Tiny cheap fluid bed: chaff collector and more testing

Coffee experiment

Last week we did some new tests with our DIY Tiny fluid bed roaster. There were two things to test. First we wanted to test the Chaff collector that was made by Tije. Secondly we wanted to configure the PID of the TC4/ Arduino to make it accurately execute pre defined roast profiles.

Tije’s chaff collector

During our previous tests the tiny fluid bed roaster blew lots of coffee chaff in Tije’s workplace. This made a lot of mess and we had to fix that. To solve the problem we needed a small but effective chaff collector. We were very happy that Tije made a creative solution for this. He invented a unique part for this purpose that’s smal and effective. It’s also easy to use & clean. To make the part he used a large herb infuser bowl that he sourced at a cook shop.

Video: Tije’s chaff collector in action

PID configuration

The replication of pre defined roast profiles is not spot on yet. We are diving into the causes of this. Because of a small bug we couldn’t use the latest version of the Artisan roast software. That version is supposed to be better at replicating predefined roast profiles. Marko Luther is again very helpful and gave us yesterday a bug fixed version that we will test next time.

PID tuning to SV

In the graph below you can see the roaster trying to heat the beans to a constant target temperature. This was quite successful. We accomplished this by using specific PID values. We assumed that those settings should also work during a background roast. That unfortunately does not seem to be the case.

pid tuning to sv

Background roast profile ‘not spot on yet’

In the graph below you can see the roaster trying to heat the beans to a moving target temperature. Although the roaster somehow follows the profile it’s not spot on yet. We have done several test roasts and we are now diving into the data and trying to make sense out of it. Next time we will try the new version of the Artisan roast software that Marko Luther prepared for us. That might give us much better results.

Background roast

As you can see we have wasted lots of coffee during our tests. Fortunately this wasn’t an expensive specialty coffee. We used Indian natural Cherry Robusta that we especially bought for testing purposes. We bought it from vintage espresso machines. They had used that coffee to season the drum of their roaster. We are looking forward to do the next test run!


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