how to monitor the fan speed tacho / alarm when low or 0

Simon 4

In my printer you can´t see the extruder fan not that good and sometimes filament is blocking it an I do not see it always.
The fan has a tacho output, which works good and is displayed in DWC.
But how can I react of a too low rpm ?

achrn

@Simon-4 do you just want a warning alert to pop up when the fan is too slow? Or do you want the printer to actually take some action when the fan is too slow (for example, it could pause printing)? What reaction do you want?

T3P3Tony

@Simon-4 see here:
https://forum.duet3d.com/topic/18617/gpio-fan-tacho-and-print-cancelation/5?_=1715860524928

T3P3Tony

@T3P3Tony I have added a feature request to use the vent system for this at some point in the future. Its low priority because it is possible to use daemon.g

Simon 4

thanks for input, I will test this linked advises.

@achrn pausing the print would be good

achrn

@Simon-4 If the fan you want to monitor is fan 1, and your tool is using heater 1 the basics would be something like this:

; pause if fan is slow
if state.status = "processing" & heat.heaters[1].current > 50 & fans[1].rpm <= 1000
    M118 S"fan problem"
    M25

Loops are indicated by the indentation, so make sure you copy the indentation - you need the equal spaces at the start of the lines after the 'if'.

This checks to see if the printer is currently printing, and heater 1 is currently at more than 50 and fan 1 is at less than 1000 rpm, if all that is true, it displays a message and does M25 to pause the print. You will need to remedy the problem before resuming the print manually.

You should create a file in sys folder, it doesn't matter what it is called, put that text in it and save it. Then rename the file to 'daemon.g'. The file will run every ten seconds, and check the fan speed.

If you want to edit the file rename it to something else (I normally just make it daemon.g.x), edit the file and then rename it back. If you just edit it when the machine is trying to run it every 10 seconds things can go wrong.