17. 07.2018

Blog of Dmitry Vassiyarov.

Reobas is the key to quiet computer operation

Greetings dear readers of my site. I am ready to delight you with a story about one very useful device. It can provide you with additional comfort while working on a personal computer. This opportunity is provided by reobas, or, in more understandable terms, a controller-regulator for the operation of system unit fans.

To be honest, I did not find an exact explanation of the term “reobass” on the Internet. But I have an assumption that this has something to do with the “rheostat”. This is a device that regulates voltage by changing resistance. There is still something in common between them.

But there is another version:

"Rheobase" is a biological term meaning the minimum current at which a muscle contracts.

And this explanation is close in meaning, since we also need to reduce the current supplied to the cooler so that it can still rotate.

Consequences of increasing power

But let's get down to business, what is this reobass for? I think it’s no secret that there is a tendency towards a constant increase in capacity personal computers. The performance of the processor and video card increases, the volume of main and RAM expands.

New ones are making the situation worse computer games with 4K resolution. As well as resource-intensive programs for video editing and creating 3D animation. For the sake of their stable operation without slowdowns, PC owners are forced to make a radical upgrade of their machines, often accompanied by overclocking the processor. As you understand, all this gives rise to a chain of interconnected processes:

• The contents of the system unit consume much more energy;
• The kilowatts expended are transformed into heat generated by microcircuits and other parts;
• To avoid overheating, additional and more powerful fans are installed, the total number of which in a PC case can reach 8-10 pieces;
• No matter how slow modern coolers are, their joint work “in an orchestra” creates not only a powerful air flow, but also a fairly loud and very unpleasant background noise. Which, in some cases, can cause headaches.

I think the ultimate problem is clearly outlined. And many of you have probably already thought about how to make ventilation cooling quieter. Moreover, such a theoretical possibility exists: a computer does not always operate at its maximum power.

This is correct, and smart people have already thought about this and created the reobas device. It does an excellent job of adjusting cooler speed depending on the system load.

What types of reobass are there?

The operating principle of the fan controller is simple and understandable to everyone: adjusting the rotation speed by changing the parameters of the current supplied to the cooler motor. Everything seems to be clear. But in reality, reobass differ in design and technical solutions, allowing you to implement the main function in different ways.

Let's take a look at what a simple handheld reobass consists of. Firstly, this is a cable for connecting to the power supply and separate wires (controllers) connected to power and control the fans or their groups. The most widespread are four-channel devices. They have three main lines for the power supply, processor, video card and one, at the discretion of the user.

A regulator is installed on each channel, by turning which you can manually set the desired speed of rotation of the blades. This process is controlled by a small LCD display located along with the adjustment knobs on the panel. The device is installed in a 5.25-inch bay on the front of the system unit. The main thing in such a scheme is a programmable chip with special software control.

But, as you understand, manual adjustment is of little use. And in the case of cooling the processor, this method can be harmful. Therefore, I immediately propose to consider the design of a rheobass, which is capable of controlling the noise and power consumption of fans in full with maximum efficiency. automatic mode. Its main differences are the presence of separate temperature sensors for each channel and a more complex operating algorithm.

How does auto-tuning work?

After turning on the computer, such a system first spins up the coolers to the maximum, records these rotation speed values ​​and takes them as 100%. Further, the speed on each channel is artificially reduced. And only then they are automatically adjusted depending on the load and heating of individual modules.

At the same time, the computer user can independently set and regulate the rotation speed for individual fans. For more comfortable work with reobass, an informative display is installed on their panel, which in some cases is made touch-sensitive and color. With its help, you can obtain current information in a convenient form:

• what is the rotation speed of the coolers;
• temperature in the area where they are located;
• power consumption of connected coolers;

Information about faults is also displayed on the display. Some models of reobass have the ability to work with special software, which simplifies the process of controlling fans.

Speed ​​control technology

By the way, about adjusting the speed. Not all engines are capable of changing it due to a decrease or increase in voltage. And this technology itself is imperfect, because at minimum U values, the torque created may not be enough to turn a fan with dirty blades or thickened lubricant.

