Duet stopped mid print, doesn'T work anymore.....

Hi,

Third day with my Duet. Everything was working fine, I had realised how to use mesh leveling, had my first good print yesterday.

Today, my second print stopped mid-print. There was a problem with the thermistors:

Heater 1 (hotend) reports fault. If I click on Heater 1, it tells me "A heater fault has occured on this particular heater. Please turn off your machine and check your wiring for loose connections."
Bed starts as off, but when I click it, it reports fault and gives me the same message.

Both the Heater 1 and Bed temperatures are reported as "error".

I also get the message "Error: Temperature reading fault on heater 0: sensor open circuit"

The mechanical parts seem to be working ok.

I am so sad right now...... What is wrong with it? How can I fix it?

If you have a multimeter, unplug the thermistor from the duet and measure its resistance. At a temperature of 25C a typical one used in printers should read 100Kohms. If it does not, then you have a thermistor or wiring problem with the thermistor that need to be fixed (which is what the Duet is reporting).

Hi,

I did what you suggested.Unplugged both the hotend thermistor wire and bed thermistor wire. The resistence I read is around 90 Kohms on both of them, which probably suggests they are OK.

Is it happening before the printer does any moves or after? If after, I suspect a bad wire or flaky connector that only shows up when flexed. If before then I'm at a loss.

Well, the printer worked well for 2 days and this problem happened just today, mid-print. Since then I can't use the heaters, as the thermistors don't report any temperature reading. I don't think it is a connector problem. It seems that there is a fuse on board (VSSA), which can blow up if there is a short somewhere. I fear that is the reason (I fear because I don't have good soldering skills, nor a good soldering iron and I probably will have to try to replace that fuse, well, not before I get a confirmation form David)

Are both temperatures reading -273C even though the thermistors are connected? If so then the VSSA fuse had probably blown. The usual cause is a short in the hot end wiring, sometimes part of the problem is an internal short in the heater cartridge between the element and the casing. Or there may be a short etween the bed heater wires and the bed thermistor. Find and fix the short, then replace or bypass the fuse.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

On the bed server they aren't reading any value (error) but on the paneldue they are both *273.1 degrees.

My hotend is an original E3DV6 with the new thermistor cartdrige so I don't think the problem is there (I'll check it). I checked the bed and saw that one of the legs of the thermistor was nude, meaning it didn't have a plastic shrinking tube or sleeve around. The other was covered but maybe, because I use a metal plate, it can create a short with the PCB heated bed. I used some isolating band around it. I don't have any fuses now, so I'll order glass fuses. I presume you still recommend a 250 mA one, right? I can't replace a SMD component, so I'll try to bypass it. Could you tell me which pins I shall solder the fuse wires? Shall I use the ones (E0 VSSA and PanelDue GND) shown on this thread (https://www.duet3d.com/forum/thread.php?id=247) . I'd like to remind you that I have a PanelDue connected, so if I have to solder to another pin, I'll do so.

You can connect the 250mA fuse between VSSA on the E0 or E1 or bed thermistor connector, and ground on the PanelDue connector, an endstop connector, or the expansion connector.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I added a 250 mA glass fuse to the E1 VSSA and an endstop ground. It was so scary!! I never has to solder a wire to an already populated pin. The good news is that Duet works again


Two questions:
1) I probably had this possible short at the heated bed for at least a year and a half.The RAMPS/Arduino didn't seem to be affected by it. Is Duet's ekectronics more sensitive to high currents?
2) Would it be possible to have some kind of resettable fuse instead of the SMD one. I am sure that this doesn't happen to a many users but it is scary to modify the board if you are inexperienced.

Quote
drmaestro
1) I probably had this possible short at the heated bed for at least a year and a half.The RAMPS/Arduino didn't seem to be affected by it. Is Duet's ekectronics more sensitive to high currents?

I think the fault on your system is probably recent. With RAMPS, if you get a short between the thermistor and the hot end, then if you are lucky the 5A fuse will blow before anything else does. But it is at least as likely that you will blow the ADC input on the Arduino. On the Duet WiFi the ADC inputs are protected, and the VSSA fuse protects the Duet from a short to the ground side.

It's conceivable that you could get something less than a direct short (say 20 ohms resistance) between the hot end heater and VSSA, which on a RAMPS would not blow anything but which on the Duet would blow the VSSA fuse.

Quote
drmaestro
2) Would it be possible to have some kind of resettable fuse instead of the SMD one. I am sure that this doesn't happen to a many users but it is scary to modify the board if you are inexperienced.

This is already done on the Duet Ethernet, and the same change is coming to the Duet WiFi.

Edited 1 time(s). Last edit at 04/21/2017 05:09PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].