Acoustic switches are devices that can remotely close an electrical circuit from a sharp or loud sound, such as a hand clap. With the help of them you can turn on the light, TV, music Center or any other electrical device... This is very convenient, because you do not need to make unnecessary movements other than clapping your palms or a loud voice. Nevertheless, the most widespread are light switches that remotely turn on and off the light. Thanks to such products, there is no need to look for electrical fittings in the dark so that it becomes light in the room.
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Acoustic switches can be of the following types:
- Devices that respond to pops and their amount. They can only fire one or two pops, depending on how they are programmed.
- Responsive to a voice or a specific command. These can be standard phrases in the form of words: "turn on the light", "turn on" and so on. But there may be non-standard options, when the home owner sets his own options that cannot be predicted. For example, a code word in the form of the spell "avada kedavra" or other magical mention. It's very convenient, pragmatic, and even fun. However, such switches are significantly more expensive than conventional ones.
- Combined devices that respond to multiple parameters. These can be combinations with sound, light, and motion sensors. For example, such switches are often installed in the entrances of multi-storey buildings. They are programmed so that they simply do not turn on in daylight. At night, they are turned on by sound.
- Acoustic devices for low-current systems. For example, with a clap, you can connect a video camera or send the required command to protect the object.
Device
The simplest switch includes the following basic elements:
- Electronic microphone. This element picks up sound a certain level.
- , it is installed in the microphone circuit. The sensitivity of the microphone is regulated by the selection of the capacitance of the condenser. The switch can be set to a loud voice or clap of the desired range.
- Amplifier on . These elements allow several times to amplify the sound that enters the microphone. As a result, the switch can function even with a slight pop. amplifies and generates electrical vibrations.
- , which is connected to the collector of the transistor and closed to the lighting network. As a result, the transistor drives, which closes or opens the contacts.
Operating principle
Acoustic switches work according to the following principle:
- The person claps their hands or utters a phrase.
- The sound is picked up by a microphone located in the switch device.
- A microphone converts sound into an electrical signal in the form of a voltage of a specific frequency.
- The voltage is amplified by the circuit, after which it is sent to a powerful transistor, then it enters the relay coil.
- A current flows through the coil, as a result of which the magnetic core is drawn in. As a result, the power contacts of the relay in the electrical circuit are closed. An electric current flows into a lighting fixture and light appears.
Some acoustic switches are set to operate continuously. That is, the person clapped his hands, turning on the light. He completed his business and decided to go to bed. All this time the light was on, in bed the man claps again and the light turns off.
But in situations where it is necessary to save electricity, acoustic devices work on a different principle. It turns off the power supply after a certain period of time. The time interval is determined by the capacitance of the capacitor, in which the voltage level is gradually lost. This leads to a loss of current in the light source. When selecting the parameters of the capacitor, you can set the required time after which the light will be turned off.
Application
Acoustic switches are used everywhere. They are often installed in the entrances of residential buildings, elevators and staircases. Thanks to such devices, it is possible to save a significant amount of electricity. Switches allow you to upgrade previously used luminaires, they add an economic component to them. Such switches are successfully used in domestic conditions, various industries, security structures, and so on.
In the conditions of our country, lighting control devices are often mounted at a fairly high distance from the floor. This is convenient for adults, but small family members experience significant inconvenience. Thanks to acoustic devices, small children can turn on the lights in the room with a simple cotton.
Such devices will be convenient for the disabled, for example, patients with a spinal fracture, bedridden, or wheelchair users. In addition, acoustic devices can be used as a signaling system to call for help. So, a slight improvement of the device allows it to give a sound signal as well. Today, acoustic devices are becoming elements of control systems under the name.
How to choose
- When choosing, you should find out for what purpose acoustic switches are bought, and where they will be used. For home use, one type of device is needed, for an entrance, a garage or an industrial facility, completely different ones. For example, in different places the level of external background noise is different. This means that a home needs a device tuned to one sound level, and a noisy industrial facility needs a device with a different sound value. Otherwise, the acoustic device will constantly work or not work at all.
- There are acoustic switches that only respond to hand claps. They are designed so that they do not have false alarms for various extraneous sounds. It will be possible to turn on the light when installing such a switch only by clapping your hands. In addition, up to four of these devices can be installed in the room, which will respond to different amounts of pops. For example, the TV will only respond to two pops, the fan will respond to three, and so on. The only thing is that claps will need to be performed in a row.
- Before purchasing the device, it is worth looking at how many bulbs are on the chandelier, how the connection is made. If one or several with parallel connection, then you can buy a switch with one key. If you have a large number of bulbs and several channels, you will need a device with a large number keys.
Non-standard application
- Taking into account the latest achievements, you can launch an assistant robot by voice or clap, which will follow your instructions.
