How to control 4 thermistors in a heated bed?

1

My print area is ~ 17x16 inches (431.8 mm x 406.4 mm = 175,158.4 mm/2). To that end I need four (4) 200mm square heaters, and associated mosfets to run it. Each heater has it's own thermistor and can potentially reach the target temp independently (theoretically they could, since there will be deviations in manufacturing).

My mainboard (the SKR Pro) has support for 4 thermistors; however my solution in this configuration has 5.

When I double the size of the printer later this year, I expect that I will need 8 heaters.

Is there a solution to control that many heaters such that non of them over shoot their temps, or am I going to have to design and build a dedicated thermal management board to control beds of this nature?

user77232

Posted 2020-05-29T04:20:19.543

Reputation: 2 090

As far as I know it hasn't been implemented in Marlin, but there is this issue tracker that says it is fairly simple to implement. Alternatively (since you need more than 2 zones), you could use an Arduino Uno to communicate with the SKR and let the Uno handle the individual heating of sub beds. E.g. return the average temperature of the 4 beds, or the lowest temperature etc. It would be a cost saving if the Uno is able to enable beds or not, for small prints, you could use the e.g. left front heater!

– 0scar – 2020-05-29T06:46:23.207

Answers

2

You can use the Klipper firmware which accepts an arbitrary number of heaters.

Then you can write a Klipper macro which takes one input and applies it to each heated bed (or not, as you prefer).

With Klipper you can also add another Arduino and connect it to klipper as well, in case you don't have enough pins on your board: klipper is not limited to controlling one single board per printer.

Check the docs.

FarO

Posted 2020-05-29T04:20:19.543

Reputation: 2 532

Therefore Klipper can operate across different µControllers by design? – user77232 – 2020-05-29T12:55:36.020

Yes. For example, my 3d printer board has soldered drivers. I want to add Trinamic drivers, but I cannot fit enough due to lack of pins. I can connect a simple Arduino Nano (5 euro?) to the Raspberry Pi in addition to my board, connect the TMC to the Nano, and Klipper will control both at the same time. – FarO – 2020-05-29T13:53:04.903

Added link to multi-mcu configuration. – FarO – 2020-05-29T13:54:44.110