Therefore, in good reobass with automatic adjustment use pulse width modulation of current.

In this case, the voltage remains constant - 12 V. But it is supplied to the fan with pauses and at different intervals.

This can be clearly seen in the figure:

This power supply scheme is more complex to implement and is performed using signal digitization. Therefore, sometimes you can find 128 levels of speed settings. But it allows you to set not only exact, but also the most minimal values, and at least 1 revolution per minute.

You can determine whether it is supported in the reobass by looking at the fan connectors. If they are 2-3 pin, this is not it. But 4 wires are just enough to supply voltage, monitor and control the speed. Do not forget that automatic devices must also have cables with sensors for monitoring temperatures.

Epilogue

And another small bonus. In expensive automatic models with a large color touch screen You won’t find anything “extra” across the entire width of the block. But in some simple reobass with knobs and buttons there is little space left on the panel. And manufacturers are trying to add functionality by placing more on it USB ports, SD sockets or other nice goodies in the form of backlighting.

Now you know what reobass is. And how you can use it to make your computer quieter. This concludes my review of this clever and useful device.

All the best and see you again on the pages of my site.

The idea to “calm down” the computer a little appeared a long time ago and here is the result.
Regulator (in common parlance - rheobass or RheoBus) is designed to reduce the speed of computer fans by reducing the supply voltage. As the voltage decreases, the current consumption decreases, resulting in a decrease in speed.

Fans with two and three pin connectors can be connected to the controller without any modification. It is possible to adjust the minimum voltage level supplied to the fan. It is also possible to change the operating indication mode of each reobass channel using jumpers.

The reobass circuit could not be simpler:

Variable resistor R1 regulates the voltage supplied to the fan. Trimmer resistor R2 sets the minimum voltage value. When the jumper is set to position 1-2, the VD1 LED will blink at a frequency equal to twice the fan rotation speed; in position 2-3 it will light constantly. If the jumper is not installed, the LED will not light up. Capacitor C1 ensures that the fan starts at a reduced supply voltage.

Transistor can be used any p-n-p with a collector current of 1 ampere. When using fans up to 80 mm inclusive, KT814, KT816, BD140 are suitable. When using larger fans, or when connecting several fans to one channel, it is better to install a more powerful transistor, for example KT837, KT835, KT818, etc. You can install any LED you like, recalculating R4 (I used a 100 Ohm resistor, since The LED operates in pulse mode; with a constant glow, it is advisable to increase its resistance).

In the assembled device, due to the simplicity of the circuit, there is nothing to configure except to set the minimum voltage for the fan with resistor R2. You also need to use a jumper to set the required LED mode.

Connectors for fans can be installed either straight or angular, trimming resistors are vertical or horizontal type SP3-38A(B), except for the rightmost channel.

Photos of the assembled device:

Due to the simplicity of the scheme, there are some disadvantages:

The adjustment is made manually (this is more of a feature);
- when the fan stops, the LED may or may not remain illuminated.

List of radioelements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
VT1	Bipolar transistor	KT837A	1	KT814, KT816, BD140		To notepad
C1	Electrolytic capacitor	100 µF 25 V	1			To notepad
R1	Variable resistor	4.7 kOhm	1			To notepad
R2	Trimmer resistor	2.2 kOhm	1			To notepad
R3	Resistor	10 kOhm	1			To notepad
R4	Resistor	100 Ohm	1			To notepad
HT	Connector		1

How to make and connect a reobass for a computer? Necessary details, diagrams with descriptions, step-by-step instruction and additional assembly recommendations, testing the reobass for PC and installation ideas. Video.

The article is dedicated to those who are tired of guessing in what position the reobass knob is, and indeed to everyone who has numerous fans mercilessly raging in their case. We will make the device with four channels, if anyone needs more, we can do more, but we settled on this number for several reasons: firstly, we don’t need any more, and secondly, it doesn’t fit into the stub anymore.

In terms of complexity, let us immediately note that it is not easy. To make this device you will need considerable experience with a soldering iron.

The entire design is based on two circuits: a transistor circuit for the rheobass and a hard drive loading indicator. We will finalize the second one a little. Let's start with what we need for this, and we will need quite a lot.

