Made Duet&PS External to enclosure. Wiring question



  • Hello,

    I extended all of my wiring this weekend, i tested the setup on Sunday and my heated bed / hotend both fired up and worked as intended. Only had an issue with my HE fan & layer fan not wanting to kick on.
    Sat down last night and put a multimeter on the fan lines and discovered they were just reverse polarity. I plugged everything back in and heated up HE, all good. Then i turned the bed on and i heard a small "click" or subtle pop. No smoke. I quickly shut everything off and gave it a few minutes.
    Turned back on, and duet powers up, i can even heat my hotend a little (~50c) but my SSR light isn't coming on and none of my always-on fans either.
    I suspect the Power Supply gave out?
    I was careful to wire everything exactly as it came from the factory. just longer wires.
    Is there anyone that can recommend a couple trouble shooting tips to diagnose G/B PS and to make sure my Duet is still okay?

    One last question, i noticed neither of my 5015 layer fans are working now, will hooking them up for a few minutes with reverse polarity really burn them out?

    Thanks in advance.
    Here is a picture of my new setup
    duet external.jpg



  • @jallen810 not too sure on the power supply. Does it give the expected 12/24V out (disconnect from the Duet before measuring)? I'd probably try powering over USB only and see if you get anything with M122 before putting 12/24V back through the Duet. I'd also do a close inspection of the Duet (unwire and take off the printer) to look for any signs of damage front or rear before putting 12/24V back in. I don't know much on SSRs, but how is the light powered? From 5V, VIN, the Duet control signal?

    When you do power up the Duet again, does it measure the correct VIN in DWC?

    On the fans, I have previously blown 5015 24V fans by wiring them up the wrong way round on my Duet and only powering them for a few seconds. TBH, I was probably lucky not to have damaged the Duet!

    Edit: side note - I'd also be careful with the driver heatsinks you've fitted. They won't do much as the heat will go through the board to the back/underside (the top of the chips ar plastic so don't conduct well) and they may hinder airflow more than they help conduction. General advice is to not fit them in case they short something and to fit a fan to cool the board (like you have done).



  • @engikeneer yeah i was wondering if my wiring gauge is too small for the bed? I used 18ga based on a web calculator's suggestion. My calculations, 200w/24v=8.3A which according to the site i used said i can run 18awg for runs up to 8.5ft? Could that have been wrong and i need to go up to 16awg for the heated bed?

    Are there particular items i need to inspect on the Duet with close detail or just look to see if anything let the smoke out?

    I will try the M122 over USB tonight without 120vac. The light on the SSR seems to be wired in-line with the rest of the wiring to the bed. Ill try to take a better picture later.

    Bummer to hear i fried my nice 5015's -_- it's always something right?

    Good to know about the heatsinks, i always assumed they would be better than not. I will also remove those now that i can use my new fan.

    Edit: this is pretty similar (if not identical, going from memory) to how i wired mine, just obviously a Duet instead of SKR
    https://user-images.githubusercontent.com/57952517/73389072-77511280-42e4-11ea-841e-b761ba411416.jpg



  • @jallen810 18AWG seems reasonable (and I would highly doubt that would be your issue!). Am I right in thinking you are putting mains power to the bed though? so the actual bed current is ~1.7A at120VAC? In which case it's likely not an issue, but I'd always be double careful with mains voltages (check all your insulation etc).

    You could check the schematics for important components, but I'm a Mechy by trade so wouldn't know too well which ones to start with. There may be a few other forum posts you can find about people in similar positions and see which components cleverer people say to check first. Before going down that route, have you checked your fuses on the Duet (and I'm hoping you have one on your mains plug)? 🙂

    Generally you'll be looking for signs of damage on the chips (plastic cover melted, discolured etc) or obvious discolouration marks on the PCB traces. Similar will apply to the PSU.

    What voltage are you using for the fans - is it the 5V duet internal, or the 24V from VIN? I can't tell from the picture.

    There is always the possibility that it is the SSR that has gone. Maybe you could disconnect it from the bed/mains, control it from the duet and see if you get continuity when it should? You can also check the Duet output at the same time. I thought SSRs were fairly bullet -proof if properly rated though so would probably test everything else first.



  • @jallen810 said in Made Duet&PS External to enclosure. Wiring question:

    will hooking them up for a few minutes with reverse polarity really burn them out?

    my (not so) limited empirical data suggest failure is pretty much instant.



  • @bearer yeah bummer good 5015’s are harder to find these days. It’s curious too bc my axial Hotend fan was hooked up backwards but it still works fine...



  • @engikeneer I sat down last night and the SSR and PS are fine. I was able to power it up, I learned the SSR light only turns on when the bed heat is called for. There is no always on indicator. TIL right lol

    Less great news I think I burned out the mosfet for PWM fan 0 and I blew the 1A fan fuse. These explain why all my fans died “simultaneously” I guess. Got replacements on the way.
    Moral of the story, fan Electronics’s are sensitive, don’t swap anything, EVER, while the power is on.
    Good news, RRF3 that I plan on upgrading to in the near future allows me to remap use any pins for fans so I should be fine.

    TL:DR- I’m a dumb monkey and I shouldn’t be in charge of anything more complicated than shoelaces.
    Thanks for advice and sounding board


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