Changing the CPU fan speed. How to choose a fan speed controller

Temperature directly affects the quality and duration of operation of computer components. That is why it is important to monitor the proper operation of the cooling system. Dust should not accumulate in it; all computer fans must operate in normal mode, increasing speed if necessary during heavy loads.

Most users work at the computer in standard mode, without loading components in productive games and applications. In this case, the coolers on the computer may not be configured, and in such a situation they will operate at maximum or close to maximum speed. To reduce noise when the computer is running, you need to adjust the operation of the coolers by reducing the rotation speed of their fans.

How can you regulate the speed of computer coolers?

The rotation speed of computer cooling fans is initially set at the motherboard level. It is determined in the BIOS, and quite often the automatically set settings turn out to be incorrect. In most cases, the rotation speed of coolers is set to maximum, which is why the computer makes a lot of noise during operation, but does not need such serious cooling.

There are 3 main ways to adjust the rotation speed of computer coolers:

Within the framework of this article, we will consider the third option for software adjustment of the rotation speed of computer coolers.

How to adjust the rotation speed of computer coolers

There are hundreds of applications that allow you to adjust the rotation speed of your computer's coolers. However, some programs allow you to regulate only the fan speed of certain components.

One of the most convenient and simple programs for adjusting the rotation speed of computer coolers is SpeedFan. The application is free and can be downloaded from the developers' website or from other trusted sources on the Internet. After downloading the program, you will need to install it and then run it. When you launch SpeedFan for the first time, an informational message may appear that you will need to close.

Checking the rotation speed of coolers

Next comes a block of indicators of the rotation speed of coolers (measured in RPM - revolutions per minute) and the temperature of computer components. Let's figure out what each of the indicators means:

It is worth noting that all the above designations are conditional and they may vary. Not every motherboard provides information about the name of a particular connector for connecting a cooler on it. For example, on some motherboards in SpeedFan you can see a picture like the image below, that is, all coolers will be connected to Fan1 – Fan5 connectors, without an exact definition of the purpose of each of them.

It is also important to note that the SpeedFan program only allows you to control coolers that are connected to the motherboard. The fact is that the 3-pin connector from the fan can be powered from the motherboard or from the power supply directly. If it is powered from a power supply, then it will not be possible to regulate its rotation speed. It is recommended to connect all coolers to the motherboard.

To the right of the cooler rotation speed symbols there is a block with information about the temperature of the computer components. It is worth noting that SpeedFan is not the most accurate diagnostic tool in this regard, and it does not always determine the temperature accurately. If you have doubts about one or more indicators, it is recommended to download more professional temperature monitoring software, for example, AIDA64 or HWMonitor.

Setting the rotation speed of coolers

As you can understand, in the top window of the SpeedFan program there are blocks with information about the operation of coolers. Below are the tools for adjusting the intensity of fan rotation in the computer. They can be designated Pwm1 – Pwm3 or, for example, Speed01 – Speed06. There is not much difference, since it is impossible to determine by such names which of the coolers this or that adjustment is responsible for.

To reduce or increase the fan rotation speed, you need to press the corresponding up and down buttons in the columns with the fan rotation intensity. When pressed, you should observe the reaction of the coolers in the diagnostic information above. This way it will be possible to determine which fan is responsible for which setting.

Important: When reducing the fan speed to reduce the noise level when the computer is running, do not forget to monitor the temperature of the system unit components to avoid overheating.

By chance, I came across a server computer that worked flawlessly for many years for its intended purpose. The device is still quite up to par - Intel Xeon 3050; 2.1 GHz; 2 cores; 5GB RAM. The video card, however, is rather weak, but I don’t play games, so this is not critical. I decided to adapt it for my amateur radio purposes - hardware log, digital communication... The old computer, previously used for these purposes, finally and irrevocably died.

Everything is good, but due to the low height of the case (only 4.5 cm), it has small but very high-speed fans, as many as 7 of them. And they hum like a plane taking off. But I don’t need maximum computer performance; the processor load and reliability requirements are much lower than on a server. Those. You can slightly reduce the cooling intensity by reducing the fan speed. Accordingly, the noise will decrease.

I had to start searching for information on how to regulate the rotation speed of fans in computers. As in many other cases, there is a lot of information on this topic on the Internet, but most of it is repeated, contains inaccuracies, and sometimes obvious errors. As usual, I had to approach the problem creatively. So, how can you reduce the fan speed?