Necessary parts for assembling a reobass with your own hands

Transistor circuit: 4 pcs.

• Transistors KT819G
• Rheostats 10 kOhm for two channels
• Radiators

Hard drive loading indicator: 4 pcs

• Printed circuit board
• Chip LM3914
• Resistors: 10 kOhm, 3 kOhm, 470 Ohm, 330 Ohm
• LEDs 10pcs
• Plume

Additionally:

• Constant resistor 750 Ohm - 4 pcs.
• Three-position switches - 4 pcs.
• Fans (we don’t need tachometers) - 4 pcs.
• CD-ROM housing - 1 pc.
• Wires
• Spring terminals for 4 contacts - 2 pcs.
• Male MOLEX connector - 1 pc.
• Case plug - 1 pc.
• Handles for rheostats - 4 pcs.

Tool:

• Soldering iron and soldering accessories.
• Drill with a set of different drill bits.
• Wire cutters.
• And of course straight arms.

Please note that in the Hard Drive Load Indicator circuit we do not need a 4N25 optocoupler and a capacitor. Also note that two-channel rheostats and switches are needed.

Assembling a reobass for a computer - diagrams and their description

You need to start by marking the stub. This is not an easy matter. You can see the optimal location below.

I wanted to do it a little differently, but the stub doesn't allow it. We assemble a transistor circuit according to the following figure:

We don't need two contacts, so we can bite them off with wire cutters. After all operations, we should have one free pair of contacts left. We will return to them later. Let’s leave what we have already soldered for a while and move on to the hard drive loading indicator board.

• Read about it on your computer

You need to make 4 printed circuit boards according to the following schemes:

Briefly about the PCB manufacturing process:

1. We cut out a piece of the required size from foil PCB and draw tracks with a marker for disks.
2. Pour ferric chloride (FeCl3) into a glass jar, dilute it with water (H2O) and throw the board into it.
3. Stir occasionally and wait until it disappears.
4. After weeding, wipe the tracks on the board with alcohol and drill with a 0.8–1 mm drill. You can use a breadboard, but it will be easier to get confused. Next we solder the parts.

Now you need to connect the two circuits according to the following figure.

Remember that couple of contacts we left? Let's use it.

We supply +12 volts to the middle contact. And we lead the output through a 750 Ohm resistor and solder it to the place that is circled, that is, on +, where the capacitor should be located. Be careful not to mix it up, otherwise you will get a Fatal Error.

• Read also how to conduct

Next, we pick up three-position two-channel switches. Why do we need three-position ones? So that you can switch according to this scheme: 12v/Reg/off.

Here is a diagram of the entire device:

We make 4 such schemes.

1. We take the CD-ROM case and stuff it all in there.
2. We drill holes (if necessary) in the back wall and bring the male-type Molex and spring terminals out.
3. Next you need to solder the wires. We lead the ground to the circuits of the hard drive loading indicators and to all the black contacts of the spring terminals. +5 only for the hard drive loading indicator. +12 to all middle contacts of switches. And we bring the wires from the + circuit to all the red contacts of the spring terminals.
4. We put everything in its place. We connect MOLEX and fans.

How to connect reobass? Examination

1. If your power supply does not have protection or you are not sure of its presence, then use a test one (if there is one), and if the latter is not there, go to a friend and check it all with him.
2. We move the switch to the middle position - the fan should not spin, not a single LED should light up.
3. We turn the switch to the lower position - the fan spins at 12, all the LEDs are on (lit). Try turning the knob, nothing should change.
4. We move the switch to the upper position - we turn the knob, the fan should change its speed, the number of LEDs should also change. In one extreme position all LEDs are lit, in the other - only one.

Ideas for assembling a reobass for PC

1. You can solder the diode matrix circuit and connect it to an existing one. Then instead of the LEDs (and maybe together with them) the numbers 1,2,3....,9 will light up. It will be cool too.
2. You can put a 1500 uF capacitor on the circuit and a 470 uF capacitor in parallel with each LED, then each LED will fade out and light up smoothly, and the capacitor on the circuit will introduce a delay.

