Thermistor temperature staying at "ok T:65 B:32"

Hi all.
For one reason or another I'm starting to think this project is just not meant to be.
It's almost one year since I slowly started building a Prusa Mendell and one problem after
another I managed to get through it but this just seems beyond me. I hope you guys can
help me out. I feel like I'm at the end of my rope.

What happened:

I have been using an Epcos 100k thermistor and a 6.8 ohm 3 watt resister but for a reason
unknown to me I could not reach above 150C. My AL. heater block is 5/8" X 5/8" x 1".
When well insulated it reached 205C but not high enough for ABS.
So I purchased a 4.7 ohm 3 watt resister and I also switched to the Honeywell 100k thermistor.

With the 4.7ohm resister I was getting temperatures in the range of 230C+ and i was
ecstatic but like an ass I decided to switch the thermistor to the Honeywell.
Big mistake!

The problem:

The thermistor reading worked to about 100C then it jumped to 321C.
I figured the thermistor was shorting somewhere so I wiggled the wires around and
then I started getting a 5C reading. Strange!
I turned everything off. Pulled out the thermistor and switched it back to the Epcos
and ever since that the reading has been stuck at:

ok T:65 B:32

Luckily I bought 3 Honeywell 100k so I tried one of those and switched to the appropriate
thermistor table. Now that reading is stuck at:

ok T:87 B:39

So, I then powered everything down and removed the thermistor all together.
The reading is stuck to the corresponding thermistor tables as if it's not taking
the thermistor reading at all,
EXCEPT, when I short the 2 wires leading to the Chipset. That thermistor reading becomes:

ok T:321 B:122

So shorting the wires gets me a reading of max temperature. And having or not having
a thermistor installed gets me a static temperature that does not correspond to
the nozzle temp. I use a thermapen to check temperatures between the hot end
and the thermistor to see how accurate it is. So I see the hot end temp rising up to
and well above the thermistor temperature that it is stuck at.

Strange as it does read the shorted wires. So why not a lower resistance of the hotter thermistor.
Isn't that how it works? High resistance = low temp and low resistance = high temp. A short
would read 0 resistance and therefore the high temperature reading?

Ohh and I do not have a bed thermistor installed and no heated bed.
So why am I all of a sudden getting a bed temperature?


This is killing me! Help!!!

I am currently using:
Mega/Ramps 1.2
Arduino 0022
Sprinter
Pronterface

What are you using for 12V power supply? Have you measured the voltage while the heater is powered on? On the RAMPS 1.2, there's a green LED that comes on when the heater is on.

I'm using a Dell computer supply.
+12VDC up to 10A so 120 Watts
I checked the voltage while the unit is powered up.
I'm getting a steady 12vdc on the nozzle side
and the power supply.

The nozzle gets hotter but the temperature stays at the
previously posted levels.
Actually the temperature levels have a range:
This is from start.
The bed is always at 5 then jumps to 40 and goes down to 37.
and back up again randomly. The nozzle temp does not change at all.

ok T:86 B:5
ok T:86 B:40
Setting hotend temperature to 230.0 degrees Celsius.
ok T:86 B:40
ok T:86 B:37
ok T:86 B:37
ok T:86 B:39
ok T:86 B:37
ok T:86 B:37
ok T:86 B:39
ok T:86 B:39
ok T:86 B:38
ok T:86 B:39
ok T:86 B:39
ok T:86 B:38
ok T:86 B:38
ok T:86 B:39
ok T:86 B:39
ok T:86 B:39
ok T:86 B:38

The bed temperature changes and this is with or without the thermistor hooked
up to the Ramps 1.2.

The green light stays on during the warming up of the nozzle.

I tried using RepSnapper and while i have the heat on, RepSnapper
does not display the current temperature at all.

I hit the reset button on the ramps and it rests then goes back to the same
temperatures.

