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Hello everyone,

On the UMO+'s board (the same as the UM2+ series), there seems to be two fan ports, a pwm one and a serial one (was it serial? I forgot. It's on the bottom of the board). Both seem to be rated for 24 V. Does this mean that I can connect two 12V fans to each one? I'm asking this because I would like to install dual print cooling fans, one for the heat break of a possible future E3D V6, and one to cool my feeder motor (I've had problems of the motor's heat softening/deforming the PLA in the feeder).



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For the hotend there's a 5v fan connector on the board that you can enable (disabled on 2.1.4 boards) installing a firmware done with the amedee experimental firmware builder (option called 'Hot-end fan')

There's also a two pin direct power near the connector, and another 19-24V fan on the end of the board.

The led pwm does work like fans pwm, it has some amps limit (around 200-250mA) and with some google you can find the info to control it by gcode (or by the ulticontroller if you install Amedee firmware). I use it with a um2 led strip to have light on my 3 umo+.

The 5v fan (with the experimental firmware) works like on a um2, they will turn on when the hotend reachs 40C) so it's cool to remove noise. On boards 2.1.2 or lower the 5V it's always on and doesn't need firmware changes.

Amedee firmware builder:


Edited by Guest

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Wow that was faaaaaaaaaaast and thorough!


So I just pulled up my board, and I see what you're talking about with the 5V fan. I'm assuming that 5V is enough for the hotend fan?

Also, I'm kind of lost here, so what your saying is that I can either use the fan port at the bottom of the board or use the led pwm as a fan output?

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Led option? It's enabled by default on umo+

Yeah you could have x4 fans + head cooling but...

You might need to send an extra gcode to control the other fans connected to the led pwm, or rewrite the gcode command that controls the fans so it controls both (or something like that).

Just be careful with how many mA you use on the led/fan pwm connections. I have burned the transistor that controls them way too many times by using more than 200-250mA. Also never connect a fan neg/pos inverted on that plugs or again the transistor dies. Check the ultimaker pdf of the board to see all connectors and check positive/negative everytime, one error and transistor dead.


Friendly warning: Go expore, but be afraid because an error burns a board.

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Okay, thank you!

I'll try to be careful :)

So as of right now, the led pwm seems to be some work....

Connecting it to the other fan port with probably be easier, but I'm still struggling with the concept of how to enable it.

This fan should work, right?


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Don't know. It doesn't specify amps, description says 12v and also 24v on other places. Also it doesn't say the mA that uses.

Sorry but fans it's a big world. Get them at a electronics shop where a guy can tell you the specs of the product.

All the fans I bought for my printers, I found that the only way to be 'semi' sure it's using a professional electronics shop like farnell or rs-online or something like that where you can see the specs of the fan. Also not all fans can be PWM (some just go full or nothing). It's quite a complex problem and sometimes it's just better to find some model that other user did use.

Check my guide for dual fans on umo+


There's some points about fans that might give you some clues. Also, good fans are expensive, cheap ones can work, or break something, but the main thing is to know the real specs of the fan before plugging it.

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