The principle of operation is simple... the thermistor is pressed against the radiator with thermal paste and a bracket, the maximum permissible temperature is set, and as soon as the radiator heats up to this temperature, the fan turns on and cools the radiator until the temperature at the thermistor drops.
An excellent solution for cooling the amplifier, because if you listen to music at a low volume, fan cooling is not needed, there is no need to create unnecessary noise. And as soon as the amplifier operates at high power and the radiator heats up to the maximum permissible temperature, the fan turns on. The maximum permissible temperature is set either “by touch” or using a thermometer. In my case, the “touch” method was quite enough.
Scheme:
Photo:
And now according to the scheme. The trimmer resistor regulates the fan threshold. Thermistor of Soviet origin, costs a penny:
The operational amplifier LM324 (4-channel op-amp) can be replaced with LM358 (dual-channel op-amp) and you will gain in size.. but they do not differ in price... The fan is a regular computer one at 12V... The transistor can be replaced with any similar structure. There is nothing more to add...
Printed circuit board four-channel, transistors were replaced with more powerful BC639, I don’t answer stupid questions “why the board doesn’t match the circuit diagram”:
Radiator mounting option.
We control the fan in the computer - the cooler (thermal control - in practice)
For those who use a computer every day (and especially every night), the idea of Silent PC is very close to its heart. Many publications are devoted to this topic, but today the problem of noise produced by a computer is far from being solved. One of the main sources of noise in a computer is the processor cooler.
When using software cooling tools such as CpuIdle, Waterfall and others, or when working in the Windows NT/2000/XP and Windows 98SE operating systems, the average processor temperature in Idle mode decreases significantly. However, the cooler fan does not know this and continues to work at full strength with maximum noise level. Of course, there are special utilities (SpeedFan, for example) that can control fan speed. However, such programs do not work on all motherboards. But even if they do work, it can be said that they are not very smart. Thus, when the computer is booting, even with a relatively cold processor, the fan operates at its maximum speed.
The way out of the situation is actually simple: to control the speed of the fan impeller, you can build an analog regulator with a separate temperature sensor attached to the cooler radiator. Generally speaking, there are countless circuit solutions for such thermostats. But the two simplest thermal control schemes deserve our attention, which we will now deal with.
Description
If the cooler does not have a tachometer output (or this output is simply not used), you can build the simplest circuit that contains a minimum number of parts (Fig. 1).
Rice. 1. Schematic diagram of the first version of the thermostat
Since the days of the “fours”, a regulator assembled according to this scheme has been used. It is built on the basis of the LM311 comparator microcircuit (the domestic analogue is KR554CA3). Despite the fact that a comparator is used, the regulator provides linear rather than switching regulation. A reasonable question may arise: “How did it happen that a comparator is used for linear regulation, and not an operational amplifier?” Well, there are several reasons for this. Firstly, 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 stage is built on pnp transistors, which are connected in a circuit with a common collector, even with a unipolar supply it is possible to work with low input voltages, located almost at ground potential. So, when using a diode as a temperature sensor, you need to operate at input potentials of only 0.7 V, which most operational amplifiers do not allow. Thirdly, any comparator can be covered by negative feedback, then it will work the way operational amplifiers work (by the way, this is exactly the connection that was used).
Diodes are often used as temperature sensors. For a silicon diode, the p-n junction has a voltage temperature coefficient of approximately -2.3 mV/°C, and a forward voltage drop of about 0.7 V. Most diodes have a housing that is completely unsuitable for mounting them on a radiator. At the same time, some transistors are specially adapted for this. One of these are domestic transistors KT814 and KT815. If such a transistor is screwed to a radiator, the collector of the transistor will be electrically connected to it. To avoid trouble, in the circuit where this transistor is used, the collector must be grounded. Based on this, our temperature sensor needs a pnp transistor, for example, KT814.
