Device for controlling the rotation of the cooler (fan, electric motor). Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Computers

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Efficient and reliable operation of electronic devices 24 hours a day largely depends on the temperature regime of the elements of each individual circuit. The heating temperature of the radioelement cases during operation, in turn, depends on the load power, stability and stabilization of the device citation voltage, and the power of the output (key) stages. Devices that require constant cooling are equipped with special fans-coolers. Miniature coolers are installed on a computer processor, system and video card chips, powerful audio amplifier heatsinks and other devices. Overheating of complex and highly integrated devices and entire electronic components is fraught not only with a malfunction directly related to these elements, but also with failure along the chain of all components of the circuit. A cooler fan that cools the heat sink of a microcircuit (or, for example, a powerful transistor) does not allow this element to overheat and fail. But the fans themselves, it happens, break. Then the element or microcircuit is directly threatened by a thermal breakdown with all the ensuing consequences.

Is it possible to control the operation of the fan itself? It turns out you can. The idea of ​​developing this simple scheme came to the author after studying and repairing the car. In domestic cars, such as the VAZ-21063, the Sobol minibus GAZ 2752 and others, the radiator cooling fan does not work constantly, but turns on periodically when the liquid in the radiator heats up over +87 ° C. The coolant temperature sensor installed directly in the car radiator is responsible for this. Unfortunately, the coolant temperature sensor often fails (in the author's practice), and therefore forced ventilation does not turn on. As a result, the liquid boils, the car has to be stopped and repaired.

The simplest solution in this case (in the field, when by all means you need to get to an auto parts store or home) is to close the contacts of the coolant temperature sensor. Thus, simulating the situation when the temperature sensor relay turns on the cooling fan. So you can reach your home, auto parts store or car service.

If we knew in advance that the fan had stopped spinning, we could have diagnosed the problem earlier and possibly avoided the time and money invested in later repairs. The analogy with cars is not accidental here. Indeed, in electronic technology, overheating of elements is undesirable and dangerous to the same extent as in automotive technology. To control the rotation of the electric motor of a cooler powered by 12 V, you will need to assemble a very simple device, the electrical circuit of which is shown in the figure.

Motor M is connected (with respect to polarity) through a limiting resistor R1. When power is applied to the device at the connection point of the lower (according to the diagram) output of the motor M and the resistor R1, using an oscilloscope, you can fix DC voltage ripples with an amplitude of 0,3-0,6 V (depending on the quality of the assembly of the motor). This pulsating (when the motor is on) voltage has a complex and chaotic shape. The isolation capacitor C1 does not pass the DC component of the voltage, so only the AC component of the control signal enters the base of the transistor VT1.

During normal operation of the electric motor Ml, the alternating voltage in the base of the transistor VT1 periodically opens this transistor, preventing the capacitor C2 from charging and opening the field-effect transistor VT2. Non-polar capacitor C2 performs another important role in the device. It stabilizes the voltage at the source-gate terminals of the VT2 field-effect transistor, thereby providing a soft sound to the HA1 capsule.

When the cooler motor stops (for any reason: an open circuit of the winding, a foreign object getting between the blades, etc.), there are no voltage ripples in the base of the VT1 transistor. The transistor is closed (shunt resistor R2 also contributes to this). The field effect transistor VT2 is open at this moment, as it receives a control voltage through the resistor R3. As soon as the voltage at the VT2 gate reaches 3 V, this field-effect transistor will open and turn on the sound capsule with the built-in audio frequency generator HA1. The sound generator has a fairly loud sound that can be heard up to 15 m away in the room. The audible alarm will remain on until the device is de-energized or until the cooler motor starts up again (for example, after removing a foreign object from its blades). The SB1 switch adds additional flavor to the device: when the SB1 contacts are closed, the electric motor M works at full strength, while another group of contacts opens the power supply circuit of the sound generator.

Establishment. The device does not need adjustment and starts working immediately after turning on the power. With a power supply voltage of 24 V (according to the controlled motor), it may be necessary to select (correct) the sensitivity of the device.

The sensitivity of the sensor depends on the elements CI, R1. With an increase in the capacitance of the capacitor C1 and the resistance of the resistor R1, the sensitivity of the device increases. You can also reduce the sensitivity of the sensor by reducing the resistance of the resistor R2.

About details. As a cooler, an additional fan is used to cool the computer case, designed for a constant voltage of 12 V and a current of 0,1 A.

The same method can be used to control the operation of other DC motors with an applied voltage of 12-25 V. For example, these may be motors such as DOT-301, DKM-1 (0,12 A), 4DKS-8, DKS-16 C), etc. Switch SB24 type MTZ-1-9 (double microswitch, designed in the form of a toggle switch). If direct manual switching on of the electric motor is not required, this switch is excluded from the circuit. Capacitor C2 type MBM, K1-10 or similar. Non-polar capacitor C17 type K2-P76 or similar.

Instead of transistors KT3102E, you can use KT3102B-KT3102D. Field-effect transistor type KP501 with any letter index or foreign analogue ZVN2120. Fixed resistors type MLT. Instead of the HA1 capsule with a built-in AF generator, any other similar capsule is used, designed for a voltage of 10-24 V. The prospect of using the device and method of the motor rotation sensor.

The prospect of using the recommended sensor is truly wide. It is important to control the rotation of the electric motor in the aquarium hobby when it is necessary to control the normal operation of the pump-pump. This is relevant today, because snails often (without exaggeration) arbitrarily crawl into the working area of ​​​​the pump, as a result of which the pump does not work, air aeration in the aquarium is not carried out, which can lead to sad consequences and ruin life in the aquarium. Therefore, the cooler rotation sensor and the method proposed by the author seem to be very important.

Author: Kashkarov A.P.

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