The most obvious and simple way is to reduce the speed through the BIOS settings. To do this, you need to go to “BIOS Setup”, find the “CPU Fan Profile”, “CPU Fan Control” or something similar parameter there and set it to a suitable value, for example, “Silent”. If the desired result is achieved, you don’t have to read any further on this page.

Well, what should you do if, as in my case, there is nothing like that in the BIOS? Let's figure it out further. There are special programs for adjusting fan speed, for example “Speed ​​Fan”. Links to these programs are not difficult to find on the Internet. Unfortunately, in most cases such programs are useless, because... work through BIOS. If the BIOS does not have the ability to adjust the speed, then the program will not be able to do anything. If such an opportunity exists, then there is no point in using any additional program. It is unlikely that while working you will constantly think about such a parameter as the fan speed and quickly adjust it.

If nothing can be done programmatically, you will have to solve the problem in hardware. There are three options for connecting fans: two-, three- and four-wire.

The simplest two-wire circuit. The motor is simply connected between the common wire and the +12 volt bus. In this case, you can reduce the voltage on it by connecting it between +5 and +12 volts, i.e. applying +7 volts to the fan. How to do this is clear from the figure.

First you need to make sure that the wires from the cooler are connected to +12 V and ground. This can be done using a multimeter. If there is some kind of regulator in the motor circuit, as is often the case in power supplies, this method CANNOT be used. For a three or four-wire connection scheme, this method is also NOT suitable. At best it won't work.

The next way to reduce the fan speed is to include an additional resistor in its power supply circuit. The method is simple, suitable for two and, with some reservations, for a three-wire connection scheme. The resistor power is at least 1, and preferably 2 watts. The rating is selected according to the desired speed reduction within 10...50 Ohms. The most convenient way is to make an adapter and connect it between the fan and the board. If you are lazy, such adapters can be purchased on Aliexpress.

With a three-wire connection diagram, there is a possibility that after the voltage on the engine decreases as a result of connecting an additional resistor, the built-in tachometer will stop working. Accordingly, the revolutions will be displayed incorrectly in the system or will not be displayed at all. It all depends on the brand of fan and this can only be verified experimentally. With a four-wire cooler connection circuit, it is definitely IMPOSSIBLE to install an additional resistor in the engine power supply circuit.

On the Internet you can find diagrams of various pulse regulators for three-wire coolers, supposedly turning them into four-wire ones. I don’t recommend repeating these schemes, the situation here is even worse. The tachometer built into the fan will be powered by pulse voltage and is guaranteed not to work.

In my case, two coolers in the power supply were connected using a two-wire circuit; it was possible to reduce their rotation speed to an acceptable value by turning on additional 20 Ohm resistors. The five remaining coolers are connected using a four-wire circuit, for which this method is not suitable due to the incorrect operation of the tachometer and, accordingly, the appearance of a system error.

A rare case - the coolers are connected using a four-wire circuit, the motherboard supports adjusting their speed, but there are no settings in the BIOS and the Speed ​​Fan program does not work. A civilized person would hardly be able to do anything in such a situation, but in Russia we are accustomed to solving impossible problems.

The cooler speed is controlled using the PWM method. The greater the duty cycle (duration) of the pulses on the 4th pin of the connector, the higher the fan speed. The pulse frequency is usually about 25 kHz, the amplitude is 3.3 V. In the extreme case, when there is a constant voltage of 3.3 V on the 4th wire, the speed is maximum.

Thus, the task comes down to reducing the duration of PWM pulses. Between the cooler and the motherboard we include the following circuit.

The 3.3 V supply voltage can be taken from the power supply, but, in my opinion, it is easier and more convenient to install a separate stabilizer than to pull an additional wire from the computer connector. Resistor R1 sets the desired fan rotation speed. It can be controlled using the free software HWiNFO.

Making 5 such separate channels seemed redundant to me, because... All coolers are controlled by one regulator, the frequencies and phases of all PWM pulses turned out to be the same. Therefore, I made a simplified version of the 5-channel circuit using just one 74HC14 housing.

The rotation speed of all 5 coolers is the same and is determined by the shortest control pulse. The circuit is assembled on a separate board and installed in a free space in the case.