Video on how to make a ZALMAN reo bass with your own hands:

A long time ago, when I was on an expensive Internet for traffic, I became obsessed with modding. I didn’t really care about the visual design part of this movement, but I really wanted silence. I came across an interesting device - a reobass. I read the text description, curiously loaded the pictures, and was brutally disappointed - the prospect of turning the knobs to set the fan speed seemed completely crazy to me. Well, really, what the hell is this? I’m lazy to the point of madness, I’ll either set it to maximum to get normal cooling and sit listening to the whistle of the wind and the howl of coolers, or I’ll forget to set it to minimum and end up getting blue screen death due to overheating of something. I had to turn on my old soldering iron and start inventing a cooler control system.

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.

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

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! So we'll go over in a cunning way– applicable 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 no power goes to the engine constant pressure, and 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

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 entrances 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 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). Good example 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.

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

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 has been posted. The printed circuit board itself is done one or two times using.

When all the parts are assembled and the board is etched, you can begin assembly. So I won’t repeat myself about how to solder correctly. You can solder resistors and capacitors without fear, 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 they should wrap it in the store, I recommend taking off your synthetic clothes 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.

Result:
I’m sitting here typing this article, but the processor isn’t loaded. The system unit, standing almost under my ear, lazily rustles its fans at half power. It’s cool outside, I opened the window slightly and the computer was completely hidden. Automation, damn it. Grace! I think the silence is worth spending an evening with a soldering iron for, what do you think? Good luck, colleague!

Are rheobass becoming a thing of the past? But no! Architecture is our everything! It would seem that the amount of heat that was emitted by top-end chips just recently can be dissipated more efficiently using water cooling, but manufacturers have proven that further increasing the frequency is not as effective as improving the architecture. Accordingly, energy consumption and heat generation have decreased.

Noise and PWM

But this was an overture, and actually I was going to talk about the reobass. The air cooling system is enough for me, but there is one problem (or rather, there was one) - the annoying noise of the fans (especially on the processor). I use my computer for a variety of tasks, including those that use minimal resources (mostly at night, when I can hear the water dripping in my neighbors’ bathroom). Why do I need a powerful cooling system at such moments? But she constantly makes noise... and noise, and so on all the time... So a completely logical idea came to mind: to make a reobass with your own hands. It’s expensive to buy a decent one, and there’s nowhere in my city (there is, of course, but it’s so indecent and obscene that it’s better to make noise). And I started searching for articles on this matter on the Internet. However, I didn’t find anything harmonious; all that was there was a Scoop (so childish, plastic). Everywhere there is a completely analog circuit, but I wanted a digital one (!), since using all kinds of variable resistors, without precise adjustment to a given fan, it is impossible to obtain the desired results. And I came to the conclusion that I had to invent everything myself from scratch. What tasks did I face? The reobass must be digital, have at least four PWM channels with two programmable modes, with an indication of the current state of the PWM channels and, if possible, on touch buttons. My hobby really helped me in all this. AVR microcontrollers(Atmel). And what? And then! It turned out even more than I wanted at the very beginning (this activity is very addictive :)). To all of the above, a hard drive loading indicator was added, and touch buttons implemented with a bang. And also, well, this is just my opinion (and my friends), we managed to achieve quite a decent appearance. But the funny thing about all this is the price. It amounted to something like $7, which is very little (if you look at ready-made reobass), plus (unlike the same ready-made ones) the possibility of improving the firmware.

We fill our pockets

Now let's see what is needed to make such a unit:

For main board:

1. AtMega8535 in DIP package – 1 pc.
2. Transistors KT815 – 4 pcs.
3. Transistors KT3107 – 5 pcs.
4. R 300 Om (smd) – 8 pcs.
5. R 1 mOm (smd) – 8 pcs.
6. R 10 kOm (smd) – 5 pcs.
7. R 620 Om (mlt 0.125w) – 4 pcs.
8. With 33 pF (smd) – 7 pcs.
9. With 560 pF (smd) – 7 pcs.
10. Diodes 1N4148 (kd522) – 4 pcs.
11. DIP-40 socket – 1 pc.
12. Zener diode 4.7 V – 1 pc.
13. MOLEX (I couldn’t find a normal one, so I took and cut an adapter for the flop).
14. The heatsink is from an old video card or from a Pentium 133 MMX (something like that).
15. Programming connector.
16. Fan connectors – 4 pcs.

