Temperature reading on 100k HW

[Luka Draženović]

Hi guys,

After changing my thermistor to 100K HW and choosing option 7 in sprinter my temperature still reads 68C when printer is idle and hotend is cool. Any toughts on this?

Best regards

Luka

[Ante Vukorepa]

Sounds like either a defective thermistor, or you have a slight conductive path somewhere between the thermistor leads.

Are you sure you've wrapped the thermistor leads in kapton tape well (all the way to the thermistor casing itself)?

I've checked Sprinter's thermistor tables and they seem to be correct.

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Ante Vukorepa

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[Luka Draženović]

It is a new thermistor Laszlo sent me this week so I suppose that a small part of thermistor wire is touching the hotend, I will  try to wrap Kapton tape around it and send some feedback tonight, thx

[Ante Vukorepa]

Just be careful not to wrap kapton around the thermistor body itself!

[Laszlo KREKACS]

Dear Luka,

I.) As Ante wrote make sure the thermistor's leg are insulated (but
not the body) using Kapton tape.
Obligatory picture here:
http://www.flickr.com/photos/48806889@N05/8420446252/
from here:
http://wiki.arcol.hu/blog:arcol-hotend-v4-2

II.) You can use thermal grease (on the thermistor body) to minimize
temperature response lag (and temp mismatch).

You need really minuscule portion.

Best,
Laszlo

[Luka Draženović]

I was wondering why my aluminum plate was getting hot, very hot. It's so hot that it bends my pla stand with rollers on x axes and the filament doesn't go out neither... Any thoughts on that? Maybe because my thermistor temperature starts at 60C and every temperature thereafter is 60C higher...

[Ante Vukorepa]

If your thermistor is reporting 60 deg C at room temperature, you’d be getting 60 degrees LESS thereafter, because the PID loop would stop applying power to the heater sooner.

E.g. 100 degrees as reported by your thermistor would be 100-(60-20)=60 degrees in reality (assuming linearity in the error). 200 degrees would actually be 160 degrees etc.

Regarding the hot aluminium plate… 

Do you have a fan blowing over the hotend’s radiator fins?

It can function without one for a while, but a fan is a very very prudent idea.

-- 

Ante Vukorepa

[Luka Draženović]

I will try with the fan.
I've put a second thermistor, put Teflon wires till the end, then also some Kapton tape over all... The only thing I didn't do exactly as on arcol blog is clamping the ends of thermistor wire with steel barrels, instead I used my hands... Stil 70C when idle... I don't get it...

[Luka Draženović]

I believe that thermistor reading is the main problem here. That's why aluminium plate is heating up, although much less after fan was installed. So how do I get the right temperature reading with hw 100k thermistor? I was looking at temp table and it's different then on wiki site... How do I change it?

All the best

Luka

[Luka Draženović]

I have an update an this issue

On my RAMPS 1.4 there are three pin slots for temperature.It seems when my thermistor burned it also burned these pins on RAMPS.

By redefining pins in Arduino "pins.h" i managed to switch pins with bed thermistor and now the temperature reading is starting from 25C room temp and it more accurate.

So it was not the problem with thermoinsulation on thermistor,it was an electronics issue.

[Ante Vukorepa]

Heh, i wasn’t aware you burnt out the thermistor (BTW, short circuit is a pretty odd failure mode for a thermistor).

Malfunctioning input pins would do that, yes.

-- 

Ante Vukorepa

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[Luka Draženović]

Any suggestions where I can buy RAMPS 1.4 from?

Are there any differences between ones from Ebay(red) and from gadgets3D(blue)

Dana srijeda, 26. ožujka 2014. 13:03:55 UTC+1, korisnik Luka Draženović napisao je:

[Ante Vukorepa]

Not really an answer to your question, but...

I'd strongly suggest buying RAMPS from a non-chinese, known seller and, if possible, in kit form, soldered by yourself.

There's a an ever rising flood of cheap RAMPS boards on eBay and elsewhere and all i seem to hear lately are issues of this or that form (from failing MOSFETS to bad solddr jobs).

That's not to say that the cheapo ones aren't usable, just that they're a bit of a lottery.

Alternatively, buy a known-to-be-working integrated board.

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[László KREKÁCS]

Hi,

> Alternatively, buy a known-to-be-working integrated board.

+1

Megatronics 2.0 and Rambo 1.2 comes to my mind.
The drawback of megatronics, that there is no servo output,
basically you hunt down the GND, 5V and the arduino pin to connect the
servo motor.

Ramps is unnecessary bulky imho.

Best,
Laszlo