Help! Axes Only Homing and Thermistors Reading ~0degC

K8200 3D Printer K8200 - Wiring and electronics
21

[quote=“Wrong Way”]Since the resistors are still in the circuit you may not get a correct reading because of the other components.
The only way to get a true reading is remove each one or at least one leg from the board.[/quote]

Good point, Wrong Way.
I should have made that more clear in my earlier post.

I still don’t believe there is a problem with the resistors.
I think there is a short somewhere that draws so much current that the regulator and Atmega heat up.

The most logical place of fault would be the Stepper modules.
If they are all pulled and it still heats, the only places to check are endstops and Thermistors.
(assumed the regulator is ok)

Dalton, you wrote you could still control the printer.
What exactly are you able to control?
Are there any error messages in repetier asides 999?

To get the Thermistors and their wiring out of question you could try and connect a 100k resistor across the heater pins on both terminals.
(thermistor plugs unconnected)
That should give a roughly 20°C reading.

22

[quote=“Barnabybear”]Hi, had a quick play this morning. If you find this section in configuration.h

[code]//===========================================================================
//=============================Thermal Settings ============================
//===========================================================================
//
//–NORMAL IS 4.7kohm PULLUP!-- 1kohm pullup can be used on hotend sensor, using correct resistor and table
//
//// Temperature sensor settings:
// -2 is thermocouple with MAX6675 (only for sensor 0)
// -1 is thermocouple with AD595
// 0 is not used
// 1 is 100k thermistor - best choice for EPCOS 100k (4.7k pullup)
// 2 is 200k thermistor - ATC Semitec 204GT-2 (4.7k pullup)
// 3 is mendel-parts thermistor (4.7k pullup)
// 4 is 10k thermistor !! do not use it for a hotend. It gives bad resolution at high temp. !!
// 5 is 100K thermistor - ATC Semitec 104GT-2 (Used in ParCan) (4.7k pullup)
// 6 is 100k EPCOS - Not as accurate as table 1 (created using a fluke thermocouple) (4.7k pullup)
// 7 is 100k Honeywell thermistor 135-104LAG-J01 (4.7k pullup)
// 8 is 100k 0603 SMD Vishay NTCS0603E3104FXT (4.7k pullup)
// 9 is 100k GE Sensing AL03006-58.2K-97-G1 (4.7k pullup)
// 10 is 100k RS thermistor 198-961 (4.7k pullup)
//
// 1k ohm pullup tables - This is not normal, you would have to have changed out your 4.7k for 1k
// (but gives greater accuracy and more stable PID)
// 51 is 100k thermistor - EPCOS (1k pullup)
// 52 is 200k thermistor - ATC Semitec 204GT-2 (1k pullup)
// 55 is 100k thermistor - ATC Semitec 104GT-2 (Used in ParCan) (1k pullup)

#define TEMP_SENSOR_0 5 //========NOT THIS LINE EVEN THOUGH IT LOOKS THE SAME========
#define TEMP_SENSOR_1 0
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 5

// This makes temp sensor 1 a redundant sensor for sensor 0. If the temperatures difference between these sensors is to high the print will be aborted.
//#define TEMP_SENSOR_1_AS_REDUNDANT
#define MAX_REDUNDANT_TEMP_SENSOR_DIFF 10

// Actual temperature must be close to target for this long before M109 returns success
#define TEMP_RESIDENCY_TIME 10 // (seconds)
#define TEMP_HYSTERESIS 3 // (degC) range of +/- temperatures considered “close” to the target one
#define TEMP_WINDOW 1 // (degC) Window around target to start the recidency timer x degC early.

