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Behmor PID Temperature Controller
I implemented a PID to regulate the temperature of the Behmor using an SSR (Solid State Relay).
The implementation is quite simple, utilizing the roaster in manual P5 mode, the PID gets it's power and regulates the temperature in the roaster instead of the roaster's control board without effecting any of the other roaster's functions or safety guards.

For detailed build instructions, schematic and parts see my instructables guide:

Hi Heli Guy and welcome to HRO! Looks like you've done a ton of work getting the Behmor able to be controlled with a sane method versus the wacko system it comes with. I'm sure a lot of our members will want to know in some detail how you are achieving valid feedback of energy being imparted to the beans since the Behmor's primary transfer of energy is via radiant to bean with ambient heat surrounding the beans being secondary. Obviously, without bean temp feedback, many have expressed concern that the Behmor necessarily causes one to "fly blind" since there is no way to measure how efficient radiant to bean transfer is as the bean absorption coefficient changes as the bean color darkens throughout the roast. This is unfortunately a problem affecting all roasters utilizing radiant heat as a primary heat source when bean temperature cannot be measured.

Great to have you on board!
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Hello Allen.
I try to keep the temperature constant at 300 throughout the roast until 1?? crack. Then I reduce power to 50% and reduce drum speed and let it coast for 3 minutes for 12oz and 4 for 1 Lbs.
The result for me is a balanced flavoured roast that tastes great to me.
It just seemed stupid to me to stand in front of the roaster and act as a thermostat pressing P5, P4 or P3, to keep the temperature at 300 when a PID could do that job better.

I realize the temperature is radiant and not bean temperature but at the end of the day, my espresso tastes great and the result is repeatable, that's all that matters.

Using a Rocket Cellini Evoluzione V2 and Ceado 37S grinder.

My espresso blend is ? Brazil Arabica, ? Indian Parchment Kaapi Royale Robusta, ? Guatemala Antigua.
amazing writeup, thank you.
I just picked up a 1600+ and my first thoughts after a couple small batches was to throw it in the river. But I will persevere through another few, my question is there a way to control the fan, either the timing or speed or both, both would be preferable. Should just toss it, but adding a pid and hopefully some fan control, it might become a suitable roaster.
The radiant scorching of the beans as an adjunct heating method is also a major problem, seems to promote uneven roasting in my single origin greens, like getting an unwanted blend after roast.
The pid will be a blessing, but needs some fan control. Also something about timeouts, rendering the machine infuriating to say the least. Is it just me, or is there a firmware bloat built into what should be a straightforward convection oven roaster. I'm thinking temperature control knob, time setting, fan speed, drum speed. I love the pid contoller, but should come standard, set temperature / time, hit start, go, adjust as necessary, airflow, drum speed. Truly a convoluted appliance with it's ridiculous buttons and timeouts / cutouts, button pushing absurdity.
Not sure how the PID could help you too much because Behmor use a complicate mix for roasting, hi radiant with low convection.
The temperature is unusual by common standards, in any corner of the machine, and is very difficult to perceive the true action on beans of the radiant component.
Maybe this is the reason that led the author to his control approach.

If I had a machine like that... I think I'll try to understand his programming, by running several cycles and measuring how power is applied, time and duty cycle.
Edited by renatoa on 11/19/2022 5:53 AM
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