---

~~~One of these days... One of these days... POW! Right in the kisser!~~~

I just removed the Ramps 1.2 from the Mega 2560
and hooked up the usb cable to it.
I ran pronterface and it displayed the following temperature readings
without Ramps hooked up or any thermistors attached:

Printer is now online.
ok T:87 B:5
ok T:87 B:5
ok T:87 B:79
ok T:87 B:79
ok T:87 B:79
ok T:87 B:79
ok T:87 B:79
ok T:87 B:79

Is the Mega 2560 fried?
Is there a way to reset it?

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

That 12V supply should be enough for the extruder but not enough for including a heated bed.

Are you sure that you have the thermistor for the extruder connected to the right terminals? It should be the ones labeled T0 in RAMPS 1.2.

Are you sure that you have set the correct thermistor table in the firmware and that the firmware uploaded properly?

I have had been using the T0 connections and it worked fine until
i shorted out the thermistor. The firmware is set to the Epcos or Honeywell.
These are the 2 thermistors that I currently have.

I thought that I may have changed something i should have not in the firmware
so I tried the original firmware that it came with Sprinter and it had no effect.
It was still showing the same readings

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

How about if you connect the thermistor to T1 and make sure that the bed thermistor type is set to the same thermistor. Do you get the correct temperature reading?

Connecting to T1 gives the following readings:

Printer is now online.
ok T:86 B:5
ok T:86 B:41
ok T:86 B:41
ok T:86 B:41
ok T:86 B:41
ok T:86 B:40
ok T:86 B:41
ok T:86 B:41
ok T:86 B:41
ok T:86 B:41
ok T:86 B:41
ok T:86 B:41
ok T:86 B:41
Disconnected.

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

Are these with the heater off (M104 S0)?

With the heater on, I checked the temperature with my Termapen until it reached
150C.
The reading i received from connecting to T0 was:

ok T:89 B:43
ok T:89 B:43
ok T:89 B:44
ok T:89 B:44
ok T:89 B:44
ok T:89 B:44
ok T:90 B:44
ok T:90 B:45
ok T:90 B:45
ok T:90 B:44
ok T:90 B:45
ok T:90 B:45
ok T:90 B:45
ok T:90 B:45
ok T:86 B:46

While the unit was still on i switched the connection from T0 to T1 and got this:

ok T:88 B:155
ok T:88 B:155
ok T:88 B:155
ok T:88 B:155
ok T:88 B:156
ok T:88 B:157
ok T:88 B:157
ok T:88 B:158
ok T:88 B:158
ok T:88 B:159
ok T:88 B:159
ok T:88 B:159
ok T:88 B:160

The T1 connection seems to be reading the correct temperature so the T0 connection is
not operating correctly.

---

~~~One of these days... One of these days... POW! Right in the kisser!~~~

has this ever happened to anyone before?
Any known fixes?