On a note:

If the letters “smd” make you feel hot, you can use MLT 0.125w, soldering them into pre-made holes in the board in place of the “spots” for smd. For capacitors it’s the same story. Although I will also talk about SMD soldering below.

R 620 are resistors for limiting the current through the base of the transistors to which the fans are connected. I took the 620 ohm rating, knowing that the maximum speed with the channel fully open would drop slightly. This only applies to powerful fans (for the processor). If this is critical, then you can take a lower rating, but not less than 330 Ohms, preferably for no more than one or two channels. Although if you simply add more cooling to the transistors, you can easily take 330 Ohms for all four channels. The DIP-40 socket is not required, but then you need to solder the crystal itself, and then the chances of “killing” it will increase tenfold.

For display:

1. 7 segment led indicator with common anode – 4 pcs.
2. Linear LED indicator (“column”) – 1 pc.
3. 20-wire cable (35 cm) – 1 pc.
4. Nails (for buttons) – 7 pcs.
5. Cutting antennae from resistors (for jumpers).

Out of my own stupidity, I bought indicators with a green film, which made them look dull. I tried to tear off the film, after which it turned out that the film was also a diffuser. Therefore, I also had to hang separate diffusers made from a transparent bag. So I don’t advise you to take exactly these indicators. Yes! Do you have a programmer for Algorithm Builder? How?! What about Algorithm Builder itself? It’s absolutely impossible without it, so we download (absolutely free) the utility (about 2 MB) from the developer’s website: http://algrom.net/russian.html

For the programmer you will need:

1. Connector for COM port (female) – 1 pc.
2. Diodes 1N4148 (kd522) – 3 pcs.
3. R 1 kOm (mlt 0.125w) – 7 pcs.
4. Postings.

Boards

Well, let's start collecting hardware? We transfer the pictures to PCB - to do this, we print them on a laser (!) printer on glossy or simply smooth paper (magazine paper is ideal), after which we transfer them by carefully ironing them with an iron onto fat-free PCB. After cooling, place it in water or simply under running water and remove the paper by rolling it up. We carefully examine the quality of the tracks (for now they are only indicated by toner). If there are thin lines between the “spots”, then they must be removed (for example, using a thin screwdriver or simply a sharp object). If somewhere the path is partially not cleared, it can be completed with tsaponlak.

Now let’s move on to etching: for this we take some non-metallic container (as long as the board fits in it), into which we pour ferric chloride (it’s better to throw in some unnecessary iron nails) and lower the board. We wait until all the excess is removed, after which we wash the board in shallow water sandpaper remove the toner. Then we drill all the necessary holes in the PCB. Once again, we carefully check everything - it is advisable to “ring” the tracks and “spots” with some kind of tester.

Now comes the fun part - soldering. I don’t use the epithet “complicated,” but this is quite a responsible matter. The only real difficulty is soldering the cable (you can't do without a vice here). One end of the cable is soldered entirely (to the display board), and the other (to the main board) is divided in accordance with the diagram according to the assignment of the lines and is also soldered. For the cable, I made additional slots in the board - this is so that it does not come off if you accidentally pull on it.

Now, as promised, about smd: apply a little solder to one “patch”, then apply the smd element (it’s more convenient with tweezers), press it with a screwdriver, and carefully melt the tin under it with a soldering iron. Now the SMD element is soldered on one side. Soldering the other one will not be difficult, since one side is already fixed. KT815 transistors should be positioned so that the metal part is not facing the board, but rather, facing the cooling. After soldering is completed, this cooling is attached to these transistors. I took a heatsink from a Pentium 133 MMX processor, cut off a half and an interfering corner, drilled it in two places, cut a thread and screwed it through the board onto all four transistors at once. If there is nothing to cut the thread with, then just a hardened bolt can easily do, because... The radiator is still made of aluminum. You can tighten/unscrew the bolt several times, after lubricating it with oil. When installing the final cooling, thermal paste will not hurt either.

