Taking temperature

Catching up on things.

Working on my Raspberry Pi lately.

Got my thermistor wired up.

I used a Thermocouple Amplifier MAX31855 breakout board and a Type-K Glass Braid Thermocouple from Adafruit.

Took a code sample from my Pi class for using the SPI protocol in Python. I combined that with an Arduino Sketch from Adafruit for the MAX31855 and surprisingly I got results the first time. Graphing the results against known temperatures (from my temperature sensing multi-meter) I programmed in software adjustments — not completely accurate, but close enough for now, within a couple of degrees.

Here is the Python program running on the Pi.


It takes a temperature reading every 2 seconds. The first column is the raw output from the MAX31855. The second column has been put through a software converter to give me Celcius. The last column is in Fahrenheit.

Here is the whole setup on a breadboard.


The Pi on the left. Breadboard on right with the MAX31855 in the middle of the board. The orange-yellow wire is the thermistor itself. Also notice a Pi Plate (blue) in the upper left. This will hold the project when it comes to soldering time. In the middle (blue on red) is a relay. This will be used to control the heater on the print bed.

Also have recently picked up 36 .22 ohm 5w resistors from U-Do-It Electronics. I will cement them on a replacement print tray made of aluminum in a combination of series and parallel. Power them with a power supply from a cast-off computer I got from a buddy.



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3 Responses to Taking temperature

  1. walt says:

    I hope this is not a dead link!
    Have you done anything with PID, your thermocouple, and the MAX31855 board?



    • admin says:

      Hi Walt,
      No, not a dead link. I have been ill for a while, hence no updates.
      No, I haven’t tried any of the above yet. For me, too, this is all a learning experience.
      The only thing that I might mention is that with the 3 ATX power supplies I’m using to heat the bed, I come barely close to the temperatures I need for PLA, no where even close to ABS. When I can add another power supply or 2, I might have to worry about getting too hot. I have a thermocouple ready for that, and a Python script on a Pi.

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