Quad Thermocouple Interface

From McLEng

The quad thermocouple interface was made out of the need to interface a microcontroller to a thermocouple. It is built based on the design of the Single Thermocouple Interface. (See the Single Interface for more details.) The quad interface was created for those who have a need to interface multiple thermocouples. A few common projects using this are furnace controls and a BBQ grill control.

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Contents 1 Tutorial 2 Version 1.3 (Current) 2.1 Board Specs 2.2 Eagle Files 3 Version 1.2 3.1 Board Specs 3.2 Eagle Files 4 Version 1.0 4.1 Board Specs 4.2 Eagle Files 5 Software

Tutorial

It is simple to get everything up and running.

1. Install a header or solder jumper wires to the pin connections, you can also use a box header and ribbon cable
2. Connect a K-Type Thermocouple to the PCB Thermocouple Connector use a Thermocouple Wire Connector if necessary
3. Wire the necessary connections to an Arduino or other microcontroller, the bare minimum connections ar +V, GND, SCK, SO, CS1, CS2, CS3, CS4
4. If using an Arduino, load one of the samples from the MAX6675 Arduino Library and you should see temperature information in the serial console. With other microcontollers you can access the chip using a standard SPI interface. See MAX6675 for more details.

Version 1.3 (Current)

The current version of the board did not make many changes from V1.2. The changes were mainly related to the manufacturing. The PCB dimensions were better specified in the gerber files sent to fab resulting in better board routing. The solder mask was also updated to correct for some errors and spacing. The fixturing holes were moved to be inside 1/8" of the border.

Board Specs

• Dimensions: 2.25" x 2.00"
• Chip: 4 x MAX6675
• Header: 2x5 0.1" Pitch
• Fixturing: Four Corner Holes (2.00'"x1.75" Spacing)
• Pinout (Unchanged from V1.2)

Eagle Files

• Board: File:TC Quad Interface V13.brd
• Schematic: File:TC Quad Interface V13.sch

Version 1.2

The next version made some changes based on some feedback of the original version and changes to the single interface. The additions included:

• The recommended 0.1µF filtering cap for each MAX6675
• Additional fixturing holes in each corner of the board to allow for flexible and rigid mounting
• A power indicator LED
• A status indicator LED that is driven by a separate pin, which is useful for displaying a status of the thermocouple from your program
• An updated pinout

Board Specs

• Dimensions: 2.25" x 2.00"
• Chip: 4 x MAX6675
• Header: 2x5 0.1" Pitch
• Fixturing: Four Corner Holes (2.20"x1.70" Spacing)
• Pinout
  • 1: CS1
  • 2: CS2
  • 3: CS3
  • 4: CS4
  • 5: SO
  • 6: SCK
  • 7: LED1
  • 8: N/C
  • 9: +V
  • 10: GND

Eagle Files

• Board: File:TC Quad Interface V12.brd
• Schematic: File:TC Quad Interface V12.sch

Version 1.0

The original version of this board was built as a simple breakout interface for the MAX6675. The first attempt to do this was using a SOIC to DIP adapter board. While this worked, it did not provide a reliable connection for a thermocouple. The solution was to use a PCB Thermocouple Connector. This version implements 4 thermocoupes in the interface

Board Specs

• Dimensions: 2.00" x 2.00"
• Chip: 4 x MAX6675
• Header: 2x5 0.1" Pitch
• Fixturing: Two Hole, 1.70" Spacing
• Pinout
  • 1: CS1
  • 2: CS2
  • 3: CS3
  • 4: CS4
  • 5: N/C
  • 6: N/C
  • 7: SO
  • 8: SCK
  • 9: GND
  • 10: +V

Eagle Files

• Board: File:TC Quad Interface V10.brd
• Schematic: File:TC Quad Interface V10.sch

Software

See MAX6675 Arduino Library for code examples.