We’ve seen a lot of coffee roaster builds over the years. [Ben Eagan] started his with a hot-air popcorn maker. If you think it is as simple as putting beans in place of the popcorn, think again. You need to have good control of the heat, and that requires some temperature monitoring and a controller — in this case, an Arduino. [Ben’s] video below shows how it all goes together.
With the Arduino and the power supply strapped to the sides, it looks a bit like something out of a bad post-apocalypse movie. But it looks like it gets the job done.
In addition to the Arduino, a thermocouple measures the temperature and that takes a little circuitry in the form of a MAX31855. There’s also a relay to turn the heater on and off. There are other ways to control AC power, of course, and if a relay offends your sensibilities you can always opt for a solid state one.
The only other wrinkle was the addition of an extra power supply so the fan could operate without the heater. There might have been some other ways to manage that, but power supplies are cheap enough and at least the strapped on power supply counterbalances the strapped on Arduino on the other side of the popper.
We’ve seen popcorn poppers used like this before, of course. Thermocouples are a great way to measure high temperatures, but there are lots of other ways to measure that particular quantity.