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Extruder Termperature Reading -423!

Hi, my extruder temperature reading is -423. The BoXYZ interface always logs "Laser Head Detected" regardless of which quick change tool head is connected. Not sure if this log message is new, but I just noticed it when troubleshooting. I have searched the Answers for troubleshooting tips. I checked the wiring of the thermistor, the quick change coupler, and the connections on the main board (see photos). I checked the EEPROM settings and confirmed that PID drive min was set to 70.

Because this temperature reading is the same, regardless of which quick change tool head is connected, and even if the quick change cable is disconnected, I assume the problem is not in the 3D printhead. But I cannot explain a temperature reading of -423; according the posts in the Answers the minimum can be -26 which reflects infinite resistance. Also, the laser head should read a temp of 989. So why is the interface detecting a laser head while displaying a temperature of -423? Mainboard or Arduino issues?

The machine responds well to manual commands: XYZ translations and filament extrusion. I can do an air pass with gcode files for the CNC tool head. But the temperature reading does not change when I turn the temperature on in the interface. Also, when I try to 3D print, BoXYZ just waits and the hot end does not get any warmer to touch.

Just came across this issue last night when I wanted to run test prints with new filament. I haven't 3D printed in several months, and don't know when this problem might have cropped up. I was hoping to print something this weekend.

Any advice is appreciated.

Thanks, Darryl

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Update (05/12/2018)

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It sounds like the arduino itself is damaged. That usually only happens when the thermistor wires short to power somehow. You should double check inside your laser, that's the most likely culprit for this type of short, though it could have been your 3d printer as well, but it sounds like you checked that. As there is a sensor wire for that circuit inside the gantry, its also possible to fry the arduino by shorting power to BoXZY's chassis, usually happens if heated bed wires wear through, but could be anything with power to it.

Once you've located the short, you can go into the firmware, locate the Pins.h tab, scroll down to Ultimaker shield, and swap the pin assignment for Temp_0_pin and Temp_2_pin, then upload the firmware. At that point you can use the middle thermistor input on the main board for the thermistor (so swap the connector with blue and green, with the one for red and white, keep the lone wire with the red and white connector). That will usually keep you from having to replace the Arduino entirely. Assuming it was just a small DC short and didn't fry the entire chip.

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Thanks JH.

I've ordered a couple of Arduino Megas as backup. I looked inside the laser head and couldn't find a visible short. What should I look for, I didn't think the laser had a thermistor? Are the ends of the quick change cable swappable, or could swapping the cable ends have caused the short?

1) If the entire Arduino chip was affected, would the BoXYZ continue to respond to manual motion controls ? And run a CNC gcode file?

2) What's the function of the blue/green wires, and will swapping them with the thermistor connector affect the blue/green wire signal?

3) If I can't find and fix the source of the short, will swapping the connectors as you recommend (or replacing the Arduino) reshort the Arduino? Dont want to risk anything until my backups arrive.

Thanks, Darryl

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No problem.

The laser does not have a thermistor, but it uses the circuit to sense when it's plugged in. Its usually a white wire that is clamped between the red top and the cylinder. If the cylinder walls or that wire contact any metal portion of the circuit board/fan assembly mounted to the red plastic, while there is power to the laser, it will fry the sensing circuit.

Yes, if enough power is put through the circuit it will destroy the ability for BoXZY to receive any and all temperature input, but the motor control can remain unaffected. Usually, it just fries the one single input; I only really ever see a full failure with a AC 110V heated bed short.

The blue and green wires are for Nozzle #2, which BoXZY is not currently equipped with, so it will have no affect on your BoXZY if completed as described.

Yes, if you cannot find the short, and it still exists, when you power on whatever item is shorting, it will reshort and damage the input.

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I swapped the connectors and updated the firmware as you recommended. The resting temperature is a little off (reads ~34 deg C when the ambient temp is ~20) but the extruder is heating and I can print. Thanks!

Maybe I'll reconnect the laser head to identify the short, when my spare Arduinos arrive.

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Hello.

Mine reads 163C regardless of the attachment. I already imported the proper EEPROM file, but the issue is the same. From what I read above, it could be Adruino issue. However, being a total beginner, the instructions in the answer are somewhat confusing to say the least. Can someone please help to explain in plain words on how to fix this.

UPD. Now interface detects attachments as “3d Printer head detected“ and Laser head is not detected as such. So from what I read above, looks like the issue is caused by 3d printer assembly :(. Did I fry the board? What’s the best way to troubleshoot it and fix the issue? I am lost.

Thank you

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Hi Viva, just to clarify, when you have nothing plugged in what does the temperature read? When you plug in the 3D printer and it's cold, what does the temperature read? Does it change?

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When nothing is plugged in it says "3D printer head detected" and extruder status is 164C. When I plug in 3D head it says Laser Head detected.

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It sounds like you have a short in your thermistor wires in the 3D printer heat that has damaged your Arduino. You will need to disassemble your 3D printer head and check for broken or damaged wires/connections. Then you will want to replace the Arduino potentially. But don't worry, that part is only around $30.

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So I double checked everything and you are right. I changed the port to A10 and downloaded a new firmware from another thread (Installed heated bed, Extruder no longer working..) and fixed thermistor short circuit.

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Glad to hear it

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Darryl will be eternally grateful.
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