Berd-Air pump configuration notes for Duet users


  • administrators

    I have seen a lot of questions about setting up a Berd-Air pump on the Duet and since I have done just that recently I figured I would post some of my experiences.

    1. If you are running a newer Duet you can wire the pump directly to the board so long as you are using an appropriate flyback diode, and follow @dc42's recommendations in this thread to make sure you are protecting the fan MOSFET adequately. I believe on older Duets you will in fact need to use the e-switch or an equivalent external relay / mosfet / opto-isolating circuit. I have an e-switch which I used initially and it requires some soldering skills to build, but worked really well. I also used the YJ-Pad which simplified the wiring somewhat.

    2. Running the pump at an adequate PWM frequency will DRAMATICALLY reduce the noise and vibration from the pump. I run mine at 25500khz with no issues. I find that the pump/tube combination is noticeably quieter than my old axial fan /shroud setup and I really barely notice the pump noise over the sound of my extruder most of the time.

    3. Running the pump at an adequate PWM frequency will DRAMATICALLY reduce the amount of heat that the motor generates. When running at a low PWM frequency my motor was often too hot to touch after running for only a few minutes. Once I bumped that up the motor gets only slightly warm after running for a few hours.

    4. If you are planning on mounting it to the frame of your printer vibration dampening is essential. I found that my piezo probe was quite helpful in this regard as I was able to test several different strategies and monitor the results by looking at the piezo sensor level. I ended up using the 3mm larger standard mount with some pieces of 1/4" ID rubber vacuum tube from an automotive shop as "insulation" between the mount and the motor, and the mount and the frame. To accomplish this I cut some lengths of tubing and then cut that tubing in half across it's diameter, this gave me a nice "arch" of tubing that I then wedged into the mount to act as a dampener as shown in this picture:

    0_1525641083851_berd-air-mount.JPG

    I used three pieces of tubing in the mount, and one between the mount and the frame. Ideally I would have also isolated the screws going into the frame as they are still quite capable of conducting vibrations but I have not yet designed that mount.

    I run the Berd-Air from about 20% - 75% in my slicer for PLA and it works great, I plan on dialing that in a little bit more but thats a good starting range.

    Hope this helps someone!

    -M



  • You're not going to be able to dampen the motor with just soft mounts if your holder is rigid. There is a floating mount for berd air motors on Thingiverse. If your fan runs hot, you can search eBay or AliExpress for "540 motor heatsink" to get a heatsink and fan combo to cool the motor down. I use an aluminum heatsink with a constant fan that is always on as soon as I turn the machine on. I also got a panel meter to give me the voltage reading based on the PWM duty cycle and the current going through the motor. The current on the stock motor fluctuates from 0.8A to 2.1A. It may need a good break-in period to stabilize.



  • I ended up using a heatsink like this one to help it cool down. Its not so bad now that its running at around 0.9A at around 8V with the PWM set at around 60-70%. I have a 12V motor.

    0_1525667943428_53b408c9-11d1-4ac2-a0bd-d3eedd0e5aa5-image.png


  • administrators

    Seriously...check the PWM frequency on the fan port you are using to drive it. Once I bumped the PWM freq up to 20k the temp on the motor dropped like a rock.



  • just to add to this we found that the 12V motors run a lot hotter than the 24V ones also the 12V ones are quite able to take out the Mosfets on the Duet (We had this happen to a friend of mine) on testing we found that the coil resistance on the 12V pumps was quite low and they could possibly draw an inrush current of around 9 amps (Coil resistance measured between 2.7 and 3.2 ohms depending on where in the rotational arc it was). The onboard fan misfit recommended max current is 1.5 amps.

    the 24V pumps are also much quieter than the 12V ones and they use 550 series motors not 540 ones (A bit larger they both use the 555 series motors.

    So I would suggest if useing 12V systems then def use a external Set board (I used the Power Expander from Reprap.me) and maybe even a separate PSU for them. I swapped mine out to 24V but still kept the power expander for a little bit of additional safety.

    Doug



  • Thanks for this!

