I have checked the M122 B1/2 comand. The firmeware update I installed in September, didn´t install the firmeware to the expansions, only to the mainboard. Now I manualy installed the 3.2beta to expansions (with the M997 B1/2) an the mainboard. I keep you updated.
Also I noticed that BigFDM page recommends to use SSRs for this size bed heaters. With Duet 3 it seems that we would be able to drive these with the four IO pins using four SSR or just connect a single SSR's input to OUT0 and then connect these four bed heaters to the SSR.
when mains powered SSR is the way to go for the beds, you could also probably run 4 SSRs off the single output. that would allow you to later reconfigure to use 4 outputs to control quarters of the bed, as well as lower the load and potential need for cooling on each SSR.
(not sure how thermal expansion affects partially heated bed in practical terms, but there are at least on thread on here that deals with it for a large printer).
Reduce the PWM of the heater. This way the heater will heat up slower along the heat to soak into the build platform at a more constant over all temperature. I believe that you can set the PWM on the heater tuning.
Careful, that link actually doesn't apply to the Duet3.
It works for my Duet3 6HC without major issues. The only piece of information missing is to pull the SBC jumpers.
Yeah you're right. Every time I look at the schematic, I get a headache.
The description for the PS_ON header says...
3-pin KK labelled PS_ON: open drain mosfet output for controlling an ATX-style power supply or a SSR. The +5V pin can also be used to provide external 5V power. A small amount of 5V power can be drawn from this pin (through an internal 220 ohm resistor), so that the control terminals of an SSR can be connected directly between the +5V and PS_ON pins. Note: on the v0.5 board this connector is rotated 180 degrees compared to the intended orientation on later version boards.
It doesn't actually say that you can PROVIDE power via that header.
The schematic does show that you can input 5V from that header but if you try to draw 5V from it, it goes through the 220ohm resistor.
Duet 3 uses CAN-FD bus to communicate between the main board and expansion boards, and we plan to make a Smart Tool board using the same CAN-FD-bus.
For devices that are just sensors, CAN is likely to be overkill. Duet 3 uses a simpler interface with a 4-pin connector to connect sensors, including endstops sensors, Z probes and filament monitors. The benefit of CAN-FD is that it can handle high data rates and it can tolerate the ground noise that stepper motors and PWM'd heaters cause.