How is the fan speed controlled? A simple fan speed controller. We adjust the speed of 6 coolers. Diagram
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 home computer Usually, several case fans and coolers (radiators with fans attached to them) are installed.
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:
- Large diameter fans work more efficiently than small ones.
- Maximum cooling efficiency is observed in coolers with heat pipes.
- Four-pin fans are preferred over three-pin fans.
There can only be two main reasons for excessive fan noise:
- Poor bearing lubrication. Eliminated by cleaning and new lubricant.
- 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
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First method: switching the BIOS function that regulates fan operation
Q-Fan control, Smart fan control, etc. functions supported by the part 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:
- 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.
- Open the “Power” section.
- Go to the line “Hardware Monitor”.
- Change the value of the CPU Q-Fan control and Chassis Q-Fan Control functions on the right side of the screen to “Enabled”.
- In the CPU and Chassis Fan Profile lines that appear, select one of three performance levels: enhanced (Perfomans), quiet (Silent) and optimal (Optimal).
- Press the F10 key to save the selected setting.
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In the foundation.
Peculiarities .
Axonometric diagram of ventilation.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:
- 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.
- 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.
- Connect the fan wires to the contacts of the Molex connector at the required voltage (see Fig. 1b).
An engine with a rated 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.
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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:
- Resistors heat up, wasting electricity and contributing to the heating process of the entire structure.
- The characteristics of an electric motor in different modes can vary greatly; each of them requires resistors with different parameters.
- The power dissipation of the resistors must be large enough.
Figure 3. Electronic circuit for speed control.
It is more rational to apply electronic circuit speed adjustment. 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.
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Fourth method: adjusting the fan speed using rheobass
Reobas – electronic device, which 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:
- Uninterrupted engine starting.
- 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 scheme 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 the 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.
Proportional control is the key to silence!
What is the task facing our management system? Yes, so that the propellers do not rotate in vain, so that the rotation speed depends on temperature. The hotter the device, the faster the fan rotates. Logical? Logical! We'll settle it on that.
Of course, you can bother with microcontrollers, in some ways it will be even easier, but it’s not at all necessary. In my opinion, it’s easier to make an analog control system - you won’t have to bother with programming in assembler.
It will be cheaper and easier to set up and configure, and most importantly, anyone, if desired, will be able to expand and build on the system to their liking, adding channels and sensors. All you need is just a few resistors, one microcircuit and a temperature sensor. Well, also straight arms and some soldering skills.
Shawl top view
Bottom view
Compound:
- Chip resistors size 1206. Or just buy them in a store - the average price of one resistor is 30 kopecks. In the end, no one is stopping you from tweaking the board a little so that in place of the resistor chip you can solder regular resistors, with legs, and there are plenty of them in any old transistor TV.
- Multi-turn variable resistor approximately 15 kOhm.
- You will also need a chip capacitor size 1206 by 470nf (0.47uF)
- Any electrolytic conductor with a voltage of 16 volts and above and a capacity in the region of 10-100 µF.
- Screw terminal blocks are optional - you can simply solder the wires to the board, but I installed a terminal block purely for aesthetic reasons - the device should look solid.
- We will take a powerful MOSFET transistor as the power element that will control the cooler's power supply. For example, IRF630 or IRF530, it can sometimes be torn out from old power supplies from a computer. Of course, for a tiny propeller its power is excessive, but you never know, what if you want to stick something more powerful in there?
- We will measure the temperature with a precision sensor LM335Z; it costs no more than ten rubles and is not in short supply, and if necessary, you can replace it with some kind of thermistor, since it is also not uncommon.
- The main part on which everything is based is a microcircuit that consists of four operational amplifiers in one package - the LM324N is a very popular thing. It has a bunch of analogues (LM124N, LM224N, 1401UD2A), the main thing is to make sure that it is in a DIP package (so long, with fourteen legs, as in the pictures).
Wonderful mode - PWM
PWM signal generation
To make the fan rotate more slowly, it is enough to reduce its voltage. In the simplest reobass, this is done using a variable resistor, which is placed in series with the motor. As a result, part of the voltage will drop across the resistor, and less will reach the engine as a result - a decrease in speed. Where is the bastard, don’t you notice? Yes, the ambush is that the energy released on the resistor is converted not into anything, but into ordinary heat. Do you need a heater inside your computer? Obviously not! Therefore, we will go in a more cunning way - we will use pulse width modulation aka PWM or PWM. It sounds scary, but don’t be afraid, everything is simple. Think of the engine as a massive cart. You can push it with your foot continuously, which is equivalent to direct activation. And you can move with kicks - that’s what will happen PWM. The longer the kick, the more you accelerate the cart.
