A simple VHDL project controlling the fan speed on the ML605 development board from Xilinx according to the current FPGA (Virtex6) temperature.
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ML605 fan controller

This module controls the speed of the fan, mounted on the FPGA (Virtex 6) of the ML605 development board from Xilinx. It regulates the speed depending on the temperature.


Just import the .xise file as a project in the Xilinx ISE. At least with version 13.4 under Linux it is compiling.


The fan controller tries to hold a temperature of 40°C and increases the fan speed continuously if the temperature rises. You can change the values if you want, they are all in the signal declaration part.

###ADC to temperature The temperature is measured at the FPGA and digitized by a system monitor that is accessible via a Xilinx IP core. The ADC values from this system monitor transfer into a temperature with this equation:

Temperature (°C) = [ADC code] * 503.975 / 1024 - 273.15

Some common temperatures would be:

616 ADC = 30 °C
626 ADC = 35 °C
636 ADC = 40 °C
657 ADC = 50 °C

###LCD information This project uses my LCD module to display current temperature and corresponding ADC values as well as the current fan speed setting.

###Fan speed The fan speed is controlled by a duty cycle. If you take for instance 10 clock cycles and only power the fan for 5 of these 10 cycles, you get the speed running at half speed.

Known Bugs

  • Sometimes the system monitor delivers strange ADC values. I seems to appear only at around 42°C where the ADC values jump to 544 (= -5°C) or 767 (= 103°C). My dirty solution is to catch these values and set them manually to 640 (= 42°C).