@diy-o-sphere Thanks. That helps a lot more than the only thing I had found about it, which was here: https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans and didn't include anything about adding more than one of anything.

I decided to replace the whole board, since I believe I short circuited something when I was doing the testing. I also broke at least one of the plastic "tongue" things, and possibly a pin, when I was doing all the plugging in and unplugging.

@phaedrux said in Confused about fan voltage.:

@blaidd said in Confused about fan voltage.:

I have two (24 volt) 5015 blowers, each red wire and each black wire are connected together so there's a single 2-way plug.

The PWM fan headers switch the negative side, so you can't share the negative wires for 2 separate fans. You can share the positive wires though.

I did have the two negative wires (and the two positive wires) connected so I could run the two blowers in parallel (one on left side, and one on right side).

It worked for a while, but I want to be sure to do it right with the new board. I noticed when I was setting up my dual Z axis there was a way to connect them to two different pins but control them with a single command from the slicer:

M584 X0 Y1 Z2:4 E3
M574 Z1 S1 P"zstop+e1stop"

Is there any way to do the same thing with the blower fans? For example, instead of twisting the wires together, plug them individually into Fan0 and Fan1 slots, and do something like:

M950 F0 C"fan0" Q500
M950 F1 C"fan1" Q500
M563 P0 D0 H1 F0:1

For what it's worth, I intend to update the new board to the newest FW and just copy the config.g (etc) files over.

@phaedrux Well, crap. I finally managed to take a really good picture of the area, and I'm thinking you're right, the mosfets do seem to have that black spot.

@phaedrux Even with a single blower fan plugged directly into the board, it still does not work.

@phaedrux Oh, and these are the blowers I used. I'm not sure which specs you're looking for, but hopefully it'll be on that page: https://www.amazon.com/gp/product/B0755BY9RH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

@phaedrux

I currently have the main part taken apart, but here's the quick connect plug I mentioned.

And here is the board itself, which is in a difficult position because I built an enclosure and attached it underneath, but I don't see anything that looks melted or blown.

If there's anything you want me to zoom in on, or if you need me to temporarily pull off the duex board for my thermistor so you can see the board underneath, let me know. If you need to see the bottom of the board, I can do that too but it's going to take a bit of work to get it out.

@fcwilt

@fcwilt said in Confused about fan voltage.:

@blaidd

So you are measuring the 2 volts with the fan connected and you are measuring across the two terminals the fan wires are connected to?

Exactly. 2.0 volts if the blower is plugged in, 20.4 (now 24) volts if the blower is not plugged in.

Does the fan speed vary with the speed settings?

Frederick

The blower fan does not come on at all, no matter how I adjust the speed or the config settings, that is the problem.

@phaedrux said in Confused about fan voltage.:

The PWM fan headers switch the negative side, so you can't share the negative wires for 2 separate fans. You can share the positive wires though.

That's what's confusing me. It was working that way several months ago. I had the two different blower fans, with the two red wires twisted together and put together into the one hole of the plug, and the two black wires twisted together and put together into the second hole. Now, I can't get it to work, but I didn't make any changes, other than not using them for several months. I'll try to take some pictures later.

@fcwilt I freely admit I don't know a whole lot about electronics, so perhaps I'm doing this wrong? I didn't even think you could measure a single pin. This is what I've been doing: I have one of those digital multimeters with a red wire and a black wire, and you can turn the dial to select what you want to measure. I set the dial to V200 (V20 gives me an error, presumably because it's above 20), then I touch the red probe where the red wire goes, and the black probe where the black wire goes. I did this on the pins themselves, and on the tiny bit of exposed metal on the connectors (the ones I'm using to connect the fan to the DB15 wire are similar to the ones that come with the Duet for connecting to the board in that you clamp a metal piece onto the wire, then shove it into the plug, and the place where it has a little piece that clicks in to lock it leaves a tiny bit of the metal showing).

I added the L0 you mentioned to the end of my M106 line, and with the fans plugged in I got the same result as before: 2.0 volts regardless of whether it's set to 0%, 100%, or anywhere in between. The change comes when I unplug the fans. Then it registers 24.0 volts at all times, instead of the 20.4 it was registering before, again regardless of whether I have it set to 0%, 100%, or anything in between.

First, the obligatory stuff:
Heavily modified Ender 3 machine,
Duet 2 Wifi,
FW version: 3.2.2,
running via web interface

I should also mention that I cut all my cables and put a DB15 cord (with the ends cut off and attached my own ends) so I can make it modular in the future, and I can just disconnect things when I'm working on the machine.

Now for my problem: Everything was working fine for a long time. I was trying to run ABS for a little while so I had the "tool fan" turned off in my slicer, although I never did get the ABS to work properly (I suspect it was because of humidity). I went to switch back to printing PLA, which had been working fine, but now I cannot get my tool fan to work. I have two (24 volt) 5015 blowers, each red wire and each black wire are connected together so there's a single 2-way plug. I have tried everything I can think of, switching it between Fan0, Fan1, and Fan2 on the Duet board, and obviously switching the relevant code in the Fans section (both M950 and M106). I left it in Fan1 because I accidentally snapped the little plastic tongue thing on Fan0 during all my testing.

