Automatic cooler rpm

Cooling fans are now in many household appliances, be they computers, stereos, home theaters. They do well, cope with their task, cool the heating elements, but at the same time they produce a heart-rending and very annoying noise. This is especially critical in music centers and home theaters, because the fan noise can prevent you from enjoying your favorite music. Manufacturers often save and connect cooling fans directly to the power supply, from which they always rotate at maximum speed, regardless of whether cooling is required at the moment or not. You can solve this problem quite simply - build in your own automatic cooler speed regulator. It will monitor the temperature of the radiator and turn on cooling only if necessary, and if the temperature continues to rise, the regulator will increase the revolutions of the cooler up to the maximum. In addition to reducing noise, such a device will significantly increase the life of the fan itself.You can also use it, for example, when creating self-made high-power amplifiers, power supplies or other electronic devices.

Circuit

Automatic cooler speed regulator
The circuit is extremely simple, it contains only two transistors, a pair of resistors and a thermistor, but nevertheless it works wonderfully. M1 in the diagram - the fan, the speed of which will be regulated. The scheme is designed to use standard coolers for a voltage of 12 volts. VT1 - low-power npn transistor, for example, KT3102B, BC547B, KT315B. Here it is desirable to use transistors with a gain of 300 or more. VT2 - a powerful n-p-n transistor, it is he who commutes the fan. You can apply inexpensive domestic KT819, KT829, again, it is desirable to choose a transistor with a large gain. R1 is a thermistor (also called a thermistor), a key element of the circuit. It changes its resistance depending on temperature. Any NTC-thermistor with resistance of 10-200 kOhm, for example, domestic MMT-4, will fit here. The value of the trimming resistor R2 depends on the choice of the thermistor, it should be 1.5 - 2 times more.This resistor sets the threshold for switching on the fan.
Automatic cooler speed regulator

Manufacturing a regulator

You can easily assemble a circuit by mounting it, or you can make a printed circuit board, as I did. To connect the power wires and the fan itself, terminal boards are provided on the board, and the thermistor is output on a pair of wires and is attached to the radiator. For more thermal conductivity, you need to attach it using thermal paste. The board is executed using the LUT method, below are some photos of the process.
Automatic regulation of cooler speedAutomatic regulation of cooler speedAutomatic cooler speed regulator
Download fee: After making the board into it, as usual, parts are soldered, first small, then large. It is worth paying attention to the transistor basement to solder them correctly. After the assembly is completed, the board needs to be cleaned of flux residues, the tracks are rung,Make sure the installation is correct.
Automatic cooler speed controllerAutomatic cooler speed controllerAutomatic cooler speed controller

Setting

It is now possible to connect a fan to the board and gently apply power by setting the trimmer to the minimum position (base VT1 is pulled to ground ). The fan should not rotate. Then, smoothly turning R2, it is necessary to find such a moment when the fan starts to rotate slightly at minimum revs and turn the trimmer quite a bit back so that it stops spinning. Now you can check the operation of the regulator - just put your finger on the thermistor and the fan will start to rotate again. Thus, when the temperature of the radiator is equal to room temperature, the fan does not spin, but as soon as it rises at least a little, it will immediately start cooling.


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