Sound signaling devices of a stop of the fan. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Computers

 Comments on the article

To create normal operating conditions for components that generate a large amount of heat, fans are widely used in modern electronic equipment. Stopping the fan is fraught with the most unpleasant consequences: due to overheating, the components "served" by the fan can fail. To prevent this from happening, various signaling devices for malfunctioning cooling systems are used. The article describes two simple devices that give an audible signal when the fan stops.

As a sensor in devices for monitoring the operation of an electric motor, a relatively low-resistance resistor is sometimes used, connected in series to its power circuit (see, for example, D. Frolov's article "Audible fan failure alarm" in Radio, 2002, No. 2, p. 34) . This solution has disadvantages. Firstly, the current consumed by the fan (for example, JAMICON KF0510B1H - 12 V, 0,13 A) consists of a constant component (0,1 A) and a variable in the form of short pulses (amplitude 0,15 ... 0,2 A). The control device responds only to the variable component, and the constant creates a voltage drop of about 1 V across the resistor, which reduces the performance of the fan. Secondly, in this case it is necessary to "infiltrate" the fan power supply circuit, which is not always possible or desirable.

You can eliminate the first drawback of the device if you turn on the throttle instead of the resistor. Then the direct component of the current will pass almost without loss, and the variable will create a pulsed voltage, to which the device reacts. The inductor can be taken unified, for example, the DM series (DM-0,2, DM-0,4, DM-1), and the inductance can be selected when adjusting within 10 ... 100 μH (depending on the specific fan). It is also permissible to use a home-made choke, winding it with a PEV-2 0,2 wire on a ring with a diameter of 5 ... 10 mm made of ferrite with a permeability of 600 ... 2000 (the number of turns is selected experimentally according to the criterion of stable operation of the device).

An audible signaling device, free from the second drawback, can be made according to the scheme shown in Fig. 1.

It consists of an inductive sensor T1, a pulse shaper on the elements DD1.1, DD1.2 and a 3H signal generator on the elements DD1.3, DD1.4, to the output of which a piezoelectric acoustic emitter HA1 is connected. The sensor is a low-frequency step-up transformer, the primary winding of which consists of several turns of the fan power wire. When a pulsed current flows through this wire, short voltage pulses appear on the secondary winding of the sensor, which are fed to the pulse shaper. At the output of the latter, pulses with a high logic level appear, which are fed through the diode VD1 to the input of the element DD1.3. Thanks to the storage capacitor C3, this input is kept logic high, so the oscillator does not work.

When the fan stops, the current pulses in its supply wires and in the windings of the T1 sensor, and, consequently, the voltage pulses at the output of the shaper (DD1.1, DD1.2) disappear, the capacitor C3 is discharged and a low logic level is set on it. As a result, the generator (DD1.3, DD1.4) is self-excited and the sound emitter HA1 gives a signal indicating that the fan has stopped. Since the device does not have a galvanic connection with the fan power supply circuit, it can be powered from any 5...12 V voltage source (at a voltage close to the lower limit, the device's sensitivity is higher).

All parts of the signaling device, except for the sensor, are mounted on a printed circuit board made of foil fiberglass, a sketch of which is shown in full size in Fig. 2,a, and the placement of parts (on a scale of 2:1) - in fig. 2b. The device can use capacitors K10-17, trimming resistors SPZ-19, constants - MLT, S2-33 or P1-4. We can replace the ZP-3 sound emitter with any other from the ZP series, the KD522B diode with any low-power silicon.

It is convenient to use the electromagnet of the relay RES-10, PCM and similar as the basis of an inductive sensor. It is desirable that the number of turns of the winding be as large as possible, that is, it is better to use the most high-resistance relay. When disassembling, the casing and moving elements of the relay mechanism are removed, and several turns of wire are wound around the coil with a magnetic circuit, through which power is supplied to the fan.

The adjustment begins with setting the oscillation frequency of the generator 3H. By connecting the secondary winding of the T1 sensor to the device (without winding from the fan power wire), set the trimmer resistor R2 to the lower (according to the diagram) position, and an audible signal should appear. The desired oscillation frequency is set with a tuning resistor R5. Then the slider of the resistor R2 is transferred to the upper (according to the scheme) position and, slowly moving it down, an audible signal is achieved. After that, 1 ... 3 turns of wire supplying the fan are wound around the sensor, while the sound signal should disappear. Since the wire can be wound in two directions, choose the one that requires a smaller number of turns. By forcibly stopping the fan, make sure the alarm occurs every time.