I don’t include printed circuit boards, because... The circuits are simple, and the sizes and configuration of the boards are determined by the available free space. The advantage of these schemes is that the operation of the speed control system is not disrupted, i.e. As the temperature in the case rises, the cooler speeds will increase up to maximum.

There was a case in my practice when it was necessary to solve the exact opposite problem. The computer periodically froze, as it turned out, due to an increase in processor temperature. In an effort to reduce the noise level, the developers lowered the cooler speed. There were no options for adjusting the speed in the BIOS; the temperature was controlled by a separate thermal sensor that had thermal contact with the heatsink. This is also a fairly rare case; usually a temperature sensor built into the processor is used.

To increase the fan speed, but not disrupt the operation of the thermal control system, I simply soldered a regular resistor parallel to the temperature sensor, choosing its value experimentally.

I note that you cannot connect a resistor in series with the temperature sensor to reduce the rotation speed. The temperature response of the sensor is not linear; an additional resistor will sharply limit the speed control capabilities, which can lead to overheating of the processor.

The above circuits on the 74HC14 also allow you to increase, rather than decrease, the rotation speed of fans connected in a four-wire circuit. To do this, you simply need to reverse the polarity of all diodes.

How to increase the speed of the cooler on a laptop if over time it starts to work a little slower, more noisy and sometimes even overheats. Overheating is one of the most inconvenient and harmful incidents for a computer because it causes additional wear and tear on the hardware and increases the chances of failure.

To eliminate this situation, you can replace the thermal paste and increase the cooling. If replacing thermal paste is not a very difficult matter, then in order to strengthen the cooling system (CO), you need to either buy a cooling pad or increase the speed of the cooler. The cooling pad is quite noisy, costs extra money, and takes up space, but you can speed up the standard cooling system absolutely free.

There are two options for how to speed up the cooler speed on a laptop:

1. Using the software
2. Using BIOS\UEFI

Before overclocking

First, let's determine what the speed of the cooler will affect:

• The higher it is, the more noise the laptop makes when operating, the faster it discharges (slightly), but at the same time the temperature of the CPU and the system as a whole is lower, which means there are fewer freezes and slowdowns due to throttling (lowering the processor frequency to reduce the thermal load). The power supply design is High Performance.
• The lower, the quieter the laptop runs, the slower the battery discharges, but under high loads there is a possibility of the device overheating. The power supply scheme is Energy Saving.

In most cases, cleaning the cooling system and replacing the thermal interface solves the problems of overheating and throttling. But if these manipulations are difficult to perform due to the complexity of disassembling or the warranty of the laptop (which prohibits disassembling the device), then to obtain the desired cooling it is better to speed up the cooler.

Overclocking a cooler via software

One of the most popular programs for monitoring and tracking system temperature - Speedfan - will answer the question of how to increase the speed of the cooler on a laptop. You can download the program on the website or via a direct download link.

Please note that not all laptops are supported by this program. It is likely that very old devices, or, conversely, new generation devices, may not display information on temperature and cooler speed. You can view the list of supported buses or axles (BUS) on the utility website.

Install and open the SpeedFan application. The main window will display main information on the temperature and rotation speed of the coolers. Click on Configure, which will open the configuration window. Select the required tracking component - for example, this is the CPU (CPU) and set the desired temperature, the cooling system will work with priority at this parameter.

The next parameter in the Speeds tab determines the speed of the coolers.

1. Minimum value – minimum value (%)
2. Maximum value – maximum value (%)
3. Automatically varied – automatic selection based on temperature

After using the utility, check the temperature readings; if they have not changed within a few minutes\hours, try changing them through the BIOS.

How to increase the fan speed on a laptop via BIOS

BIOS allows you to configure various device parameters - from boot parameters to login password and regulation of processor or memory frequency. Not all laptops have the ability to overclock CO, so you need to check this option on your laptop.

To enter the BIOS\UEFI of your computer when rebooting, press the corresponding key:

If you have a classic BIOS, open the Power tab and select Hardware Monitor

Then, if you have the ability to control the minimum cooler speed or set a target temperature value, set the necessary settings.

• For temperature - the lower the better – 40-55 C°
• For speed - it is better to test on your device - select from 100% to 35% in steps of 5-10% to determine the acceptable noise level and temperature.

For owners of laptops with UEFI, the interface is slightly different, but the functionality is much richer.

The desired settings will be in the Monitor, Hardware or Advanced tabs. Settings may vary depending on manufacturer and UEFI version.

