volts, you can remove the relay from the circuit and connect the load instead. If you need to control loads powered by the mains, then you definitely need a relay. During the clap, the microphone receives a wave, and feeds the power amplifier, they in turn amplify the signal received from the microphone.
Already amplified signal enters the base of the key, its value allows the transistor to work, and at this moment the transistor junction opens, and conducts current. It powers the connected load or relay. With repeated cotton, the generation is interrupted and the relay is de-energized.
Instructions for making an acoustic switch
First you need to make a printed circuit board. The printed circuit board has special holes for the diode VD1. The diode is necessary to protect the transistor VT3 from the EMF of the relay coil. If you want to connect a light load to the switch, you can replace it with a jumper.
After making the board, it is necessary to drill holes and tin it. Next, open the signet in the sprint-layout 6.0 program and by the location of the parts and solder them in place.
Note! 
Looking at the photo of the finished acoustic switch, we see a compact sensor that is easy to install. It is a small board with soldered parts.
When assembling, it is necessary to observe all the ratings of the parts, even a slight slope can lead to incorrect operation of the switch. The device reacts not only to pops, but also to any low-frequency noise.
Power comes from a DC source with a voltage of 5 to 12 volts. Mandatory from stabilized DC voltage sources, when using switching power supplies, the device may not work.
In order to make an acoustic switch with your own hands, parts are needed, they can be purchased at any radio store, they are affordable and inexpensive.
You can use parts soldered from old boards. The circuit is very simple, and even people who are not familiar with radio electronics can use this circuit to assemble this device.
Photo of acoustic switch
Note! 
Note! 
A person who lives in an apartment turned to me, and as usual, such people have a staircase, during the day they are usually even more or less illuminated by natural light, but at night or in the evening there is no light, and looking for a switch on the walls is not very convenient and not modern. It is better to do something to open the key and turn on the light bulb at a certain noise level or voice, which was done.
Device diagram
The scheme is well-known, you can also use analogues of parts if you are going to repeat this scheme, you can also import parts, as convenient and more affordable. Another good option, without chips, but with good sensitivity, see.
The microphone used an imported capsule, which has good sensitivity and good sensitivity, due to the fact that the pre-amplification stage is usually already placed inside such microphones - an electret microphone, as they are commonly called in narrow circles of radio amateurs, compared to conventional microphones, when powered through the output from which sound is picked up, the microphone's internal amplifier starts to work, so that even with low fluctuation sound waves a rather high level signal appears at the output and it is not required to block the preamplifiers on operational amplifiers. Only now, according to the signal and power, then you will have to make a decoupling and think over the power. But this is already much easier.
And another plus of the switch is that it hears, for example, the slam of the entrance or exit door, and with this it can turn on the light in its secondary circuit.
After the sounds stop, a kind of delay will turn on (from 5 seconds to 2 minutes), after which the lighting will turn off. Floor lighting circuit breaker has high sensitivity, is powered directly from the lighting network and does not require the use of other stabilizers.
It works as follows: when an audio signal is detected, a weak AC voltage from the microphone output through an isolation capacitor it enters a two-stage amplifier made on transistors VT1 and VT2, and after amplification to a voltage of 5 ... Each such pulse opens the emitter follower VT3, which amplifies the current signal, and quickly charges the capacitor C5. At the inputs of the DD1.2 element, a logic 1 level is formed, which, inverting, closes the key transistor VT4 and forms on its collector, thanks to the resistor R12, a logic 1 level voltage that allows the operation of the thyristor control circuit.