    I've confirmed much improved noise level and less heat running at the higher frequency both on 12V and 24V Berd-Airs.



  • @msquared The PWM had nothing to do with my high temps and high current. I was running it directly from my variable bench power supply at a fixed DC level and it was still overheating. It has stopped doing it now, but it was not related to the PWM frequency. I did run my motor through a break-in and cleaned all the residue out. It has functioned fine since. I have been running the motor at different voltage levels and I know it randomly goes up in current. It may have been due to friction on the sleeve bearings. Its running at around 8.2V at 0.85A, which is very good. It runs very cool and quiet.



  • I'm a bit confused about PWM. I have a Berd-Air pump on fan 0 through an e-switch mosfet.
    If I add an F25500 parameter to the M106 I have very little control over fan speed.
    If I leave off the F parameter I can vary pump speed from 0 to full speed. It seems that the higher the PWM frequency the less control over fan speed.

    When you run with a high PWM frequency are you still going through an e-switch?


  • administrators

    @davea said in Berd-Air pump configuration notes for Duet users:

    I'm a bit confused about PWM. I have a Berd-Air pump on fan 0 through an e-switch mosfet.
    If I add an F25500 parameter to the M106 I have very little control over fan speed.
    If I leave off the F parameter I can vary pump speed from 0 to full speed. It seems that the higher the PWM frequency the less control over fan speed.

    When you run with a high PWM frequency are you still going through an e-switch?

    I was not. I still have my e-switch lying around and I may get a chance to test that later tonight or tomorrow and let you know my results. It is very possible that the e-switch may not respond to high PWM values as well as the pump does directly. If that is the case I have a DC-DC SSR lying around and I may give that a shot to see if it makes a difference.


  • administrators

    For reference here is a DB monitor of the pump running at very near full speed during a print. This is with the phone about 1" from the pump.

    0_1525796801115_IMG_7722.jpg



  • @msquared

    Brushless? ☺


  • administrators

    @klcjr89 said in Berd-Air pump configuration notes for Duet users:

    @msquared

    Brushless? ☺

    This was actually the brushed version. I will put up something with the brushless in a day or so.



  • @msquared About the flayback diode, your link points to a 1N4007.
    I have first tried this one, but it got pretty hot.
    After some googling I think the reason is that the diode is just too slow for a high frequency of 25kHz (reverse recovery time of 30us).
    I have replaced it by a schottky diode that doesn't get warm.

    And I would like to know what motors temperatures you observed with the standard pump?
    For example, mine has reached about 50°C after a while running at 50%... I don't know if this is good or not...


  • administrators

    If you are using a high PWM frequency (you mentioned 25kHz), please check also that the mosfet isn't getting hot.



  • I've been using:

    • The flyback diode provided with the eSwitch kit, sans the rest of the kit.
    • The current limiting thermistor DC42 linked to.

    I'm getting great results at 25kHz freqency. Prior to changing the frequency, my minimum operating range was about 25%. I'm now able to operate at 20%, and my understanding is the current limiting thermistor is dropping voltage a touch based on the ~30 Ohm resistance I measured when checking my circuit.



  • @dc42 Yeah, the mosfet gets indeed a bit hot.
    Hard to measure that tiny thing with a thermometer, but from touching it, I would say roughly around 60°C as I can still touch it for at least a couple of seconds.


  • administrators

    Duet boards with PCB revision 1.02 and later have flyback diodes already included on all fan outputs.



  • @gen2eng

    So you've set M106 with F25500 as PWM frequency parameter? I've got the same configuration and mofset is well cooled, just asking before changing the configuration.



  • @hergonoway said in Berd-Air pump configuration notes for Duet users:

    @gen2eng

    So you've set M106 with F25500 as PWM frequency parameter? I've got the same configuration and mofset is well cooled, just asking before changing the configuration.

    Correct, I'm using F25500 on a 24V (1.03 Duet Wifi) and 12V (0.85 Duet) without issue. I've got a flyback on both. The 0.85 needs the external flyback, but the 1.03 does not. I am not using the eSwitch module.



  • @MSquared Any progress with the brushless pump? 🙂


 

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