[FR] Redundant bed temperature sensors

[echo465]

Currently temperature sensor types are defined in configuration.h like so:

#define TEMP_SENSOR_0 1
#define TEMP_SENSOR_1 0
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_3 0
#define TEMP_SENSOR_4 0
#define TEMP_SENSOR_BED 1

TEMP_SENSOR_1 can be defined as redundant to TEMP_SENSOR_0 for safety:

#define TEMP_SENSOR_1_AS_REDUNDANT
#define MAX_REDUNDANT_TEMP_SENSOR_DIFF 10

Unfortunately, there doesn't seem to be a way to define a temperature sensor to be redundant to the bed temperature sensor or any other sensor, it can only be configured that TEMP_SENSOR_1 is redundant to TEMP_SENSOR_0. In the interest of increased safety, there should be some way to define a sensor to be redundant to TEMP_SENSOR_BED. More broadly, it would be 'nice to have' for one sensor to be redundant for any other sensor.

My motivation - one of my printers had TEMP_SENSOR_BED vibrate loose and land in the insulation underneath the bed while printing with a bed temp at 60c. The printer responded by increasing power to the heater and the heater was able to keep the sensor reading 60c, so "Thermal Runaway" wasn't triggered. Eventually, I smelled burning and cut power. I measured bed temperature at 125c with an infrared thermometer several minutes after cutting power.

[Spawn32]

Too bad there isn't a up-vote button here :)

Having a redundant sensor to the bed would be nice, even better if we could you use all temp sensors as redundant :)

[panecki]

This should be one of the basic functions. Safety first 👍

[slowbro]

I'm trying to give this a go, as it's something I was wanting recently, as well.

[thisiskeithb]

#22085 has been merged, closing.

Thanks for implementing this feature @slowbro!

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