Ultimaker 2 Fan PWM not working properly

[garthondo 0]

I recently upgraded my ultimaker 2 go to use an e3d v6 hotend. Something that has been annoying me is that the hotend fan is constantly on, since it is plugged into a pin that can't be controlled with gcode. I want to use the either the fan/led pwm to controll the 24v fan (I think that both pins are basically the same). However, I also connected 2 24v part cooling fans in parallel to the fan pwm circled in the image, but during that process, I think I may have busted something about that pin. Now, that pin doesn't seem to output nearly as much voltage as it is supposed to, and is at 100% power when I set that pin to 0% (in klipper), and the output decreases in output power as I increase the requested output. I was wondering if anyone knows if this pin is just busted and unusable now, or if it is potentially fixable.

 

 

[jaysenodell 18]

Check the klipper references (https://www.klipper3d.org/Config_Reference.html) on how to set that pin properly. Effectively that pin is operating with "high" as the default and inverted (ex val = HIGH - val is how that is managed in mcu land). Sometimes this is done with a hardware default (v+ -- fet -- pin  with the fet controlled by the pwm pin) in which case you will need to tell klipper to invert the signal. Something like

map(val, high, low, low, high); // stdio map function

Given klipper's open arch you should be able to write a couple lines of python to achieve this with ease. 

 

I"m neither a ultimaker or klipper person, but I do recognize the patterns here. Good luck.

[garthondo 0]

Thanks for the suggestion. I was able to invert the pin per your suggestion via a "!" as a prefix when defining the pin name after looking at the config reference. However, the pin now has a voltage of ~15.5v when at 0% and ~16.1v when at 100% when it is supposed to be ~0v at 0% and 24v at 100%. I believe the pin worked fine before I messed with the fan wiring, so I still suspect that it was possible that I damaged it, but not sure. I also looked at some klipper config files for a similar machine (um2) that uses the exact same board and the pin is not inverted. Maybe that extra info about the voltage might be useful to some?

[gr5 2,224]

Those 2 fan output connectors are controlled by a transistor (actually probably a mosfet) that can die pretty easily.  Especially if you put a heavier than expected load on them.  They can die in many different ways.  The most common I think is an open (always off) and the second most common is a short (fan always on) but I wouldn't be surprised at all if there are other failure modes for that poor little "transistor".

 

Even without heavier than expected loads those transistors occasionally fail.  Switching the fans on and off 20X per second (normal operation when fans are anywhere from 1% to 99%) can cause them to get pretty hot.

[jaysenodell 18]

Yeah... I would replace that mosfet based on those voltages. Not sure on UM systems (especially the old ones) but a bunch of manufactures are now making this plugable for just this reason. Sorry for the less than great news.