Trouble reading the extruder thermistor.

[rald...@mac.com]

Folks,

I'm having trouble getting a valid reading from the extruder thermistor (CTC1).  I'm using this board on an existing Prusa printer, which uses the same Epcos 100k thermistor on both the heated bed, and the extruder.

I modified the thermistor tables in firmware, so that both the heated bed and the extruder were using the same table.

The temperature reported for either thermistor when it is connected to the extruder connector is 1c.

The temperature reported for either thermistor when it is connected to the the bed connector is 21c (room temperature), and the heated bed works properly.

I added some debugging code to the firmware, and it reports ADC values  in the range of 4085 to 4095 for the extruder connector, regardless of whether a thermistor is connected.

Any ideas?  I'm about to bodgewire the CTC1 ADC pin (79) over to an unused pin, to see if I can make it work that way, but I'd like to know if I'm in danger of blowing another pin because of the Epcos 100k thermistor?

- Ron

[Jorge Pinto]

2013/4/19 <rald...@mac.com>

I added some debugging code to the firmware, and it reports ADC values  in the range of 4085 to 4095 for the extruder connector, regardless of whether a thermistor is connected.

Any ideas?  I'm about to bodgewire the CTC1 ADC pin (79) over to an unused pin, to see if I can make it work that way, but I'd like to know if I'm in danger of blowing another pin because of the Epcos 100k thermistor?

Hi Ron.

Can you please measure the voltage on CTC1 ADC pin (79), with different temperatures on the sensor, so we can see if the analog circuit behaves as expected?