In Amateur practice, it is frequently necessary to announce the inclusion of any homemade or industrially produced household electronic appliance, equipment or device — which is unusual, pleasant to the ear (if picked up a soft tone audible signal). This is especially true when the appliances operated with a remote control — an acknowledgement signal confirms that the received command. For example, when the operation control of air conditioning — when it is turned on or the mode is changed as a response to user, sound short and melodious sound signal duration of 1 — 2 seconds.
The sound is a kind of status indicator that is different from the light first of all, the fact that it can be controlled remotely. As a rule, electronic devices (for better control of their condition) used an integrated display and sound and light.
Assembled on the proposed scheme, the device is successfully applied in everyday life to control the light in the apartment or the room, adding to the usual and familiar interior of a certain “sound flavor”. And it is enough even for a skinny wallet. So, when the light is heard a short soft beep. You can apply the device in the toilet for sound information on the employment of this room.
The host audio is connected directly parallel, but to the power contacts of the device, the inclusion of which it aims to control.
A prototype of the proposed device serve as long been used in imported (and more recently in domestic) home appliances electronic devices audible alarm.
In the basis of such electronic unit is a popular timer КР1006ВИ1. Thanks to the use of a buzzer to the circuit, there is no need to enter any pulse generators or amplifiers.
A simple and reliable circuit design such sound devices shown in the wiring diagram (Fig. 1).
As capacitor C1 charges through resistors R1 and R2 and the inner node of the timer changes the state of the IC output. When the voltage on the plates of the capacitor C1 reaches 2/3 of the supply voltage, the internal trigger circuit switch and low voltage output high DА1 will change. The constant voltage across the buzzer will be negligible, and it will cease to generate oscillations of audio frequency.
If specified in the diagram the values of elements R1, R2, and C1 delay the turn off sound will be about 8 s. It can be increased, accordingly increasing the capacitance of the capacitor C1.
About the details. As capacitor C1 is better to use non-polar type K10-17 or to make it two series-connected electrolytic capacitors (of the type K50-6) with a capacity of 2 microfarads each for a working voltage not less than 6 V. As shown, non-polar capacitor as the timing capacitor provides a more stable time interval than that of the oxide, heavily influenced by the ambient temperature. The time interval can easily be reduced by reducing the resistance of the resistor If it is to install a variable resistor with linear characteristic, you get a device with adjustable delay. Transformer power supply is connected in parallel to the controlled device in a network 220 In — the-lamp.
Features of the device. The function of this electronic unit can be reversed — that is, to make the buzzer first 10 sec after the filing of the power device. To do this, the top (the scheme) the output of the buzzer should be connected to the common wire. In this embodiment, the device without any changes can be used for sound signaling device open (excess) of the refrigerator door. In addition, applications of this simple and reliable devices are endless and they are limited only by the imagination of Amateur radio.
The button on the circuit SA2 is used to reset the device to its original state (it will be useful for the control of the refrigerator door). If not needed it from the schema rule. To reset to the initial state, the device can Razumkov circuit power switch SA1.
Installation. The elements of the device is fixed on the circuit Board.
The case is suitable. All fixed resistors type MLT-0,25.
Non-polar capacitors — type MBM, K10-23, K10-17.
Buzzer BZ may be any volt 4…20 VDC, for example FMQ-2015D, FXP1212.
The power supply is stable, providing output voltage 5… 15 V in this range the chip DA1 operates stably.
Current consumption in active mode of the audio signal with the specified in the diagram elements is 12…15 mA.
The device is in adjustment is not needed.
The sound volume is such that the signal heard at a distance of 10 m.
Alternative. The same site is not difficult to collect on logic elements other CMOS circuits (e.g., К561ЛЕ5, К561ТЛ1). The most simple circuit design shown in figure 2.
The basis of this electronic unit —• popular chip K561LA7. Thanks to the use of one of their logical elements, and the use of a primer with a built-in generator audio frequency (AF), in the scheme there is no need to enter any pulse generators or amplifiers.
When the DC voltage on the piezoelectric capsule with a built-in generator HA1 will be almost equal to the supply voltage of the device, the primer goes into the mode of generation of oscillations of audio frequency.
As capacitor C1 charges through resistor R1 and the inner node of the element DD1.1 a change in the state of the IC output. When the voltage on the capacitor plates 1 reach the level shift IC, it will switch and the high voltage level at the output of DD1.1 change low. The transistor VT1 is closed. DC voltage on the piezoelectric capsule with a built-in generator HA1 will be almost equal to zero, and the capsule will go into standby mode.
If specified in the diagram the values of elements R1 and C1 delay the turn off sound will be about 3 seconds. It can be increased, accordingly increasing the capacitance of the capacitor C1, which is better to use an oxide of the type K50-29, K50-35 and similar with small leakage current. The time interval can easily be reduced by reducing the resistance of the resistor R1. If instead you set the variable resistor with linear characteristic, you get a device with adjustable delay.
The function of this electronic unit can be reversed, that is, to make the piezoelectric capsule HA1 was silent for the first three seconds after applying the power supply device, and then the rest of the time worked.
For this, the oxide capacitor C1 and timing resistor R1 should be reversed (with the correct polarity to the inclusion of the oxide of the capacitor positive electrode to the “plus” power). The average point connectivity between terminals 1 and 2 elements DD1.1 is maintained. In this embodiment, the device without any changes can be used for sound signaling device open (excess) of the refrigerator door. In addition, applications of this simple and reliable devices are endless and they are limited only by the imagination of Amateur radio.
Installation. The elements of the device is fixed on the circuit Board. The case is suitable. The device is in adjustment is not needed.
About the details. Fixed resistors R1, R2 of the type MLT-0,25. Piezoelectric capsule can be any, volt 4…20 VDC, for example FMQ-2015D, FXP1212, KPI-4332-12.
The transistor VT1 is any silicon low and medium power structures of p-R-p, for example, КТ603, КТ608, КТ605, КТ801, КТ972, КТ940 with any alphabetic index. The power supply is stable, providing output voltage 5 — 15V. In this range the chip DA1 operates stably.
The elements VD1, R3 provide the function of protecting the device from voltage jumps. Due to the limiting resistor and Zener diode at this node can be “painless” to apply a constant voltage to 24 — 26 (which is important when using the device in circuits with 24 V supply, e.g. in trucks).
Zener diode VD1 provides the voltage stabilization in the range of 9 — 12 V. It can be replaced by Д814А — Д814Д, BZX55, 1N4740A, 1N4742A and similar.
If such protection is not needed, the elements VD1, R3 from the schema rule, and the supply voltage is connected to the point A.
Current consumption in active mode of the audio signal with the specified in the diagram elements is 10 to 12 mA.
The sound volume is chosen such that the signal is well heard in the room at a distance up to 10 meters.
A. KASHKAROV, St. Petersburg
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