Big Heatedbed with 16 separated pid regulated heaters

Goodspeed

Hello im new here
i have question about Duet 3 6hc is it posible connect expansion board Duex 5 and use on printer 16 small separated heaters for big heatbed.
the idea is more precise control temperature on heatbed cca 1200x1200
than one realy big heater and one termistor
thx for help

@Goodspeed said in Big Heatedbed with 16 separated pid regulated heaters:

is it posible connect expansion board Duex 5

no, you'll need to use the duet 3 expansion boards that use can bus

deckingman

@Goodspeed Assuming that you find a control solution for 16 heaters, I'm curious as to how you plan to separate and/or prevent thermal transfer between the 16 separate heat zones.

Goodspeed

the idea is use 16 heated bed 250x250 and make a one big,
with separate PSU and operated via 16. SSR reley, but when i operate all at one PID timing than the temperature goes inconsistent but when i use 16 thermistors to 16 separate inputs then its posible more precise control the temperature. sorry for my english

deckingman

@Goodspeed Best of luck with that.

Goodspeed

and use duet and epansion with can bus, but it is posible operate this cluster of heaters by board and automatic with printing first layers on preheated temperature and than on printing temperature. i now thats posible by separated circuit but i want to complete wing only with duet

ChrisP

It is possible to do this - I've done it (ish). But you quickly run out of sensor channels (I'm currently looking at ~20 heaters/sensors oveall). Using expansion boards is possible, but you need quite a few to cover all the inputs.

A good while ago, @T3P3Tony suggested using a MCP3208 to make an SPI daughterboard similar to the PT100/thermocouple ones. I bought some but haven't yet had the change to build the board. @AJ-Quick has already done work to use these for current loop sensors (https://forum.duet3d.com/topic/15508/m308-and-current-loop-temperature-sensors) but again, the lack of time means I haven't had a chance to play.

I see large format/scale systems becoming more popular so it'd be great to see a CAN expansion board with just 16+ pairs of outputs and thermistor inputs at some point.

dc42

@ChrisP said in Big Heatedbed with 16 separated pid regulated heaters:

I see large format/scale systems becoming more popular so it'd be great to see a CAN expansion board with just 16+ pairs of outputs and thermistor inputs at some point.

Use 2x Sammy-C21? They would need customised firmware though.

ChrisP

@dc42 Ah, yes! I looked at those when you tweeted about them a while back but they weren't available with the Duet bootloader at the time. Now they do, I've just ordered on to have a play with