Overview of the Hermetheus 2.0 2kg drum roaster (DIY coffee roaster)

This is a brief overview of my custom-built 2kg coffee roaster. The roaster itself is commercial-grade, using heavy gauge steel and commercial bearings for the drum. The control system is more "maker grade", using Phidgets as the interface and RC servos for control of gas and air (although they are heavy-duty, metal geared servos). The entire roaster is run via Artisan software, but could just as easily be converted to run manually using a gas knob from a propane grill.
This roaster was used for HUNDREDS of batches of coffee before an entire rebuild in 2020 (hence the "2.0" designation). The 2020 rebuild replaced the carrier bearings and added the entire Artisan control system, as well as the variable speed fan for airflow control.
It's worth noting that the fan is completely optional... the hundreds of batches of coffee that were done on the 1.0 version of this used naturally occurring convection currents to move air through the roaster (it draws in cool air from beneath the drum motor, then exhausts from the bean hopper).

[@eugeniolira8240]

Thanks Jason. Your videos are a great piece of information. I’m applying your designs into an air roaster I’m building and next into a propane drum roaster.

[@hermetheuscoffee]

Thank you! You should consider joining the Fluid Bed coffee roaster forum on Facebook. They have some helpful folks who have built their own air roasters and could help if you get stuck. Good luck!

[@larryduran1047]

I see in your below comments you no longer have the drum roaster and have seen in other videos you are now on the Artisan 6. Where you able to control the drum roaster via PID?

[@hermetheuscoffee]

I never tried. It. It’s certainly possible from a technical standpoint. (Just follow my other video on using PID… the servo doesn’t know/care if it’s hooked to a gas valve or an SSR potentiometer.
Having said that, it probably wouldn’t have worked well enough to be useful on my drum roaster. Most drum roasters are SLOW to respond to temp changes. You’d have to use such low Proportional values and insanely high Derivative values, it wouldn’t be much different from just making a few manual changes.
Other drum roasters could be a bit more responsive than mine was though. But my Artisan is super responsive to heat. It can turn on a dime, heat-wise.

[@sb129w]

Awesome build!! Can you show the inside? Perforated drum? Single burner? What’s the capacity?
Do you have enough control with the servo motor ball valve vs a needle valve?
Can’t wait to start mine!

[@hermetheuscoffee]

Thanks! I don’t have this roaster any longer (I switched to a larger fluid bed roaster), but yes, it was just perforated steel that was used for the drum. The burner element was a simple modified ribbon burner. It has a 2kg capacity. The servo control gives really great control over the heat. You have control in 1 degree rotation, so that’s PRETTY small movement. A needle valve would have been better, but the ball valve + servo worked just fine. They’re just not very linear. So at the extremes, you have to make larger adjustments to have an impact, but just as the ball valve is opening, it becomes very sensitive. Good luck on your build!

[@johanhong3605]

What board do you control the gas burner on? plc?

[@hermetheuscoffee]

Yes, i used a PC, but Phidgets can work on other operating systems (as well as Artisan software). I’ve never tried it though.