At PWM When powering the engine, it is not a constant voltage, but rectangular pulses, as if you are turning the power on and off, only quickly, tens of times per second. But the engine has strong inertia, and also the inductance of the windings, so these impulses seem to be summed up with each other - integrated. Those. The larger the total area under the pulses per unit time, the greater the equivalent voltage goes to the motor. If you apply narrow impulses, like needles, the engine barely rotates, but if you apply wide ones, with virtually no gaps, it is equivalent to direct switching on. We will turn the engine on and off MOSFET transistor, and the circuit will generate the pulses.
Saw + straight = ?
Such a cunning control signal is obtained in an elementary way. For this we need comparator drive the signal sawtooth shapes and compare him with anyone permanent tension. Look at the picture. Let's say our saw goes to a negative output comparator, and the constant voltage is positive. The comparator adds these two signals, determines which one is greater, and then makes a verdict: if the voltage at the negative input is greater than the positive one, then the output will be zero volts, and if the positive is greater than the negative, then the output will be the supply voltage, that is about 12 volts. Our saw runs continuously, it does not change its shape over time, such a signal is called a reference signal.
But the DC voltage can move up or down, increasing or decreasing depending on the temperature of the sensor. The higher the temperature of the sensor, the more voltage comes out of it, which means the voltage at the constant input becomes higher and, accordingly, at the output of the comparator the pulses become wider, causing the fan to spin faster. This will happen until the constant voltage cuts off the saw, which causes the engine to turn on at full speed. If the temperature is low, then the voltage at the sensor output is low and the constant will go below the lowest tooth of the saw, which will cause the cessation of any impulses at all and the engine will stop altogether. Uploaded, right? ;) Nothing, it’s good for the brain to work.
Temperature mathematics
Regulation
We use as a sensor LM335Z. Essentially this thermozener diode. The trick of the zener diode is that a strictly defined voltage drops on it, like on a limiting valve. Well, with a thermozener diode this voltage depends on temperature. U LM335 th dependency looks like 10mV * 1 degree Kelvin. Those. counting is carried out from absolute zero. Zero Celsius is equal to two hundred seventy-three degrees Kelvin. This means that in order to get the voltage output from the sensor, say at plus twenty-five degrees Celsius, we need to add two hundred and seventy-three to twenty-five and multiply the resulting amount by ten millivolts.
(25+273)*0.01 = 2.98V
At other temperatures, the voltage will not change much, by the same 10 millivolts per degree. This is another setup:
The voltage from the sensor changes slightly, by some tenths of a volt, but it must be compared with a saw whose tooth height reaches as much as ten volts. To get a constant component directly from a sensor for such a voltage, you need to heat it up to a thousand degrees - a rare mess. How then?
Since our temperature is still unlikely to drop below twenty-five degrees, everything below is not of interest to us, which means that from the output voltage from the sensor we can isolate only the very top, where all the changes occur. How? Yes, just subtract two point ninety-eight volts from the output signal. And multiply the remaining crumbs by gain, let's say thirty.
We get exactly about 10 volts at fifty degrees, and down to zero at lower temperatures. Thus, we get a kind of temperature “window” from twenty-five to fifty degrees within which the regulator operates. Below twenty-five - the engine is turned off, above fifty - it is turned on directly. Well, between these values, the fan speed is proportional to the temperature. The width of the window depends on the gain. The larger it is, the narrower the window, because... the limiting 10 volts, after which the DC component on the comparator will be higher than the saw and the motor will turn on directly, will occur earlier.
But we don’t use a microcontroller or a computer, so how are we going to do all these calculations? And the same operational amplifier. It’s not for nothing that it’s called operational; its original purpose is mathematical operations. All analog computers are built on them - amazing machines, by the way.
To subtract one voltage from another, you need to apply them to different inputs of the operational amplifier. The voltage from the temperature sensor is applied to positive input, and the voltage that needs to be subtracted, the bias voltage, is applied to negative. It turns out that one is subtracted from the other, and the result is also multiplied by a huge number, almost by infinity, we get another comparator.
