Firmware for Techzone Thermocouple A-D converter with OneWire

@robotdad - Perhaps your changes could be merged into the official distribution? It would sure make debugging a techzone mendel easier if the correct firmware wasn't so nearly impossible to find.

Hi,

Not sure if this is the right place to post this problem but here goes. I have a techzone remix lasercut mendel. I have been having lots of problems getting the thermocouple to work. I had been using the firmware available at: [www.reprap.org] but I always got a '1970' reading back for temperature (both to reprap and to repsnapper).

I then tried using the firmware which brnrd has posted (thanks very much for this); and with it I can confirm at least my thermocouple is good - because it does read sometimes; but most of the time it returns 0. If I enter 'M105' in the 'send a GCode' box of repsnapper once every 5-10 times it responds with a correct temperature reading.

Any ideas out there on what might be causing this problem. I'm pretty sure its not faulty or loose connections because I'm not touching any of the wires or board between 'M105's. Could it be something to do with the communication speed settings in the firmware? Any help would be much appreciated.

- Khalid

Yes. This is consistent with my experience which was also confirmed by Techzone with the Thermocouple A-D. If you look at the log in repsnapper, you will see that when you get a reading of 0, there is an error code associated with it which are usually communication timeout errors. I think that the problem is that the extruder controller is taking too long to read the temperature from the AD chip that the RS485 requests from the motherboard times out before the EC can respond to it. It seems to still maintain the tip temperature during this. But, I was also experiencing problems with the extruder controller loosing the temperature setting and shutting the heat off or the MB stopping the print at random times. This continued even after I switched back to a thermistor. So, I eventually abandoned the TZ gen 3 remix altogether and went to RAMPS 1.2. This fixed all my problems. So, if you're not experiencing problem with your print stopping or the tip losing temperature, then you're fine. It's not a big deal if you can't always read the temperature from the EC.

Hi,

Have recently fitted the "Universal Hot - End 3mm Filament" from emakershop to my techzone mendel (with gen 3 electronics). I uploaded firmware which brnrd posted here but with configuration.h modified to use thermistor (thermistor uncommented and other options commented out), and with temperature.h modified to have the correct thermistor calibration table.

On running repsnapper generally the printer seems to be working OK but temperature is not being reported correctly. 'M105' keeps returning 0 for bed and extruder temperatures. If I set a temperature and then turn the tip heat on it does come on and eventually toggles on and off so appears to be settling at a temperature.

However I set the temperature at 70'C as a test, and when I measured the temperature with my DVM+thermocouple I got a steady temperature of around 160'C so clearly something not right. Also when I did a trial print the heater just seemed to stay on so the plastic overheated and did not extrude well. I checked with a DVM and the resistance across thermistor does drop when the tip is heated.

Any thoughts out there on what might be causing these issues? Anyone have a version of brnrd's code already set-up to use thermistor? Anyone had a thermistor correctly reporting temperature back to repsnapper?

Cheers,

- K

Is your thermistor place anywhere near where the thermcouple was, or is it further from the heat source? Tacking on afterthought thermowidgets generally means you're reading something lower (possibly much lower) than you're really heating it to.

Are you sure that the thermistor table is correct? Also, check to make sure that there are no error codes in the response to M105.

I'm also not familiar with the hot end but have you tried using bang-bang control on the extruder? You can modify one of the modules in extruder_class.pde as follows:

void extruder::controlTemperature()
{   
//  extruderPID->pidCalculation(targetTemperature);
  extruderPID->bangBangContro(targetTemperature);
//  bedPID->pidCalculation(targetBedTemperature);
  bedPID->bangBangControl(targetBedTemperature);



  // Simple bang-bang temperature control

//  if(targetTemperature > currentTemperature)
//    digitalWrite(HEATER_OUTPUT, 1);
//  else
//    digitalWrite(HEATER_OUTPUT, 0);

 
}