The sound signaling device of malfunction of the fan. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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The sound signaling device of malfunction of the fan. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric motors

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To improve the removal of heat generated by radio elements in radio equipment and computers, forced ventilation is often used. However, its failure is dangerous overheating and failure of the entire device. The proposed signaling device will allow you to find out in time about the stop of the fan.

The signaling device circuit is shown in fig. one.

Fan failure buzzer

Resistor R1, connected in series to the power supply circuit of the fan motor M1, produces a voltage proportional to the current flowing. During normal operation of the fan, the current consumed by it is a pulsating complex shape. The variable component of the ripple through the capacitor C1 enters the base of the transistor VT1. As a result, the transistor, periodically opening, discharges the capacitor C2, preventing the voltage from reaching the switching threshold of the element DD1.1 on it.

If the fan stops, the current ripple stops, which leads to the charging of the capacitor C2. As soon as the voltage on it reaches the switching threshold of the element DD1.1, log. 1 from its output will switch the element DD1.2 and the operation of the multivibrator on the elements DD1.3 and DD1.4 will be allowed. Multivibrator pulses with a frequency of approximately 2 Hz open the transistor VT2, in the collector circuit of which a sound emitter with a built-in generator (“beeper”) HA1 is included. Similar emitters are used in imported electronic alarm clocks.

The printed circuit board of the signaling device with the layout of parts on it is shown in fig. 2.

Fan failure buzzer

The board is designed to install fixed resistors MLT-0,125 (R1 - MLT-0,5). Capacitors - K10-7, KM. Instead of the K561LA7 chip, you can install K176LA7, KR1561LA7, K561TL2, KR1561TL2. Transistors VT1, VT2 - KT3102 series with any letter index. Sound emitter HA1 - HRM14AX or another with a built-in generator.

The signaling device is suitable for operation with any DC fan with a supply voltage of 9...15 V. Sometimes it is required to select resistor R1 and capacitor C1.

In the absence of an emitter with a built-in generator, you can use a conventional piezoelectric emitter, for example, from the ZP series (ZP-1, ZP-18, ZP-22), assembling the signaling device according to the diagram shown in Fig. 3.

Fan failure buzzer

This device is similar to the one discussed above, but contains two multivibrators, the second being controlled by a signal from the first and generating a signal with a frequency of approximately 3000 Hz. A selection of elements C4 and R6 will produce a sound signal of the desired tone.

Author: D.Frolov

See other articles Section Electric motors.

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