Duet 3 powering via ext 5v

Hutch118

Looking for some clarification on using an external 5V power supply with Duet3 v0.6 board. The SBC that I am planning on using can pull 3-4A + screen usb etc. I plan to direct wire 5v to the SBC and to the Duet3 so that neither is pulling power through the board but parallel.

I see the [ext_5v] 5V in and ground to connect the external 5V supply.

Then for the jumpers I have become confused. Internal 5v En jumper (off) / SBC->5V (on?) / 5V->SBC (off).

Or maybe just power the SBC separately from external 5V supply and leave the internal 5v enabled for Duet. Like 5V En jumper (on) / SBC->5V (off) / 5V->SBC (off)?

gtj0

If you're direct wiring 5v to both the duet3 and sbc you want NO jumpers installed on any of the 5v options pins.

Hutch118

@gtj0 Thanks. Do you think that's the best way to go in my situation (direct wire both)?

Seems that I could keep the internal 5v powering the duet (keeping protection intact) and external power the SBC. Also removing the +5V (pin2,4) from the ribbon cable.

Is there a board schematic somewhere? I'm only seeing the duet2.sch on github

gtj0

@Hutch118

As long as the same power supply is powering both boards I think it's fine. That's how I have it. If you use the internal supply, you lose the ability to turn on or off the Vin supply from the ATX_PWR pin. If you're worried about protection, you could always place in-line fuses in the supply lines to each board. Don't worry about removing the 5v lines on the ribbon cable. As long as you have no jumpers on the 5v->SBC or SBC->5v headers, you're OK.

I don't think @T3P3Tony has published the Duet3 schematics yet.

dc42

See the second bullet point at https://duet3d.dozuki.com/Wiki/Duet_3_Mainboard_6HC_Wiring_Diagram.

Hutch118

@dc42 If I configure like the second option- "If you want the SBC to provide 5V to the Duet then remove the jumper from 5V->SBC and from Internal 5v En. Place a jumper on SBC-5V". Then power is going to the SBC then up the ribbon cable (pin 2,4) to power the Duet? Where does ext_5v fit here?

gtj0

@Hutch118 Actually those instructions from the Wiki are incorrect.
To power the Duet from the SBC you need both the 5v -> SBC and the SBC -> 5v jumpers installed.
ext_5v does not fit at all. You can still use the ATX_PWR pin on that connector to control the Vin power supply though.

Hutch118

@gtj0 Thanks. And just to rest my mind [both the 5v -> SBC , SBC -> 5v jumpers installed and 5v En jumper (off)]. The power will go to SBC, up the ribbon cable to power the duet.

I keep getting distracted on wanting to use those ext_5v pins because they are there. I don't know why this was so difficult for me. I've wired up a few other Duets honest 0-o.

gtj0

@Hutch118 Yep, that's it!

Hutch118

@gtj0 !celebrations! ᕕ( ՞ ᗜ ՞ )ᕗ

frontofit

I found this post when googling for more information about the EXT_5V input and see that this post resolved to the SBC powering the 6HC and doesn't fully address the issue brought up in the title.

In the scenario where I want to supply an external 5v source to my 6HC AND external 5v source to my SBC (Raspberry Pi 4) -

Would I use the EXT_5V input to provide an external 5v source to my 6HC?
What jumper strategy should I use OR should I just remove all power jumpers?

I would normally just "try" something like this out but really want to avoid damaging my board haha. Any guidance would be greatly appreciated.

gtj0

@frontofit Exactly how do you plan to supply the external 5V to the Duet?

Oh...and do you plan on connecting to the Duet via USB and if so, will you be powering it that way? If you want USB connectivity but don't want to power it that way, you'll need a power blocking cable, or a pair of wire cutters.

frontofit

@gtj0 the power source for 5v is an LRS-100-5 meanwell power supply that I am using to power the raspberry PI. I saw the ext 5v plug on the board but no official docs for it and can’t find a clear answer about how to use it. I don’t need USB access to mainboard as I have an SBC and the SBC connected by ribbon cable. I guess maybe I need to back up a little - is the ext 5v plug meant for supplying the 6HC with an external 5V source? Or is it something completely unrelated?

Nurgelrot

@frontofit I'm looking for the same information you are. If you figure it out make sure you post your solution. I have the same 5v PSU as you and given the power draw of the PI4 I want to power them separately. (and only run 5v when not printing) Think most of the power problems people are seeing is starvation on the SBC side.

frontofit

@nurgelrot I will be sure to post as soon as I find out! You are correct about the starvation on the Pi side when it comes to a Pi 4 as the power requirements (for the Pi) are somewhere in the ballpark of 5A whereas the Duet is only able to supply 3A max on top of any other peripherals that require a 5v source. The symptoms usually show up as a warning on the Pi.

I have also read about solutions where the SBC can power the mainboard but something about it just feels wrong, also since that LRS-100-5 can supply up to 18A, I figure why not use it to also supply the duet.

I figured with all of the people on this thread it should have been a slam dunk to get an answer by now. I will post my findings if I decide to give it a go on my own. Hopefully I don't cook any boards haha

gtj0

@frontofit Yeah it's a little confusing and I believe the schematic isn't actually correct with respect to the power control jumpers. Anyway, the +5V pin on the EXT_5V connector is really meant for control only. It has a 220ohm resistor in series and is meant to supply voltage to an external SSR. This way, when the PS_ON pin goes low, the SSR is energized and turns something (presumably an external 12/24V PSU) on. You can't really provide power to the board via this connector.

There is no dedicated pin for providing external 5V power but you still have a few options...

If you don't plan on using the PS_ON pin to control an external 12/24V PSU and you're going to have your 12/24V PSU on all the time, then you can use the internal 5V regulator to power the logic.

If you are, then you can do what I do... Remove the MIDDLE jumper from the power control header and connect your 5V supply to the middle left pin on that header. That's the same pin that would be supplying power to the Duet from the SBC if the jumpers were in place. Note though that there's no protection on those pins so your supply has to be fairly stable. Since it's the same one powering the Pi, then that should be no problem.

One other thing I do that you might find handy is run the Duet's 5V supply through a relay or switch so you can quickly power off the Duet if you have to.

gtj0

@gtj0

oops, had an error in the original pic.

You need to jumper the two bottom pins and provide power to the middle left pin.

Nurgelrot

Sigh. All I want to do is trun on and off the 24v supply with M80/81 while the pi keeps running... So friggin confusing...

gtj0

@nurgelrot said in Duet 3 powering via ext 5v:

Sigh. All I want to do is trun on and off the 24v supply with M80/81 while the pi keeps running... So friggin confusing...

What's still confusing? Jumper the two bottom pins and provide power to the middle left pin.

Alex.cr

@Nurgelrot
The following write up applies to the Duet 3 as well.

https://duet3d.dozuki.com/Wiki/Power_Wiring

Apply 5v and ground to the respective pins of the 5v header, run 5 v power from your supply to the control pin on the SSR and ground to the ps-on pin. Everything will work, this is what I am doing. I removed all jumpers for 5v power.

Edit: M80/81 will drive the SSR like you are looking for.

Also one downside I have noticed is if you are using expansion boards they will not have power on start up and this will cause all kinds of errors upon start up. You can put M80 in your start code but I am also using this to cut power if my mains heated bed has an SSR runaway. Still have to find a work around for that.