On Thu, Aug 11, 2022 at 01:59:18PM -0700, Rich Shepard wrote: > There are inexpensive units that do this but the maximum temperature is > limited to about 150F, and I need a range to 500F.
As a cheap wildass alternative, can you use a second controllable fan to mix room air with your roasting chamber output air, aim the output mix setpoint at 150F (or whatever) with a thermostat, then estimate temperature from the mix ratio and physical gas laws? This kludge would require calibration (use dried peas, cheaper than coffee beans?), but you could implement it with cheap hardware store tech and calibrate it with algebra and a Rubber Bible. Maybe not; I presume roasting coffee beans emit a lot of steam, with a crazy-varying specific heat compared to room air. Which implies that an electronic sensor must be steam-resistant; very hot steam is corrosive. It also suggests that your roasting set point (for whatever kind of controller) should also adjust to moisture content for different kinds of coffee bean. Roast temperature is a proxy for output product, perhaps you will discover a better proxy. But maybe, after enough cups of coffee, you can invent a cheap fix, perhaps invent a profitable product. You aren't the only customer who cares beans about coffee. Keith -- Keith Lofstrom [email protected]