You can, of course, simply use one of the transistor junctions as a diode. But here we can be smart and do something more cunning :) The fact is that the temperature coefficient of the diode is relatively low, and measuring small voltage changes is quite difficult. Here noise, interference, and instability of the supply voltage interfere. Therefore, in order to increase the temperature coefficient of a temperature sensor, a chain of diodes connected in series is often used. For such a chain, the temperature coefficient and forward voltage drop increase in proportion to the number of connected diodes. But we don’t have a diode, but a whole transistor! Indeed, by adding just two resistors, you can build a two-terminal network on a transistor, the behavior of which will be equivalent to the behavior of a chain of diodes. This is 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 Tcvd*(R3/R2+1), where Tcvd is the temperature coefficient of one p-n junction. It is impossible to increase the resistor ratio indefinitely, since along with the temperature coefficient the forward voltage drop also increases, which can easily reach the supply voltage, and then the circuit will no longer work. In the described regulator, the temperature coefficient is selected to be approximately -20 mV/°C, while the forward voltage drop is about 6 V.
The temperature sensor VT1R2R3 is included in the measuring bridge, which is formed by resistors R1, R4, R5, R6. The bridge is powered by a parametric voltage stabilizer VD1R7. The need to use a stabilizer is due to the fact that the +12 V supply voltage inside the computer is quite unstable (in a switching power supply, only group stabilization of the output levels +5 V and +12 V is carried out).
The unbalance 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. Trimmer resistor R5 allows you to shift the adjustment characteristic, and changing the value of feedback resistor R8 allows you to change its slope. Capacities C1 and C2 ensure the stability of the regulator.
The regulator is mounted on a breadboard, which is a piece of one-sided foil fiberglass (Fig. 2).
Rice. 2. Installation 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 get by with ordinary elements. The board is secured to the cooler radiator using a screw securing the transistor VT1. To do this, you should make a hole in the radiator, in which it is advisable to cut an M3 thread. As a last resort, 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 accessibility of the trimming resistor when the radiator is inside the computer. In this way, you can attach the board only to radiators of a “classical” design, but attaching it to cylindrical radiators (for example, like Orbs) can cause problems. Only the temperature sensor transistor should have good thermal contact with the radiator. Therefore, if the entire board does not fit on the radiator, you can limit yourself to installing one transistor on it, which in this case is connected to the board using wires. The board itself can be placed in any convenient place. It is not difficult to attach the transistor to the radiator; you can even simply insert it between the fins, ensuring thermal contact using heat-conducting paste. Another method of fastening is to use glue with good thermal conductivity.
When installing a temperature sensor transistor on a radiator, the latter is connected to ground. But in practice this does not cause any particular difficulties, at least in systems with Celeron and PentiumIII processors (the part of their crystal in contact with the heatsink has no electrical conductivity).
Electrically, the board is connected to the fan wires. If desired, you can even install connectors so as not to cut the wires. A correctly assembled circuit requires practically no adjustment: you only need to use trimming resistor R5 to set the required fan impeller rotation speed corresponding to the current temperature. In practice, each specific fan has a minimum supply voltage at which the impeller begins to rotate. By adjusting the regulator, you can achieve fan rotation at the lowest possible speed at a radiator temperature, say, close to ambient. However, given that the thermal resistance of different heat sinks varies greatly, adjustments to the control slope may be necessary. The slope of the characteristic is set by the value of resistor R8. The resistor value can range from 100 K to 1 M. The higher this value, the lower the radiator temperature the fan will reach maximum speed. In practice, very often the processor load is only a few percent. This is observed, for example, when working in text editors. When using a software cooler at such moments, the fan can operate at significantly reduced speed. This is exactly what the regulator should provide. However, as the processor load increases, its temperature rises, and the regulator must gradually increase the fan supply voltage to the maximum, preventing the processor from overheating. The radiator temperature when full fan speed is reached should not be very high. It is difficult to give specific recommendations, but at least this temperature should “lag” by 5 - 10 degrees from the critical temperature, when the stability of the system is already compromised.
Yes, one more thing. It is advisable to first turn on the circuit from some external power source. Otherwise, if there is a short circuit in the circuit, connecting the circuit to the motherboard connector may damage it.
Now the second version of the scheme. If the fan is equipped with a tachometer, then it is no longer possible to connect the control transistor to the ground wire of the fan. Therefore, the internal comparator transistor is not suitable here. In this case, an additional transistor is required, which will regulate the +12 V fan circuit. In principle, it was possible to simply slightly modify the circuit on the comparator, but for variety, a circuit assembled with transistors was made, which turned out to be even smaller in volume (Fig. 3).
