Wiring thermocouples via MakerGeeks board

[Steven DeRose]

I'm almost done building an oversize MendelMax 2, but can't seem to get my extruder thermocouples working. I understand they don't work the same as thermistors, and bought converter boards from http://www.makergeeks.com/thsebov2uset.html to connecxt them to the RAMPS 1.4. These boards are not SPI like some others; they are supposed to connect directly to an analog pin on RAMPS. I've tried the instructions on that page, including Configuration.h and pins.h, but no luck. I did noticed that #defines for TEMP_0_PIN occur in 37 (!) places in pins.h. All I get in pronterface is a temperature out of range message, and immediate shutdown.

I have a regular thermistor for the heated bed, which works fine (of course, without any converter board); and motion and heat all work with test programs. I've checked the wiring, power to the boards, continuity, etc. many times, and those all seem fine.

Any ideas on what to check next?

[Steven DeRose]

I should mention that a test sketch that does an analogRead() on A3 and A4 (which have the signal lines from the thermocouple converter boards) reports values around 800 for one, and 300 for the other. The value varies a little, but doesn’t seem to correlate with whether the extruder heaters are on.