// The minimal temperature defines the temperature below which the heater will not be enabled It is used
// to check that the wiring to the thermistor is not broken.
// Otherwise this would lead to the heater being powered on all the time.
#define HEATER_0_MINTEMP 5 //========CHANGE THIS VALUE FROM 5 TO 0========
#define HEATER_1_MINTEMP 5
#define HEATER_2_MINTEMP 5
#define BED_MINTEMP 5
[/code]
and change this line ‘#define HEATER_0_MINTEMP 5’ to ‘#define HEATER_0_MINTEMP 0’ reflash the firmware using a version of arduino NOT highter than 1.0.6, it will remove the safety feature that prevents the axis moving if the extruder therimistor is not connected. [color=#BF0000]Please do not leave the printer powered up unatteneded or request any heating to the extruder with this feature disabled, it is to test the steppers only.[/color]
Note there is a line abave that looks very simalar.

Whilst it will not cure the thermister problem, it will verify that the axis are working. I’m not sure that the heat and resistance values are a distraction from a broken wire or bad connetor.[/quote]

Thanks Barnabybear. You’ve gone over and beyond by helping with reprogramming the board, but I’m not able to to carry out that troubleshooting step as I cannot programme the board. When I first got the printer, I though I didn’t know the came pre-programmed, so I tried to upload the firmware myself. Despite shorting the JPROG pins, using the correct COM port, installing the drivers, and using Arduino 1.0.6, I cannot upload firmware to the board. I get the following errors everytime:

[quote]avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer[/quote]

At the time I suspected that my board didn’t have the arduino bootloader installed. When I realised that the board came pre-programmed, I connected the power supply, ran Repetier, and had no issue controlling the printer for a few months until my recent issues.

23

[quote=“ichbinsnur”][quote=“Wrong Way”]Since the resistors are still in the circuit you may not get a correct reading because of the other components.
The only way to get a true reading is remove each one or at least one leg from the board.[/quote]

Good point, Wrong Way.
I should have made that more clear in my earlier post.

I still don’t believe there is a problem with the resistors.
I think there is a short somewhere that draws so much current that the regulator and Atmega heat up.

The most logical place of fault would be the Stepper modules.
If they are all pulled and it still heats, the only places to check are endstops and Thermistors.
(assumed the regulator is ok)

Dalton, you wrote you could still control the printer.
What exactly are you able to control?
Are there any error messages in repetier asides 999?

To get the Thermistors and their wiring out of question you could try and connect a 100k resistor across the heater pins on both terminals.
(thermistor plugs unconnected)
That should give a roughly 20°C reading.[/quote]

As resistors R28/29/30/31 are grounded at one end, correct me if I am wrong, but I do not think that there could be any issue with measuring them without disconnecting them from the board. There could be an issue when measuring R7 and R8, but I do not think that this is the problem.

The PCB still heats when only 15V power supply is connected. It heats up with all of the stepper driver modules, end-stops, fan, heaters, and thermistors disconnected.

By controlling the printer, I am talking about manual control which does not rely on minimum temperature issues. I can control the fan the home the axes. As the axis homing works correctly, this indicates to me that the steppers and the end stops are working correctly. The only error I get in Repetier is the M999 temperature one.

I have tried to troubleshoot by connecting 100 kohm resistors in place of the thermistors, but this does not solve my issues. Temperature is still being read as ~0 degC. Connecting/Disconnecting anything from the THERM pins does not appear to make any difference.

24

[quote=“Dalton”]
As resistors R28/29/30/31 are grounded at one end, correct me if I am wrong, but I do not think that there could be any issue with measuring them without disconnecting them from the board. There could be an issue when measuring R7 and R8, but I do not think that this is the problem.[/quote]

As long as the capacitors are not completely discharged it can surely affect the readings.
It’s nearly impossible to measure resistors that are in circuit correctly, as Wrong Way stated.

By controlling the printer, I am talking about manual control which does not rely on minimum temperature issues. I can control the fan the home the axes. As the axis homing works correctly, this indicates to me that the steppers and the end stops are working correctly. The only error I get in Repetier is the M999 temperature one.

