Speed modern computer It is achieved quite high price - power supply, processor, video card often need intensive cooling. Specialized cooling systems are expensive, so home computer Typically set several cabinet fans and coolers (radiators with fans attached to them).

It turns out an efficient and inexpensive, but often noisy cooling system. To reduce noise levels (provided that the efficiency is maintained), the fan speed control system needs. Miscellaneous kind of exotic cooling systems will not be considered. It is necessary to consider the most common air cooling systems.

So that noise when working fans is less without reducing cooling efficiency, it is desirable to adhere to the following principles:

1. Large diameter fans work more efficiently than small ones.
2. The maximum cooling efficiency is observed in coolers with heat pipes.
3. Four-contact fans are preferable than three-contact.

The main reasons why there is an excessive fan noise, can only be two:

1. Bad lubricant bearings. Eliminated by cleaning and new lubrication.
2. The engine rotates too fast. If it is possible to reduce this velocity while maintaining the permissible level of cooling intensity, then it should be done. The most accessible and cheap ways to control the speed of rotation are considered.

Fan rotation speed controls

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First method: Switching to the BIOS function regulating fans

The functions of the Q-Fan Control, Smart Fan Control, etc. supported by part of motherboards, increase the frequency of rotation of the fans with an increase in the load and decrease during its fall. You need to pay attention to the method of such a fan speed control using the example of Q-Fan Control. You must perform a sequence of actions:

1. Log in BIOS. Most often for this you need to press the "Delete" key before downloading the computer. If before downloading at the bottom of the screen instead of the "PRESS DEL TO ENTER SETUP" inscription, a proposal appears to press another key, do it.
2. Open the "Power" section.
3. Go to the line "Hardware Monitor".
4. Replace to "Enabled" The value of the functions of the CPU Q-Fan Control and Chassis Q-Fan Control on the right side of the screen.
5. In the CPU and Chassis Fan Profile strings appeared, select one of three performance levels: reinforced (Perfomans), quiet (Silent) and optimal (Optimal).
6. By pressing the F10 key, save the selected setting.

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In the foundation.
Features.
Aksonometric ventilation scheme.

Second method: fan speed control by switching method

Figure 1. Distribution of voltages on contacts.

For most fans, the voltage in 12 V. When decreasing this voltage, the number of revolutions per unit of time decreases - the fan rotates slower and less noise. You can use this circumstance, switching the fan into 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 it can remove three different voltage values \u200b\u200bfrom it: 5 V, 7 V and 12 V.

To ensure such a method for changing the fan rotation speed:

1. Opening a de-energized computer case, remove the fan connector from its socket. Wires that go to the power supply fan is easier to drop out of the board or simply have a snack.
2. Using a needle or awl, free the cutting legs (most often the wire of the red color is plus, and black is minus) from the connector.
3. Connect the fan wires to Molex connector contacts to the required voltage (see Fig. 1b).

The engine at a nominal rotation speed of 2000 rpm at a voltage of 7 V will be given per minute of 1300, at a voltage of 5 V - 900 revolutions. The engine with a nominal value of 3500 rpm - 2200 and 1600 revolutions, respectively.

Figure 2. Scheme of the sequential connection of two identical fans.

A special occasion of this method is the sequential connection of two identical fans with three-pin connectors. For each of them there are half of the operating voltage, and both rotate slower and are less noisy.

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

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

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Third way: Adjusting the fan rotation speed by changing the power of the feed current

To limit the rotational speed of the fan, you can order constant or variable resistors to the circuit of its power. The latter also allow you to smoothly change the speed of rotation. Choosing such a design, you should not forget about its minuses:

1. Resistors warm, uselessly spending electricity and making their contribution to the process of warming up the entire design.
2. Characteristics of electric motor B. different modes They can be very different, for each of them resistors with different parameters are needed.
3. The scattering capacity of resistors should be large enough.

Figure 3. Electronic speed adjustment circuit.

Rationally apply electronic circuit Adjusting the speed of rotation. Its simple variant is shown in Fig. 3. This scheme is a stabilizer with the ability to adjust the output voltage. The DA1 chip (CR142A5A) input is supplied to a voltage in 12 V. On the 8-reinforced output of the VT1 transistor, a signal is fed from its output. The level of this signal can be adjusted by a variable R2 resistor. As R1 it is better to use a rapid resistor.

