Strange Temperature problem ...

I'm running an older Botmill (Mendel Prusa), with Gen6 w/Marlin, MK-IVB hotend, 100k thermistor and I'm having a devil of a time controlling temp. I've been able to print, but was always baffled by having to use 220 deg C just to print PLA. Anything below that and the extruder would jam and skip. Once I got past that temp, it would print, but never to a quality you'd like. I was searching the net and it made we wonder what temp I was actually getting at the hotend vs the pronterface reading. I got a temp probe and when pronterface says 235 deg C, the hotend is ~135 deg C - BIG DIFFERENCE. At room temp both pronterface and the temp sensor read the same ~24 deg C, which is accurate. I used the thermistor supplied with the hotend, and have read repeately that I'm to use thermistor table 1, which I always have. The marlin config for temp looks like this;

#define HEATER_0_USES_THERMISTOR
#define THERMISTORHEATER_0 1
#define HEATER_0_MINTEMP 0
#define HEATER_0_MAXTEMP 275
#define BED_CHECK_INTERVAL 5000
#define TEMP_RESIDENCY_TIME 10
#define TEMP_HYSTERESIS 3
#define TEMP_WINDOW 1
#define TEMP_SENSOR_AD595_OFFSET 0.000000
#define TEMP_SENSOR_AD595_GAIN 1.000000
#define CooldownNoWait true
#define HEATING_EARLY_FINISH_DEG_OFFSET 1

I checked wiring - seems ok. I used the PID settings that came wth the marlin setup for this machine;

#define PIDTEMP
#define PID_MAX 255
#define PID_INTEGRAL_DRIVE_MAX 255
#define K1 0.95
#define PID_dT 0.128
#define PID_PID
#define DEFAULT_Kp 63.0
#define DEFAULT_Ki (2.25*PID_dT)
#define DEFAULT_Kd (440/PID_dT)
#define PID_ADD_EXTRUSION_RATE

But I've have read I need to adjust those. Could this be the problem? I entered M303 in pronterface (as suggested in another post), and while it sent it, nothing happened after that - no response (was I supposed to get a response?). Then I entered M301 and got an instant response that simply matched the original settings.

I've had the machine for 9 months, but still feel like a nube on it. Any thoughts on this will be greatly appreciated....
T.

---

in beautiful southern, Maryland...

Hi, not an expert by any means but thought id respond
this is what i have in my conf.h file

// PID settings:
// Comment the following line to disable PID and enable bang-bang.
#define PIDTEMP
#define PID_MAX 255 // limits current to nozzle; 255=full current
#ifdef PIDTEMP
//#define PID_DEBUG // Sends debug data to the serial port.
//#define PID_OPENLOOP 1 // Puts PID in open loop. M104/M140 sets the output power from 0 to PID_MAX
#define PID_INTEGRAL_DRIVE_MAX 255 //limit for the integral term
#define K1 0.95 //smoothing factor withing the PID
#define PID_dT ((16.0 * 8.0)/(F_CPU / 64.0 / 256.0)) //sampling period

// If you are using a preconfigured hotend then you can use one of the value sets by uncommenting it
// Ultimaker
#define DEFAULT_Kp 24.85
#define DEFAULT_Ki 0.68
#define DEFAULT_Kd 226.78

// Makergear
// #define DEFAULT_Kp 7.0
// #define DEFAULT_Ki 0.1
// #define DEFAULT_Kd 12

// Mendel Parts V9 on 12V
// #define DEFAULT_Kp 63.0
// #define DEFAULT_Ki 2.25
// #define DEFAULT_Kd 440
#endif // PIDTEMP

The only thing i see from your list is that Ki and Kd have values that match what my file refers to as "Mendle Parts V9 on 12V" but are divided by PID_dt which ive never seen before
Note the values im using are the values ive input (under the heading Ultimaker) after running M303

WHen i send M303 my FW repsonds with " PID autotune start"

Good luck

Edited 1 time(s). Last edit at 03/29/2013 09:28PM by bigfilsing.

If you want to check your temp sensor you can maybe try the following

Get a thin plactic bag ( something that can take 100C) micro wave bag or similar , The thinner the better.
Try and suck all the air out with a drinking straw and tape the bags opening and your wires up

Figure our a way to put the bag with the temp sensor in it into boiling water . Boiling water being 100 degrees C
Melting ice = 0 degrees C ( or as near as damnit)

Good luck

I had finished my 3d printer.
but accured temperature problems.
I use 'Lambo' board and 'Honeywell thermistor 135-104LAG-J01'.
When i connect the printer to my computer, the temperature grow up very slowly, and start from 56 deg C.
There are much differences from monitor temperature to real temperature of hotend.
How can i solve this problem.
Please help me!!