Ultimately, I discovered the following: The regular hot-end fan (in always-on position 1) always has 24 volts running to the fan itself, whether the fan is plugged into my makeshift quick-connect plug or not. However, regardless of which position I put the blower fan plug on the board (Fan0, Fan1, or Fan2), it always has 2.0 volts running to it even when the tool fan is set to 0%. If I do NOT have the blower fans plugged into my quick-connect plug, and I set the tool fan control to 100%, I measure 20.4 volts... but if I do plug the fans in I still only get the 2.0 volts. I have no idea what's going on, or why I'm getting different results based on whether the blower fans are plugged in or not.

Edit: I should also point out that when I put the blower fans quick-connect plug into the quick-connect plug for the hot-end fan, they both came on at full speed, so the blowers themselves are working properly.

contents of config.g:

; Configuration file for Duet WiFi (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.1 on Mon Jun 01 2020 01:24:07 GMT-0700 (Pacific Daylight Time)

; General preferences
G90                                                ; send absolute coordinates...
M83                                                ; ...but relative extruder moves
M550 P"Ender 3"                                    ; set printer name

; Network
M552 S1                                            ; enable network
M586 P0 S1                                         ; enable HTTP
M586 P1 S0                                         ; disable FTP
M586 P2 S0                                         ; disable Telnet

; Drives
M569 P0 S1                                         ; physical drive 0 goes forwards
M569 P1 S1                                         ; physical drive 1 goes forwards
M569 P2 S0                                         ; physical drive 2 goes backwards
M569 P3 S1                                         ; physical drive 3 goes forwards
M569 P4 S0                                         ; physical drive 4 goes backwards
M584 X0 Y1 Z2:4 E3                                 ; set drive mapping
M350 X16 Y16 Z16 E16 I1                            ; configure microstepping with interpolation
M92 X162.24 Y160.92 Z804.32 E824.1                 ; set steps per mm
M203 X9000.00 Y9000.00 Z600.00 E6000.00            ; set maximum speeds (mm/min)
M566 X480.00 Y480.00 Z60.00 E300.00                ; set maximum instantaneous speed changes (mm/min) aka jerk
M201 X600.00 Y600.00 Z120.00 E5000.00              ; set accelerations (mm/s^2)
M906 X1680 Y1680 Z1680:1680 E900 I45               ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                            ; Set idle timeout

; Axis Limits
M208 X0 Y6 Z0 S1                                   ; set axis minima
M208 X235 Y235 Z260 S0                             ; set axis maxima

; Endstops
M574 X1 S1 P"xstop"                                ; configure active-high endstop for low end on X via pin xstop
M574 Y1 S1 P"ystop"                                ; configure active-high endstop for low end on Y via pin ystop
M574 Z1 S1 P"zstop+e1stop"                         ; configure active-high endstops for low end on Z via pins zstop and e1stop

; Z-Probe
M558 P0 H5 F120 T6000                              ; disable Z probe but set dive height, probe speed and travel speed
M557 X10:220 Y10:220 S20                           ; define mesh grid

; Bed
M308 S0 P"bedtemp" Y"thermistor" T98801 B4185      ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0                              ; create bed heater output on bedheat and map it to sensor 0
M140 H0                                            ; map heated bed to heater 0
M143 H0 S120                                       ; set temperature limit for heater
M307 H0 R0.187 C637.8 D3.69 S1.00 V23.7 B0         ; disable bang-bang mode for the bed heater and set PWM limit

; Hotend
M308 S1 P"spi.cs1" Y"rtd-max31865"                 ; create sensor number 1 as a PT100 sensor in the first position on the daughter board
M950 H1 C"e0heat" T1                               ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 R2.995 C175.4:167.5 D4.62 S1.00 V23.6 B0   ; disable bang-bang mode for heater and set PWM limit

; Fans
M950 F0 C"fan1" Q500                               ; create fan 0 on pin fan1 and set its frequency
M106 P0 S0 H-1                                     ; set fan 0 value. Thermostatic control is turned off

; Tools
M563 P0 S"Hotend" D0 H1 F0                         ; define tool 0
G10 P0 X0 Y0 Z0                                    ; set tool 0 axis offsets
G10 P0 R0 S0                                       ; set initial tool 0 active and standby temperatures to 0C

; Custom settings
M572 D0 S0.08                                      ; set pressure advance K-factor

; Miscellaneous
M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" ; set voltage thresholds and actions to run on power loss
T0                                                 ; select first tool

Well, we've established the problem is not with the Duet (or, more accurately, the settings I adjusted on my Duet). So I'll just delete my Cura custom profile and start over with the Chep profile that I know functions properly. I'll have to spend a few hours calibrating stuff all over again, but half the stuff (the ones I saved in Duet config.g) is already done.