Marlin temperature sensor problem
In the actual Marlin Firmware all supported printer boards are listed within the file "boards.h". This file contains the following entries for the RAMPS 1.4:


#define BOARD_RAMPS_13_EFB  33 // RAMPS 1.3 / 1.4 (Power outputs: Extruder, Fan, Bed)
#define BOARD_RAMPS_13_EEB  34 // RAMPS 1.3 / 1.4 (Power outputs: Extruder0, Extruder1, Bed)
#define BOARD_RAMPS_13_EFF  35 // RAMPS 1.3 / 1.4 (Power outputs: Extruder, Fan, Fan)
#define BOARD_RAMPS_13_EEF  36 // RAMPS 1.3 / 1.4 (Power outputs: Extruder0, Extruder1, Fan)


The most common version may be the variant . In this case you have to set the value as the following lines show.


#ifndef MOTHERBOARD
  #define MOTHERBOARD BOARD_RAMPS_13_EFB
#endif


Enable Display


#define REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER


Ok, it's time to make the adjustments specific to your 3d printer. You might first check the setting for the amount of extruders at around line 58. Most 3d printer rookies may start with one extruder, so the default entry of '1' is quite sufficient.

// This defines the number of extruders


#define EXTRUDERS 1


At around line 70 you have to set up the thermistors connected to the RAMPS for the extruder and the heatbed. Depending on your hardware configuration you have to change the last value in the defines.


#define TEMP_SENSOR_0 -1
#define TEMP_SENSOR_1 -1
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 0


The define for TEMP_SENSOR_0 determins which thermistor type is assembled at the hotend of extruder 1. This termistor has to be connected to the first sensor input (see also wiring schema). The thermistor for the heatbed has to be connected to the second sensor input. The thermistor type is configured with the define line of 'TEMP_SENSOR_BED'. If you use a thermistor of the type EPCOS B57560G104F (100K, Beta = 4036), you write the value '1' into the matching define. In case you have a thermistor with 100k and Beta = 3950, you have to set the value '60' in the corresponding define. So the defines will look e.g.:

For EPCOS (Beta = 4036) on hotend and heatbed:


#define TEMP_SENSOR_0 1
#define TEMP_SENSOR_1 -1
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 1


For Beta = 3950 on hotend and heatbed:


#define TEMP_SENSOR_0 60
#define TEMP_SENSOR_1 -1
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 60