prusa i3 3dprinterczar wrong heatbed temperature from thermistor

Hey,

I´m building a Prusa i3 from 3dprinterczar and i finished the mechanical and electrical assembly and wiring.

It´s working with an Arduino 2560 and RAMPS 1.4.

Right now I´m having trouble with the heatbed thermistor.
I attached a picture of it here. I didn´t get any infos from the vendor so i tried every options in the thermistor settings and my latest configuration is:

#define TEMP_SENSOR_0 1
#define TEMP_SENSOR_1 1
#define TEMP_SENSOR_2 1
#define TEMP_SENSOR_BED 1

The hotend thermistor works fine (20.6 C in my room) but the heatbed gives me 81.4 C!
I have a 2nd thermistor and connected it to the board as well and it´s the same temperature.

As i said I tried all options but option no. 1 was the closest!

Does anyone have the same problem or knows the solution?

Best regards
Alex

Edited 1 time(s). Last edit at 05/09/2014 07:35AM by zippi.

Set temp sensor one and two set them to zero check your wiring

Edited 1 time(s). Last edit at 05/09/2014 08:10AM by cnc dick.

Quote
cnc dick
Set temp sensor one and two set them to zero check your wiring

i changed it to zero and checked my wiring, everything seems to be fine.

Do you have the the thermistor plugged in the T-1 which is the second place on the ramps 1.4. Secondly in the configuration H file do you have the right motherboard picked should be 33 make sure you don't have it set up for dual extruders. If the hot end thermistor is working correctly you can test this by temporarily plugging heat bed thermistor to the hot end spot see if it works should read ambient Temp don't run the heat this way

Quote
cnc dick
Do you have the the thermistor plugged in the T-1 which is the second place on the ramps 1.4. Secondly in the configuration H file do you have the right motherboard picked should be 33 make sure you don't have it set up for dual extruders. If the hot end thermistor is working correctly you can test this by temporarily plugging heat bed thermistor to the hot end spot see if it works should read ambient Temp don't run the heat this way

Yes the heatbed thermistor is plugged in the T1 and the hotend thermistor in T0. I already switched them but when the heatbed thermistor is in T0 it also say it´s 80 degrees C.

yes the motherboard is set to 33 = RAMPS 1.3 / 1.4 (Power outputs: Extruder, Fan, Bed) and the nuber of extruders is set to #define EXTRUDERS 1.

The hotend thermistor is working correctly.

Then obviously it is the thermistor that's wrong or wiring buy some more one hundred K thermistors they are cheap plus it's good to have spares if you find out it's the thermistors throw the ones you have a way so you don't get confused with them again. And if you plug the hot end in the T-1 it's reading ambient. The thermistor works on variable resistance so if you have a bad wiring connection resistance would be higher or if the wiring is long or has a high resistance it will throw it off

Edited 1 time(s). Last edit at 05/12/2014 10:15AM by cnc dick.