But we don’t need infinity, since in this case our temperature window narrows to a point on the temperature scale and we have either a standing or furiously rotating fan, and there is nothing more annoying than the compressor of a scoop refrigerator turning on and off. We also don’t need an analogue of a refrigerator in a computer. Therefore, we will lower the gain by adding to our subtractor feedbacks.
The essence of feedback is to drive the signal from the output back to the input. If the output voltage is subtracted from the input, then this is negative feedback, and if it is added, then it is positive. Positive feedback increases the gain, but can lead to signal generation (automaticians call this loss of system stability). A good example of positive feedback with loss of stability is when you turn on the microphone and poke it into the speaker, usually a nasty howl or whistle is immediately heard - this is generation. We need to reduce the gain of our op-amp to reasonable limits, so we will use a negative connection and drive the signal from the output to the negative input.
The ratio of feedback resistors and input will give us a gain that affects the width of the control window. I figured that thirty would be enough, but you can calculate it to suit your needs.
Saw
All that remains is to make a saw, or rather, assemble a sawtooth voltage generator. It will consist of two opamps. The first, due to positive feedback, is in generator mode, producing rectangular pulses, and the second serves as an integrator, turning these rectangles into a sawtooth shape.
The feedback capacitor of the second op-amp determines the frequency of the pulses. The smaller the capacitance, the higher the frequency and vice versa. Generally in PWM The more generation the better. But there is one problem: if the frequency falls into the audible range (20 to 20,000 Hz), then the engine will squeak disgustingly at the frequency PWM, which is clearly at odds with our concept of a silent computer.
But I was unable to achieve a frequency of more than fifteen kilohertz from this circuit - it sounded disgusting. I had to go the other way and push the frequency into the lower range, around twenty hertz. The engine began to vibrate a little, but it is not audible and can only be felt by the fingers.
Scheme.
Ok, we've sorted out the blocks, it's time to look at the diagram. I think most have already guessed what's what. But I’ll explain anyway, for greater clarity. The dotted lines in the diagram indicate functional blocks.
Block #1
This is a saw generator. Resistors R1 and R2 form a voltage divider to supply half of the supply to the generator; in principle, they can be of any value, the main thing is that they are the same and not very high resistance, within a hundred kilo-ohms. Resistor R3 paired with capacitor C1 determines the frequency; the lower their values, the higher the frequency, but again I repeat that I was not able to take the circuit beyond the audio range, so it’s better to leave it as it is. R4 and R5 are positive feedback resistors. They also affect the height of the saw relative to zero. In this case, the parameters are optimal, but if you don’t find the same ones, you can take about plus or minus a kilo-ohm. The main thing is to maintain a proportion between their resistances of approximately 1:2. If you significantly reduce R4, you will have to reduce R5 as well.
Block #2
This is a comparison block, where PWM pulses are generated from a saw and a constant voltage.
Block #3
This is exactly the circuit suitable for calculating temperature. Voltage from temperature sensor VD1 is applied to the positive input, and the negative input is supplied with a bias voltage from the divider to R7. Rotating the trimmer knob R7 you can move the control window higher or lower on the temperature scale.
Resistor R8 maybe in the range of 5-10 kOhm, more is undesirable, less is also possible - the temperature sensor may burn out. Resistors R10 And R11 must be equal to each other. Resistors R9 And R12 must also be equal to each other. Resistor rating R9 And R10 can, in principle, be anything, but it must be taken into account that the gain factor, which determines the width of the control window, depends on their ratio. Ku = R9/R10 Based on this ratio, you can choose denominations, the main thing is that it is no less than a kilo-ohm. The optimal coefficient, in my opinion, is 30, which is ensured by 1kOhm and 30kOhm resistors.
Installation
Printed circuit board
The device is printed circuit board to be as compact and neat as possible. The drawing of the printed circuit board in the form of a Layout file is posted right there on the website, the program Sprint Layout 5.1 for viewing and modeling printed circuit boards can be downloaded from here
The printed circuit board itself is made one or two times using laser-iron technology.
When all the parts are assembled and the board is etched, you can begin assembly. Resistors and capacitors can be soldered without danger, because they are almost not afraid of overheating. Particular care should be taken with MOSFET transistor.