---

~~~One of these days... One of these days... POW! Right in the kisser!~~~

this is the code i have in Sprinter "Pins.h" file


#else // RAMPS_V_1_1 or RAMPS_V_1_2
#define HEATER_0_PIN 10 // RAMPS 1.1 and RAMPS 1.2
#define HEATER_1_PIN 8 // RAMPS 1.1 and RAMPS 1.2
#define FAN_PIN 9 // RAMPS 1.1 and RAMPS 1.2
#endif

#define TEMP_0_PIN 2 // MUST USE ANALOG INPUT NUMBERING NOT DIGITAL OUTPUT NUMBERING!!!!!!!!!
#define TEMP_1_PIN 1 // MUST USE ANALOG INPUT NUMBERING NOT DIGITAL OUTPUT NUMBERING!!!!!!!!!
#endif

I never changed this. should i switch the numbers for now?

Edited 1 time(s). Last edit at 11/13/2011 09:41PM by thestranger77.

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

Quote

#define TEMP_0_PIN 2 // MUST USE ANALOG INPUT NUMBERING NOT DIGITAL OUTPUT NUMBERING!!!!!!!!!
#define TEMP_1_PIN 1 // MUST USE ANALOG INPUT NUMBERING NOT DIGITAL OUTPUT NUMBERING!!!!!!!!!
#endif

I never changed this. should i switch the numbers for now?

Yes, you can switch them for now so TEMP_0_PIN is 1 and TEMP_1_PIN is 2 and see if your extruder reaches a stable temperature.

BTW, I don't think shorting the thermistor terminals would break RAMPS or Arduino.

I switched the numbers around and connected the thermistor to T1
and managed to get the temperature to 194C. I need to get some sleep
so I'll see what i can come up with tomorrow. Here is the last few lines
of my temp reading. For some reason as the T1 temp (nozzle) rises so does the
T0 temp (bed).

ok T:193 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98
ok T:194 B:98

I appreciate you taking the time to help me out. Have a good night buddy.

Edited 1 time(s). Last edit at 11/13/2011 10:49PM by thestranger77.

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

Please post a picture of your hot end along with your configuration.h file?

Here are some pictures and design drawings i made.

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

here is the config.h file i'm currently using:

#ifndef CONFIGURATION_H
#define CONFIGURATION_H

// BASIC SETTINGS: select your board type, thermistor type, axis scaling, and endstop configuration

//// The following define selects which electronics board you have. Please choose the one that matches your setup
// MEGA/RAMPS up to 1.2 = 3,
// RAMPS 1.3 = 33
// Gen6 = 5,
// Sanguinololu up to 1.1 = 6
// Sanguinololu 1.2 and above = 62
// Teensylu (at90usb) = 8
// Gen 3 Plus = 21
// gen 3 Monolithic Electronics = 22
// Gen3 PLUS for TechZone Gen3 Remix Motherboard = 23
#define MOTHERBOARD 3

//// Thermistor settings:
// 1 is 100k thermistor
// 2 is 200k thermistor
// 3 is mendel-parts thermistor
// 4 is 10k thermistor
// 5 is ParCan supplied 104GT-2 100K
// 6 is EPCOS 100k
// 7 is 100k Honeywell thermistor 135-104LAG-J01
#define THERMISTORHEATER 6
#define THERMISTORBED 6

//// Calibration variables
// X, Y, Z, E steps per unit - Metric Prusa Mendel with Wade extruder:
//float axis_steps_per_unit[] = {80, 80, 3200/1.25,700};
// Metric Prusa Mendel with Makergear geared stepper extruder:
//float axis_steps_per_unit[] = {80,80,3200/1.25,1380};
// MakerGear Hybrid Prusa Mendel:
// Z axis value is for .9 stepper(if you have 1.8 steppers for Z, you need to use 2272.7272)
//float axis_steps_per_unit[] = {104.987, 104.987, 4545.4544, 1487};
// VS's setting for his current machine 10/31/11 80,80 due to belt and gear being metric. 2267.716 due to 5/16"-18 direct drive rods. 500 due to 5/16"-18 hobbled bolt size
float axis_steps_per_unit[] = {80, 80, 2267.716,500}; //By VS

//// Endstop Settings
#define ENDSTOPPULLUPS // Comment this out (using // at the start of the line) to disable the endstop pullup resistors
// The pullups are needed if you directly connect a mechanical endswitch between the signal and ground pins.
//If your axes are only moving in one direction, make sure the endstops are connected properly.
//If your axes move in one direction ONLY when the endstops are triggered, set [XYZ]_ENDSTOP_INVERT to true here:
const bool X_ENDSTOP_INVERT = false;
const bool Y_ENDSTOP_INVERT = false;
const bool Z_ENDSTOP_INVERT = false;

// This determines the communication speed of the printer
#define BAUDRATE 115200

// Comment out (using // at the start of the line) to disable SD support:
//#define SDSUPPORT


//// ADVANCED SETTINGS - to tweak parameters

#include "thermistortables.h"

// For Inverting Stepper Enable Pins (Active Low) use 0, Non Inverting (Active High) use 1
#define X_ENABLE_ON 0
#define Y_ENABLE_ON 0
#define Z_ENABLE_ON 0
#define E_ENABLE_ON 0

// Disables axis when it's not being used.
const bool DISABLE_X = false;
const bool DISABLE_Y = false;
const bool DISABLE_Z = true;
const bool DISABLE_E = false;

// Inverting axis direction
const bool INVERT_X_DIR = true;
const bool INVERT_Y_DIR = true;
const bool INVERT_Z_DIR = true;
const bool INVERT_E_DIR = false;

//// ENDSTOP SETTINGS:
// Sets direction of endstops when homing; 1=MAX, -1=MIN
#define X_HOME_DIR -1
#define Y_HOME_DIR -1
#define Z_HOME_DIR -1

const bool min_software_endstops = false; //If true, axis won't move to coordinates less than zero.
const bool max_software_endstops = true; //If true, axis won't move to coordinates greater than the defined lengths below.
const int X_MAX_LENGTH = 200;
const int Y_MAX_LENGTH = 200;
const int Z_MAX_LENGTH = 100;

//// MOVEMENT SETTINGS
const int NUM_AXIS = 4; // The axis order in all axis related arrays is X, Y, Z, E
float max_feedrate[] = {200000, 200000, 240, 500000};
float homing_feedrate[] = {1500,1500,120};
bool axis_relative_modes[] = {false, false, false, false};

// Min step delay in microseconds. If you are experiencing missing steps, try to raise the delay microseconds, but be aware this
// If you enable this, make sure STEP_DELAY_RATIO is disabled.
//#define STEP_DELAY_MICROS 1

// Step delay over interval ratio. If you are still experiencing missing steps, try to uncomment the following line, but be aware this
// If you enable this, make sure STEP_DELAY_MICROS is disabled. (except for Gen6: both need to be enabled.)
//#define STEP_DELAY_RATIO 0.25

// Comment this to disable ramp acceleration
#define RAMP_ACCELERATION

//// Acceleration settings
#ifdef RAMP_ACCELERATION
// X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.
float max_start_speed_units_per_second[] = {25.0,25.0,0.2,10.0};
long max_acceleration_units_per_sq_second[] = {1000,1000,50,10000}; // X, Y, Z and E max acceleration in mm/s^2 for printing moves or retracts
long max_travel_acceleration_units_per_sq_second[] = {500,500,50,500}; // X, Y, Z max acceleration in mm/s^2 for travel moves
#endif

// Machine UUID
// This may be useful if you have multiple machines and wish to identify them by using the M115 command.
// By default we set it to zeros.
char uuid[] = "00000000-0000-0000-0000-000000000000";


//// AD595 THERMOCOUPLE SUPPORT UNTESTED... USE WITH CAUTION!!!!

//// PID settings:
// Uncomment the following line to enable PID support. This is untested and could be disastrous. Be careful.
//#define PIDTEMP 1 // uncommented this because hot end did not get hot enough to melt PLA. Checking to see if this helps // tried this and didn't help with low temp, by VS
#ifdef PIDTEMP
#define PID_INTEGRAL_DRIVE_MAX 80 // too big, and heater will lag after changing temperature, too small and it might not compensate enough for long-term errors
#define PID_PGAIN 2560 //256 is 1.0 // value of X means that error of 1 degree is changing PWM duty by X, probably no need to go over 25
#define PID_IGAIN 64 //256 is 1.0 // value of X (e.g 0.25) means that each degree error over 1 sec (2 measurements) changes duty cycle by 2X (=0.5) units (verify?)
#define PID_DGAIN 4096 //256 is 1.0 // value of X means that around reached setpoint, each degree change over one measurement (half second) adjusts PWM by X units to compensate
// magic formula 1, to get approximate "zero error" PWM duty. Take few measurements with low PWM duty and make linear fit to get the formula
#define HEATER_DUTY_FOR_SETPOINT(setpoint) ((int)((187L*(long)setpoint)>>8)-27) // for my makergear hot-end: linear fit {50,10},{60,20},{80,30},{105,50},{176,100},{128,64},{208,128}
// magic formula 2, to make led brightness approximately linear
#define LED_PWM_FOR_BRIGHTNESS(brightness) ((64*brightness-1384)/(300-brightness))
#endif

// Change this value (range 1-255) to limit the current to the nozzle
#define HEATER_CURRENT 255

// How often should the heater check for new temp readings, in milliseconds
#define HEATER_CHECK_INTERVAL 500
#define BED_CHECK_INTERVAL 5000
// Comment the following line to enable heat management during acceleration
#define DISABLE_CHECK_DURING_ACC
#ifndef DISABLE_CHECK_DURING_ACC
// Uncomment the following line to disable heat management during moves
//#define DISABLE_CHECK_DURING_MOVE
#endif
// Uncomment the following line to disable heat management during travel moves (and extruder-only moves, eg: retracts), strongly recommended if you are missing steps mid print.
// Probably this should remain commented if are using PID.
// It also defines the max milliseconds interval after which a travel move is not considered so for the sake of this feature.
#define DISABLE_CHECK_DURING_TRAVEL 1000

//// Temperature smoothing - only uncomment this if your temp readings are noisy (Gen6 without EvdZ's 5V hack)
//#define SMOOTHING
//#define SMOOTHFACTOR 16 //best to use a power of two here - determines how many values are averaged together by the smoothing algorithm

//// Experimental watchdog and minimal temp
// The watchdog waits for the watchperiod in milliseconds whenever an M104 or M109 increases the target temperature
// If the temperature has not increased at the end of that period, the target temperature is set to zero. It can be reset with another M104/M109