Additionally

How else can you increase the speed of the cooler on a laptop:

• For older devices, special utilities AMD OverDrive or Riva Tuner may be suitable. The list of supported devices is extremely small and mostly consists of outdated laptops based on Windows XP, Vista or sometimes version 7.
• There have been cases where dust interfered with the cooling system so much that the bearings needed to be lubricated
• Don't rule out the possibility of replacing the cooler if the speed is very different from the advertised speed.

Have a great day!

The operation of a computer cooling system is tied to the eternal balance between noise and efficiency. A powerful fan operating at 100% will irritate with a constant noticeable hum. A weak cooler will not be able to provide a sufficient level of cooling, reducing the service life of the hardware. Automation does not always cope with the issue itself, so to regulate the noise level and cooling quality, the cooler rotation speed sometimes has to be adjusted manually.

When you may need to adjust the cooler speed

The rotation speed is adjusted in the BIOS, taking into account the settings and temperature on the sensors. In most cases this is enough, but sometimes the smart adjustment system fails. Imbalance occurs under the following conditions:

• overclocking the processor/video card, increasing the voltage and frequency of the main buses;
• replacing the standard system cooler with a more powerful one;
• non-standard connection of fans, after which they are not displayed in the BIOS;
• aging cooling system with noise at high speeds;
• contamination of the cooler and radiator with dust.

If the noise and increase in cooler speed are caused by overheating, you should not reduce the speed manually. It is best to start by cleaning the fans from dust; for the processor, remove them completely and replace the thermal paste on the substrate. After several years of use, this procedure will help reduce the temperature by 10–20°C.

A standard case fan is limited to around 2500–3000 revolutions per minute (RPM). In practice, the device rarely operates at full power, producing about a thousand RPM. There is no overheating, but the cooler still continues to idle several thousand revolutions? You will have to correct the settings manually.

The heating limit for most PC elements is about 80°C. Ideally, you need to keep the temperature at 30–40°C: cooler hardware is only interesting to enthusiastic overclockers; this is difficult to achieve with air cooling. You can check information on temperature sensors and fan speeds in the AIDA64 or CPU-Z/GPU-Z information applications.

How to set the fan speed on your computer

You can configure it both programmatically (by editing the BIOS, installing the SpeedFan application) and physically (by connecting the fans via rheobass). All methods have their pros and cons and are implemented differently for different devices.

On a laptop

In most cases, laptop fan noise is caused by blocked or dirty vents. Reducing the speed of coolers can lead to overheating and rapid failure of the device.

If the noise is caused by incorrect settings, then the issue is resolved in several steps.

Via BIOS

1. Go to the BIOS menu by pressing the Del key in the first phase of booting the computer (on some devices - F9 or F12). The login method depends on the BIOS type - AWARD or AMI, as well as the motherboard manufacturer.
   

   Go to BIOS settings

2. In the Power section, select Hardware Monitor, Temperature or any similar item.
   

   Go to the Power tab

3. Select the desired cooler speed in the settings.
   

   Select the desired cooler rotation speed

4. Return to the main menu, select Save & Exit. The computer will restart automatically.
   

   Save the changes, after which the computer will automatically restart

The instructions deliberately indicated different BIOS versions - most versions from different hardware manufacturers will differ at least slightly from each other. If a line with the desired name is not found, look for one that is similar in functionality or meaning.

SpeedFan utility

1. Download and install the application from the official website. The main window displays information about the temperature on the sensors, data on processor load and manual adjustment of the fan speed. Uncheck the “Auto-adjust fans” checkbox and set the number of revolutions as a percentage of the maximum.
   

   In the “Indicators” tab, set the desired speed indicator

2. If the fixed number of revolutions is not satisfactory due to overheating, the required temperature can be set in the “Configuration” section. The program will strive for the selected number automatically.
   

   Set the desired temperature setting and save the settings

3. Monitor the temperature under load mode, when running heavy applications and games. If the temperature does not rise above 50°C, everything is fine. This can be done both in the SpeedFan program itself and in third-party applications, such as the already mentioned AIDA64.
   

   Using the program, you can monitor temperature indicators at maximum load

On CPU

All methods for adjusting coolers indicated for a laptop also work perfectly for desktop processors. In addition to software adjustment methods, desktops also have a physical one - connecting fans via rheobass.

