Multiple Thermistors in the Heatbed

I was just wondering if anyone has tried, to have the bed split into different controllable sectors that can each control their temperature independently of each other. Multiple thermistors could be used to control the bed temperature and ensure that the bed is the same temperature all over.
Would be great to hear from anyone who has tried this

Is this possible? Sure. You'd need a custom heatbed, but controlling each bank of power resistors shouldn't be that hard. The PID software allows for autotuning, so that should make stabilizing the heatbed temperature pretty easy. An arduino UNO has 6 analog ins and 6 PWM outputs, giving you 6 zones of control. Should be fairly straightforward. Might even slave an UNO off of RAMPS.

Food for thought.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

It's been on my todo list for awhile. I think the concept might also be useful to lower the instantaneous current demands by taking advantage of thermal inertia to trade the lower current requirements for greater heatup time.

A custom heatbed could be expensive, What about if i was to use multiple small heatbeds? Then use a sheet of aluminuim or Polycarbonate to conduct the heat and ensuring the heat is evenly spread out.

Yep. That should work - four peltier elements on a cast aluminum bed would be an interesting experiment.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Couldn't you just put 3-4 thermistors in series, then modify the firmware to divide the measured resistance by the number of thermistors? This seems like it would give you the average temperature of the thermistors and a more accurate overall bed temperature.

I guess you could, but an average bed temp isn't really all that useful. How to alleviate hotspots/coldspots? I notice a 30C change from the center of my heated bed to the edge. If I could independently boost the edge temp to match the center temp I'd be very happy.

Wheels are turning.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]