16 Channel Thermocouple Multiplexer for Raspi

This is coming soon.

Projected that there will be stackable boards 32 Thermocouple channels for each board, theoretically up to 256 channels.

I have uploaded a newer version which cleaned up some rogue tab indentations. This has been tested under Pi OS version Bullseye.

Warning: A problem has been identified with Ubuntu running this application on the Raspberry Pi. A mapping issue occurs between the ncurses library and Python3. This is being investigated with the developers.

A reported bug that prevented the software starling sometimes and getting caught in the Starting 1 loop has been coded around. Anybody who still sees this bug can you report it please.

I have tested the V1.3 PCB and it works. My previous observation regarding the +/- symbols was in error and they are in fact the right way around. My next task is to design a enclosure to 3D print. At the moment I have the board inside the cardboard box that my Pi came in. To optimise performance you should minimise temperature gradients on the board. The best way to do this is to enclose it, even in a cardboard box!

A minor bug was fixed that caused the application to close if the hosting terminal window was smaller than the displayed text. This has been resolved by specifying a minimum display window.  Although this prevents the application from closing you may need to manually resize the window after the application starts to see all printed text.

A small start up bug fixed and new minor version uploaded.

The Ver.1.3 PCBs arrived today. I sent the Gerber files on Monday night and the PCBs were on my doorstep Friday afternoon. The price was AU$2.00 for the boards and AU$27.00 for DHL delivery. 

I will attempt to get one assembled and tested over the week end.

I just noticed looking at them that I have the +- symbols on the overlay around the wrong way..........Bugger!

Posted version 1.3 PCB file and compressed Gerber files. The PCB has been modified but is untested. It "Should" work but it will b e a couple of weeks before I get around to testing it. If you are not feeling brave, the version 1.2 PCB is still available. It works but has 2 unnecessary resistors that have been removed in 1.3. You can fit any value from 0 to a few hundred ohms and it will work.

Updated circuit diagram to Ver 1.2

The circuit has been revised to reflect the removal of the two series resistors. This is as a result of the observation by Hwansoo Suh questioning the function of these components. They are there to protect the input of the converter chip from excess common mode voltage. As the multiplexer will be destroyed by anything much over +3/-0.6 volts the resistor seems a bit pointless. 

The PCB is yet to be updated. At this stage if you use the Ver 1.1 PCB any value between 0 Ohm to 1K will work. I will publish an updated version as time permits.