A really nice project! It is good to see they are using the relatively new MAX31855KASA+ part instead of the older MAX6674. But unfortunately I have to (as usual) complain about the unit price/availability of Maxim parts. Around eight bucks for this thing! (At post-time I see Mouser has a bunch though – but Only at Mouser – per Octopart).
To be fair; mixed-signal IC’s like the MAX31855KASA+ are expensive to design and produce, and the take-up has a relatively narrow market.
How long until we see Chinese clones of this design on ebaY? If they do show up, is this a good thing or a bad thing? (opinions?)
How does "open-source" hardware and software licenses protect the developers from use/misuse of this thing from the corrupt and venomous Trial Lawyers in (e.g.) the U.S…? Remember, PID controllers like this typically target mains-powered applications (death possible).
The 10A relay board is nice, but if you want to use this with something like a reflow rig, remember that cold heater element current can be a Lot higher compared with when the elements are hot (but controlling this is what PID thing is all about). For a "hackable" device, I would recommend relays (or SSRs) with a much higher rating – for when your software goes wrong during development. Just to be safe.
Oh yes, about the price… $85 USD; not too bad as long as it includes the enclosure. Keep in-mind this is a start-up. I would like to see options for bare boards only though. You can get Chinese PID controllers with LED 7-segment displays (Industry standard PV and SV) for around $30 USD on ebaY (yeah, like the very dubious thing from Sure Electronics). But YMMV (big-time)…