On a note:

Look carefully to see if the radiator is in contact with anything other than the transistors, because it is shorted to ground!

On a note:

When soldering, try not to overheat the elements too much - and this applies not only to SMD!

There should be no issues with soldering the remaining elements. Now we very carefully remove the flux residues; if possible, we check the soldered resistors, diodes, etc. with a tester. And only after all checks can the crystal be inserted into the crib. You have to be very careful with him - there is no problem in “killing” him simply with static from your hands! If you look closely at the photo of the main board, there will be no zener diode on it, I actually didn’t provide for it. But motherboard, as it turned out, supplies the hard drive loading indicator LED with a voltage of not 0-3 V, but 2-5 V. In connection with this, a zener diode appeared. But the printed circuit boards have already been corrected and provide for this modification. As for the “buttons” on the display, they were made like this: I took small nails, clamped them into the drill chuck and sanded them first with a file and then with fine sandpaper. At this stage, you don’t have to solder the beautiful studs, since you still need to first test the performance of the entire system. Therefore, it is easier to solder pieces of paper clips. Everything seems to be ready – can we test it? No, it's still early. Now let's move on to flashing the Mega.

Crystal firmware

The entire project is written in Algorithm Builder 5.15. Algorithm Builder is a graphical assembler, the most convenient, in my opinion, environment for developing programs for AVR. You just need to download it for free and make a very simple programmer. The programmer circuit is in the description on Algorithm Builder. Launch the program and press , after which manual will open. On page 35 the diagram is presented. I made the programmer without a board at all, I simply soldered everything in the connector housing for the COM port according to the diagram.

Now open the reobass project (Reobus 8535.alp). You can do whatever your heart desires with it (although it’s not a fact that after this it will work :)), but first I advise you to check the functionality of the soldered boards. We connect the programmer to the COM port and to the main board of the rheobass (the location of the lines for programming is in the diagram). Reobas is powered by the same power supply as system unit, so there is simply no point in connecting 0 V signal signals from the programmer to the reobass. Click “Program” -> “Run with crystal”.

If you click on the counter, Algorithm Builder will contact the crystal and show the number of times it has been reprogrammed, and if something is wrong (there is no connection between the computer and the crystal), it will display the message: “The crystal is unavailable.” If such a message appears, and everything is connected correctly and power is supplied to the rheobass, then go to “Options” -> “Environment Options” -> “Port”. The “Via adapter” checkbox should not (!) be checked (it is set for programming via an active programmer). We try to change the port number, and even if this does not help, then we look for and delete conflicting devices for the COM port in the device manager (for me it turned out to be an infrared port). Let's start flashing the crystal: “Program” -> “Launch with crystal”.

From operations we set:

1. Checking the crystal type.
2. Cleaning the crystal.
3. Write to program memory.
4. Write EEPROM.
5. Record fuse bits.

Confidently press “Start”. This is all. Now, when power is applied, the crystal begins to execute the recorded program.

On a note:

Setting fuse bit recording is actually not necessary, since the required frequency for this project is 1 MHz, and the Mega8535, like many other Atmel crystals, comes with exactly this internal resonator frequency set. But if bits have already been recorded on your fuse crystal, then it is better to overwrite them.

On a note:

Attention! If you want to change the settings of the fuse bits or blocking bits yourself, be careful - this may result in problems with further reprogramming the crystal and reading it!