If the load current is not more than 0.2 A (one fan), the KR142EN microcircuit can be used without heat sink. When it is presented, the output current can reach the value of 3 A. at the input of the scheme, it is desirable to turn on the ceramic capacitor of a small capacity.

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Fourth Method: Adjusting the fan rotation speed using a refusal

Refobas - electronic devicewhich allows you to smoothly change the voltage supplied to the fans.

As a result, the speed of their rotation varies smoothly. The easiest way to buy ready-made refobas. Inserted usually in the 5.25 compartment. The disadvantage is perhaps only one: the device is expensive.

The devices described in the previous section are actually a refuses that allow only manual control. In addition, if a resistor is used as a regulator, the engine may not start, because the current value is limited at the start of the start. Ideally, full-fledged refobas must provide:

1. Uninterrupted engine launch.
2. Control speed rotation not only in manual, but also in automatic mode. With an increase in the temperature of the cooled device, the speed of rotation should increase and vice versa.

A relatively simple scheme corresponding to these conditions is presented in Fig. 4. Having appropriate skills, it is possible to make it with your own hands.

Changing the fan power voltage is carried out in a pulse mode. Switching is carried out using powerful field transistors, the resistance of the channels in the open state is close to zero. Therefore, the start of engines occurs without difficulty. The highest rotational speed will also not be limited.

The proposed scheme works like this: in the initial moment, the cooler, which cooled the processor, operates at the minimum speed, and when heated to a certain maximum permissible temperature, switches to the limiting cooling mode. When reducing the temperature of the processor, the refoiss again translates the cooler for the minimum speed. The remaining fans support manually set.

Figure 4. Adjustment scheme with refusal.

The basis of the node controlling the operation of computer fans, the DA3 integral timer and the VT3 field transistor. Based on the timer, a pulse generator was assembled with a pulse frequency of 10-15 Hz. The wellness of these pulses can be changed using a R5 trimming resistor, which is part of the R5-C2 RC chain. Due to this, you can smoothly change the speed of rotation of the fans while maintaining necessary magnitude Current at the time of start.

The C6 capacitor carries out smoothing pulses, thanks to which the rotors of the engines rotate softer, without making clicks. These fans are connected to the XP2 output.

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

First, the thermostat. When choosing a scheme, such factors were taken into account as its simplicity, the availability of elements necessary for the assembly (radio components), especially used as thermal sensors, the manufacturability of the assembly and installation in the BP housing.

According to these criteria, the most successful, in our opinion, was the scheme of V. Portunov. It allows you to reduce the wear of the fan and reduce the noise level created by it. The circuit of this automatic fan speed controller is shown in Fig. 1. The temperature sensor serves VD1- VD4 diodes included in reverse direction In the circuit of the base transistor VT1, VT2. The choice as a sensor of diodes led to the dependence of their back current from the temperature, which has a more pronounced character than a similar dependence of the resistance of thermistors. In addition, the glass housing of these diodes allows you to do without any dielectric pads when installed on the heat sink of power supply transistors. An important role was played by the prevalence of diodes and their accessibility for radio amateurs.

The R1 resistor eliminates the possibility of failure of VTI transistors, VT2 in the case of a thermal breakdown of diodes (for example, when the fan electric motor is jammed). His resistance is chosen based on the extreme permissible meaning Current database VT1. R2 Resistor Defines the regulator's trigger threshold.
Fig.1

It should be noted that the number of temperature sensor diodes depends on the static transmission coefficient of the composite transistor VT1, VT2. If, with the indicated NA, the resistance diagram of the resistor R2, room temperature and power on the fan impeller is fixed, the number of diodes should be increased. It is necessary to ensure that after supplying the supply voltage, it confidently started to rotate with a small frequency. Naturally, if with four sensor diodes, the speed of rotation is too high, the number of diodes should be reduced.

The device is mounted in the power supply housing. The conclusions of the VD1-VD4 diodes are soldered together, placing their housings in one plane close to each other, the resulting block is glued with BF-2 glue (or any other heat-resistant, for example, epoxy) to the heat sink of high-voltage transistors from the reverse side. The transistor VT2 C soldered to its conclusions R1, R2 resistors and the VT1 transistor (Fig. 2) is installed with an emiter with a hole "+12 in the fan" of the BP board (the red wire from the fan was connected there. The device's establishment is reduced to the recruitment of the resistor R2 after 2 .. 3 minutes after turning on the PC and warm-up transistors of BP. Temporarily replacing R2 variables (100-150 com), it is picking up such resistance so that the heat sinks of the power supply of the power supply of the power supply are heated at no more than 40 ºС.
To avoid defeat electric shock (Heat sinks are under high voltage!) "Measure" the temperature to the touch can only turn off the computer.