//#define WATCHPERIOD 5000 //5 seconds

// Actual temperature must be close to target for this long before M109 returns success
//#define TEMP_RESIDENCY_TIME 20 // (seconds)
//#define TEMP_HYSTERESIS 5 // (C°) range of +/- temperatures considered "close" to the target one

//// The minimal temperature defines the temperature below which the heater will not be enabled
#define MINTEMP 5

//// Experimental max temp
// When temperature exceeds max temp, your heater will be switched off.
// This feature exists to protect your hotend from overheating accidentally, but *NOT* from thermistor short/failure!
// You should use MINTEMP for thermistor short/failure protection.
#define MAXTEMP 275

// Select one of these only to define how the nozzle temp is read.
#define HEATER_USES_THERMISTOR
//#define HEATER_USES_AD595
//#define HEATER_USES_MAX6675

// Select one of these only to define how the bed temp is read.
#define BED_USES_THERMISTOR
//#define BED_USES_AD595

//This is for controlling a fan to cool down the stepper drivers
//it will turn on when any driver is enabled
//and turn off after the set amount of seconds from last driver being disabled again
//#define CONTROLLERFAN_PIN 23 //Pin used for the fan to cool controller, comment out to disable this function
#define CONTROLLERFAN_SEC 60 //How many seconds, after all motors were disabled, the fan should run

// Uncomment the following line to enable debugging. You can better control debugging below the following line
//#define DEBUG
#ifdef DEBUG
//#define DEBUG_PREPARE_MOVE //Enable this to debug prepare_move() function
//#define DEBUG_BRESENHAM //Enable this to debug the Bresenham algorithm
//#define DEBUG_RAMP_ACCELERATION //Enable this to debug all constant acceleration info
//#define DEBUG_MOVE_TIME //Enable this to time each move and print the result
//#define DEBUG_HEAT_MGMT //Enable this to debug heat management. WARNING, this will cause axes to jitter!
//#define DEBUG_DISABLE_CHECK_DURING_TRAVEL //Debug the namesake feature, see above in this file
#endif

#endif

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

Any changes made in the config file I commented with "By VS" so I could keep track of my machine setup.

I'm running the nozzle right now to see what temp i can get it too and after running it
for about 15 min it hit 194C and It's having difficulty going above that.
How long does a resister based hot end take to fully warm up?

Edited 1 time(s). Last edit at 11/14/2011 05:18PM by thestranger77.

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

thestranger77 Wrote:
-------------------------------------------------------
> Here are some pictures and design drawings i made.


I think the aluminum tube with heatsinks between the nozzle and PTFE with the PTFE insulator is taking away too much heat. Actually, I think you have to replace the aluminum rod with thin stainless steel or PEEK which would have a lower thermal contuctivity. Perhaps that would work better.

I can do that. Should i use the Aluminum heat sinks on the stainless steal rod?

The temperature hit 200C and keeps jumping between 199 and 200.
I will have to change the Aluminum tube like you said.

Edited 1 time(s). Last edit at 11/14/2011 05:40PM by thestranger77.

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

Quote

Any changes made in the config file I commented with "By VS" so I could keep track of my machine setup.

I didn't see anything that would affect the nozzle temperature in the configuration.h file.

Quote

I can do that. Should i use the Aluminum heat sinks on the stainless steal rod?

You might want to adapt a similar design to a recent post about a simple hot end. In addition to replacing the aluminum tube with a thin stainless steel tube, replace the wood block with a 1/4" aluminum plate to serve as heat sink and mounting plate. The PTFE rod above the aluminum plate can center the stainless tubing/PTFE liner into the extruder.

Here is the updated hot end.
I replaced with aluminum threaded rod with a stainless steel bolt with a 1/4"
hole drilled through it, allowing for the 1/4" PTFE tube.

The hottest I managed to get it was 215C. The ABS was melting out of the
nozzle but I feel like it was still not extruding easily enough.
15C more.

Should I remove 1 or 2 of the aluminum fins? Or keep adding kapton tape
on the nozzle and on part of the Stainless bolt that is showing.
Also, what if i remove the steel bolt on the tip of the nozzle and replace
it with a small piece of PTFE.? That bolt is not doing anything for the nozzle.

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~~~One of these days... One of these days... POW! Right in the kisser!~~~

I removed the Aluminum fins altogether and i reach 230C no problem now.

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~~~One of these days... One of these days... POW! Right in the kisser!~~~