Rice. 3. Schematic diagram of the second version of the thermostat
The schematic diagrams of these two thermostat options have much in common. In particular, the temperature sensor and the measuring bridge are completely identical. The only difference is the bridge imbalance voltage amplifier. In the second option, this voltage is supplied to the cascade on transistor VT2. The base of the transistor is the inverting input of the amplifier, and the emitter is the non-inverting input. Next, the signal goes to the second amplifier stage on transistor VT3, then to the output stage on transistor VT4. The purpose of the containers is the same as in the first option. Well, the wiring diagram of the regulator is shown in Fig. 5.
Rice. 5. Installation diagram of the second version of the thermostat
The design is similar to the first option, except that the board is slightly smaller. The circuit can use ordinary (non-SMD) elements, and any low-power transistors, since the current consumed by fans usually does not exceed 100 mA. I note that this circuit can also be used to control fans with a large current consumption, but in this case the VT4 transistor must be replaced with a more powerful one. As for the tachometer output, the TG tachogenerator signal directly passes through the regulator board and goes to the motherboard connector. The method for setting up the second version of the regulator is no different from the method given for the first option. Only in this option, the adjustment is made using trimming resistor R7, and the slope of the characteristic is set by the value of resistor R12.
conclusions
Practical use of the thermostat (together with software cooling tools) has shown its high efficiency in terms of reducing the noise produced by the cooler. However, the cooler itself must be quite efficient. For example, in a system with a Celeron566 processor operating at 850 MHz, the box cooler no longer provided sufficient cooling efficiency, so even with an average processor load, the regulator raised the cooler supply voltage to the maximum value. The situation was corrected after replacing the fan with a more efficient one, with an increased blade diameter. Now the fan reaches full speed only when the processor is running for a long time at almost 100% load.
The circuit proposed below provides simple adjustment of fan speed without speed control. The device uses domestic transistors KT361 and KT814.
Fig.1 Schematic diagram of the regulator.
Structurally, the board is placed directly in the power supply, on one of the radiators and has additional seats for connecting a second sensor (external) and the ability to add a zener diode, which limits the minimum voltage supplied to the fan.
Fig.2 Appearance and topology of the printed circuit board.
Cooler rotation indicator
The circuit reacts both to a complete stop of the cooler and to a loss of revolutions. Indication is provided by the "Power" LED, which is usually connected to the well-known "Power led" connector on the motherboard. The operating logic is simple: if the LED is on, everything is fine, if not, it’s time to remove the cooler for “prevention.” The circuit is very simple and, if desired, can be equipped with an additional sound alarm or an additional key that generates a “Reset” or “Power Off” signal.
To be continued...
Source: evm.wallst.ru
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As you know, active cooling systems with fans are now used instead of large and heavy radiators. In the era of microprocessors and microcontrollers, fans are controlled mainly using PWM (Pulse-Width Modulation), that is, the width of the pulse supplied to the fan is regulated. In some cases, it is not a good idea to drive a fan in pulse mode due to the increased risk of interference that may occur in other parts of the circuit. Then we will need such an analog speed controller.
This circuit was designed for active cooling and allows you to control the rotation of 4 fans at once. The temperature sensor here is a BD139 transistor, since accuracy is not important, and the use of a transistor of this type allows us to reduce the cost of the entire thermal control system.
In addition, the housing of this transistor is easily screwed to the heatsink, providing good thermal contact. The speed control consists of a smooth change in the output voltage, therefore it does not create any electrical interference, making it ideal even for low-noise power amplifiers. When listening quietly to the UMZCH, where the power loss is low and the radiator is cold, you can’t hear the fans at all.
Schematic diagram of the regulator
Schematic diagram of an analog motor speed controller The basis is a dual operational amplifier U1 (LM358). The choice of this operational amplifier is dictated not only by its low price and availability, but, above all, by the ability to operate at output voltages close to the lower power rail, that is, near ground potential.
The first half of the op-amp (U1A) operates in a differential amplifier configuration with a gain of 1. The gain is set using resistors R4-R7 (100k) and can be changed if necessary by changing the ratio of R7/R4 while maintaining the same ratio of R6/R5.
