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Problems with 5V fan connector on 2.1.4 board

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I'm in the final stages of building an Ultimaker 2 Extended clone (from a project on Thingiverse).  I've searched the forum and read various threads on fan issues (seems to be a common problem) but my issue is slightly different.  I'm using an E3D V6 hotend, and was planning to use the fixed (non-PWM) 5V output (J34) to power the fan.

First I tried it with the regular Ultimaker 2 Marlin firmware and that didn't work.  Then  I learned about the Amedee builder, but I already had firmware mostly configured the way I want, so I took the changes from that firmware and applied them to mine to enable that connector but it still isn't working.

One odd thing I noticed is that when the fan should be off (hotend temperature below 40c), I measure 4.9v and when it should be on, I measure 3.6v.  The fans never come on in either case.  I tested the fans with an external power supply and they work fine.  I also checked my cable with an ohm and volt meter and it's good.

I haven't yet gotten the viewer for the schematic files, so I don't know, but I assume that since this is switchable on the 2.1.4 board that there must be a transistor involved.  When I first had the fans connected, I unfortunately had the polarity reversed. Did I perhaps blow out a transistor?  I don't know what to make of the voltage readings.

Edited by Guest

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@amedee builder is for umo/umo+ so the bed size, the limit Z and some other settings will be off. To build that clone you will need to make your own firmware or use the one that the thingiverse clone made.

The 2.1.4 5V fan plug has a transistor and to use it you need to read how the firmware works to enable that pin.

This is the dirty code used on um2 to enable that pin


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Thanks for the quick response! I didn't explain myself very well. I already had the full Marlin source specifically configured for my UM2 and I knew that the Amedee build didn't support that, so I looked at the source in the Github repository to determine the changes required to support that pin (I just replaced setExtruderAutoFanState in temperature.cpp, and changed EXTRUDER_0_AUTO_FAN_PIN to 255 ) and recompiled.

Maybe I made a mistake or missed something, but after making those changes, the output still doesn't work (although the voltage does change right at the specified hot end temperature). The voltage readings are a bit confusing to me so that's why I wondered if there was a hardware issue.

Thanks for the pointer to the other thread though. I think I'll post something over there as well.

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