Two (2) Bed Heaters on Duet Wifi

MacNite

Hey Guys,

I am building a large Format using a 410850mm Bed. For Heating I use 2 400400mm Silicone Heaters with 600W each.
Using the two Beds independently works fine:

M140 H1
M140 H2

But I want to use both heaters simultaniously with one single command. I found an old thread where it was mentioned that you could use

M140 H1:H2

To define a Single Bed with 2 heaters.

This does Not Work. If I Set the Temperature in DWC it does only Heat Bed1/Heater1, Not both

Any Suggestion in how to fix this.

Greets
Max

Phaedrux

@macnite said in Two (2) Bed Heaters on Duet Wifi:

I found an old thread where it was mentioned that you could use
M140 H1:H2

Do you have a link to that thread? I can't find anywhere that indicates that.

What firmware version are you using?

MacNite

@phaedrux

Yes , of course. But after further Investigation I think I miss-read that....the M140 H1:H2 only seems to bei a suggested solution, Not an implemented one in the Firmware yet.

https://forum.duet3d.com/topic/3516/using-multiple-bed-heaters/3

Phaedrux

Ah, yes, that seems like a suggested solution, but I don't think that's been implemented.

I'm not sure how you would gang together 2 heaters to act as a single one in software. If you're using 2 SSR you could connect the control signals for both to the same heater terminal I suppose.

Is there a reason you don't want independant control?

deckingman

Here is a fudge which might work. Completely off the cuff and untested. But if you create a dummy tool (say T3) and assign both bed heaters to it, then you could use G10 to set the standby temperatures for both heaters. You'd likely need to set the active temperatures too. Then if you initial make that tool active, it should start to heat, but when you make the normal hot end tool active, the dummy tool (the bed heaters) should maintain the standby temperatures. To use G10 with multiple heaters, you use the colon separator for the S and R values which means that each heater is given its own set value. So you could run one at say 60 and the other at say 70. Although in practice, thermal conduction might preclude that from happening.