Thermistor and pull up reisitor

I'm having trouble getting my Azteeg X3 pro board going. I have the X,Y,& Z moving and homing fine using either repeteir with repeteir firmware or using Proterface using Marlin firmware.

Regardless of firmware or controlling software I can't get the bed to heat. I have set the mothorboard in the Config files, and I have set the thermistor settings to use a 100k thermistor and a 4.7k pull up resistor. First question: Is the pull resistor internal to the board, or do I have to install a pull up resistor? Has anyone else had these problems? Looking through the pin.h file it's the same as a RAMPS board, it just has additional connections for extruders and thermistors.

A thermistor pullup is typically included in the board and you don't need to install it externally. It isn't the pro, but the Azteeg X3 (non pro) at [reprap.org] has 4.7Ks in its schematic. You can check the thermistor and pullup with a DMM across the thermistor leads: without a pullup, there would be no voltage. With a pullup, the voltage across the leads should be between 0 and 5 V, depending on the resistance of the thermistor at temperature. At idle/25C, the thermistor should be 100K, and the pullup is 4.7K, so you should see about 5V*100/(100+4.7)=4.77V.

Are you getting power to the heatbed? When idle, the MOSFET switch should be open, and both terminals should be at +12V. If only one terminal is high, then there's an open circuit on your heatbed circuit. When trying to heat, the MOSFET should drive one of the heatbed terminals low and heat should be generated. If the MOSFET isnt pulling a terminal low, it could be a dead MOSFET. If it pulling the terminal low, I'd try probing the gate of the MOSFET and seeing if it is getting a signal from the controller chip.

Thanks. I have checked and there is a pull up resistor on each thermistor input. I found a couple lines in the firmware that I needed to enable and now the thermistors and heaters are working.

Time to start putting this beast together. I'm retro-fitting a z-corp powder printer to be a reprap printer. The print envelope will be 24"W x 30"L x 20"T.

Glad to hear more people are using professional grade printers and utilizing the mechanics they are built much sturdier. It's been my opinion for a long time that a lot of repraps would perform much better with a well-designed frame and supported linear bearings

It's had a few challenges. The x and y axis use DC servos, but I found drives that use the encoder information and are driven by the step and direction from the Azteeg board. The Z axis uses four 4 amp steppers, which also required separate larger drives, also driven by the Azteeg. With such a large platen we had to use AC heaters for the bed, which are controlled by a separate heat controller. We're looking forward to getting it together, I think when we're done it will outperform our Airwolf printer we have.

Quote
Schultz
It's had a few challenges. The x and y axis use DC servos, but I found drives that use the encoder information and are driven by the step and direction from the Azteeg board. The Z axis uses four 4 amp steppers, which also required separate larger drives, also driven by the Azteeg. With such a large platen we had to use AC heaters for the bed, which are controlled by a separate heat controller. We're looking forward to getting it together, I think when we're done it will outperform our Airwolf printer we have.

maybe start your own post Z Corp conversion to reprap once you get started make sure to post some pictures for us

Edited 1 time(s). Last edit at 04/29/2014 10:12AM by cnc dick.

OK will do.

@Schultz: Hi, I am also facing the issues with the pull up resistors and I think I am facing the issues in firmware. Could you please tell me in detail how can I enable or check the pull up resistors in the firmware?

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pcb assembly

The firmware-enabled resistors are different than the possibly higher-precision resistor used in the thermistor circuit. [hydraraptor.blogspot.com] is a good reference for how the pullup resistor and the thermistor works.

In Marlin, you can enable the endstop pullups individually around [github.com]

In Teacup, it is [github.com]