Detecting beans in drum


New member
Dec 6, 2006
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My customer has a drum roaster that can hold up to 450 Lbs of green beans.

I've been asked to work on the PLC program to improve the overall process, and one thing I've noticed is the presence of capacitve proximity sensors to detect coffee at almost all stages, but there's nothing to detect the presence of coffee in the drum itself.

Since this is a very hot environment, and the beans may or may not be in motion, what type of detection could be used in there ? Some kind of non-contact infra-red or laser photoeye ?

Has anyone succesfully solved this kind of problem ?

Thank you


Fresh Roaster

New member
Jun 30, 2006
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Yes. We have dealt with this. But you're going to need our permission or a license to use it as we have a patent on the process for using a photo collector for heat treatment of food products.
Put the whole damn roaster on a scale table and you'd know. You'd notice a significant drop in drum temp when beans are dumped into it for roasting. If the loader is automated I'm sure some micro switch could detect the movement of the mechanical action. No movement of the beans? IN the drum? at roasting temp! What the! Geeze seems that if you are expected to design a system you should understand the system. My NW JAVA .02


New member
Feb 20, 2007
Clearwater, Fl
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If you are monitoring the bean temp- the most foolproof way is the drop in temp you get when the beans are first loaded. Depending on whether you are using TCs or RTDs it can be as quick as 10 degrees/second at the initial drop. If you set your system up to detect that quick drop it will catch it every time.