Providing Power to Duet for Hot End and Heated Bed

Finally bit the bullet today now that the 0.85 Duet is available in the US from Filastruder. However, in looking it over, it looks like there is only one input for power, unlike my current RAMPS 1.4 board that has one input for the board and hot end plus a second for the heated bed (at least that's my understanding).

I was planning to use an old ATX power supply with two 12V rails, 12VA and 12VB, with each going to a separate input since they are rated at 15A each. How would I use the power supply with the Duet board? Its been a long time since I took electronics, but can I wire the two lines together into the input (both yellow wires to positive, both black to ground) or do I need a different power source?

Sorry for the rudimentary question.

what is the wattage of ur bed heater. i own a 0.6 vereion of of the duet and i think one 12v rail is enough to run ur printer and hot end/bed.
on he other hand you have nothing to lose if you connect the two rails the way you told. . ur psu is pretty strong there is no need to look another one.

In general you cannot put power supplies in parallel, as there is no guarantee the load will be shared evenly.

Thanks greenman, was thinking that wiring the two might cause an issue.

I might try measuring the amps being pulled during heat-up. I think 15A is the bare minimum I need, so Gaou might be right about using a single rail. Definitely easier to wire.

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greenman100
In general you cannot put power supplies in parallel, as there is no guarantee the load will be shared evenly.

i know for two different psu_s it isn't a must . but on a good psu_s with internal controlled voltage and amperage is it bad? that's what it has to do ( power 2 vgas for example).

edit:another solution is to power with the one rail the duet and through a relay power the hot bed with the other rail . this way you ll have plenty of power for both of them without pushing them to the limits.

also it is good if ur psu is so powerfull to use the 5v rail to plug it in the duet so you dont have to use the onboard 5v regulator.

and finally it would be good if you could measure these 3voltages ( 5v, 12va, 12vb ) under load.

Edited 1 time(s). Last edit at 02/06/2016 02:20AM by Gaou.

To power the bed heater independently, connect it between your chosen positive power supply output and the negative bed heater output. Connect the corresponding negative psu output to the Duet power input terminal block along with the one from the other 12V power supply output.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
To power the bed heater independently, connect it between your chosen positive power supply output and the negative bed heater output. Connect the corresponding negative psu output to the Duet power input terminal block along with the one from the other 12V power supply output.

So 12VA to the Duet power input, 12VB to the heated bed, both 12V GNDs from the PSU to the Duet ground on the power input, and GND form the heated bed to the GND on the Duet for the heated bed? That seems reasonable.

Kurzaa is it a server's psu or an ordinary one ?

I know it old, I believe I salvaged it from a Dell Workstation. Not your standard ATX form factor, it is thin and stretched out with a 20 pin and 24 pin header. Likely around the time MBs first required 24 pin headers.

Thought of salvaging another Dell ATX power supply from a more recent box, but it only supported a 14A 12V rail, not two, and had wires coming out of 2 holes rather than just the one.

I may just buy a more traditional 20A LED power supply like I see a lot of other printers using if this won't work. I also am trying to figure out a way to attach a plug to the heated bed so I can remove it from the printer when not needed or trying to remove a print (Rostock Mini). Leaning towards a 2.1mm DC jack right now, but was originally hoping for a 2 wire DC adapter plug. Found one at Goodwill in the recycle bin, but they refused to sell it to me.

I would not use 2.1mm DC jack on a heated bed. If you have a hobby store nearby see if they carry EC3 or XT60 connectors. For a 20A setup those will easily do the job with very little power loss (I use them on my multi rotors pulling 45A). They should also carry nice silicone stranded wire which is designed for high power situations.

For typical heated bed currents, the smaller EC2 or XT30 connectors would be fine but they are harder to find.

Instead of removing the bed when the print is stuck solidly to it, you could do what most people do, which is to print on glass that is clipped to the bed. When the print is finished, remove the glass bed with the print so it can cool faster, and if necessary put it in the freezer. Meanwhile you can clip another glass plate on and start your next print.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I believe I have an extra set of XT60 plugs in a box somewhere, though they are always a PITA to disconnect. Though I am wondering if DC42 is correct and I need to rethink how I am going to setup the bed. Permanently mounting it won't be as easy as with a Kossel or the SeeMeCNC Rostock's that include heated bed by default.

Thanks for the feedback everyone.

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Kurzaa

Quote
dc42
To power the bed heater independently, connect it between your chosen positive power supply output and the negative bed heater output. Connect the corresponding negative psu output to the Duet power input terminal block along with the one from the other 12V power supply output.

So 12VA to the Duet power input, 12VB to the heated bed, both 12V GNDs from the PSU to the Duet ground on the power input, and GND form the heated bed to the GND on the Duet for the heated bed? That seems reasonable.

Sorry guys for bringing this up but this is what you mean?



If somebody can confirm this i would be gratefull.

edited 6 times. if you guys think i am stupid u r absolutely right .....!

Edited 3 time(s). Last edit at 02/26/2016 02:39PM by Gaou.

I believe that is correct for a Duet 0.6. On the Duet 0.8.5, the bed heater + and - terminals are reversed.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks David .

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Delta Printer
Duet 0.8.5 firmware 1.19

Few weeks late, but thanks for providing the reference graphic Gaou. And I will make sure to confirm polarity before wiring everything together.