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Thursday, December 31, 2020

Programming Step

Added Several functions to the MCP9600 library.

I now own the status register and the config register.  This allows me to monitor temperature alerts by monitoring LEDs on the amplifier board.

Added Documentation

I added a page for the Cold Trap and its purpose.

Wednesday, December 30, 2020

In the Beginning

At the time I started this blog, I had a few parts of the freeze dryer working. Additionally, I have obtained most of the parts I thought I would need.

I have successfully interfaced the thermocouples to the RPi using two MCP9600 Thermocouple amplifiers.  These amplifiers have a convenient multi-function digital interface that can communicate with several protocols.  I will be using the Inter-Integrated Circuit (I2C) 2-wire interface for most things.

I have written temperature conversion routines for the general-purpose library so it can be used for various other tasks in the future.  The library currently supports direct temperature conversion for Celsius, Kelvin, Fahrenheit, and Rankin.

I am writing all code in C++ using the WiringPi library in the CodeLite Integrated Development Environment.

The MCP9600 supports several thermocouple types including K, J, T, N, S, E, B and R. I chose the K-type thermocouple for its performance at low temperatures.

I currently have routines that configure the thermocouple type, configure the noise tolerance, fetch the hot junction temperature and fetch the cold junction temperature.

I have obtained an adequate vacuum pump, a refrigerator, a vacuum chamber, most parts for the control system and a small AC unit to help the refrigerator reach levels of cold it was not designed to reach.