The temperature sensor is transistor T1 (BD139), or rather its base-collector junction, connected in the direction of the desired conductivity. Resistor R1 (22k) limits the current that flows through T1. The voltage at the base of transistor T1 at room temperature will be within 600 mV and, as in a typical PN connector, will change with increasing temperature by about 2.3 mV/K.
Capacitor C1 (100nF) filters the voltage, which is then applied to resistor R4, that is, the input of differential amplifier U1A. The divider is built on R2 (22k), P1 (5k) and R3 (120R) and it allows you to regulate the voltage that is supplied to resistor R5 - the non-inverted input of amplifier U1A. Capacitor C2 (100nF) filters the voltage. In the simplest case, using potentiometer P1, it is necessary to set the voltage on C2 equal to the voltage on C1 at room temperature. This will cause the output voltage of amplifier U1A (pin 1) to be 0 (at room temperature) and will increase by approximately 2.3 mV/K with increasing temperature.
The second half of the microcircuit (U1B) is an amplifier with Ku 61, the value of which is determined by elements R9 (120k) and R8 (2k). The gain is set by the ratio of these resistors increased by 1.
The actuator is a Darlington transistor T2 (TIP122), which acts as a voltage buffer with a high maximum output current. Resistor R10 (330R) limits the base current of the transistor.
The voltage from the output of U1A increases by more than 60 times, and then goes to transistor T2. The current flowing through the transistor is supplied through diodes D1-D4 (1N4007) to connectors GP2-GP5, to which the fans are connected. Capacitors C5-C8 (100uF) filter the fan power supply and, in addition, eliminate the noise that the fans generate during operation.
About the thermal controller power supply. The system is powered by a voltage of 15 V with a current corresponding to the ratings of the motors. The supply voltage is supplied to connector GP1, and capacitors C3 (100nF) and C4 (100uF) are its filters.
Circuit assembly
Installation of the motor control system is not difficult; soldering should begin by installing one jumper. The order of connecting the remaining elements to the board is arbitrary, but it is convenient to start with resistors and LEDs, and ultimately with electrolytic capacitors and connectors. The installation method of transistor T2 and temperature sensor T1 is very important.
It should be borne in mind that transistor T2 operates linearly, so a large loss power is generated, which is directly converted into heat. The board is designed so that it can be screwed to a heatsink. Transistors T1 and T2 must be mounted on long leads and bent so that they can be installed on the radiator. Don't forget the gaskets to isolate them electrically from the radiator.
Launch and setup
A circuit assembled from serviceable components should work immediately. You just need to remember to adjust the threshold using potentiometer P1 so that the fans spin slowly at room temperature. The voltage on the fan in this mode is about 4 V and reaches 12 V for a temperature of 80 degrees, that is, with an increase of about 60 degrees.
Knowing the required range of output voltage changes and the corresponding range of temperature changes, you can calculate the gain of op-amp U1B. This will lead to a change in the output voltage range, expressed in millivolts, and therefore to a change in temperature from a constant value of 2.3 mV/K. Then you will only need to use potentiometer P1 to adjust the operating point such that at room temperature the output voltage is equal to that required when calculating the lower limit.
Managing the cooler (thermal control of fans in practice)
For those who use a computer every day (and especially every night), the idea of Silent PC is very close to its heart. Many publications are devoted to this topic, but today the problem of noise produced by a computer is far from being solved. One of the main sources of noise in a computer is the processor cooler.
When using software cooling tools such as CpuIdle, Waterfall and others, or when working in the Windows NT/2000/XP and Windows 98SE operating systems, the average processor temperature in Idle mode decreases significantly. However, the cooler fan does not know this and continues to work at full strength with maximum noise level. Of course, there are special utilities (SpeedFan, for example) that can control fan speed. However, such programs do not work on all motherboards. But even if they do work, it can be said that they are not very smart. Thus, when the computer is booting, even with a relatively cold processor, the fan operates at its maximum speed.
The way out of the situation is actually simple: to control the speed of the fan impeller, you can build an analog regulator with a separate temperature sensor attached to the cooler radiator. Generally speaking, there are countless circuit solutions for such thermostats. But the two simplest thermal control schemes deserve our attention, which we will now deal with.
