Wednesday, September 11, 2013

Cooling Fan speed control via Azteeg PWM Fan Pin Output

The Azteeg X3 Controller has four low powered outputs which can be used to drive fans or even LEDs. These outputs can be controlled by the host-software or called on when printing by gcode commands inserted by the slicing software. Marlin firmware is configured to call on the Azteeg pin D4 when the M106/M107 (Fan On/Off) gcode commands are used. (Azteeg full wiring diagram here.)

I'm currently experimenting with the Azteeg board controlled by Reperier-Host software and Marlin firmware onboard. That combination enabled immediate testing of the newly wired (two-wire) cooling fan on my 'scratch build' Mendel 90. But I soon found that despite the suggestion of possible speed control by Repetier-Host, with it's 0% - 100% Fan Output slider, the fan would only run when the slider control was near or at 100%. A little more research revealed that the simple two-wire fan could utilise the PWM (Pulse Width Modulation) Fan Pin Output of the Azteeg board if two simple common components, a capacitor and diode, were added to the fan circuit. I had to try it! (There was an article on the Bukobot site which gave full details on this hack: Credit and thanks!)

I first bread-boarded the two components to test that it would work... and it did! This basic set-up, the 10uF capacitor in parallel with the fan wires, and the common diode (1N4148 / 1N914 diode) in series on the negative wire provided the speed management of the fan.

I then placed the components on my stepper mounted connector board and wired them in. Pict below:

The following short video best shows fan speed control being tested.

The true benefit will come when I enable Auto Cooling within Slicer and the commands to switch on/off, and change cooling percentages are applied to the sliced gcode and called on during the print job. Slic3r now contains such settings... see screenshot below:

Other controller boards may also provide PWM Pin Output, and this simple two component addition to the  fan wiring gives great control of print cooling when combined with the Slic3r Auto-Cooling features.

Hope you found it of interest.

Thanks for viewing!

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