I have tried to troubleshoot by connecting 100 kohm resistors in place of the thermistors, but this does not solve my issues. Temperature is still being read as ~0 degC. Connecting/Disconnecting anything from the THERM pins does not appear to make any difference.[/quote]

Then there must be a fault in the Therm circuits.
Maybe one or both capacitors are damaged.

btw. flashing the board only works with Jprog jumper short AND 15V power connected.

cheers,

Christian

25

Hi, R7 & R8 are connected to 5V at one end & a capacitor at the other depending on the length of time the board has been powerd down & which way round you have the test leads you could get some strange results. When you measure resistance you effectively measure the effect that a resistor has on a voltage provided by the test equipment. If another voltage is pressent it can have an effect. Also capacitors can charge using the voltage from the test equipmnet affecting the result.
You can check for any voltage at each end of the resistor measuring to ground (0v) before testing & hold the test leads in place for some time to let any capacitors charge to the test voltage then you will get a ‘more’ correct reading.
As stated by Wrong Way disconnecting one end of a component is the only way to get a accurate result. Nearly impossable with surface mounted components, and I dont recomend that you attempt that without more testing as that many not be the problem.

Edit: it might be worth powering the board with a direct 5V and seeing if it still gets warm. You can’t use the normal power terminals as by the time the voltage had passed the input diode and the regulator you would only end up with at best 4V. However on the display output terminals there is both 5V and 0V. If you have a set of header pins, it might be worth soldering them in and powering the board that way with drivers removed. You should still get communication with the PC, and as the Atmega and the regulator share cooling via the ground plane it would iliminate heating from the voltage regulator. If all says cool you can replace the drivers one at a time. It should give you a better idea of where the heat is comming from.[/quote]

Do you mean to connect 5 V across the two points I’ve highlighted below?

26

[quote=“ichbinsnur”][quote=“Dalton”]
As resistors R28/29/30/31 are grounded at one end, correct me if I am wrong, but I do not think that there could be any issue with measuring them without disconnecting them from the board. There could be an issue when measuring R7 and R8, but I do not think that this is the problem.[/quote]

As long as the capacitors are not completely discharged it can surely affect the readings.
It’s nearly impossible to measure resistors that are in circuit correctly, as Wrong Way stated.

By controlling the printer, I am talking about manual control which does not rely on minimum temperature issues. I can control the fan the home the axes. As the axis homing works correctly, this indicates to me that the steppers and the end stops are working correctly. The only error I get in Repetier is the M999 temperature one.

I have tried to troubleshoot by connecting 100 kohm resistors in place of the thermistors, but this does not solve my issues. Temperature is still being read as ~0 degC. Connecting/Disconnecting anything from the THERM pins does not appear to make any difference.[/quote]

Then there must be a fault in the Therm circuits.
Maybe one or both capacitors are damaged.

btw. flashing the board only works with Jprog jumper short AND 15V power connected.

cheers,

Christian[/quote]

If the resistors are damaged as I believe them to be, would this be a source of my problems. I do not have/know a way of checking the capacitors without fully disconnecting them from the PCB. I am hoping that they may be okay.

Are the capacitors more likely to damage than the resistors?

Thanks for the advice about flashing the board, I will try to do it with the 15 V connected now. A stupid oversight on my part. I will try to amend the code as Barnaby suggested.

27

Yes If you apply 5v to those terminals it will power all the logic components on the main board and on the stepper drivers.
You need to ensure that the polarity is correct and doesn’t exceed 5.5V.
The steppers, heaters and fan will not work, but the endstops and thermisters should work as normal.

28

[quote=“Dalton”]
If the resistors are damaged as I believe them to be, would this be a source of my problems. I do not have/know a way of checking the capacitors without fully disconnecting them from the PCB. I am hoping that they may be okay. [/quote]

Try to measure the capacitors for continuity.
If they have an internal short they would let current though.

[quote=“Dalton”]
Thanks for the advice about flashing the board, I will try to do it with the 15 V connected now. A stupid oversight on my part. I will try to amend the code as Barnaby suggested.[/quote]
No big deal :wink:

What you can try is measuring the current draw on the 15V terminal when the printer is powered.
That will possibly give a hint of the printer drawing too much current in idle state.

