Frequency Discrepancy Between Two Duet2Ethernet Boards



  • Hey there!

    I am having an interesting bit of confusion going on with my two Duet2Ethernet boards. Oneoperates differently than the other in terms of the PWM controls for the part cooling fan, but the printer setups are identical. For the first one, I can change the operating frequency in the config.g file from 1 to 1000 Hz and it works at different all different speed settings, no problems. The second one only works with operating frequency of 1 to 10 Hz to be able to operate at all different speed settings. If I change the frequency >10 Hz, the fan only works at the 100% speed setting. This would be fine if the fan cooled the same on 10 Hz (second board) as the one at 250 Hz (first board), but it does not. I can hear the fan trying to start up, it creates a buzzing, but even "kick starting" it with a little spin doesn't get it going.

    Troubleshooting I tried:

    1. Changing the fan port on each printer and the fans function the same.
    2. Voltage from each PSU is 24.0 +/- 3 V (it seems the boards don't pull constant loads from the PSU and it fluctuates a bit). Changed voltage to 25.0V and still same results.
    3. Tried swapping fans between the printers and even using a third fan (going on a different board and printer). Same issue.
    4. Tried starting at 100% and working the speed down, and after 90% the fan stops.
    5. Changed electrical outlets and circuits. Same issue.
    6. I tried working the port a little and ran the print fan for an hour, and that didn't do anything, to change the frequency range.
    7. Just in case it was causing an issue, I also replaced the fuse. Issue still occurs.

    Any idea what is causing the variance? Which board is operating correctly? I don't like the idea that I'll have to create two different profiles between identical printers, besides the fact that one board is clearly not operating correctly and could lead to other problems in the future.

    Thanks!


  • administrators

    Are both boards running the same firmware version? Send M115 to check.



  • Printer One:

    2/12/2020, 12:50:46 PM M115

    FIRMWARE_NAME: RepRapFirmware for Duet 2 WiFi/Ethernet FIRMWARE_VERSION: 3.0 ELECTRONICS: Duet Ethernet 1.02 or later FIRMWARE_DATE: 2020-01-03b3

    Printer Two:

    2/12/2020, 12:50:52 PM M115

    FIRMWARE_NAME: RepRapFirmware for Duet 2 WiFi/Ethernet FIRMWARE_VERSION: 3.0 ELECTRONICS: Duet Ethernet 1.02 or later FIRMWARE_DATE: 2020-01-03b3

    I also based the settings for the second printer off the ones I got working on the first one. So they have identical everything except the part cooling fan frequency.



  • Do you see a control (slider) for these fans in Duet Web Control? If so, does moving slider lead to any insights?



  • @Danal That's how I have been controlling the speed % and can tell at which speeds the fan turns on/off.



  • Excellent.

    Here is an absolutely weird long shot: DWC does cache certain thing about the configuration, and can potentially store them on browser local storage (that is the PC or Mac), and/or it can store certain things in a file on the Duet itself.

    Again, a long shot... Try a completely different browser or PC. If you've been using Chrome, use Brave or Edge. Etc. See if there is any difference.

    Edit: Oh... and turn OFF the setting to store configuration on the Duet SD card.



  • Just tried on Edge and Firefox (I use Chrome, usually) and it didn't work. I also have a PanelDue attached and adjusting using that, instead of Duet Web Control, also doesn't make a difference.



  • Yeah, it was a shot in the dark.

    Well, you have a very intriguing mystery on your hands. I am truly stumped for things even to diagnose this! Maybe sleeping on it...



  • Do you have an oscilloscope? Tried to look at the output PWM signals?

    (even a cheapo DIY kit should do https://www.aliexpress.com/item/32588011154.html )


  • Moderator

    Just to confirm, you've moved the same fan between both printers to eliminate the fan itself, right?



  • @zapta I have access to one. That seems like a lot of unnecessary work at the moment, though. Maybe if it's the difference between getting a replacement board and being stuck with this one (assuming this second board is faulty), then sure, I'll do a little diagnostics work like this.



  • @Phaedrux I have tried all three fans I have on all 3 ports -- fan0, fan1, & fan2. One is on the first board, as described above, and it has the same issues on the second board that the other two fans have. The other two fans are new and were purchased at different times -- about a month apart.

    Edit: All the fans work fine on the first board.



  • How about swapping the 24v power supplies between boards (or boards between power supplies)?


  • administrators

    Are the fan voltage select jumpers in the same places on both boards?

    Are you getting 24V out of the fan ports when they are full PWM? CAUTION: be VERY CAREFUL when measuring it - users frequently short the fan pins together when trying to measure the output voltage, and that blows the mosfet.



  • @dc42 said in Frequency Discrepancy Between Two Duet2Ethernet Boards:

    CAUTION: be VERY CAREFUL when measuring it - users frequently short the fan pins together when trying to measure the output voltage, and that blows the mosfet.

    Oh so true <sigh>


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