A simple and reliable scheme suggested I. Lavrushov (UA6HJQ). The principle of its work is the same as in the previous scheme, however, the NTC thermistor is applied as a temperature sensor (nominal 10 comes uncritical). The transistor in the scheme is selected type Kt503. As determined by experimentally, its work is more stable than other types of transistors. The trimming resistor is desirable to apply a multi-turn, which will make it possible to more accurately adjust the temperature threshold of the transistor and, accordingly, the frequency of rotation of the fan. The thermistor is glued to the diode assembly of 12 V. in the absence of it can be replaced by two diodes. More powerful consumption current fans greater than 100 mA should be connected through a compound transistor scheme (second transistor Kt815).

Fig. 3.

The schemes of the other two, relatively simple and inexpensive regulators of the rotational speed of the Fan fans, are often brought on the Internet (cqham.ru). Their feature is that the integral stabilizer TL431 is used as the threshold element. It is quite simple to "extract" this chip in the disassembly of the old BP of the ATX PC.

The author of the first scheme (Fig. 4) Ivan Shore (RA3WDK). Upon repetition, the expediency was revealed as a rapid resistor R1 to apply a multi-turn of the same nominal. The thermistor is attached to the radiator of the cooled diode assembly (or on its body) through the thermal chaser of the CCT-80.

Fig.4

A similar scheme, but on two included parallel to CT503 (instead of one KT815) applied Alexander (RX3DUR). With the numbers indicated in the scheme (Fig. 5), the nominal details on the fan flows 7B, rising when the thermistor is heated. CT503 transistors can be replaced by import 2SC945, all 0.25W resistors.

A more complex circuit of the cooling fan speed regulator is described in. For a long time, it successfully applies in another BP. Unlike the prototype, television transistors are applied in it. I will depart readers to the article on our website "Another universal BP" and the archive, which presents a printed circuit board (Fig. 5 in the archive) and a coffee source. The role of the radiator of the adjustable transistor T2 on it performs the free plot of foil left on the front side of the board. This scheme allows, in addition to automatically increasing the frequency of fan speed when the radiator is heated by the radiator of the cooled transistors of the BP or diode assembly, to set the minimum rotational threshold frequency manually, up to a maximum.
Fig.6.

Cooling fans are now in many household appliances, be it computers, music centers, home theaters. They are good, copier with their task, cooled the heating elements, but they are published in this case, and very annoying noise. This is especially critical in music centers And home theaters, because the noise of the fan can prevent enjoy your favorite music. Manufacturers often save and connect cooling fans directly to power, from which they are always rotating with maximum revolutions, regardless of whether cooling is required in this moment, or not. It is easy to solve this problem simply - to embed your own automatic circulator speed control. It will monitor the temperature of the radiator and only if necessary, turn on cooling, and if the temperature continues to rise, the regulator will increase the cooler speed up to the maximum. In addition to the reduction of noise, such a device will significantly increase the service life of the fan itself. It is also possible to use it, for example, when creating homemade powerful amplifiers, power supplies, or other electronic devices.

Scheme

The scheme is extremely simple, contains only two transistors, a pair of resistors and a thermistor, but, nevertheless, it works great. M1 on the scheme - a fan whose revisions will be adjusted. The scheme is intended for the use of standard coolers on a voltage of 12 volts. VT1 - Little powerful N-P-N Transistor, for example, KT3102B, BC547B, KT315B. It is advisable to use transistors with a gain of 300 and more. VT2 is a powerful N-P-N transistor, it is it that switches the fan. You can apply inexpensive domestic KT819, KT829, again, it is desirable to choose a transistor with a large gain coefficient. R1 is a thermistor (also called a thermistor), key link scheme. It changes its resistance depending on temperature. It will suit any NTC-thermistor with a resistance of 10-200 com, for example, domestic MMT-4. The rating of the R2 trigger resistor depends on the selection of the thermistor, it should be 1.5 - 2 times more. This resistor sets the fan turning threshold.

