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Hotend fan riddle


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After weeks of equal amounts of successful prints and hot end clogs I finally noticed something very odd. I was watching my hot end fan like a hawk because I considered it the main reason for my frequent clogs. First print went well, the fan turned on at 50 degrees. But by the second I noticed while Mainsail reported Hot end fan : on at 50degrees,  it actually wasn't turning at all.
How is it possible that Mainsail reports this ? Or does "fan on" only mean : the signal has been sent, if it actually works I don't know ?

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1 minute ago, mbunjes said:

Would like to use the Fly SB2040 with my Octopus pro board.

Got these running on two printers - Trident and Voron 2.4 350mm build. Never looked back.

Have a look at this thread to get started. 

The following may be helpful:

1. This to update the octopus board to canbus

2. This to explain canboot

3. The uploaded manual to tie it all together.

Hope this helps

How to Use CAN Toolhead Boards Connected Directly to Octopus.pdf

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10 hours ago, mbunjes said:

Or does "fan on" only mean : the signal has been sent,

In this case just means "signal has been turned on" unless you've got one of those 4 wire fans (that includes the tacho....and appropriate software) the board will never actually know if the fan is spinning or not.

CANbus will solve some problems but will bring a whole new set 🤣. Good luck and remember to enjoy the ride.

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15 hours ago, mbunjes said:

This is already the second fan I've tried. It's probably a bad connection somewhere but the idea of diving in the wiring hell of these printers makes me shudder.

I feel you. I was looking down that abyss when chasing the first bad  heater core. I managed to eliminate wiring as my issue by doing two things. First, I checked continuity of the specific wires with the multimeter--unplugged each end while still in the harness to make sure I had a good connection. Second, I just built a quick patch cable to plug to part to the controller without running through the whole harness. In this way I was able to dodge that bullet by proving that the harness wiring was good. So, it might help you to eliminate or confirm that the wiring is the problem or not.

Another thought: have you tried plugging the fan into another fan output on the controller?

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Since this is an issue that occurs sporadically, al these tests are inconclusive. I could try another output and have it fail after a week of printing. No. I've ripped out all the wiring to the toolhead and will go canbus if it kills me.

On that note, babysteps required : could someone explain : what is canboot ? (strike that, it's the easy way to update your controller it seems) 

I understand you can use the Octopus directly through the RJ11 connector but a lot of people are using an extra board. What is the reasoning behind that ? Easier on the RPI ?

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6 hours ago, mbunjes said:

could someone explain : what is canboot ?

Eliminates a USB cable in order to flash the canbus board. Handy when it comes to updating the mcu later down the tract.

6 hours ago, mbunjes said:

What is the reasoning behind that ?

Eliminates the "middle man" (pihat, UTOC, Waveshare board,etc). Something less that can go wrong, I suppose. The process, once figured out was straight forward. This now seems to be well documented in this forum and on github. The signal path to the canbus board changes from:

Pi --> UTOC --> Canbus board on toolhead 


Pi -->Octopus --> Canbus board on toolhead

There may be other advantages/disadvantages but I have not come across these as yet.

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23 minutes ago, mbunjes said:

So there's no extra strain on the Octopus when omitting the UTOC ? Damn, I ordered an UTOC as well.

Running a 350 V2 and a 250 Trident with octopus and canbus and have not noticed any deterioration in speed or signal issues.

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