Experiments have shown that the signaling device is also operable with a simplified sensor (without winding the wire supplying the fan), if it is placed directly above the fan motor. In this case, the magnetic field that occurs in the motor windings induces a pulsed voltage in the sensor coil, to which the device responds.

A schematic diagram of a similar device that responds to the rotation of the fan blades is shown in fig. 3.

It can be used with any kind of fans. Here, the sensor is an optocoupler, consisting of two IR emitting diodes. One of them (VD1) is used as an emitter, and the other (VD2) is used as a photodetector. A voltage amplifier is assembled on transistor VT1, and a key is assembled on VT2. Elements DD1.1, DD1.2 with resistor R6 and capacitor C4 form an infra-low frequency generator, and elements DD1.3, DD1.4 with elements R7, C5 form an audio frequency signal generator.

The device works as follows. The optocoupler diodes are located close to each other and aimed at the fan blades (if they are dark in color, at least one of them, closer to the edge, must be painted with reflective paint, for example, white). When the blades rotate at the moments when the shaded area is opposite the diodes, IR radiation enters the photodetector VD2, and a pulsed voltage appears on it, which is amplified by the transistor VT1. The amplified voltage from the engine of the resistor R3 through the capacitor C1 is supplied to the base of the transistor VT2. As a result, it opens and capacitor C2 is charged from the power source. At the same time, a high logic level is created on it and the generators on the elements DD1.1, DD1.2 and DD1.3, DD1.4 do not work.

When the fan stops, the pulse voltage at the gate of the transistor VT1 disappears, the transistor VT2 stops opening and the capacitor C2 is quickly discharged (a low logic level is set on it). As a result, both generators start to work and an intermittent sound signal appears, indicating the emergency operation of the fan.

The device can use resistors and capacitors of the same types as described above. Instead of KP303A, it is permissible to use a field-effect transistor KPZ0ZE, we can replace the KT361B transistor with any low-power p-n-p structure.

All parts of the signaling device, except for the optocoupler, are mounted on a printed circuit board made of foil fiberglass. Her life-size sketch is shown in Fig. 4,a, and the placement of parts (on an enlarged scale) - in fig. 4b.

The adjustment begins with the installation (by ear) of the required oscillation frequencies of the generators with trimming resistors R6, R7 with the VD2 LED unlit. Then the diodes are directed to the blades of the working fan and the resistor R3 makes the sound signal disappear. When the fan stops, a signal should appear. To increase the sensitivity of the device, the diodes should be placed as close as possible to the blades.

Author: I. Nechaev, Kursk

See other articles Section Computers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive All Samsung electronics will be equipped with artificial intelligence 02.06.2018 Kim Hyun-suk, head of consumer electronics at Samsung Electronics, said in a recent interview that in a couple of years, all of the company's electronics and home appliances will be able to communicate with users. Samsung has set an ambitious goal for itself: by 2020, absolutely all of the company's electronic and household products will be connected to the Internet and will be equipped with artificial intelligence systems. By this time, the staff of the Samsung Research division will be increased to 1000 people. Samsung wants to change the rules of the game in the artificial intelligence industry by opening three new centers. The Samsung Bixby personal assistant, which was introduced more than a year ago, is still noticeably inferior to Amazon Alexa and Google Assistant in terms of voice recognition and functionality. Perhaps the situation will change with the release of Bixby 2.0, which should debut in the Galaxy Note 9 smartphone.

Other interesting news:

▪ Satellites will fly in a mirror pair

▪ Unlock Knock smartphones LG

▪ Fujitsu's new architecture will speed up PCs by 10 times

▪ Tonometer works by touch

▪ Europe will spend 1,3 billion euros on Jupiter

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the Electrician website. Article selection

▪ Paracelsus article. Famous aphorisms

▪ article What is the traditional name of the oceanic spaces in the 40th latitudes of the Southern Hemisphere? Detailed answer

▪ article Heart-shaped linden. Legends, cultivation, methods of application

▪ article Delayed sweep in the oscilloscope. Encyclopedia of radio electronics and electrical engineering

▪ article Electrostatic wind farm. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024