You can use this as a roughly comparision :
youtube.com/watch?v=WUhRoChmauw

cheers,

Christian

29

Okay, amending the Marlin firmware to allow the printer to run at 0degC instead of 5degC has worked as hoped. With this amendment, I can control the axes correctly, so there doesn’t appear to be an issue with the stepper drivers.

When I connect a 5 V source to the LCD points as instructed only the AtMega chip heats up. I cannot control the steppers with only the 5 V connected this way, but this nonetheless shows that the issues do not lie with the 5 V regulator.

I have desoldered R7 and R8 resistors and both are actually measuring 4.7 kohm when separated from the circuit. This probably indicates that the issue may lie with the C7 and/or C8 capacitors?

Is it possible to adjust the Marlin firmware to comment out the portions of the code associated with the pins going to the thermistor circuits? This would make it easy to see if the thermistor circuits are causing the current heating. If it doesn’t work, it would indicate that the fault lies elsewhere.

Thanks again.

30

If you unsolder the THERM resistors the circuit is out of business.
That way you can figure out if that is the problem.

Did you try and measure the current consumption?

31

[quote=“ichbinsnur”]If you unsolder the THERM resistors the circuit is out of business.
That way you can figure out if that is the problem.

Did you try and measure the current consumption?[/quote]

Thanks. I should have figured that out when I looked at the schematic myself. I think I have found the source of my issue now too.

I have removed both resistors, but there is still a continuity between the two surface mount ads for the R8 resistor. This short must be the source of my current heating. There is no solder visible between both pads so I think it must be an internal short too. I am not sure how I can fix this, as I don’t think I can now drop voltage before the AtMega sensing point.

The only solution I can think of is to physically scratch away a track connecting the R8 resistor to the 5V line.

32

[quote=“Dalton”][quote=“ichbinsnur”]If you unsolder the THERM resistors the circuit is out of business.
That way you can figure out if that is the problem.

Did you try and measure the current consumption?[/quote]

Thanks. I should have figured that out when I looked at the schematic myself. I think I have found the source of my issue now too.

I have removed both resistors, but there is still a continuity between the two surface mount ads for the R8 resistor. This short must be the source of my current heating. There is no solder visible between both pads so I think it must be an internal short too. I am not sure how I can fix this, as I don’t think I can now drop voltage before the AtMega sensing point.

The only solution I can think of is to physically scratch away a track connecting the R8 resistor to the 5V line.[/quote]

Do you have the Thermistors disconnected?
If not, the voltage must com from the THERM connector or the respective wiring.
Maybe look at the Backside of the board for any solder bridges.

33

Like said there is a short somewhere in the board because the 5 volt regulator is getting very hot.
If there is a short somewhere else in the board this would more then likely throw most measurements off.

Changing the firmware may get it running but would cause more damage down the road or cause a fire.
You should replace or repair the board.

Just my thoughts

34

[quote=“ichbinsnur”][quote=“Dalton”][quote=“ichbinsnur”]If you unsolder the THERM resistors the circuit is out of business.
That way you can figure out if that is the problem.

Did you try and measure the current consumption?[/quote]

Thanks. I should have figured that out when I looked at the schematic myself. I think I have found the source of my issue now too.

I have removed both resistors, but there is still a continuity between the two surface mount ads for the R8 resistor. This short must be the source of my current heating. There is no solder visible between both pads so I think it must be an internal short too. I am not sure how I can fix this, as I don’t think I can now drop voltage before the AtMega sensing point.

The only solution I can think of is to physically scratch away a track connecting the R8 resistor to the 5V line.[/quote]

Do you have the Thermistors disconnected?
If not, the voltage must com from the THERM connector or the respective wiring.
Maybe look at the Backside of the board for any solder bridges.[/quote]

Yes, the thermistors are disconnected. There are no visible solder bridges anywhere which I can see.

35

Is there any voltage reading on the Atmega side of the pad to ground?

