Heated Bed Too Hot

hotbutteredhtml

So I've finally got my home built printer up and running. But I've run into an issue with the heated bed. I have it set to pre-heat to 60° C, but it overshoots and levels at 120° C. Here is my current setup:

Firmware - 1.0.3 Dev

Controller - RADDS 1.5

Bed Heater - 750w@110v controlled via SSR

Bed Thermister - NTC 100K 3950

Initial Firmware Settings:

// ############# Heated bed configuration ########################

#define HAVE_HEATED_BED 1
#define HEATED_BED_PREHEAT_TEMP 60
#define HEATED_BED_MAX_TEMP 120
#define SKIP_M190_IF_WITHIN 3
#define HEATED_BED_SENSOR_TYPE 14
#define HEATED_BED_SENSOR_PIN TEMP_1_PIN
#define HEATED_BED_HEATER_PIN HEATER_1_PIN
#define HEATED_BED_SET_INTERVAL 5000
#define HEATED_BED_HEAT_MANAGER 0
#define HEATED_BED_PID_INTEGRAL_DRIVE_MAX 255
#define HEATED_BED_PID_INTEGRAL_DRIVE_MIN 80
#define HEATED_BED_PID_PGAIN_OR_DEAD_TIME 196
#define HEATED_BED_PID_IGAIN 33
#define HEATED_BED_PID_DGAIN 290
#define HEATED_BED_PID_MAX 255
#define HEATED_BED_DECOUPLE_TEST_PERIOD 300000
#define MIN_EXTRUDER_TEMP 150
#define MAXTEMP 275
#define MIN_DEFECT_TEMPERATURE -10
#define MAX_DEFECT_TEMPERATURE 290
#define MILLISECONDS_PREHEAT_TIME 30000

It doesn't matter if I pre-heat from the RADDS display or Octoprint. Either way it heats to, and stays around max temp.

I tried lowering the max temp to 60° C using the following settings:

// ############# Heated bed configuration ########################

#define HAVE_HEATED_BED 1
#define HEATED_BED_PREHEAT_TEMP 60
#define HEATED_BED_MAX_TEMP 60
#define SKIP_M190_IF_WITHIN 3
#define HEATED_BED_SENSOR_TYPE 14
#define HEATED_BED_SENSOR_PIN TEMP_1_PIN
#define HEATED_BED_HEATER_PIN HEATER_1_PIN
#define HEATED_BED_SET_INTERVAL 5000
#define HEATED_BED_HEAT_MANAGER 0
#define HEATED_BED_PID_INTEGRAL_DRIVE_MAX 255
#define HEATED_BED_PID_INTEGRAL_DRIVE_MIN 80
#define HEATED_BED_PID_PGAIN_OR_DEAD_TIME 196
#define HEATED_BED_PID_IGAIN 33
#define HEATED_BED_PID_DGAIN 290
#define HEATED_BED_PID_MAX 255
#define HEATED_BED_DECOUPLE_TEST_PERIOD 300000
#define MIN_EXTRUDER_TEMP 150
#define MAXTEMP 275
#define MIN_DEFECT_TEMPERATURE -10
#define MAX_DEFECT_TEMPERATURE 290
#define MILLISECONDS_PREHEAT_TIME 30000

With these settings, the bed hits around 70° C and then generates a sensor error.

At room temperature, I'm seeing the following temps:

Room: 26.5° C

Enclosure: 27.6° C

HotEnd: 28.1° C

Bed: 28.4° C

Repetier

Try lowering #define HEATED_BED_PID_INTEGRAL_DRIVE_MIN 80 in eeprom.

Does the firmware report the high temperatures? Check the temperature curve in Repetier-Host along with bed output. That normally gives you an idea what firmware does. I guess your bed is somehow overpowered so it is easy to reach 120 with bed PID values. Maybe first just test bang-bang as method and see how it behaves. There it gets disabled > 60°C and enabled below so it will swing a bit around the target temperature, which is no problem for a bed.

Your PID values look quite extreme so these will be the main problem I think.

hotbutteredhtml

Heat-bed control is currently set to bang-bang for SSR

#define HEATED_BED_HEAT_MANAGER 0

Loaded Repetier host onto my laptop and connected the printer directly instead of through Octoprint.

Set the bed to 60° C and heated it up

The bed will now hover with +/- 1 degree of 60° C

As soon as I activate the extruder heater, both start heating up. The bed reached 120° C before I shut it off.

Repetier

Ok, so bed alone is working fine and if you enable extruder bed runs too hot?

So what happens if you only turn on the extruder does bed also heat up and does extruder heat up as well? In that case I would check the hardware. There might be a bridge on the board between extruder and bed pin so extruder pin also enables bed mosfet. I would suspect the same then if you heat the bed, meaning heating up extruder also.

Or you have set same pin for both outputs in configuration.

hotbutteredhtml

When i activate the extruder, the bed starts to heat. I double checked the firmware, I have the extruder set to Pin 0:

#define EXT0_HEATER_PIN HEATER_0_PIN

And the bed set to Pin 1:

#define HEATED_BED_HEATER_PIN HEATER_1_PIN

Not sure about a bridge in the hardware. I'm running an Arduino Due (genuine) with a RADDS 1.5 shield. I do have a common heatsink that spans all of the mosfets. I would think that if that was the cause, then the extruder would also heat up when the bed was active. I will try removing the heatsink and see if that helps. Thank you.

hotbutteredhtml

Well that did it. Seems that the common heatsink was shorting out the mosfets. Removed it and now my heaters are both behaving. Thanks for pointing me in the right direction!