Testing

Before you start testing, you need to figure out how the rheobass is controlled. I suggest connecting some kind of fan to it (for convenience, I made my own extension cable for each fan). Those “buttons” that are located below the indicators perform the function of a channel selector. If you “click” on one of them, a dot will light up on the corresponding indicator. While the dot is on, and it is on for about 6 seconds after “pressing” one of the “buttons,” you can use the upper right and left “buttons” to change the fan speed on this channel. The central top “button” saves the current state of all four channels into the microcontroller’s memory. And if no dot is lit, then the upper right and left “buttons” control mode switching. The gradation of rotation speed goes from L (fan stopped) to H (maximum speed), with intermediate positions from 1 to 9. After turning on the power, for the first seconds all channels are open to maximum (this gives the fans the opportunity to spin up), after which the first mode is loaded from memory . When the speed changes from L to 1 for the same purpose, the channel operates at maximum for two seconds, and only then switches to 1. How does the fan rotation speed change? Of course, the rheobass controls the channels using pulse-width modulation, that is, for a certain period of time, only part of this time a positive signal is present. I have heard many times that PWM creates such a whistling noise that it even drowns out the noise of the fans themselves. This is far from true. No, there is some noise, but it is quieter than the noise of the fans and is practically inaudible against their background. In general, if you are an ardent PWM hater, then you can put resistors in parallel with the transistors, then the noise should disappear (however, you need to select your own resistor for each fan). The wiring of the hard drive loading indicator (the one that is soldered to the main board next to the zener diode) is connected to the LED circuit on the front panel of the case and the motherboard. The program makes ten samples, divides the total result by two and displays it on the hard drive loading indicator. But the minimum output value is one division. I tried not to output anything at all as the minimum value, but it was not very easy to read and was very annoying.

Connection diagram. Well, is everything working? Let's move on.

Appearance

This is the final stage. It determines how impressive the entire project will look. For the display board you need to make a front panel - I made it from a regular five-inch plug. Printed it out on a printer printed circuit board display (already on plain paper) and glued it to the plug. With a reserve, I outlined the points for the holes for the indicators and went to the balcony to drill holes along the marked lines with a thin drill. I also drilled holes for the buttons (their diameter depends on the thickness of the polished nails). Then I carefully broke out the windows for the indicators and processed them with a file. There is no need to strive for special beauty and perfection of the windows; the most important thing is to check whether the indicators pass through them. After the next action, the inhabitants of the apartment did not talk to me for a long time. We are, of course, talking about painting :).

On a note:

Advice: you should not paint on the balcony - no matter how hard you try, the smell of paint will still appear in the apartment. It makes sense to go outside and paint.

You need a can of black paint (the cheapest one possible) and something to degrease. We apply paint to the grease-free plug in several layers, let it dry a little and take everything back home (but it’s better to take the “fragrant” plug to the same balcony for now).

Now you need a tint film. It can be obtained from the automobile market. I had it in the garage (that’s where I had to paint it) - 50% black. I cut a piece a little larger than the plug and went to the bathroom. I poured water over the plug (so that there were no air bubbles) and very carefully applied the film. Then, moving all the time in one direction, he smoothed out the water.

It's time to remember button studs. We unsolder what was soldered as buttons. We insert the display into the plug and fasten both parts by soldering nails! The main thing in this matter is not to scratch the tinted plug on the table.

The boards can be coated with tsapon varnish. Next comes the installation of the device at its place of work - in the system unit. I did not make a full-fledged closed case for the main rheobass board - these would be unnecessary problems when connecting/disconnecting fans. I wanted to attach the board to the side wall of the 5.25 basket through an insulating substrate, but I ran into the result of my stinginess: I took a cable that was too short (less than 20 cm) to connect the boards to each other. I had to simply lay the insulating substrate on the bottom of the 5.25 basket and secure the board here. The insulation is made simply from a mouse pad.

That's it now. You can enjoy the silence... But everything was not so simple for me, since before the final installation of the reobass inside the system unit, I continued to test and refine it for some time. For about two weeks my rheobass was simply hanging in the air between the unscrewed front panel of the case and, in fact, the case itself. All this time the programmer was connected to it. He passed the test with dignity. My main fear was that the transistors would overheat, but this did not happen. Yes, under heavy load the transistor cooling radiator heats up, but within reasonable limits (after all, it needs to have some kind of temperature difference with the air in the room).

What is the overall result of the work done?

Firstly, it became much quieter. Now, when I sit down at the computer, I am no longer annoyed by the noise of the fans (but I can hear the rumble of the hard drive :)). If I need to use all resources to the maximum (which causes a sharp increase in heat generation), I can simply switch the mode on the rheobass to switch to efficient cooling. And secondly, I made a full-fledged digital piece of hardware myself, which is what I wish for you too!