How to limit the speed of the hot-end heatsink fan?
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My config file has this command which I got originally from the online configurator which works well.
M106 P1 S1 I0 F500 H1 T45
How do I set heatsink fan to turn at 75% rather than 100%? I tried to play with the S and X parameters but could get it to work, the fan didn't turn on at all.
(motivation: I would like to experiment with quieter cooling).
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haven't tested it in a while buy i'm pretty sure my RRF2 config for Maestro was something like
H1 T50:150 L50 X75I think it may be the second temperature for the T paramter you're missing?
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Using the t parameters you suggest is, I believe, to turn the fan on at 50 degrees and reaches maximum speed at 150 degrees. This probably requires use of the 'L' parameter to set the minimum speed at 50 degrees (your command sets minimum speed at half speed I believe)
If a single fan speed is wanted, the 'S' parameter can be used. S1 is full speed and S0.5 is half speed.
https://duet3d.dozuki.com/Wiki/Gcode#Section_M106_Fan_On
Some fans require full power to get started and that is where the 'B' parameter comes in. You might want to go to a full second on that.
Apparently some fans don't like PWM at all ....
Don't reduce the cooling of the heatsink too much or you will experience very difficult to trace hot end blockages
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The fan probably doesn't like starting at 50% PWM. You can try adding a blip off full on speed with B to get it kick started. If that doesn't work, you can try experimenting with the PWM frequency with F. 10Hz to 30000Hz are viable.
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A quick followup
I tried today to change PWD ratio and frequency with an oscilloscope connected. The duet does the right thing but that little Sunon fan does not respond well to PWM. It works on S255 but if I drop to even S200 it stops working. If I reduce the frequency all the way to 5Hz it kind of responding but I can hear the 5Hz acceleration/deceleration.
Ended up connecting a serial resistor of 50ohms to drop the voltage from 12V to 10V. I measure the heatsink temperature with an IR camera at 12V and at 10V (hot end at 250C) and didn't notice a difference.
Conclusion, if you want PWM to work, make sure to get a fan that supports PWM.
Edit: replaced the 50ohm resistor with 3 silicon diodes in series. This way the voltage is stable , even when the motor consumes higher current for startup. I verified that the fan starts successfully on the reduced voltage, even if I stop it by hand (it takes a second or so to start, as if it has some timeout).
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@zapta said in How to limit the speed of the hot-end heatsink fan?:
Conclusion, if you want PWM to work, make sure to get a fan that supports PWM.
Yes, they don't all play nice.
What model specifically was the fan?
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@Phaedrux, this one
https://www.digikey.com/product-detail/en/sunon-fans/MC30101V1-000U-A99/259-1550-ND/2757778
It is great otherwise, holding much better than the chineese one I used before.
They seem to have this one with 3 wires, not sure what the third wire does.
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I've used that same fan in the past. I found it so quiet (at least compared to the stock E3D fan) that I never had the desire to slow it down.
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@zapta said in How to limit the speed of the hot-end heatsink fan?:
They seem to have this one with 3 wires, not sure what the third wire does.
Tachometer probably.
