Hi,
I have a big heated bed with 4 heaters. I would like to alternate between them so only two would be on at the same time as to not trigger the overcurrent protection.
I’m unfortunately unable to google any documentation on this.
Could anyone please point me in the right direction?
Thanks
Welcome to this really nice place where people help each other (for free!).
The process of asking is easy and simple, but it does involve a little more effort from your side though.
Before anybody can give you any sensible answers, they need to know your complete situation. That is why the section has these questions at the start.
I understand that if you are still at the initial stages of your build, you may not have a klippy.log yet, but at least tell us the hardware, your intentions and why?
In your case why would you be worried about an over-current? If this was the case the most logical solution would be to correct the root fault, I.E. upgrade the power supply to the bed.
But again, without any information at all it is near impossible to answer your question. Especially if it is not something that Klipper is designed to do and you want to find out of normal solutions.
So please explain a little more and come back. I may not be the sharpest knife on klipper, but I am a qualified machine designer and builder with over 25 years experience. So if it is simply a case of advising you on hardware issues related to heaters and power supplies I am sure I can help you.
As I’m building the machine I don’t have any config files yet.
It’s simply the limitation of my power supplies. I would prefer to be able to alternate between them like the newest Prusa printer does. This printer won’t be connected to mains power.
Or perhaps at least be able to run the beds independently of each other? With each segment having it’s own thermistor it would be neat if for example the outer heaters compensated for heat loss by running longer than the central heaters.
PID tuning would be a mess tho…
To be honest I think everything will be a mess, not only the PID tuning.
Just imagine the temperature loss on the pads you are not firing on and then the incredible draw on your power supply when the unused pads are kicking in again. Your temperature graph will likely be all over the place and I would not be surprised if the temperature drop in one section of your bed would not cause adhesion problems or print accuracy trouble otherwise.
I like the idea of a sectioned build plate but not for this reason. I would section a build plate so you can simply only use those sections needed for your print.
In your case I would solve the problem at its root, the power supply.
If you up your design to a mains powered bed, you would let the mains power take care of the bed heating via a solid state relay instead of your power supply.
The signals from the MCU would not go straight to the bed but to your SSR instead.
This way you can make use of the power modulation and have a rock solid temperature graph.
Again, I do understand what you try to do. I just do not think it is the right way forwards and even not sure if klipper could handle this particular situation.
Even if it could, the result would still be temperature fluctuations that are larger then normal and which most likely will affect your printing process in a negative way.
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