Controlling a brushless part fan?

pkirill

I've got a nice 24v brushless 5015radial fan that puts out a very quiet 6cfm. The problem is it doesn't like to be PWM controlled. Anything under 100% and it stops spinning. It does a fine job when I connect it to my bench power and adjust the voltage up and down. I was wondering if there is anywhere I can connect on a Duet 2 Wifi to control the fan using voltage? If not the Duet 2, how about the Duet 3 mini? Alternate question - would adjusting the frequency (currently 500) make a difference?

Thanks for any help!

Alex.cr

@pkirill
Adjusting the frequency should help. I have fans that run at 60hz very quietly. I have also had some success higher frequencies as well. Try this before looking for alternate means.

There are some Pwm to voltage modules(including a few people on the forum that have designed them), but these seem overkill to me for most situations.

pkirill

@alex-cr I'll give it a shot! Much appreciated!

pkirill

So after a few more tests, I’m discovering that my two always on fans work, but I’ve only got one working PWM fan. I’ve tested the continuity ban the jumper pin and V at the mains and I get it. I tested the three little mosfets and i think that’s where the problems are…

I may try to trouble shoot some more or maybe kick for a new new board… I welcome any additional thought on the matter, Thanks!

dc42

@pkirill it's quite common for 2- and 3-wire radial fans not to work with PWM. Solutions include:

find a 4-wire radial fan
use 65kHz PWM frequency (not possible with DueX fan outputs) and a LC filter
use a board to convert the PWM to analog

Egon.Net

@dc42 said in Controlling a brushless part fan?:

use a board to convert the PWM to analog

I went that route:

https://forum.duet3d.com/topic/21680/designing-a-pwm-to-analog-mini-board-for-fans

pkirill

@dc42 Ah! - will give that a try... And I probably should have started a new topic with my last post - while waiting for response to my original, I was working out settings for a "normal" 24v radial and 3010 hot end fan (E3d V6). I've had this board for a couple years, but it's been off for the last 6 months. I'm starting to remember why I had the HE fan on an always on port and the part fan on Fan 1. I seem to recall that of the PWM locations, only the middle (Fan 1) was working. I have some questions on how to test for that, but will start another thread...

For Google's sake, I'm going to put my heater and fan settings here (the terminal block for E0 is wicked loose so I moved it to E1):

(firmware version 2.03, board version 1.04)
; Heaters
M307 H0 B0 S1.00
M305 P0 T100000 B4138 R4700
M305 P1 B4725 C7.06e-8e
M143 H0 S120
M305 P1 T100000 B4138 R4700 X2
M143 H1 S285
M305 P2 T100000 B4138 R4700
M143 H2 S285

; Fans

M106 P1 T75 S255 H1:2
M106 P0 S0 I0 F500 H-1
M106 P2 S0 I0 F500 H-1
M143 S285

pkirill

@egon-net That is awesome - Thank you!