[Homeroast] THE home roaster

Allon Stern allon at radioactive.org
Fri Dec 17 01:37:36 CST 2010

On Dec 15, 2010, at 1:11 PM, Tom & Maria - Sweet Maria's Coffee wrote:

> One way to approach this that might get around some legal hurdles (because a really GOOD home roaster is probably not going to be idiot-proof, and I am sure would be classified as a fire hazard by some agency) is to make a kit. If it was build around some commonly available heat source, and you had to put it together, but gave control of heat/air, manual control of roast curves, physical sampling from the roast chamber, and cooled outside the roast chamber in 4 min or less, that would hit most of my targets.

This is the approach I took to my homebuilt roaster/mods - I separated the control from the device.

That is, I built a generic controller, which has a single plug that plugs into the wall, a pair of outlets on top - one is controlled by a dimmer, for manual fan speed control. The other is controlled by a solid-state relay, which is driven by a PID; the PID has a thermocouple socket on the front of the unit.

Currently it drives an iRoast2 body from which I stripped out all the control electronics. Of course, I could drive the heat and not the fan and watch the thing burn up, if not for the thermal switch built into the iRoast's heater, though I expect I might damage something that way.

This unit could be used to drive any coffee roaster consisting of a 120V fan and 120V heater. The trick is being able to apply enough heat to follow the roasting curves defined in the profile programmed into the PID - if the roast profile requires more heat than the machine can apply, then it will not be a good roaster.

Theoretically, I could use the same lash up (with a different SSR) to drive a 240VAC @40A roaster that could really pour on the heat.  The hard part is finding/building such a beast. And to be honest, I don't think I want to; With the iRoast2 I can push 170g roasts, if I'm careful, and if the profile is gentle enough. With the stock iRoast2, having to baby it along to get it to follow a profile, 150g is not enough; doing multiple back to back roasts was not fun. With the modified PID iRoast, I can run back-to-back roasts easily, and while it roasts, I have not much else to do than watch the PID run the profile, tweak the fan to get good bean circulation without driving it too fast (and running all my heat out the exhaust), and maybe clean up the basement a little bit at the same time.


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