07-20-2016, 10:50 PM
You can build a fan motor speed controller using a ULN2803 driver, and either software or hardware PWM.
... basically, you build a motor controller that comes on only when the temperatures on the SoC require it... and then only at a speed appropriate for the situation. I leave my fan running all the time, but running very slowly ( a hushed whisper really ). When the SoC is loaded and the temps come up... then the fan steps up ( I have two speed levels at the moment ) until the temps come down. The ULN2803 is a very inexpensive eight channel driver circuit. (I'm driving two fans with one chip). The ULN2803 is the driver on the Gertboard, if you have one of those, or want to experiment with it in a controlled way.
You may use any motor controller you choose, of course.
Keep in mind that a brushless fan can run for years with no ill affects... just let it run... if the noise bothers you then a simple pwm speed reduction circuit is all you need. Then, if you want to add some smarts to it all, make the fan run only when the temps are high.!
marcushh777
... basically, you build a motor controller that comes on only when the temperatures on the SoC require it... and then only at a speed appropriate for the situation. I leave my fan running all the time, but running very slowly ( a hushed whisper really ). When the SoC is loaded and the temps come up... then the fan steps up ( I have two speed levels at the moment ) until the temps come down. The ULN2803 is a very inexpensive eight channel driver circuit. (I'm driving two fans with one chip). The ULN2803 is the driver on the Gertboard, if you have one of those, or want to experiment with it in a controlled way.
You may use any motor controller you choose, of course.
Keep in mind that a brushless fan can run for years with no ill affects... just let it run... if the noise bothers you then a simple pwm speed reduction circuit is all you need. Then, if you want to add some smarts to it all, make the fan run only when the temps are high.!
marcushh777