u/ManufacturerAny849

Hi all, I'm a hobbyist trying to add temperature logging to a small consumer appliance and would love some sanity-checking on my approach before I order parts.

Quick context on the device, just so the constraints make sense. It's a small countertop appliance, basically a rotating drum with a heating element and a fan that pushes hot air through the drum. There's a single exhaust outlet at the back where the heated air exits after passing through the drum. The drum itself rotates during operation so I can't easily put a probe inside, but the exhaust air path is fixed and accessible. Operating temperatures at the exhaust are roughly 180 to 250 degrees Celsius, runtime per session is around 15 minutes, and there's a heating element plus a small AC motor right next to where I'd want to place the sensor.

What I want to do is log the exhaust air temperature once per second over USB to my MacBook, then feed it into a small web app I've already built for visualization. I don't need extreme precision, I care about reproducibility across sessions much more than absolute accuracy.

My current plan is a Type-K thermocouple, a MAX6675 or MAX31855 breakout board, and an Arduino Nano sending JSON lines over serial.

My questions for the more experienced folks here. First, probe placement. I can either drill a small hole into the exhaust duct and use an M6 screw-in probe for a tight mechanical mount, or I can clamp a bare wire probe externally to the outlet vent with a stainless hose clamp. The clamp option is reversible and faster to try, but I'm worried the thermal contact through the duct wall is too indirect to get useful curves. Has anyone here compared the two approaches in practice? Second, MAX6675 versus MAX31855. For exhaust temperatures in the 180 to 250 range, is the precision difference between the two chips actually visible in real measurements, or is the cheaper MAX6675 fine? Third, EMI. With a heating element and AC motor running about 10 cm from the probe, do I need shielded thermocouple wire from the start, or can I get away with the standard fiberglass-insulated stuff and add software smoothing if needed?

Not looking for a full design, just the gotchas you'd want a beginner to know before committing to parts. Thanks!

Hey, I've been roasting on a Gene Cafe CBR-101 for a while and want to start tracking exhaust temperature so I can build proper roast profiles instead of going purely by sight, sound, and timer.

I searched this sub and the rest of Reddit and was surprised how little I found. Lots of people talking about adding a thermocouple to a Gene Cafe, almost no one posting an actual working setup. So I figured I'd ask directly.

My plan is the budget DIY route. A MAX6675 or MAX31855 breakout board, a Type-K thermocouple, an Arduino Nano sending data over USB serial to my MacBook, and a small Node.js bridge that feeds my own roast tracker. The tracker is already built, it just needs a live data feed. I'm not going the Artisan route, I want the data in my own software.

If you've actually done this or have similar experiences on a Gene Cafe, I'd love to hear where you put the probe. Did you drill into the exhaust duct with an M6 screw-in probe, or clamp a wire probe externally to the outlet vent? Any regrets either way? How stable were the readings, did you need shielded thermocouple wire or any software smoothing because of EMI from the heater and motor? And MAX6675 vs MAX31855, was the upgrade worth it for exhaust readings in the 180 to 250 degree range, or overkill? Anything you wish you'd known on day one would also be gold.

If nobody on a Gene Cafe has done it, I'm also curious to hear from people who've added thermocouple logging to any hot-air or non-Artisan-supported roaster. The placement and EMI lessons probably transfer.

Happy to write up whatever I end up building if it's useful. Thanks!