The fact is that he is afraid of static electricity. Therefore, before taking it out of the foil in which you should wrap it in the store, I recommend taking off your synthetic clothing and touching the exposed radiator or faucet in the kitchen with your hand. The microhull can overheat, so when you solder it, do not hold the soldering iron on the legs for more than a couple of seconds. Well, finally, I’ll give advice on resistors, or rather on their markings. Do you see the numbers on his back? So this is the resistance in ohms, and the last digit indicates the number of zeros after. For example 103
This 10
And 000
that is 10 000
Ohm or 10kOhm.
Upgrading is a delicate matter.
If, for example, you want to add a second sensor to control another fan, then it is absolutely not necessary to install a second generator, just add a second comparator and a calculation circuit, and feed the saw from the same source. To do this, of course, you will have to redraw the printed circuit board design, but I don’t think it will be too difficult for you.
The main problem with fans that cool this or that part of the computer is increased noise level. Basic electronics and available materials will help us solve this problem on our own. This article provides a connection diagram for adjusting fan speed and photographs of what a homemade rotation speed controller looks like.
It should be noted that the number of revolutions primarily depends on the level of voltage supplied to it. By reducing the applied voltage level, both noise and speed are reduced.
Connection diagram:
Here are the details we will need: one transistor and two resistors.
As for the transistor, take KT815 or KT817, you can also use the more powerful KT819.
The choice of transistor depends on the fan power. Mostly simple fans are used direct current with a voltage of 12 Volts.
Resistors must be taken with the following parameters: the first is constant (1 kOhm), and the second is variable (from 1 kOhm to 5 kOhm) to adjust the fan speed.
Having an input voltage (12 Volts), the output voltage can be adjusted by rotating the sliding part of resistor R2. As a rule, at a voltage of 5 Volts or lower, the fan stops making noise.
When using a regulator with a powerful fan, I advise you to install the transistor on a small heat sink.
That's all, now you can assemble the fan speed controller with your own hands, without making any noise.
Best regards, Edgar.
First, the thermostat. When choosing a circuit, factors such as its simplicity, availability of elements (radio components) necessary for assembly, especially those used as temperature sensors, manufacturability of assembly and installation in the power supply housing were taken into account.
According to these criteria, in our opinion, V. Portunov’s scheme turned out to be the most successful. It allows you to reduce wear on the fan and reduce the noise level created by it. The diagram of this automatic fan speed controller is shown in Fig. 1. The temperature sensor is diodes VD1-VD4, connected in the opposite direction to the base circuit of the composite transistor VT1, VT2. The choice of diodes as a sensor determined the dependence of their reverse current on temperature, which is more pronounced than the similar dependence of the resistance of thermistors. In addition, the glass housing of these diodes allows you to do without any dielectric spacers when installing power supply transistors on the heat sink. The prevalence of diodes and their accessibility to radio amateurs played an important role.
Resistor R1 eliminates the possibility of failure of transistors VTI, VT2 in the event of thermal breakdown of the diodes (for example, when the fan motor is jammed). Its resistance is selected based on the maximum permissible value of the base current VT1. Resistor R2 determines the response threshold of the regulator.
Fig.1
It should be noted that the number of diodes of the temperature sensor depends on the static current transfer coefficient of the composite transistor VT1,VT2. If, with the resistance of resistor R2 indicated in the diagram, room temperature and the power on, the fan impeller is motionless, the number of diodes should be increased. It is necessary to ensure that after the supply voltage is applied, it confidently begins to rotate at a low frequency. Naturally, if the rotation speed is too high with four sensor diodes, the number of diodes should be reduced.
The device is mounted in the power supply housing. The terminals of the diodes VD1-VD4 of the same name are soldered together, placing their cases in the same 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 on the reverse side. Transistor VT2 with resistors R1, R2 and transistor VT1 soldered to its terminals (Fig. 2) is installed with the emitter output in the “+12 V fan” hole of the power supply board (previously the red wire from the fan was connected there). Setting up the device comes down to selecting resistor R2 2.. 3 minutes after turning on the PC and warming up the power supply transistors. Temporarily replacing R2 with a variable (100-150 kOhm), select such a resistance so that at rated load the heat sinks of the power supply transistors heat up no more than 40 ºС.
To avoid electric shock (heat sinks are under high voltage!), you can only “measure” the temperature by touch after turning off the computer.