Reobas allows you to adjust speed without using software

Reobass or fan controller is a device that allows you to control the speed of coolers directly. Control elements are most often placed on a separate remote control or front panel. The main advantage of using this device is direct control over the connected fans without the participation of the BIOS or additional utilities. The disadvantage is that it is cumbersome and redundant for the average user.

On purchased controllers, the speed of the coolers is adjusted via an electronic panel or mechanical knobs. Control is implemented by increasing or decreasing the frequency of pulses supplied to the fan.

The adjustment process itself is called PWM or pulse width modulation. You can use the rheobass immediately after connecting the fans, before starting the operating system.

On the video card

Cooling management is built into most graphics card overclocking programs. The easiest way to deal with this is AMD Catalyst and Riva Tuner - the only slider in the Fan section precisely regulates the number of revolutions.

For video cards from ATI (AMD), you should go to the Catalyst performance menu, then enable the OverDrive mode and manual cooler control, setting the indicator to the desired value.

For AMD video cards, the cooler rotation speed is adjusted through the menu

Nvidia devices are configured in the Low-Level System Settings menu. Here, manual fan control is checked, and then the speed is adjusted with a slider.

Set the temperature adjustment slider to the desired setting and save the settings

Setting up additional fans

Case fans are also connected to the motherboard or rheobass through standard connectors. Their speed can be adjusted in any of the available ways.

With non-standard connection methods (for example, directly to the power supply), such fans will always operate at 100% power and will not be displayed either in the BIOS or in the installed software. In such cases, it is recommended to either reconnect the cooler via a simple rheobass, or replace or disconnect it completely.

Running fans at insufficient power can lead to overheating of computer components, causing damage to electronics, reducing quality and lifespan. Only correct cooler settings if you fully understand what you are doing. For several days after changes, monitor the temperature of the sensors and watch for possible problems.

Comments:

The performance of a modern computer is achieved at a fairly high price - the power supply, processor, and video card often require intensive cooling. Specialized cooling systems are expensive, so several case fans and coolers (radiators with fans attached to them) are usually installed on a home computer.

The result is an effective and inexpensive, but often noisy cooling system. To reduce noise levels (while maintaining efficiency), a fan speed control system is needed. Various exotic cooling systems will not be considered. It is necessary to consider the most common air cooling systems.

To reduce fan noise without reducing cooling efficiency, it is advisable to adhere to the following principles:

1. Large diameter fans work more efficiently than small ones.
2. Maximum cooling efficiency is observed in coolers with heat pipes.
3. Four-pin fans are preferred over three-pin fans.

There can only be two main reasons for excessive fan noise:

1. Poor bearing lubrication. Eliminated by cleaning and new lubricant.
2. The motor is spinning too fast. If it is possible to reduce this speed while maintaining an acceptable level of cooling intensity, then this should be done. The following discusses the most accessible and cheapest ways to control rotation speed.

Methods for controlling fan speed

Return to contents

First method: switching the BIOS function that regulates fan operation

The functions Q-Fan control, Smart fan control, etc., supported by some motherboards, increase the fan speed when the load increases and decrease when it drops. You need to pay attention to the method of controlling the fan speed using the example of Q-Fan control. It is necessary to perform the following sequence of actions:

1. Enter BIOS. Most often, to do this, you need to press the “Delete” key before booting the computer. If before booting at the bottom of the screen instead of “Press Del to enter Setup” you are prompted to press another key, do so.
2. Open the “Power” section.
3. Go to the line “Hardware Monitor”.
4. Change the value of the CPU Q-Fan control and Chassis Q-Fan Control functions on the right side of the screen to “Enabled”.
5. In the CPU and Chassis Fan Profile lines that appear, select one of three performance levels: enhanced (Perfomans), quiet (Silent) and optimal (Optimal).
6. Press the F10 key to save the selected setting.

Return to contents

Second method: fan speed control by switching method

Figure 1. Stress distribution on contacts.

For most fans, the nominal voltage is 12 V. As this voltage decreases, the number of revolutions per unit time decreases - the fan rotates more slowly and makes less noise. You can take advantage of this circumstance by switching the fan to several voltage ratings using an ordinary Molex connector.

The voltage distribution on the contacts of this connector is shown in Fig. 1a. It turns out that three different voltage values ​​can be taken from it: 5 V, 7 V and 12 V.

