Zak Kemble build an AVR based PWM fan controller. He writes:
So this is a bit of a continuation on my 555 timer based PWM controllers, but now using microcontrollers and MOSFETs instead of 555 ICs and transistors. I made 2 versions, one with switches for speeding up and down and the other with a potentiometer like the previous controllers. I used ATtiny25 controllers running at 31.25KHz (8MHz internal RC / 256 prescaler) with a 3.3V supply, the MOSFETs I used are STP36NF06L with 0.045Rds and 2.5Vgs max, perfect for 3.3V, the MOSFETs only generate ~180mW of heat at 2A ((0.045Rds * (2A * 2)) = 0.18W) so no heatsink needed, you can barely feel them getting warm.
AVR microcontroller based PWM fan controller - [Link]
Sometimes even a small fan significantly improves thermal conditions in a device. For these cases will serve you the new types of small fans.
Sunon, as an innovative producer of fans and the creator of progressive technologies (VAPO, MAGLEV,…) consistently extends its portfolio, or replaces older types by new ones. This is also the case of new types in our offer – EB40201S2-999, EB60201S1-999 with a sleeve bearing, MB40101V2-A99, MB40201V1-G99, MB50101V2-A99 and MB60101V2-A99 with a VAPO bearing, which gradually replace the KD and KDE series.
New types feature even higher reliability thanks to a construction with a lower count of mechanical parts. They also feature a higher air flow (better flow/pressure characteristics) while keeping the same or a lower noise. If you consider adding an active cooling to your device, whether from the necessity or for increasing of reliability of your device in extreme cases, you can choose from more Sunon, types which we keep in stock. Upon request, we´re able to provide you with any other type from the Sunon portfolio.
New 40, 50 and 60mm Sunon fans will blow away excess heat - [Link]
Any electronic system generates waste heat during normal operation. This heat must be removed – otherwise, it might damage the system components and cause malfunctions. Whether you are designing a system or diagnosing a system’s cooling requirements, you need to know which parameters to look at and how to estimate the airflow that will maintain a safe temperature within the system.
In a typical cabinet-mounted system, there are usually one or two power supplies, electronic circuits and displays, all of which can be assumed to generate heat within the cabinet. From the system’s power requirements, a fair idea of the power input may be estimated. If the system is cooled by simple convection, the thermal capacity of air can be taken to be 0.569W-minute/°C/ft³.
That means, every cubic foot of moving air can remove 0.569 W of dissipated heat every minute when its temperature changes by 1°C. To express it reciprocally, to dissipate 1W of heat, and maintain a 1°C change in temperature, an air stream of 1.757cfm (1.757 cubic feet per minute) will be required. Therefore, once you have estimated the heat dissipation within the system, estimating a cooling fan’s rating in cfm will depend on the internal temperature rise you allow. However, until you have completed your measurements and fitted the right size of fan, there will always be the risk of failure of system components. Therefore, for experimentation, what you need is a representative model.
This application note describes the operation of 12 volt DC cooling fans typically used to supply cooling air to electronic equipment: These fans are typically based on two-phase Brushless DC (BLDC) motors drawing between 1 and 50 watts of power. Single-phase brushless DC motors are also used in fans, but this is outside the scope of this application note.
Further discussion describes the addition of an Atmel ATtiny13 microcontroller and the benefits this offers, such as variable speed by external thermistor input. An additional input is a PWM pulse width-varying signal, which also controls fan speed.
App note: PC fan control using an ATtiny13 - [Link]
Geoff designed this USB PC case fan controller. It is used to control the speed of your fans depending on the temperatures in your case. Software that was developed for this project allows you to customize the temperature profiles for your computer.
The project is based on the PIC18F2550 that is connected to the computer via the USB and uses the standard Molex 4pin connector to access computer’s power supply. It has 4 analog inputs for temp sensors, and can control up to 8 fans.
One thing to note is that all the fan outputs work with 3 pin fans, while two are universal and work even with 4 pin PWM versions. The 3 pin fans are driven with a buck convertor. The UDN2981 provides the high side switch and diode that are driven from PIC’s PWM signals. A 100uH inductor and a 479uF capacitor complete the buck topology, thus providing variable analog output for the 3 pin fans.
Intelligent Fan Controller - [Link]
I’ve got a new tool on my workbench – portable fume extractor. It’s 92mm fan that works from 4 AA batteries and has a variable speed. Mobility is a really good thing, especially when you’ve got a tons of equipment and cables on a bench you can drown in.
Portable Fume Extractor / Fan - [Link]
I’m really very happy to present this circuit! This is a very special page, and what’s special about it is that this circuit is designed NOT by me, but from a PCB Heaven reader, which happens to be also one of my students in my PIC classes. As a matter of fact, he is my first student… Well, ok, he is my only student . So, this is the very first circuit page that i host in my site which is designed by a PCB Heaven reader. Special thanks to Panagioti Kalogeri, which you will find him trolling around my site with the id _Pike…
This circuit is the result of an exercise that i asked him to make, in order to practice with the Timer modules of the PIC. The PIC will read the tacho output of a PC fan. The rpm is then translated into a number of LEDs turned-on on the bar-graph. The minimum rpm during which only one LED is turned on is 600 rpm, and the maximum is 1200 – which is also the max speed of the fan. Panagiotis was asked to implement the rpm measurement with the Reverse Frequency Measuring as described here.
PC Fan RPM Bargraph Meter with PIC - [Link]
This project is a temperature controlled FAN based on LM311 IC. The fan is activated only when it is necessary. Working temperatures are 0C to 150C.
Temperature control circuit – [Link]
This project is a temperature controller that is able to control a fan according to temperature. It’s a simple design and uses simple components. Check schematic and PCB on the link below.
0C to 150C Temperature controller – [Link]
Th1, the 50K thermistor, is a standard type. Mine was a bar or rectangular looking thingy. Available from Tandy/Radio-Shack. Almost any type will do. I experimented with different models from 22K to 100K
and all worked fine after replacing the trimmer pot. The one used in the above circuit diagram was a 50K model. This 50K was measured at exactly 25 °C and with 10% tolerance.
Automatic Fan Controller - [Link]