k type thermocouple setting

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k type thermocouple setting

Postby gyrogearloose » Thu Aug 01, 2013 1:34 pm

I am trying to use a Chinese made extruder with a K type thermocouple on my X3 board from Panucatt and cannot find a Marlin/Arduino setting that matches the sensor. I have tried all temperature sensor presets on config h and none work. Temperature readings are either way to high (up to 900deg) or to low. What to do? The sensor is described as follows:
K-type thermocouple (PT100 reference temperature of 0 degrees)
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Re: k type thermocouple setting

Postby cvoinescu » Thu Aug 01, 2013 2:03 pm

I assume you have the version of Azteeg X3 with thermocouple inputs (they're optional). Can you find out what thermocouple amplifier there is on the X3? It's on the shield. I can't seem to find schematics for it anywhere. I found an X3 schematic here, but it doesn't have the shield (so no thermocouple amplifier, no extra thermistor inputs). Also, I don't know which input pin the thermocouple inputs would connect to -- you need to know that to configure Marlin correctly (my guess would be one of the pins on the EXP2 connector -- A4, A5, A11 or A12). Note that you can't connect a thermocouple to a thermistor input -- you have to use a proper thermocouple input, with an amplifier. Also note that it matters which way you wire the thermocouple. When heated, it generates a tiny DC voltage, which the circuit measures, so it needs to be plugged in the right way round. This may help with testing: with the thermocouple disconnected and the input pins shorted, the firmware should read room temperature (assuming a compensated amplifier, which is usually the case).
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Re: k type thermocouple setting

Postby gyrogearloose » Thu Aug 01, 2013 10:25 pm

You know what, my X3 shield does not have the optional thermocouple inputs. I just did not read the manual. Thanks for setting me right.
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Re: k type thermocouple setting

Postby cvoinescu » Fri Aug 02, 2013 1:36 am

Bummer. You know, you could build a thermocouple amplifier. It's basically one IC and not much else.
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