To ensure this method of changing the fan speed you need:

1. Open the case of the de-energized computer and remove the fan connector from its socket. It's easier to unsolder the wires going to the power supply fan from the board or just cut them out.
2. Using a needle or awl, release the corresponding legs (most often the red wire is positive and the black wire is negative) from the connector.
3. Connect the fan wires to the contacts of the Molex connector at the required voltage (see Fig. 1b).

An engine with a nominal rotation speed of 2000 rpm at a voltage of 7 V will produce 1300 rpm per minute, and at a voltage of 5 V - 900 rpm. An engine rated at 3500 rpm - 2200 and 1600 rpm, respectively.

Figure 2. Diagram of serial connection of two identical fans.

A special case of this method is the serial connection of two identical fans with three-pin connectors. They each carry half the operating voltage, and both spin slower and make less noise.

The diagram of such a connection is shown in Fig. 2. The left fan connector is connected to the motherboard as usual.

A jumper is installed on the right connector, which is fixed with electrical tape or tape.

Return to contents

Third method: adjusting the fan speed by changing the supply current

To limit the fan rotation speed, you can connect permanent or variable resistors in series to its power supply circuit. The latter also allow you to smoothly change the rotation speed. When choosing such a design, you should not forget about its disadvantages:

1. Resistors heat up, wasting electricity and contributing to the heating process of the entire structure.
2. The characteristics of an electric motor in different modes can vary greatly; each of them requires resistors with different parameters.
3. The power dissipation of the resistors must be large enough.

Figure 3. Electronic circuit for speed control.

It is more rational to use an electronic speed control circuit. Its simple version is shown in Fig. 3. This circuit is a stabilizer with the ability to adjust the output voltage. A voltage of 12 V is supplied to the input of the DA1 microcircuit (KR142EN5A). A signal from its own output is supplied to the 8-amplified output by transistor VT1. The level of this signal can be adjusted with variable resistor R2. It is better to use a tuning resistor as R1.

If the load current is no more than 0.2 A (one fan), the KR142EN5A microcircuit can be used without a heat sink. If it is present, the output current can reach a value of 3 A. It is advisable to include a small-capacity ceramic capacitor at the input of the circuit.

Return to contents

Fourth method: adjusting the fan speed using rheobass

Reobas is an electronic device that allows you to smoothly change the voltage supplied to the fans.

As a result, the speed of their rotation smoothly changes. The easiest way is to purchase a ready-made reobass. Usually inserted into a 5.25" bay. There is perhaps only one drawback: the device is expensive.

The devices described in the previous section are actually reobass, allowing only manual control. In addition, if a resistor is used as a regulator, the engine may not start, since the amount of current at the moment of starting is limited. Ideally, a full-fledged reobass should provide:

1. Uninterrupted engine starting.
2. Rotor speed control not only manually, but also automatically. As the temperature of the cooled device increases, the rotation speed should increase and vice versa.

A relatively simple diagram that meets these conditions is shown in Fig. 4. Having the appropriate skills, it is possible to make it yourself.

The fan supply voltage is changed in pulse mode. Switching is carried out using powerful field-effect transistors, the resistance of the channels in the open state is close to zero. Therefore, starting the engines occurs without difficulty. The highest rotation speed will also not be limited.

The proposed scheme works like this: at the initial moment, the cooler that cools the processor operates at a minimum speed, and when heated to a certain maximum permissible temperature, it switches to the maximum cooling mode. When the processor temperature drops, the reobass again switches the cooler to minimum speed. The remaining fans support manually set mode.

Figure 4. Adjustment diagram using rheobass.

The basis of the unit that controls the operation of computer fans is the integrated timer DA3 and field-effect transistor VT3. A pulse generator with a pulse repetition rate of 10-15 Hz is assembled on the basis of a timer. The duty cycle of these pulses can be changed using the tuning resistor R5, which is part of the timing RC chain R5-C2. Thanks to this, you can smoothly change the fan rotation speed while maintaining the required current value at the time of start-up.

Capacitor C6 smoothes the pulses, making the motor rotors rotate more softly without making clicks. These fans are connected to the XP2 output.

The basis of a similar processor cooler control unit is the DA2 microcircuit and the VT2 field-effect transistor. The only difference is that when voltage appears at the output of operational amplifier DA1, thanks to diodes VD5 and VD6, it is superimposed on the output voltage of timer DA2. As a result, VT2 opens completely and the cooler fan begins to rotate as quickly as possible.