Hot end and bed temps grossly inaccurate

Hi All,

I have just upgraded to DC42's latest firmware after having not done so for six months.

My hot end and bed temps are now floating around 200C as apposed to room temperature here that is around 27C.

Both temps were accurate a few hours ago before the firmware upgrade.

I see there appears to be temperature offsets... What is the easiest way going about re-calibrating the probes?

I've hooked up my resistor box to the pins for the temp prob in the Hot End. I put 220 and 100k through it and the temperature readout on varied 10C or so. The temps are at a constant 200C or there abouts.

I also noticed that the bed temp followed the temp rise and fall even though the resistance was only fed into the hot end probe.

Any ideas?

Temperatures read outs on both the bed and the hot end rise when I supply power to the hot end have only the hot end heat up.

I have never had any such drastic changes to temperature throughout firmware upgrades (from the original fw that shipped from reprappro through all of dc42's versions), except a weird glitch I had a couple weeks back when hotend temperatures read about 20-30° too high. That went away on its own though, I suspect a bad connection or something.

Overall, it does sound like something is a bit wonky. If you measure the resistance through the thermistors at ambient temperature, what do you get? While they are disconnected from the Duet, what readings do you get there? With a thermistor disconnected, it should read absolute zero (~ -273.1°C), and I think resistance at ambient temperature should be in the neighbourhood of 90-100KΩ. I would also double check the connections, to make sure the thermistor pins are not in contact with anything else.

The ADC corrections should get set to zero when you upgrade the firmware. You can set and check them using the M305 command. To check the values for the heated bed, send M305 P0. To check the values for the hot end, send M305 P1. The H and L values should be reported as 0.0 in both cases, assuming you have not set them with an M305 command in config.g.

See [reprap.org] for a description of the M305 command.

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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].

The hot end temp probe reads 91.8k ohms on the multimeter at around 27C room temperature. I unpluged the hot end connection and noticed that the Y axis readout in the web interface reads either -273.1 or -16.8.

The Y axis reads around 27 when the hot end is plugged back in.

The hot end and bed temps still read around 205C regardless whether they are plugged in or not.

I've checked the duet board over and there doesn't seem to be any shorts or burning etc. All the connections are secure and appear correct.

The Z probe numbers are also unstable and jump between 450 and 500.

Have you checked yet whether and ADC corrections have been set accidentally? See my previous reply.

You are running incompatible versions of the firmware and the web interface. If you are running my recent firmware, then you need web interface 0.95 or later, available here [github.com].

Edited 1 time(s). Last edit at 08/18/2014 07:23AM 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].

You are spot on dc42. I had just done exactly that before I rechecked the forums and sure enough you were right on the money,

I reflashed to 65k. I then realised that I had not included the web interface update.

All is working now. Hopefully someone else gets something out of my screw up.

Thanks again for your help!