Manufacture of a regulator

The scheme can be easily assembled by mounted installation, but can be made pCBHow I did. To connect the power wires and the fan itself, terminals are provided on the board, and the thermistor is displayed on the wiring pair and is attached to the radiator. For greater thermal conductivity, it is necessary to attach it using a thermal column. The board is performed by the LUT method, below presents several photographs of the process.

Download fee:

(Dropping: 833)

After making the board in it, the details are usually searched, first small, then large. It is worth paying attention to the base of the transistors to get them correctly. After completing the assembly, the fee must be laundered from the remnants of the flux, ring the tracks, make sure that the installation is correct.

Setting

Now you can connect the fan to the board and gently feed power by installing a rapid resistor to the minimum position (the Base VT1 is tightened to the ground). The fan should not rotate. Then, smoothly turning R2, you need to find such a moment when the fan starts to rotate slightly on the minimum turnover and turn the trimmer is completely slightly back so that it stops rotating. Now you can check the operation of the regulator - it is enough to make a finger to the thermistor and the fan will begin to rotate again. Thus, when the temperature of the radiator is indiscriminately, the fan does not spin, but it should be climbing at least a little bit, it will immediately start cooling.

Manage the cooler (thermocontrol fan in practice)

Those who use the computer every day (and especially every night) is very close to the idea of \u200b\u200bSilent PC. This topic dedicated to many publications, however, today the problem of noise produced by the computer is far from solving. One of the main sources of noise in the computer is a processor cooler.

When using cooling software, such as CPUIDLE, Waterfall and others, or when working in operating windows systems NT / 2000 / XP and Windows 98SE The average processor temperature in the IDLE mode is significantly reduced. However, the cooler fan does not know and continues to work in full force with the maximum level of noise. Of course exist special utilities (Speedfan, for example), which can control fan turnover. However, such programs work far from all motherboards. But even if they work, then you can say, not very reasonable. So, at the stage of the computer loading, even with a relatively cold processor, the fan operates on its maximum turns.

The output of the position is actually simple: To control the fan impeller, you can build an analog controller with a separate thermal sensor fixed on the cooler radiator. Generally speaking, there are countless circuitry solutions for such thermostators. But our attention deserves the two most simple schemes of the thermocontrolle, with whom we will now understand.

Description

If the cooler does not have the output of the tip (or this output is simply not used), you can build the most simple schemawhich contains the minimum number of parts (Fig. 1).

Fig. one. Schematic scheme First version of the thermostat

Since the "fours", a regulator collected according to such a scheme was used. It is built on the basis of the LM311 comparator chip (domestic analog - kr554s3). Despite the fact that the comparator is applied, the regulator provides a linear, not key regulation. A reasonable question may arise: "How it happened that a comparator is used for linear regulation, and not an operational amplifier?". Well, there are several reasons for this. First, this comparator has a relatively powerful open collector output, which allows you to connect a fan to it without additional transistors. Secondly, due to the fact that the input cascade is built on p-N-P transistorah, which are included according to a circuit with a common manifold, even with single-polar diet, you can work with low input stresses that are practically on the potential of the Earth. Thus, when using a diode as a thermal sensor, you need to work with the potentials of the inputs of only 0.7 B, which does not allow most of the operating amplifiers. Thirdly, any comparator can be covered with negative feedback, then it will work as operating amplifiers work (by the way, it is such an inclusion and used).

Diodes are very often used as a temperature sensor. Silicon diode p-N Transition It has a temperature coefficient of voltage approximately -2.3 mV / ° C, and a direct voltage drop is about 0.7 V. Most diodes have a housing that is completely inappropriate for their fixing on the radiator. At the same time, some transistors are specifically adapted for this. One of these are domestic transistors KT814 and KT815. If a similar transistor to scout to the radiator, the collector of the transistor will turn out to be electrically connected with it. To avoid trouble, in the scheme where this transistor is used, the collector must be grounded. Based on this, the P-N-P transistor is needed for our thermal sensor, for example, KT814.

