Temperature is controlled by regulating the fan speed of the fan. In user mode, the user has control over the speed of the fan via 2 trimpots (right side of Fig. 1) that directly adjusts the fan supply voltage from ~7-12V. In autonomous mode, Fan 1 is controlled by voltage regulation with a 4-bit R-2R DAC that is optoisolated from the fan motors. An enable pin switches the fan on/off with a TIP31A NPN transistor.
This is one of the smallest fan controllers I’ve seen. It does the same job as others, it controls the fan speed according to a temperature sensor. The main utility is that you save power this way, and second its noise reduction, the fan will now run most of the time at lower speeds. The whole circuit its based on 3 parts:
- A MOSFET Power transistor (N-Channel), price between $1 and $2
- A 10K spindle trimming potentiometer, price around $1
- A 10K NTC temperature sensor, price around $1
These are really easy to get parts, so you wont have any trouble. As a last word this is a very useful and simple to build project. Good luck building it.
Fan Temperature Controller: [Link]
This is a really coool project from spritesmods.com they had the idea of creating a clock in such a way: make a red, a green and a blue ‘hand’ and by lighting up the three dies of an RGB-led, you can control exactly at what angle the image of every hand shows up. Apart from the hands, the fan itself doesn’t need to be modified: the led, in conjunction with a microcontroller, does all the work.
This is the fan itself. I glued three pieces of paper to it and used a felt tipped pen to colour them in: red for the hour hand, green for the minute hand and blue for the second hand. Eventually, I remove the blue piece: it wasn’t colored in completely OK and the green piece reflected enough blue to give an indication of where the hand indicating the seconds is. Btw: The angle you put the hands in isn’t inportant: the software can compensate for any decision you make when you initialize the hardware.
The software mainly works by using three interrupts: the first one kicks in 500 times a second and is used for button debouncing and keeping time. The second one is dynamically adjusted to kick in 60 times per rotation of the fan and handles the showing of the hands by enabling and disabling the three colors of the RGB-led. The third one kicks in every time the fan generates an RPM-pulse. When that happens, the microcontroller will evaluate the speed at which the rotation-timer happens and adjust it when necessary. The software for the clock is written in avr-gcc and released under the GPL v3, so if you want, you can modify it to display a clock on anything rotating quickly enough.
Watch the clock in action
If you like this project visit its page Link