PS_ON with expansion boards

engikeneer

Following on from this thread earlier today: https://forum.duet3d.com/topic/24391/power-wiring-6hc-1lc-main-relay, I've been having a few thoughts about how best to use the PS_ON function when using expansion boards.

Background - I have a Duet Wifi in my current printer with an external 5V supply and a relay on the 24V supply connected to PS_ON. I like this because it means I can play with settings, get thing uploaded etc without fans running or accidentally turning heaters on, espiecially as I'm not always in front of my printer when I'm using it (it's in the garage). I also like the idea that it could kill the power if it detected a fault, but I'd be able to see what fault had occurred.

Now, I'm planning on building a new printer (or more likely rebuilding my current printer) as a tool changer with a D3 Mini and toolboards (and maybe either a 3HC, or a second D3 Mini as an expansion). So how do I go about setting up the PS_ON to work like on the D2Wifi?

If I connect it all up the same as my current printer, the toolboards won't power up til I turn on the relay, so the config.g will fail...

Option 1 - So as the linked OP did and just turn on the relay in config. Kinda defeats part of my aims with it, but I still get the fault safety working. What happens if the heater fault that tripped it was on one of the tooboards that is now turned off?

Option 2 - Run a bare minimum config, and have a second config macro that turns on the relay and maps all the toolbaords etc which I call when I'm ready to start printing. Similar to Option 1 but get some ability to interface with DWC without Vin applied

Option 3 - Do away with PS_ON

Option 4 - any other magic ideas...?

While I'm asking, is it possible to provide external 5V to the 3HC? It is for the D3Mini, but would this also power CAN (e.g. if I had two of them), or would that need Vin applied?

DIY-O-Sphere

@engikeneer
I would expect that

M80                               ; switch Duet on
G4 S1                             ;wait for expansion boards to start

in the printing start code would be sufficient.
Maybe the S Parameter needs to be increased a little.

The other possibility is something like described here, but with this the whole machine is powered on or off.
I can confirm that this also works perfectly with the toolboard.

engikeneer

@diy-o-sphere so you can map pins on a toolboard (in config.g) that isn't powered/connected? I didn't know if that might cause errors etc which impact the config running?

DIY-O-Sphere

@engikeneer
I have just recently tested this for you and it really does not work. The relay is not switched permanently when the toolboard has no power.

Edit:
Therefore option 2 may work.

dc42

@engikeneer the Duet 3 expansion and tool boards are not designed to accept an alternative source of 5V power. Therefore, if you start up your system with 5V power only, you must defer using commands that refer to devices on tool and expansion boards until you have applied 24V power and waited a couple of seconds to allow the power to stabilise - as you describe in option 2 in your post.

The CAN transceivers are powered from 5V, therefore it would be possible to communicate with and configure a Duet 3 Mini used as an expansion board without VIN power, if that was also provided with separate 5V power.

A possibility for your 3HC is to supply it with VIN from both 24V and e.g. 9V power fed via two Schottky diodes (one from each supply) so that it gets 24V when the 24V PSU is on and 9V otherwise. A 24V heater supplied with 9V will produce 14% of its normal power so it would be relatively safe if it gets turned on.

engikeneer

@DIY-O-Sphere thanks for checking for me!

@dc42 thanks for clarifying. I think I'll stick with two D3Minis in that case. I'm planning triple z, x and y on the main board, then the coupler and a cyclops as bowden from the expansion, with the other tools as toolboards. Keeps room for expansion for a height adjustable nozzle wiper or something else in the future if I go D3Mini and I'm not sure if I'll need the higher currents of the 3HC.

Will have to think how best to setup the PS_ON macro and main config.g but all sounds doable