You can, of course, just use one of the transistor transitions as a diode. But here we can show a mixture and go more slyly :) The fact is that the temperature coefficient at the diode is relatively low, and the small stress changes are sufficiently difficult. There are noises, and interference, and the instability of the supply voltage. Therefore, often, in order to increase the temperature coefficient of the temperature sensor, the chain of sequentially turned on diodes is used. In such a chain, the temperature coefficient and the direct drop in the voltage increase in proportion to the number of diodes turned on. But we do not have a diode, but a whole transistor! Indeed, adding only two resistors, you can build a two-meter on the transistor, whose behavior will be equivalent to the behavior of the chain of diodes. What is done in the described thermostat.

The temperature coefficient of such a sensor is determined by the ratio of resistors R2 and R3 and is equal to C CVD * (R3 / R2 + 1), where T CVD is the temperature coefficient of one P-n of the transition. It is impossible to increase the ratio of resistors to infinity, since, together with the temperature coefficient, a direct voltage drop is growing, which can easily achieve supply voltage, and then the scheme will not work. In the described regulator, the temperature coefficient is selected equal to about -20 MV / ° C, while the direct voltage drop is about 6 V.

The VT1R2R3 temperature sensor is included in the measuring bridge, which is formed by resistors R1, R4, R5, R6. The bridge feeds from the parametric voltage stabilizer VD1R7. The need to use the stabilizer is caused by the fact that the supply voltage is +12 to inside the computer quite unstable (in the pulse power source, only group stabilization of the output levels is +5 V and +12 V).

The inspection voltage of the measuring bridge is applied to the inputs of the comparator, which is used in linear mode due to the action of negative feedback. R5 rapid resistor allows you to shift the adjustment characteristic, and the change in the rating of feedback resistor R8 allows you to change its slope. C1 and C2 tanks provide the stability of the regulator.

The regulator is mounted on a dumping board, which is a piece of one-sided foil fiberglass (Fig.2).

Fig. 2. Mounting diagram of the first version of the thermostat

To reduce the size of the board, it is advisable to use SMD elements. Although, in principle, you can do the usual elements. The board is fixed on the cooler radiator using the VT1 transistor fastening screw. To do this, in the radiator, a hole should be done in which it is desirable to chop the M3 thread. In the extreme case, you can use a screw and nut. When choosing a place on the radiator to secure the board, you need to take care of the availability of a trimmed resistor when the radiator will be inside the computer. In this way, you can attach a fee only to the radiators of the "classic" design, but the mounting of it to the cylindrical radiators (for example, like ORB) can cause problems. A good thermal contact with the radiator should have only a thermal sensor transistor. Therefore, if the entire board does not fit entirely on the radiator, it can be limited to the installation of one transistor on it, which in this case is connected to the board using wires. The board itself can be located at any convenient location. Fasten the transistor on the radiator is easy, you can even insert it between the ribs, ensuring thermal contact with the help of heat-conducting paste. Another way to fasten is the use of glue with good thermal conductivity.

When installing the thermal sensor transistor to the radiator, the latter turns out to be connected to the ground. But in practice, this does not cause special difficulties, at least in systems with Celeron and PentiumIII processors (part of their crystal, in contact with the radiator, has no electrical conductivity).

Electrically, the board is included in the fan wire break. If you wish, you can even install the connectors so as not to cut the wires. The correctly collected scheme practically does not require configuration: only you need to install the desired frequency of rotation of the fan impeller, corresponding to the current temperature. In practice, each specific fan has a minimum supply voltage at which the impeller begins to rotate. Configuring a regulator, you can achieve a fan rotation at minimally possible revs at a radiator temperature, say, close to the surrounding. However, given the fact that the thermal resistance of different radiators is very different, it may be necessary to adjust the inclination of the control characteristics. The slope of the characteristic is set by the R8 resistor rating. The resistor denomination can be between 100 to 1 m. The more this nominal, the more at the lowest temperature of the radiator, the fan will achieve maximum revolutions. In practice, very often the processor load is read more. This is observed, for example, when working in text editors. When using a software cooler at such moments, the fan can work on significantly reduced revs. That is what should provide a regulator. However, with an increase in the processor load, its temperature rises, and the regulator must gradually raise the fan supply voltage to the maximum, without allowing the overheating of the processor. The temperature of the radiator when complete fan turns are achieved, should not be very high. Specific recommendations are difficult, but at least this temperature should "fall behind" at 5 - 10 degrees from critical when the stability of the system is already disturbed.

Yes, one more thing. The first inclusion of the scheme is desirable to produce from any external source Nutrition. Otherwise, in the case of a short circuit in the scheme, connecting the circuit to the connector motherboard May cause its damage.