A simple and reliable scheme was proposed by I. Lavrushov (UA6HJQ). The principle of its operation is the same as in the previous circuit, however, an NTC thermistor is used as a temperature sensor (the 10 kOhm rating is not critical). The transistor in the circuit is of the KT503 type. As determined experimentally, its operation is more stable than other types of transistors. It is advisable to use a multi-turn trimmer, which will allow you to more accurately adjust the temperature threshold of the transistor and, accordingly, the fan speed. The thermistor is glued to the 12 V diode assembly. If it is missing, it can be replaced with two diodes. More powerful fans with a current consumption of more than 100 mA should be connected through a compound transistor circuit (the second KT815 transistor).
Fig.3
Diagrams of the other two, relatively simple and inexpensive power supply cooling fan speed controllers, are often provided on the Internet (CQHAM.ru). Their peculiarity is that the TL431 integral stabilizer is used as a threshold element. You can quite simply “get” this chip by disassembling old ATX PC power supplies.
The author of the first diagram (Fig. 4) is Ivan Shor (RA3WDK). Upon repetition, it became clear that it was advisable to use a multi-turn resistor of the same value as a tuning resistor R1. The thermistor is attached to the radiator of the cooled diode assembly (or to its body) using KPT-80 thermal paste.
Fig.4
A similar circuit, but on two KT503 connected in parallel (instead of one KT815), was used by Alexander (RX3DUR). With the component ratings indicated in the diagram (Fig. 5), 7V is supplied to the fan, increasing when the thermistor heats up. KT503 transistors can be replaced with imported 2SC945, all resistors with a power of 0.25 W.
A more complex cooling fan speed controller circuit is described in. It has been successfully used in other power supplies for a long time. Unlike the prototype, it uses “television” transistors. I will refer readers to the article on our website “Another universal power supply” and the archive, which presents a version of the printed circuit board (Fig. 5 in the archive) and a magazine source. The role of the radiator of the adjustable transistor T2 on it is performed by a free section of foil left on the front side of the board. This circuit allows, in addition to automatically increasing the fan speed when the radiator of the cooled power supply transistors or diode assembly heats up, to set the minimum threshold speed manually, up to the maximum.
Fig.6
Cooling fans are now found in many household appliances, be it computers, stereo systems, or home theaters. They do their job well, cool the heating elements, but at the same time they emit a heart-rending and very annoying noise. This is especially critical in stereo systems and home theaters, because fan noise can interfere with enjoying your favorite music. Manufacturers often save money and connect cooling fans directly to the power supply, which makes them always rotate at maximum speed, regardless of whether cooling is currently required or not. You can solve this problem quite simply - build in your own automatic cooler speed controller. It will monitor the temperature of the radiator and only turn on cooling if necessary, and if the temperature continues to rise, the regulator will increase the cooler speed up to the maximum. In addition to reducing noise, such a device will significantly increase the service life of the fan itself. It can also be used, for example, when creating homemade powerful amplifiers, power supplies or other electronic devices.
Scheme
The circuit is extremely simple, containing only two transistors, a couple of resistors and a thermistor, but nevertheless it works great. M1 in the diagram is a fan whose speed will be regulated. The circuit is designed to use standard 12-volt coolers. VT1 – low power npn transistor, for example, KT3102B, BC547B, KT315B. Here it is advisable to use transistors with a gain of 300 or more. VT2 – powerful n-p-n transistor, it is this that switches the fan. You can use inexpensive domestic KT819, KT829, again it is advisable to choose a transistor with a high gain. R1 is a thermistor (also called a thermistor), a key link in the circuit. It changes its resistance depending on the temperature. Any NTC thermistor with a resistance of 10-200 kOhm, for example, the domestic MMT-4, is suitable here. The value of the tuning resistor R2 depends on the choice of thermistor; it should be 1.5 - 2 times larger. This resistor sets the threshold for turning on the fan.
Manufacturing of the regulator
The circuit can be easily assembled using surface mounting, or you can make a printed circuit board, which is what I did. To connect the power wires and the fan itself, terminal blocks are provided on the board, and the thermistor is output on a pair of wires and attached to the radiator. For greater thermal conductivity, you need to attach it using thermal paste. The board is made using the LUT method; below are several photographs of the process.
Download the board:
(downloads: 833)
After making the board, parts are soldered into it, as usual, first small, then large. It is worth paying attention to the pinout of the transistors in order to solder them correctly. After completing the assembly, the board must be washed from flux residues, the tracks must be ringed, and the installation must be ensured correctly.
