DavidNP's design can suit 4 thermocouples. It just involves plugging 2 more $3 TC amp units into the system. The programming is already there, I believe. And the TCs don't HAVE to be built into the damper.
Not sure if it's that simple. The code has been modified to operate with an ESP8266 WiFi unit as well, and I think it handles the JSON data quite differently. Also, the wiring on the board would need to be modified.
It's a good project, and a cheap one, and my suggestion to you would be to study it a little more, instead of chastising it as you seem to be doing in the last few posts.
I don't SEE... where Ralph was "chastising anything.........he has given good ideas to JohnW.........seems to me that someone has a burr up his butt! But thats just my observation, why can't everyone just get along??
looking at that octo TC board is kinda 'neat'.... if it actually works (I found other shields/schematics online that have a TC multiplexed as well).... that would be super simple/cheap to support 4-8 TCs... Seems that it needs 125ms between switch/read but that's not too bad. You could read all 8 TCs just over 1 second.
a $3 max TC with a multiplexer chip would be simple to build (or get one of those already done)... maybe have single TC board for pittemp (fast read) and another 4-8 TC board food (slow read)....(HM only supports 4)
Are you saying they have a single amp circuit for the TC and mulitiplex it to to the sensors to collect the readings? If so, I wonder if HM could be adapted slightly to use its single TC Amp circuit where the ports could be externally multiplexed and time divided for readings. For example, the HM could could be added with a how many external thermocouples are you using feature and then it could time split the readings sending a signal out the RJ45 jack to control the external multiplexer chip that switches the TC sensors which feed their data back to the currently existing TC port lines.