# diy fluid bed roaster



## PhilDawes (May 1, 2020)

Morning everyone!

I reached some limitations with my Severin popper based coffee roaster and built a new one around a heatgun and blower.






I put some pictures and a components list here if anyone is interested


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## Zal (May 7, 2020)

Looks interesting 

one disadvantage of my Kaffelogic is that you cant see through


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## PhilDawes (May 1, 2020)

I guess the advantage is that they've done the research and have the temperature probe positions and PID and airflow stuff figured out.

I've probably got a few weeks of fiddling about with probe positions and pid parameters.

Out of interest, has anybody written a custom controller for a fluid bed? It feels like I should be able to do better than vanilla PID given advance knowledge of how a roast curve should behave.


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## Rob1 (Apr 9, 2015)

It should be fairly straightforward to integrate with artisan. You'd need something to connect to multiple SSRs as triggers, thermocouple amplifiers for two or more thermocouoles, and an arduino uno or something similar (i think you need 5v to switch ab ssr).


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## Beeroclock (Aug 10, 2015)

There's a fairly active Fluid Bed group on Facebook - might be worth checking out...


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## PhilDawes (May 1, 2020)

Thanks Rob1, I have it setup with artisan (using the TC4 protocol but with a couple of MAX 31856s and an SSR instead of the tc4 board). My main problem is learning about airflow and probe positioning.

If the bean probe is away from the air stream then driving the PID is tricky because of the lag between heater change and bean probe temp change. If it is in the air flow then it isn't really reading anything close to bean temperature. That might be ok, I just need to experiment and try a lot of coffee I think.


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## PhilDawes (May 1, 2020)

Thanks Beeroclock, I didn't know about that group


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## Rob1 (Apr 9, 2015)

PhilDawes said:


> Thanks Rob1, I have it setup with artisan (using the TC4 protocol but with a couple of MAX 31856s and an SSR instead of the tc4 board). My main problem is learning about airflow and probe positioning.
> 
> If the bean probe is away from the air stream then driving the PID is tricky because of the lag between heater change and bean probe temp change. If it is in the air flow then it isn't really reading anything close to bean temperature. That might be ok, I just need to experiment and try a lot of coffee I think.


 There's always going to be lag whatever you do, you need to anticipate the roast stages and adjust in advance. You should have at least two thermocouples, one in the air stream and one in the bean mass, and maybe one additionally in next to the heating element.


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