CPAP/Centrifugal Blower

[dhusolo]

I'm trying to setup a WS7040 centrifugal blower and 24v driver on my Duet3 + RPI4.

Before I installed it I had it connected with a 24v power supply and used my bench top power supply with + connected to VSR and GND to GND. The fan would turn on when I would apply .6v or more.

Now connected to the duet by the attached wiring and configured as

M950 F0 C"0.out9" Q2000
M106 P0 C"CPAP Fan1" S0 B0.1 H-1

I've also tried a number of values between Q500 and Q65535.

The issue is the turbine won't turn on until the fan slider is at 15%. While troubleshooting I used a volt meter and probed the VSR pin and the 24v - on the driver board with the fan set to 5% and the turbine started to spin. Do I need to invert 0.out9 or what am I missing?

Or do I need to purchase a frequency to voltage converter like this

[Heartleander81]

I have the same too.
I haven't inverted anything either and only use 15% or more in the slicer.

But if there is a possibility that it starts under 15% I would be interested in it.

[dc42]

@heartleander81 @dhusolo fans generally have a minimum rpm (and hence PWM) that they can turn at.

[jackantubis]

I have the same type of CPAP, I can't go under 15% too, the board seems to have a minimum voltage startup. @dhusolo

Maybe you can configure in RRF 0% for the slicer matching 15% for the FAN to keep easier slicer setting to avoid false 0% with 10% set in the slicer. @dc42 ?

If someone found the CPAP board schematics I could investigate deeply (I'm electronic engineer)

[dc42]

@jackantubis if you set the L parameter in the M106 command to 0.15 then I think a command for 10% PWM should be translated to 15% PWM.

[dhusolo]

@dc42 I was hoping to figure out a way to not have to set min/max speed. Would it be possible to use an open extruder heater port?