14 Volts?

  • Hello, I was wondering if there was any information available about whether it would be okay to adjust the pot on my 12v power supply up to about 14v? The two main reasons I wanted to do this were:

    • I was hoping it would help to improve the heat up time of the hotbed for when I print with ABS(60deg isn't too bad, but getting up to 90deg takes a long time).

    • I was also wondering if it would help with the Recover from power loss event? From what I saw the recommendation is to use a 24v power supply for this, as it gives a bit more time to move the hot-end away from the print and save the file progress. Would setting it to 14 v and having a recover file fire if the power dropped below 12v be a reasonable option?

    I don't want to fry my duet though, but I thought I saw someone on this forum mention that they had turned their power supply pot up and were getting betting heat-up times. Unfortunately, I don't have a link to that particular post, but I did find a video from Thomas Sanladerer, https://www.youtube.com/watch?v=pRX_uvG9Z-w , where he talked about doing this with a Prusa.

    So the big question: Is this a terrible idea, or will it be helpful?

  • Duet is fine up to 27V, why boosting to 14V should be a problem?
    Only problems possible:

    • fans can have shorted live time, but most of them are ok with 14V
    • check if you power supply have enough power reserve, increasing voltage will also draw more power from you power supply.

  • have you got proper isolation under your hotbed?
    that can have a significant effect on the heat up time.
    a thick layer of cork or something similar.

  • Moderator

    I think that would be alright. The Duet is tolerant up to 26v or so 25v, so it won't mind. Your heaters will heat faster. You'd want to redo your PID tuning.

    Bear in mind that any other 12v components may not like the extra voltage. Fans will run faster, and if they are poor quality may burn out.

  • @dragonn @Phaedrux the limit is 25V - because of the capacitors on the board: https://duet3d.dozuki.com/Wiki/Choosing_the_power_supply

  • administrators

    The limit is because of the 30V rating of the stepper drivers. The capacitors are rated 35V or 50V.

  • So after seeing dragonn's reply I went looking and found/calculated my power draw to be about 240w when running at 12v. If I ran at 14v I believe that draw would go up to about 280w. My current power supply is rated at 360w so I believe that I should have enough power reserve to run at 14v.

    In reply to Veti, I have been running with a layer of cork under the hotbed, and that has definitely helped, but even then my heat-up time to get to 90deg is still painfully long. (Disclaimer, that may be because I am using my old Anet hotbed, I redid the cables though so that it should be safer and betterable to handle the required currents).

    I am also running noctua fans, so I am not too worried about the wearing out, and if they do, then I might be able to upgrade to the PWM Noctua fans and have better control of them for layer cooling.

    Thanks for the feedback, it doesn't sound like there is much of a technical problem with running at 14v. Does anyone know if it would be able to help with the power loss recovery at all though?

  • Moderator

    @grudairian said in 14 Volts?:

    PWM Noctua fans

    You shouldn't need to use the actual PWM Noctua fans to get control of the fans. The Duet should be able to control regular fans just fine with the way it does PWM. You may need to experiment with different PWM frequency in the M106 F parameter to get good low speed results. I think the default frequency is around 200hz, but you can go all the way up to 30000hz or down to 10hz. Adding a small amount of full power blip time can also help get the fans spinning.

  • administrators

    It's unlikely that recovery from power failure would work with much less than 24V power. You need reserve power to lift the head and retract filament enough to prevent the head getting stuck to the print when it cools.

    If you are worried about running 12V fans on 14V, you can put 1 or 2 1N4001 or similar diodes in series with them. Each diode will drop a little less than 1V.

  • here is a very good analysis of the A8 hotbed inclusing higher voltage.

  • @Phaedrux Thanks for the tip about M106, I changed a few things, and now my fan actually works at all power levels. 😃 Before it would only kick in at about 80% or higher.

    @dc42 Thanks for the reply, I just thought it might have been enough extra power to make a difference, but oh well.

    @Veti That's a neat breakdown, the part that seems most immediately useful though is the printed cork support he was using, as my cork has gotten a little saggy. I'm starting the print now!

  • Moderator

    @grudairian said in 14 Volts?:

    printed cork support

    There's a good chance the printed support could soften and deform from the bed heater. On my old i3 I used some high temp RTV silicone to attach the cork to the PCB directly and it worked great.

  • @grudairian
    calculate properly power consumption. It's not linear. In worst case going up from 12V to 14V with consumption of 240W at 12V, at 14V it can be up to 326W! Still in spec, just be aware. I'm running my 3D printer (rated 12V) at 14.7 without load, with load it goes down to ~14.2 and it's without problems over a year.

  • administrators

    @grudairian, increasing voltage from 12V to 14V will increase heater power by 36%. So definitely worth trying if bed heating is too slow. Remember to re-run heater tuning on both hot end and bed.

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