Now the second version of the scheme. If the fan is equipped with a bandwidth, then you can not turn on the regulating transistor in the "earth" wire of the fan. Therefore, the internal transistor of the comparator is not suitable here. In this case, an additional transistor is required, which will be adjusted by the +12 chain in the fan. In principle, it was possible to simply finalize the scheme on the comparator, but for a variety, a scheme was made, assembled on transistors, which was even smaller in volume (Fig. 3).

Fig. 3. Schematic diagram of the second version of the thermostat

Since the board placed on the radiator heats up all entirely, then predict the behavior of the transistor scheme is quite difficult. Therefore, it took a preliminary simulation of the scheme using PSPICE package. The modeling result is shown in Fig. four.

Fig. 4. Scheme modeling result in PSpice package

As can be seen from the figure, the fan power voltage is linearly raised from 4 at at 25 ° C to 12 V at 58 ° C. Such behavior of the regulator, in general, meets our requirements, and on this stage of modeling was completed.

Circuits of these two variants of the thermostat have a lot in common. In particular, the temperature sensor and the measuring bridge are completely identical. The difference lies only in the bridge loss voltage amplifier. In the second embodiment, this voltage enters the Cascade on the VT2 transistor. The transistor base is an inverting input of the amplifier, and the emitter is non-converting. Next, the signal goes to the second amplifying cascade On the VT3 transistor, then on the output stage on the VT4 transistor. Appointment of containers is the same as in the first version. Well, the control circuit of the regulator is shown in Fig. five.

Fig. 5. Mounting scheme of the second version of the thermostat

The design is similar to the first option, except that the board has a little smaller dimensions. In the diagram, you can apply conventional (non-SMD) items, and transistors - any low-power, since the current consumed by the fans usually does not exceed 100 mA. I note that this scheme can also be used to control fans with a large value of consumed current, but in this case the VT4 transistor must be replaced with a more powerful one. As for the output of the tachometer, the TG tach generator signal passes directly through the regulator board and enters the connector of the motherboard. The method of setting up the second version of the regulator is no different from the technique shown for the first option. Only in this embodiment, the setting is made by the R7 stroke resistor, and the slope of the characteristic is set by the R12 resistor ratio.

conclusions

The practical use of the thermostat (together with software cooling) showed its high efficiency in terms of reducing the noise produced by the cooler. However, the cooler itself should be quite effective. For example, in a Celeron566 processor, operating at 850 MHz, a box cooler no longer provided sufficient cooling efficiency, so even with an average processor load, the regulator lifted the supply voltage of the cooler to maximum value. The situation was corrected after replacing the fan to a more productive, with an increased diameter of the blades. Now the fan is full of turnover only with a long-term operation of the processor with almost 100% loading.

This controller can be used wherever the automatic adjustment of the fan rotation speed is necessary, namely, amplifiers, computers, power supplies, and other devices.

Device scheme

The voltage created by the voltage divider R1 and R2 sets the initial speed of rotation of the fan (when the thermistor is cold). When the resistor is heated, its resistance drops and the voltage of the transistor VT1 is increasing, and the voltage of the VT2 transistor ehmiter increases, therefore, the voltage of the fan power supply and its rotation speed increases.

Device establishment

Some fans can be unstable, or do not start at all under reduced supply voltage, then you need to select resistance resistors R1 and R2. Usually new fans are launched without problems. To improve the launch, you can turn on the chain of a sequentially connected resistor on 1 com and electrolytic capacitor between + power and the Base VT1, parallel to the thermistor. In this case, during the charge of the capacitor, the fan will operate on maximum speed, and when the capacitor charges the fan speed to fall to the value of the R1 and R2 installed by the divider. This is especially useful when using old fans. The capacitance of the capacitor and the resistance are approximate, you may have to choose them when setting up.

Making changes to the scheme

Appearance of the device

Montage

List of radio elements

Designation	A type	Nominal	number	Note	Score	My notebook
VT1	Bipolar transistor	Kt315b	1			In notebook
VT2.	Bipolar transistor	KT819A.	1			In notebook
R1	MMT-4 thermistor	10 com	1	Select when setting up		In notebook
R2.	Resistor	12 com	1	SMD 1206.		In notebook
R3	Resistor