- In a cotton apartment, you can even open and close the curtains on the window. Such a solution will allow you to enchant guests and immerse them in the world of magic. To do this, you will additionally need to purchase.
V recent times became very popular LED lamp and various toys in which the “clap switch” principle works. In our article we will assemble something similar, but instead of a lamp, we will use a 3 Volt LED.
Here is the diagram itself (for a more detailed display, click):
If you put a relay coil instead of the HL1 LED, then even incandescent bulbs can be ignited, while VD1 will appear in the circuit, which will protect the VT3 transistor from self-induction in the relay coil when it is turned off. If you make a circuit with an LED, then this diode is not needed.
It will look something like this:
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So, the most important details of the circuit are:
Two KT315G. Can be used with any other letter. The pinout (pinout) and labeling of these transistors can be found in this article.
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In this circuit, we will also use the 3107B transistor.
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And here is its pinout:
where K is the collector, B is the base, and E is the emitter.
And of course, the most important detail of our circuit is the microphone.
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Attention here! Microphones are different. I think we will not list the classification of microphones. I will say one thing, now the so-called electret microphones:
The picture shows the EM-6050 electret microphone, which is used in my circuit.
What is the joke? The thing is that they have, roughly speaking, there is polarity... One of the microphone leads is attached to the microphone body. This can be easily seen from the printed wires that connect one of the microphone pins to the housing. You can also ring out by attaching one probe to the microphone body and the other to the microphone terminal.
In our circuit, the microphone output, which rings on the case, is connected to the minus of the power supply, and the other output, respectively, to the plus.
My circuit works fine with a supply voltage of 5-9 Volts, which can be seen in the video below:
We bring to your attention several interesting and simple schemes of acoustic relays that can be used at home, in an entrance or on the street to turn on and off lighting and household equipment. Try to assemble one of them to appreciate the convenience of controlling the light in the cotton room.
Automatic lighting switch.
Here is the first scheme, the principle of its operation is as follows: original state we have a logic 0 level at the output 5 of the DD1.1 flip-flop and 9 of the DD1.2 flip-flop. VT2 transistor is closed, relay K1 is free of voltage.
When a sound signal is given (you can clap your hands), the sound by the BM1 microphone is converted into an electrical impulse, which will be amplified by the VT1 transistor.
From the collector of the transistor, the amplified signal comes to input 4 - the DD1.1 flip-flop, which operates according to the one-shot circuit.
After that, from output 5 DD1.1, a positive pulse goes to the clock input of the trigger DD1.2, connected according to the T-trigger circuit, switches it, the transistor VT2 opens and turns off relay K1, switching the load with its contacts (not shown in the diagram).
Trigger DD1.2 changes its state after each new sound signal and at its output 9 there is an alternation of logic 0 and 1 levels. As a result, the transistor VT2 opens or closes synchronously. If a second sound signal follows, the K1 relay will turn off and de-energize the load.
Setting up the circuit consists in the need to select the resistance of the resistor R1. It should be borne in mind that the microphone should only be carbon.
Sensitive acoustic relay.
The device works on the principle of a trigger with two stable states, which, in response to a short sound signal, picked up by the microphone, transfers the trigger to another state, turning the load on and off in this way.
The sound signal (clap of hands) hits the carbon microphone (type MK16-U), after which it is filtered by the C1R2 circuit (only passes the signal with the frequency of sound vibrations of the clap in the hands).
This signal is amplified by transistor VT1, it is recommended to use a transistor with a high current gain. The amplified signal from the VT1 collector is fed to the input of the trigger assembled on transistors VT2, VT3.
The inverse state on the collectors VT2 and VT3 relative to each other is ensured feedback passing through the resistor R6. Signal from high level c collector VT3 through VD3 and resistor R13 turns on the key to VT4 and relay K1, this relay switches the load with its contacts. Various actuators can be used for the load, but due to design features relay through its contacts, do not use a powerful load. In the case of a powerful load (more than 60 W), an appropriate relay should be used or the terminal switching node should be replaced with a key on the thyristor.
The BM1 microphone can be taken from a conventional telephone. Diodes KD 522 or other silicon or germanium, D220, D9.
As a relay, you can use RES 9 (passport RST.524.204.), The response voltage is 10 V. When the voltage of the power source decreases, it is possible to use RES 10, RES 15.
This scheme tested in practice and demonstrated good stability, also positive quality this circuit is good sensitivity (reacts from 10-15 m) and noise immunity of oscillations in the network. Power supply from 9 to 16 V can be used, the results show good working capacity. When the voltage changes, the appropriate relay must be selected.
The question of how to assemble an acoustic switch at home is sooner or later asked by every radio amateur, since such an electrical circuit closure device gives a lot of scope for use, from connecting a simple lamp to using in complex security systems and a “smart” home.