Description
If the cooler does not have a tachometer output (or this output is simply not used), you can build the simplest circuit that contains a minimum number of parts (Fig. 1).
Rice. 1. Schematic diagram of the first version of the thermostat
Since the days of the “fours”, a regulator assembled according to this scheme has been used. It is built on the basis of the LM311 comparator microcircuit (the domestic analogue is KR554CA3). Despite the fact that a comparator is used, the regulator provides linear rather than switching regulation. A reasonable question may arise: “How did it happen that a comparator is used for linear regulation, and not an operational amplifier?” Well, there are several reasons for this. Firstly, 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 stage is built on pnp transistors, which are connected in a circuit with a common collector, even with a unipolar supply it is possible to work with low input voltages, located almost at ground potential. So, when using a diode as a temperature sensor, you need to operate at input potentials of only 0.7 V, which most operational amplifiers do not allow. Thirdly, any comparator can be covered by negative feedback, then it will work the way operational amplifiers work (by the way, this is exactly the connection that was used).
Diodes are often used as temperature sensors. For a silicon diode, the p-n junction has a voltage temperature coefficient of approximately -2.3 mV/°C, and a forward voltage drop of about 0.7 V. Most diodes have a housing that is completely unsuitable for mounting them on a radiator. At the same time, some transistors are specially adapted for this. One of these are domestic transistors KT814 and KT815. If such a transistor is screwed to a radiator, the collector of the transistor will be electrically connected to it. To avoid trouble, in the circuit where this transistor is used, the collector must be grounded. Based on this, our temperature sensor needs a pnp transistor, for example, KT814.
You can, of course, simply use one of the transistor junctions as a diode. But here we can be smart and do something more cunning :) The fact is that the temperature coefficient of the diode is relatively low, and measuring small voltage changes is quite difficult. Here noise, interference, and instability of the supply voltage interfere. Therefore, in order to increase the temperature coefficient of a temperature sensor, a chain of diodes connected in series is often used. For such a chain, the temperature coefficient and forward voltage drop increase in proportion to the number of connected diodes. But we don’t have a diode, but a whole transistor! Indeed, by adding just two resistors, you can build a two-terminal network on a transistor, the behavior of which will be equivalent to the behavior of a chain of diodes. This is 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 T cvd *(R3/R2+1), where T cvd is the temperature coefficient of one p-n junction. It is impossible to increase the resistor ratio indefinitely, since along with the temperature coefficient the forward voltage drop also increases, which can easily reach the supply voltage, and then the circuit will no longer work. In the described regulator, the temperature coefficient is selected to be approximately -20 mV/°C, while the forward voltage drop is about 6 V.
The temperature sensor VT1R2R3 is included in the measuring bridge, which is formed by resistors R1, R4, R5, R6. The bridge is powered by a parametric voltage stabilizer VD1R7. The need to use a stabilizer is due to the fact that the +12 V supply voltage inside the computer is quite unstable (in a switching power supply, only group stabilization of the output levels +5 V and +12 V is carried out).
The unbalance 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. Trimmer resistor R5 allows you to shift the adjustment characteristic, and changing the value of feedback resistor R8 allows you to change its slope. Capacities C1 and C2 ensure the stability of the regulator.
The regulator is mounted on a breadboard, which is a piece of one-sided foil fiberglass (Fig. 2).
Rice. 2. Installation 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 get by with ordinary elements. The board is secured to the cooler radiator using a screw securing the transistor VT1. To do this, you should make a hole in the radiator, in which it is advisable to cut an M3 thread. As a last resort, 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 accessibility of the trimming resistor when the radiator is inside the computer. In this way, you can attach the board only to radiators of a “classical” design, but attaching it to cylindrical radiators (for example, like Orbs) can cause problems. Only the temperature sensor transistor should have good thermal contact with the radiator. Therefore, if the entire board does not fit on the radiator, you can limit yourself to installing one transistor on it, which in this case is connected to the board using wires. The board itself can be placed in any convenient place. It is not difficult to attach the transistor to the radiator; you can even simply insert it between the fins, ensuring thermal contact using heat-conducting paste. Another method of fastening is to use glue with good thermal conductivity.
