Thermister
June 04, 2014 03:42PM
i'm commisioning a ormeroid,

Thermister on the extruder does not work, I get a reading of -273. At the plug connections I get 120KO resistance (room temp) dropping to 10KO when I heat it with hot air gun. The pins have 3.7 V on them from a simple usb connection. Putting a small resistor between the pins causes no change in the reading.

What to try?
Re: Thermister
June 04, 2014 03:48PM
If you put a 1k resistor between the pins, does the voltage across it reduce by half, and does the temperature reading change?

Edited 1 time(s). Last edit at 06/04/2014 03:49PM by dc42.



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].
Re: Thermister
June 04, 2014 05:23PM
Once a temperature fault has been registered, it will stay at -273C until the the board is reset, or the g-code to reset the temperature fault (M562 P0 for the heated bed, M562 P1 for the hot end) is sent. So disconnecting and then reconnecting the thermistor may not then show the temperature.

It's possible you have a Duet where the temperature reported at room temperature is always out of range; see the third point here, which has some further tests: [reprappro.com]

If so, we'll exchange the Duet. Email me on support at reprappro dot com with you full name and address, proof of purchase (RS order reference, or other information) and whether you have a kit with red or green printed plastic parts.

Ian
RepRapPro tech support
Re: Thermister
June 05, 2014 02:36AM
Quote
droftarts
Once a temperature fault has been registered, it will stay at -273C until the the board is reset, .....
Ian
RepRapPro tech support

I feel that this may benefit from some sort of revision. I remember when commissioning and having a doggy connection at the thermistor it was difficult to determine which one, it would be nice if you could 'wobble a lead' and see the reading change as it connects or breaks. (it's still on my list to make these connections robust).

I understand the benefit for 'melt down' protection while running, but perhaps now the software is getting so good [Thanks DC] some of these issues could be considered for those doing a new build?


Ormerod #007 (shaken but not stirred!)
Re: Thermister
June 05, 2014 03:17AM
Hi 007, yes I am already thinking about this. The idea would be to have the web interface show the current temperature and a separate fault indication. Not sure what to do about the temperature reported to Pronterface though.



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].
Re: Thermister
June 06, 2014 01:50AM
I had the same problem, IBDunne, due to a problem with the Duet board's analogue/digital converter being on the limits of what it can cope with at low temperatures. RRP offered to exchange the Duet, but because of the reported problems with later Duets burning out for a reason they hadn't got to grips with, I decided not to jump from frying pan into fire. Instead I solved the problem based on a suggestion, by DC42 I think it was, in another thread, by putting a resistor in parallel with the thermistor. 180k was just right for mine. When cold, the reported hot-end temperature was then within a degree of the bed temperature. At working temperatures, the additional resistor has an insignificant effect on the reported hot-end temperature.

Ken.
Re: Thermister
June 09, 2014 08:09PM
Hi DC, I haven't my printer with me, so you might already have done this, but when I was using Pronterface to control the printer instead of the Web interface, I was able to alter the Temps while printing, which was pretty handy.
When I was using the Web interface I couldn't alter the temps. Would there be any possibility of adding that to the Web interface.
Also, if I recall (I was using Chrome at the time), where you enter the G code commands (top right) there was an add button to recall regularly used G/Mcodes... I wasn't able to add any.
You might have altered this since I last used it.


Please send me a PM if you have suggestions, or problems with Big Blue 360.
I won't see comments in threads, as I move around to much.
Working Link to Big Blue 360 Complete
Re: Thermister
June 10, 2014 02:25AM
Kim, yes I put a fix in the web interface a few versions ago so that you can use the temperature setting buttons during a print.



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].
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