Principle of operation
A primitive model of an acoustic device, can be assembled by surface mounting with a test light and an 8 volt power supply. In this case, the following are used:
- powerful bipolar direct conduction transistor type KT818, or foreign analogs,
- push-pull microphone amplifier,
- regular microphone (for example, from a tape recorder or headphones)
Such a device of an acoustic switch allows you to visually trace the mechanism of converting a noise signal into an electrical one. The microphone receives a wave signal and transmits it to the amplifiers, after which a transistor is triggered through the base of the key, starting the current connection.
Build option
The circuit of a simple acoustic switch with a power supply from 4.5-12 volts, and with a range of action at a distance of 2-3 m, is assembled on a printed circuit board or breadboard and consists of more parts.
Such devices are also called “clap” devices for their functional feature - sequential switching off and off with a sharp sound signal, similar to the clapping of palms.
The KT818 transistor connected to a relay with a 9 volt power coil is responsible for the power section.
The sensitivity of the electret microphone is set by a 10 kΩ power resistor and a 0.1 μF capacitor. Adjust it based on the resistance of the resistor and the capacitance of the capacitor, and by using more sensitive transistors. The resistor value can start from 2kΩ, depending on the power supplied to the circuit.
Then there are two amplification stages with bipolar transistors KT315 (you can use imported analogs, for example 2N5551). Resistance ratings can be varied by 50%. A protective diode must be installed for the electromagnetic relay. A silicon 1N4148 or 1N401 is suitable for this function. An LED can be installed in the power section to indicate the operation of the circuit.
As can be seen from the photo, homemade acoustic switches are quite compact, it is easy to pick up a case for them and use them in mobile and static devices, ordinary batteries are used for power. You can also use charging device from mobile phones with an output voltage of 5 volts.
When testing, you need to pay attention to the reaction of the device, since a clear and sharp clap must be made to start and turn off a correctly assembled acoustic switch.
An effective demonstration response to more vague and washed out noises can make the instrument much more difficult to use, causing it to turn on or off unintentionally during background noise. It is also important to consider the most optimal location for the microphone.
For the manufacture of built-in sound sensors, you can use circuits with a power supply of 220 volts, which can be mounted with standard key switches for lighting devices. They use thyristor triggers and key mechanisms.
The transistor trigger is powered by a diode and a resistor. The circuit provides voltage equalizers. A complicated circuit provides for the presence of a comparator - an additional zone that cuts off interference and improves the quality of the circuit breaker.
Acoustic switch with microcontroller
Instructions for making a switch with your own hands can be considered using the example of using an Arduino microcontroller, with two boards connected to it: a sound module, i.e. microphone with amplifiers and a power relay. A 5 volt power supply will be needed, and USB cable to connect to a PC.
After installation computer program for the firmware that is downloaded from the official website, you can adjust some parameters for an individual request: adjust the sound sensitivity, response speed after a beep and set the threshold value, in order to avoid interference and false signals.
Photos of acoustic switches
The work of the circuit. When you clap or click, the carbon 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 the separating capacitor C1, 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 a slightly open state. The variable component supplied to the base is amplified by the transistor and, from the collector through the capacitor C2, is fed to the doubler rectifier assembled on the elements DD1, DD2, C3. The doubled constant voltage is accumulated on the capacitor C3, which is discharged along the circuit: minus the capacitor, resistor R1, base-emitter T1, plus the capacitor. At the same time, the transistor opens like an avalanche, relay P1 is triggered, its contacts are closed for the duration of the 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 from a wave of the hand near the microphone. It all depends on the type of relay used. The circuit can be roughened 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 circuit of such a trigger on a polarized relay is shown in Figure 2 - it has not been printed anywhere before.
When a sound signal (clap, click) is given, the contacts of the KR1 relay are temporarily closed. AC voltage 220 V through the lamp L1, diode D1 is applied with a positive half-period to the end of the second winding of the RP-4 relay pin 8, the beginning of the winding pin 7, current limiter resistor R1, capacitor C1, closed contacts of relay KR1, terminal 220V. The charging current of the capacitor C1 switches the relay armature to the left according to the scheme, the L1 light comes 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 operation. When the next sound signal is received, the contacts of the relay P1 KP1 are closed. The voltage of 220 V through the lamp L2 and the diode D2 is applied by a plus 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. A polarized relay switches the armature to the right-hand contact. Diode D2 is blocked and D1 is ready for next cycle. Lamp L1 goes out and lamp L2 comes on. Thus, upon admission sound signals alternate load switching occurs. In order for the trigger to perform the function of turning on and off only one light bulb, it is necessary to exclude one of the light bulbs from the circuit, and instead turn on a series circuit from a 0.33μF x 300 V capacitor and a 5–10 kOhm, 2 W resistor. When setting up the trigger, 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 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 one microcircuit, and a piezoelectric element is used as a sensor.
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