25.1V under no load, but 24.2 under load. Okay?



  • So I replaced the power supply on my printer. (I have a collection of Meanwell supplies that have arrived with the cases deformed by rough handling in shipping, most still work fine, they just look terrible.) Attached pic is the box the current PSU came in, and it's one of the least damaged.
    0_1547743796222_psubox.png

    DWC is reporting that this one is running 25.1V when the printer is under zero load, and the adjustment pot is pretty close to it's minimum setting. (I dislike setting trimpots to their stops in general, but if this is potentially problematic, I will. Or I'll live with the dented case PSU for a while longer.)

    While printing, if anything is using much current (The bed heater is guaranteed to drop voltage read.) the voltage drops a bit, and it seems to hang around 24.2-24.4 while the motors are moving and the heaters are on.!

    Anyway, if this voltage isn't going to cause a problem, then I'll let it be. If it is a problem, then I'll put the old PSU back on.


  • administrators

    Yes that's OK. The voltage measured by the Duet isn't as accurate as a good multimeter.



  • f you want to see less voltage drop, just go for thicker wires, or much shorter, between the PSU and the Duet.



  • @dc42 said in 25.1V under no load, but 24.2 under load. Okay?:

    Yes that's OK. The voltage measured by the Duet isn't as accurate as a good multimeter.

    Good enough. I was pretty sure that my multimeter was reading in the 24.x range, but I couldn't remember if I had heaters running while I measured it. I suppose that I should measure again.

    @catalin_ro said in 25.1V under no load, but 24.2 under load. Okay?:

    f you want to see less voltage drop, just go for thicker wires, or much shorter, between the PSU and the Duet.

    I'm running 14AWG now, the wires are a little longer than I'd usually treat as ideal, since the PSU is opposite the Duet on the printer for cooling reasons, but I didn't see a difference in drop using 12AWG wires only 20mm long when testing. I'd use the 12AWG wire, but I on;y have enough of one colour, and I dislike wiring DC with the same colour for positive and negative. I suppose that I could twin the 14AWG, but really, it ought to be adequate. Nothing gets hot, which is my largest concern. The 12V supply to the V_Fan connector is 18AWG, but considering that's going through the 1A fuse, I don't see a problem there. 🙂


  • administrators

    @supraguy said in 25.1V under no load, but 24.2 under load. Okay?:

    The 12V supply to the V_Fan connector is 18AWG, but considering that's going through the 1A fuse, I don't see a problem there.

    The 1A fuse won't help you, because it is connected between VIN and the VIN end of the fan voltage selection jumper block.



  • More good to know, but I've also got a 1A fuse on the 12V supply, right at the buck/boost. The supply is supposed to be capable of supplying 5A, but I have the fuse at the supply. I'll add that i have a 15A fuse at the 24V PSU, since there's about 450mm of wire between it and the Duet where the input power fuse is.

    I'm a car guy. We believe in fuses at the power source.


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