Show HN: A Digital Twin of my coffee roaster that runs in the browser

I've never paid attention to the minute differences, but if you're the kind of roaster who believes in the art of it versus the science, I think it'd be cool to try to map this model to certain outcomes - eg more or less fruity, chocolate, etc. Or actually throw in stuff like humidity, bean age, time of day, etc.

I've done a few hundred roasts, but by hand cranking a flour sifter over a heat gun. My model inputs are noise, smell, appearance. I've never been interested in pursuing a roast curve or profile, because I'm a barbarian.

I put in 265 grams of dry process coffee - usually some Ethiopian from Sweet Marias - set the temp to 449°F, set the time to 19 minutes, start it up and the set a timer for 16 minutes. At that point I start watching it and hit the stop button when it is a little lighter than I want.

The Gene Cafe is notorious for its slow cool-down cycle, so if you stop the roast when it looks perfect, it will end up too dark. But I've gotten pretty good at guesstimating it. And I do two roasts back to back: a lighter one for myself, and a darker one for my friend who prefers that. So if the first roast is lighter or darker than I planned, I adjust the time for the second one.

One time I thought I would get more precise, so I bought a cooling device on eBay. With this, you run the roast until it looks perfect, hit the emergency stop, and dump the beans into the cooler. (Use a hot pad because the handle will burn you!) But this left way too much chaff mixed in with the beans. So I went back to my imprecise guesstimating method.

I used to have to replace the heater element every couple of years when it burned out, but the last one has been good for ten years. The only current problem is that the rotary knobs - especially the temperature knob - have gotten twitchy. If you turn it a bit, it doesn't reliably go up or down smoothly but jumps around randomly.

Having had some prior experience with rotary encoders, I knew right away what the silly mistake was that the designers made, and how they could have prevented it at little or no additional parts cost. Just for fun, I also described the problem to ChatGPT, and bless her silicon heart, she figured it out too.

Would anyone like to take a stab at this question? What was the mistake, and how could they have kept these rotary encoders from getting jumpy after years of use?

When this machine finally does break down completely, I won't be getting another Gene Cafe. Not because of the problems above, but because of a new "safety" feature they added a few years ago where twice during the warmup, it beeps at you and you get 30 seconds to push a button to keep it going. I roast outside, and I like being able to ignore the machine for 16 minutes.