No heat reading off Reprap host

I know that the thermistor is connected because when I unplug the thermistor, the hot end does is not hot and when it is plugged in the hot end gets hot.
The thermistor I am using is a 100K and I have selected it in the firmware.

I was wondering if different makes of the same thermistors value give different resistance at a certain heat. This is the thermistor I have. Is it suitable?

Should I see a temperature reading even if the hot end is off?

My running Sanguinololu electronics with sprinter firmware.

Thanks

mapexmbirch Wrote:
-------------------------------------------------------
> I know that the thermistor is connected because
> when I unplug the thermistor, the hot end does is
> not hot and when it is plugged in the hot end gets
> hot.
> The thermistor I am using is a 100K and I have
> selected it in the firmware.
>
> I was wondering if different makes of the same
> thermistors value give different resistance at a
> certain heat.

Yes different thermistors have different values of beta which specifies how the resistance changes with temperature.

>This is the thermistor I have. Is it suitable?

No it is only rated for 125C. You need a glass bead thermistor rated for 300C.

>
> Should I see a temperature reading even if the hot
> end is off?

Yes.

>
> My running Sanguinololu electronics with sprinter
> firmware.
>
> Thanks

Edited 1 time(s). Last edit at 11/22/2011 09:03AM by nophead.

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[www.hydraraptor.blogspot.com]

Thanks nophead

I just bought the Honeywell thermistor
It shows the thermistor table there for the firmware. How do I put that into sprinter?

In the thermistortables.h tab of the sprinter. Could I just replace the numbers for one of them and then in the configuration I could select the one I changed. Would that work?

So I changed the thermistor and put in the new values into the firmware (correctly I think) and it is still not giving me a temperature reading.
Can someone show me how to put the thermistor values in because I think that is causing the problem?
What software does everyone use? I use Repsnapper for testing the motors and the hot end but there is no heat bed option. So I use the Reprap host for the heat bed.

I get no heat reading for either the hot end or heat bed in the Repsnapper or the Reprap host. I have no clue why.

Any help would be great.
Thanks

Did you enable the temperature update in the print tab. It should be bright green if enabled.

Also select the Communication Log tab in the Print tab. You should see some response from the printer showing the temperature of the bed after"..T:".

Yep I did click the enable temperature update and I have attached a picture of what is says in the communication tab.

You're getting a reading of 12C for the nozzle. If the thermistor is plugged in and you're not doing this outdoors, then your thermistor table is probably wrong.

If you set the temperature to something higher than 12, like 150, it should still heat up your nozzle and the reading should go up and stabilize to set value.

Thank you, maybe my bedroom is 12C I did that screen shot when it was off so the hot end was not hot.

I got the values of the Wiki so they should be right, depending on the tolerance. It has a tolerance of 10% so that could be why it is showing 12C when it is more like 16C but it's close enough.

Calibrate thermistor. Look at your temp table in firmware. Identify the column of temp (right side), and write down all temp values (teacup has temps*4 so divide to that). Put a thermocouple inside the heater barrel (thanks to Mr Nophead for this tip), and then set the software for first temp in table. When it reports it reached that temp, write down your real temp (thermocouple reading) for whatever set temp was in table. Do same for all values in table, or at least for the interval of special interest. For next table replace each of the old "set" temperatures in that column with what thermocouple said "real" temperatures. Re-upload new table and double check by setting new temps and have the thermocouple read being close to the computer screen. How good this works depends on how patient you were or how slow it was done (e.g. not reading overshot temps).

Do this with any new thermistor or even when thermistor mount has changed - e.g. took it off and putted back in.

For the best, start with a table that has like 350-400-500C top reading (not ~800) and the values are spread either equal or more dense in the areas of interest. Not a table where one value is 180C and next consecutive one is 240C. Best something like approx 10-15-20C intervals in between temps. Note that its the actual spread of adc values that matters most in the end, but starting temps should somewhat follow that with default table creation.

Edited 1 time(s). Last edit at 11/27/2011 07:04PM by NoobMan.