Project:Sanguinololu Thermocouple: Difference between revisions

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[[File:MAX31855 memory map.PNG]]
[[File:MAX31855 memory map.PNG]]


<!--Sample code:
<code>
signed int getTemp(pSCK, pMISO, pCS) {
    unsigned char buffer[4];
    buffer[0] = shiftIn(pMISO, pSCK, MSBFIRST);
    buffer[1] = shiftIn(pMISO, pSCK, MSBFIRST);
    buffer[2] = shiftIn(pMISO, pSCK, MSBFIRST);
    buffer[3] = shiftIn(pMISO, pSCK, MSBFIRST);


    if(buffer[1] & 0x01) // error!
MAX31855 is somewhat backwards compatible with the MAX6675 however it is 32 bits instead of 16 bits. I shall test to see if this poses a problem.
    {
 
        // short to VCC
Have to take the "MAX6675_SS" lines from the RAMPS section of pins.h and transpose it to Sanguinololu section.
        // short to GND
 
        // open circuit
under <code>#define SDSS    31</code> write <code>#define MAX6675_SS    31"</code>.
    }
 
 


    return 0; // temperature
}
</code>-->


/Lines to change in Sprinter/Marlin/etc... /
/Lines to change in Sprinter/Marlin/etc... /

Revision as of 23:10, 19 November 2012

[[|Sanguinololu Thermocouple]]
Created 03/11/2012
Version 1
Members Pinski1
Project Status Awaiting PCBs
QR code


Introduction

I wanted to add a thermocouple to my 3D printer's hot end. Ideally it would improve the quality of my printed objects as it would provide more accurate temperature readings with greater immunity from electronic noise generated by the stepper motors.

Features

The PCB I have designed has the following features:

  • Fits onto the expansion headers already present on the Sanguinololu
  • Adds a MAX31855 thermocouple to digital convertor chip
  • Enables temperature readings between -200°C to +1350°C ±2°C
  • Has a resolution of 0.25°C
  • Can sample at 10Hz

Files

Schematic

Sanguinololu Thermocouple Schematic.png

The Eagle 5.11 schematic file.

PCB Layout

Sanguinololu Thermocouple Layout.png

The Eagle 5.11 board file.

Bill of Materials

Qty Value Ident Description
1 TXB0104D IC1 SOIC14 Bi-Directional level translator chip
1 TPS73033DBVT IC2 Could be any SOT23-5 +3V3 voltage regulator
1 MAX31855KASA+ IC3 SOIC8 Thermocouple-to-Digital chip
2 2.2uF C1, C2 Ceramic 1206 decoupling capacitors
3 10nF C3, C4, C5 Ceramic 0805 decoupling capacitors
1 SV1 2x5 way, straight, 2.54mm, female header
1 X1 2way, screw terminal, 5.08mm
1 Thermocouple, K Type

Pictures

Top Bottom
Sanguinololu PCB top eagle.png Sanguinololu PCB bottom eagle.png The Eagle CAD layout.
Sanguinololu PCB Render.png The Eagle CAD 3D render
Sanguinololu PCB top.png Sanguinololu PCB bottom.png The PCB renders of OSH Park
To come To come The delivered PCBs.

How to Build

Tools required:

  • soldering iron
  • solder
  • tweezers

Tools that would be useful:

  • solder sucker
  • solder wick
  • magnifier

Soldering

  1. Start by soldering the MAX31855KASA+ into position. Ensure pin 1 is correct and all the pins are lined up.
  2. Next solder in the TXB0104B, agin ensure pin 1 is correct and the pins line up.
  3. Solder in the final IC the +3V3 reg. This is the smallest package so special care will need to be taken to ensure the pins like up correctly.
  4. With the ICs done now solder in the passives. Start with the larger 1206 2.2uF capacitors, these will only fit in two places.
  5. Then solder in the smaller 0805 10nF capacitors, there should be 3 of these.
  6. With the surface mount components in place put the 2x5way female header such that it points out the bottom of the board (see the render) and solder it.
  7. Finally solder in the 2way screw terminals

Testing

You will need a Bus Pirate or something equivalent to communicate with the board and a K type thermocouple to sense the temperature.

Adding to your 3D printer

Now the board is complete and tested to work correctly it needs to be fitted to your 3D printer.

Attaching to the Sanguinololu

/images of the board attached/

Modifying the code

As we are replacing an analogue thermistor with a thermocouple-to-digital device we will need to make changes to the code.

More information can be found out specifically about the MAX31855KASA+ here. The most important piece of information from this is the bit map of the 32bit data packet. MAX31855 memory map.PNG


MAX31855 is somewhat backwards compatible with the MAX6675 however it is 32 bits instead of 16 bits. I shall test to see if this poses a problem.

Have to take the "MAX6675_SS" lines from the RAMPS section of pins.h and transpose it to Sanguinololu section.

under #define SDSS 31 write #define MAX6675_SS 31".



/Lines to change in Sprinter/Marlin/etc... /

Licence

This design is licensed under Creative Commons BY-NC-SA

This design is modified from Sanguinololu SD

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