Printrboard MinTemp Error

Hi everyone! I'm having a problem that after several days I'm unable to solve. My hotend ocassionally triggers the MINTEMP error for some reason. It did it yesterday and when I unplugged the printrboard from the computer, waited a few seconds and then plugged it back in the error went away.

My machine is a Rapidbot 3.0 which was printing fine until I had a filiment jam. Ever since the jam the hotend temp will not read more than 120-125 degrees Celcius. My first thought was the thermister had a short or just plain went bad so I replaced it but got the same results as above. I then tried another thermister, same results. Lastly I tried a whole new hotend complete with all new plugs, resistor and thermister but got the exact same results. I do suspect that the actual temperature of the hot end may be higher than the readout but I have no way to verify my suspicion.

I really did think there may have been a short somewhere considering all the new parts I tried. I'm really at a loss as to what to try next. I searched the forum for the last two days and could not find a situation the same as mine, not to say there isn't one but I've been unable to find it. If anyone has any advice it would be greatly appreciated! I just recently got into 3D printing and have gotten addicted to it and am very anxious to get my machine going again.

My setup is a Printrboard running the Marline firmware using Pronterface and Sli3er.

Thanks in advance,

Bob

Edited 2 time(s). Last edit at 05/02/2013 10:17AM by new to3Dbob.

Are you sure you didn't accidentally edited the maxtemp setting in Marlin?

could you possibly have a short between the hotend thermistor and bed thermistor? The hotend could be triggering the bed max temp if you do.

@ lazzymonk: I will definitly check to make sure the two thermisters are not shorting tonight, thanks for the suggestion.

@Ohmarinus: Do you mean change the settings in the Marling firmware itself or in the slicer or pronterface programs? I know where to look for the temp settings in the programs but not the firmware, the board came preleaded so I doubt I would have changed anything there unless there is a way I could have accidentally done it via Pronterface or sli3er which I am unaware of how to do. Would I had to have reloaded the firmware to change the settings you are referring to?

Thanks a lot!

Bob

Okay, yes then I think the chance of you having changed any of the firmware settings is virtually impossible.

Btw, did you realize, with your account name, that in a year you're not 'New to 3D' anymore?

I only registered 7 weeks ago. I suppose I will have to eventually change it though.

The makemendel support recommended that I reload the firmware. Have you ever heard of firware becomming corrupted for no reason? Thanks,

Bob

Edited 2 time(s). Last edit at 05/02/2013 09:54AM by new to3Dbob.

I made a mistake in my original post. The error that I am getting is a "MINTEMP triggered!" error not maxtemp. I'm guessing the short would probably not be likely now.

Do you have any other suggestions now that I have told you what the corrected error is. Sorry for the confusion.

Bob

mintemp is triggered by a failing thermistor in my experience

Thats what I was initially thinking, but 3 bad ones in a row, one of them pre-installed in a new hot end seems unlikley. I do have more on order but at this point it hard to imagine them all being bad. Maybe there is a problem with my Printrboard??

are you just replacing the thermistor or the wiring all the way to the board? if your using the same wiring, try replacing that. there could be a break in the cable.

Yes this, and even check if the molex connector is ok

lazzymonk Wrote:
-------------------------------------------------------
> are you just replacing the thermistor or the
> wiring all the way to the board? if your using the
> same wiring, try replacing that. there could be a
> break in the cable.

Unplug the thermistor from the board and use an Ohm meter to measure the resistance.

If it reads good figure out how to connect the Ohm meter solid and then move, jiggle, tap
the hot end.

If it changes then your short is on the thermistor side (most common I have seen is thermistor wires
touching each other or the hot end).

If it stays good then the problem could be with your board. I had a Printrboard fail very similar to
this.

Try switching the hotend and bed thermistor connections see if you get a good reading either way.

Initially I was only replacing the thermistor. My most recent attempt at correcting the issue was using a brand new hot end pre-built which included all new wiring and plugs.

I will measure the resistance tonight and if the reading is good I will attempt to get a solid connection and tap the hot end.

I guess if the reading remains good then I will have to order a new board as my next troubleshooting step. I have a friend with a RAMPS board he is not using, maybe I will borrow that board for troubleshooting. Thanks everyone.

Bob

While I am waiting for my new board to arrive I decided to have another go at trouble shooting this board.

I measured the resistance of the hot end thermistor and it was not working. I replaced the thermistor with one that measured correct and also showed the correct temperature at room temperature. I no longer have the problem with the min temp error however the original problem still persists.

The hot end will not heat up past 125C. I decided to run the auto temperature PID using M303 185 process to see if I can get to my target temperature of 185C during the test. The hottest the end would get was still 125C. Please see the attached image for reference. If anyone has any other idea that I can try I would greatly appreciate it. Has anyone ever known of a board to fail in this way or does anyone still the problem can lie elsewhere. Thanks for any help.

Bob

what is the resistance of your heating element, and ar you aware you can change power settings for pwm in configuration.h around the line # in code where the pid settings are?

Few thoughts, might be helpful.
Thermistors will read min temp if the leads are shorted together. The leads are uninsulated and the hot end is brass so if the bulb is too far into the head the leads might be touching the brass.
If the Molex were giving way or if any joins were suspect the fault would be max temp - same as if you unplug the thermistor from the board. This also rules out a dry joint on the electronics as it is failing the other way..
In Marlin config.h check you have the right thermistor setting, there are two 100K types plus a few others although this probably wouldn't be enough to casue a min temp fail.

Edited 1 time(s). Last edit at 05/09/2013 05:38AM by Wired1.

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Richmond, New Zealand
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The resistor that I am using measure 6.9 ohms. The two spares I have measure the same. I was looking through the configuration.h file around the PID settings but was unable to determine what you meant by pwm. I can't take the credit for most of the setting entered for my printer since it was a kit and the firmware came preloaded with the settings already customized. It was working great for about a week until I had my first blockage. From that point on it would never reach past the 125C temperature. The spare resistors came with the kit and I did try replacing the resistor after the blockage. Sorry for the ignorance but could you tell me what pwm stands for? If I can adjust a setting to try and correct my problem I am more that willing to take any advice. Thanks,

Bob