36

Hi, is this the same for the two R7 pads?
Don’t forget that the AtMega is conected to 5v and one of the solder pads. I’m not sure of the powered off state of the pin that is used for the thermister, but this could be giving the impression of a short. Also if the capacitor is still charged it could give the impression of a short even if there is no connection.

37

Hi, is this the same for the two R7 pads?
Don’t forget that the AtMega is conected to 5v and one of the solder pads. I’m not sure of the powered off state of the pin that is used for the thermister, but this could be giving the impression of a short. Also if the capacitor is still charged it could give the impression of a short even if there is no connection.[/quote]

Yep! Good point!

btw, the connection from R7/R8 to the Atmega are used as analog input for the thermistor voltage. (ADC)

38

Hi, my best guess is that if you power up the board with R7, R8 removed and the thermisters disconnected you will get random temperatures reported & possably an over temperature waning. If you connect the thermisters one at a time you will get a high temperature (around 700 deg) an over temperature warning. Both should do the same thing.

39

Hi, is this the same for the two R7 pads?
Don’t forget that the AtMega is conected to 5v and one of the solder pads. I’m not sure of the powered off state of the pin that is used for the thermister, but this could be giving the impression of a short. Also if the capacitor is still charged it could give the impression of a short even if there is no connection.[/quote]

No, it is only the case for the R8 pads, which is why I think the R7 continuity is a sign of a short. The capacitors should be discharged.

40

Hi, I had a quick look at the board and it appears that the R8 track from the AtMega passes through 3 through holes before reaching the thermistor and once again to secure the connector. That means it has 4 chances to short. If the short in in one of the through holes or the connector, 3 have easy fixes, the other will test your skill & resolve.
I’m assuming that as you have removed some components that you have no warranty now.
The photo (you will need to click & zoom) below shows a through hole next to R8 (in yellow) and the other through holes that I used a a referance (in red).

From the other side it is possible to identify the through hole and have a good guess as to its path in the areas that are obscured by components (AtMega, capacitor & connector). Again the red is to identify the reference.

The easiest problem / fix is the R8 through hole.
R8 has already been removed, so on the back cut the track each side of the R8 through hole, link the two tracks skipping the R8 hole and attach a 4.7k resistor from the thermister terminal to 5v (the display socket that you used to test with is probably what I would use).
Next is the capacitor through hole.
Cut the track between the red reference line and the R8 hole and remove the capacitor, link again but this time from the track to the thermistor terminal. Then a resistor as above, but you would also need a capacitor (same value as the one on the front) between the thermistor terminals.
Next is the thermistor connector hole.
Same as above but you need to remove the connector and put the components and connector on a bit of prototype board.
Last, most difficult the AtMega.
As the short is it between the top and bottom layers, you will need to drill out the through hole to remove the short between the layers without damaging the AtMega.
Then solder a wire onto the correct pin of the AtMega to the R8 through hole (if you haven’t done all the others first).
So what to do? Time for a quick review me thinks.
If the R8 pads are shorted together at some point, this would effectively remove the pull up resistor from the thermistor circuit. That would have the same effect as an open circuit thermistor (the AtMega pin seeing 5V), which we know results in the axis travel being inhibited and incorrect temperature readings being reported. All of which we have.
The bit’s I can’t get my head round is why this would result in any additional heat being created. The short would need to be to 5V, not ground. A short to ground I could understand would draw additional current and create heat both in the fault and the voltage regulator.
It could well be that the voltage regulator and AtMega are both running within their normal temperature ranges (-40 to +85 deg C) but until a fault occured it hasn’t been noticed how hot they get.
Secondly I can’t see an obvious place for the short to 5V to be. Ok we can’t see under AtMega so it could be there. It appears that a lot of the 5V tracks run on the top or bottom, so even if the board is multi-layer why put 5V top, bottom and inside?
There is a 5V track next to R8 but any short would be visible & there could be a bit of material shorting the neighbouring pins of the AtMega, but again that would be visable.
Comments please.