When installing a temperature sensor transistor on a radiator, the latter is connected to ground. But in practice this does not cause any particular difficulties, at least in systems with Celeron and PentiumIII processors (the part of their crystal in contact with the heatsink has no electrical conductivity).
Electrically, the board is connected to the fan wires. If desired, you can even install connectors so as not to cut the wires. A correctly assembled circuit requires practically no adjustment: you only need to use trimming resistor R5 to set the required fan impeller rotation speed corresponding to the current temperature. In practice, each specific fan has a minimum supply voltage at which the impeller begins to rotate. By adjusting the regulator, you can achieve fan rotation at the lowest possible speed at a radiator temperature, say, close to ambient. However, given that the thermal resistance of different heat sinks varies greatly, adjustments to the control slope may be necessary. The slope of the characteristic is set by the value of resistor R8. The resistor value can range from 100 K to 1 M. The higher this value, the lower the radiator temperature the fan will reach maximum speed. In practice, very often the processor load is only a few percent. This is observed, for example, when working in text editors. When using a software cooler at such moments, the fan can operate at significantly reduced speed. This is exactly what the regulator should provide. However, as the processor load increases, its temperature rises, and the regulator must gradually increase the fan supply voltage to the maximum, preventing the processor from overheating. The radiator temperature when full fan speed is reached should not be very high. It is difficult to give specific recommendations, but at least this temperature should “lag” by 5 - 10 degrees from the critical temperature, when the stability of the system is already compromised.
Yes, one more thing. It is advisable to first turn on the circuit from some external power source. Otherwise, if there is a short circuit in the circuit, connecting the circuit to the motherboard connector may damage it.
Now the second version of the scheme. If the fan is equipped with a tachometer, then it is no longer possible to connect the control transistor to the ground wire of the fan. Therefore, the internal comparator transistor is not suitable here. In this case, an additional transistor is required, which will regulate the +12 V fan circuit. In principle, it was possible to simply slightly modify the circuit on the comparator, but for variety, a circuit assembled with transistors was made, which turned out to be even smaller in volume (Fig. 3).
Rice. 3. Schematic diagram of the second version of the thermostat
Since the entire board placed on the radiator heats up, it is quite difficult to predict the behavior of the transistor circuit. Therefore, preliminary modeling of the circuit using the PSpice package was required. The simulation result is shown in Fig. 4.
Rice. 4. Result of circuit simulation in PSpice package
As can be seen from the figure, the fan supply voltage increases linearly from 4 V at 25°C to 12 V at 58°C. This behavior of the controller, in general, meets our requirements, and at this point the modeling stage was completed.
The schematic diagrams of these two thermostat options have much in common. In particular, the temperature sensor and the measuring bridge are completely identical. The only difference is the bridge imbalance voltage amplifier. In the second option, this voltage is supplied to the cascade on transistor VT2. The base of the transistor is the inverting input of the amplifier, and the emitter is the non-inverting input. Next, the signal goes to the second amplifier stage on transistor VT3, then to the output stage on transistor VT4. The purpose of the containers is the same as in the first option. Well, the wiring diagram of the regulator is shown in Fig. 5.
Rice. 5. Installation diagram of the second version of the thermostat
The design is similar to the first option, except that the board is slightly smaller. The circuit can use ordinary (non-SMD) elements, and any low-power transistors, since the current consumed by fans usually does not exceed 100 mA. I note that this circuit can also be used to control fans with a large current consumption, but in this case the VT4 transistor must be replaced with a more powerful one. As for the tachometer output, the TG tachogenerator signal directly passes through the regulator board and goes to the motherboard connector. The method for setting up the second version of the regulator is no different from the method given for the first option. Only in this option, the adjustment is made using trimming resistor R7, and the slope of the characteristic is set by the value of resistor R12.
conclusions
Practical use of the thermostat (together with software cooling tools) has shown its high efficiency in terms of reducing the noise produced by the cooler. However, the cooler itself must be quite efficient. For example, in a system with a Celeron566 processor operating at 850 MHz, the box cooler no longer provided sufficient cooling efficiency, so even with an average processor load, the regulator raised the cooler supply voltage to the maximum value. The situation was corrected after replacing the fan with a more efficient one, with an increased blade diameter. Now the fan reaches full speed only when the processor is running for a long time at almost 100% load.