To the store to buy a hood and install it in the kitchen is relatively simple — it requires only money, time and skills to screwed into the wall screws. But to diversify the inclusion of a drawing and automate it so that your hood has become to surprise the neighbors and, most importantly, to have added comfort in your kitchen — the case for the present enthusiastic radio Amateur.
Imagine sitting in the cozy kitchen, you no longer have to get up and turn on the switch on the extractor fan to ventilate the room (for example, if you or your guests stoned). Clap softly hit the table or say a sharp word with the volume more than usual, and wonder hood itself begins to work, and the kitchen immediately becomes cooler and more comfortable.

A new theme for the kitchen after this conversation you provided. How is this done? With the help of simple devices that react to a sharp sound medium volume (e.g., clapping from a distance of up to 5 m). The device of automatic inclusion of extrude converts the acoustic vibrations into an electrical current, which controls the trigger — electronic unit with two stable States. The output of the trigger, in turn, controls a low-voltage electromagnetic relay which your contacts enables/disables the blower motor.

The basis of the scheme of this device taken the trigger transistors . It reacts to short the audio signal, turning on and off relays.

The sound signal is detected by the carbon microphone ВМ1 (type МК16 Y), then is filtered by the RC-chain on the elements of C1, R4. This RC circuit is a bandpass filter audio frequencies and passes only a signal with a frequency close to sound vibrations from the clap your hands.

Electric circuit device of the automatic drawing with sharp sounds

Electric circuit device of the automatic drawing with sharp sounds

The signal picked up by the microphone, amplified by the VT1 transistor with high gain current h 21E. With the collector of transistor VT1 amplified signal is supplied to the trigger input transistors VT2,VT3.

Feedback through the resistor R6 provides the inverse condition on the collectors of these transistors relative to each other. With the collector VT3 VD3 through the diode and the limiting resistor R13 high level signal enables the terminal stage (the current amplifier) and VT4 relay K1. Relay (its contacts K1.1) switches the actuator (blower motor — not shown in the diagram).


Microphone ВМ1 taken from an ordinary phone. KD522 diodes may be replaced by silicon or germanium, for example Д220, D9 with any alphabetic index. As used K1 relay RES 9 (passport RS4.524.204.) the response voltage of 9 — 10 V. If the power supply voltage is slightly lower, you can use a more economical relay RES 10, РЭС15.


Scheme tested and showed very good results stability. One of the positive qualities are a good sensitivity to the signal (responds to claps from 5 — 8 m) and good noise immunity at voltage fluctuations of the lighting network 220 V.

As the applied power supply stabilized power supply with output voltage 12V type AC-220-S-12-1000. The current consumption of the device (if the relay) does not exceed 60 mA. The tests showed good performance of the device when the voltage of the source power of 8.5 to 17 V. In this case, normal operation of the device will need to change the relay K1.

The load can also be used with any actuator, but due to the limited (structural features relays) current via the contacts of its power must not exceed 100 watts. Otherwise, you must use a suitable relay or replace the terminal switching unit electronic key on the thyristor.


The device is mounted in any suitable enclosure. In the original applied the plastic case from the old Amateur radio transceiver. Decorative grille in the body, as it is impossible by the way, is suitable for the inner side was attached to it a microphone. Before installation in the housing of the microphone is wrapped in foam that eliminates false triggering of the device against mechanical impacts and vibrations of the room. The body features outside the hood so that it can not affect even the quiet sound of the fan exhaust.

The relay contacts connect with electrical wire and terminals-nick to the contacts of the mechanical switch of a blower motor inside its body. Proper and accurate connection of the control device to the exhaust suggests that the device will remain externally invisible.

The device is in adjustment is not needed. When serviceable items and their correct connection (according to the wiring diagram) it starts working immediately.


The device is unpretentious to the environment. Able to work well as a room light switch. One cotton — a light went on, the other cotton — off. However, from experience I do not recommend to use this sound machine in areas with a high level of noise on the streets, in living rooms, a large gathering of people. At the time, the author observed the sudden shutdown of the lighting at the celebration in the fall dishes from the wedding table. Few adults, much to the delight of the children excitedly began to clap again to seek the light. Kitchens noisy celebrations now not carried out, therefore, the use of recommended devices to control the hood it seems appropriate and convenient.

Using a different bandpass filter (instead of С1R4) with appropriate parameters and adding the amplifier stage (as shown), you can turn this simple machine as a device that responds to words and expressions. For example, you can have a reaction trigger on the words “light” and “night” with the predominance of the vowel sounds “E” and “O”, suggesting a variety of sound dynamics.

In addition, you can add a circuit device short-time audible alarm enable. Then when you turn on the blower motor it will respond to short-term (1 — 2) audio signal, because the noise of the electric motor is almost inaudible in the kitchen.

In addition to regulating the speed of rotation of the motor for the cooker hood, the switching contacts of the relay K1.1, you can enable and rupture of the lamp circuit lighting mounted inside of the hood frame. This lamp usually is a low-power (up to 40W), and the inclusion of such local lighting in the kitchen with cotton in their hands also is the original decision of the hams.

All of these simple additions ham radio can do yourself, developing your creative flair.

A. KASHKAROV, G. S. – P e t e R b u R g

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