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Thread: Behmor modded

  1. #1
    Senior Member brettreaby's Avatar
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    Behmor modded

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    here is my behmor which i have modified by fitting a PID temperature controller.

    This setup allows me to put behmor into PID controller mode and control the main heaters by Solid state relay and on temperature. Attached also is the second roast profile showing the temperature profile obtained, which i am happy with.*

    The dip in the graph at the 7 1/2 minute mark is unavoidable as the BM pull heat out of the roast when the afterburner comes on- dont know if this is a good thing or a bad thing.

    The PID mod however is not very straightforward because i did not want to bypass the existing control or safety cutouts so need to also monitor for when the roast starts and also cutout when the roast goes to cooling. The switches allow me to restore BM to regular control if I need to.

    So far i am really happy with the result - i think the roasts will be slightly longer than the standard result ( because the PID controller stops temp overshoot ) but the results will be far more predictable and repeatable as the temperature controller will negate many of the usual variables of ambient temperature and supply voltage.

    I will also be able to adjust the roast easily by changing the temp setting as i go.* Currently i started with 200C and got a 19:20 long roast overall ( I was trying for a really dark roast and let it go into C2 longer)

    I have to say i really love my BM gadget modified or not, but this gives me the temp control the standard behmor doesnt provide.* I have fitted the thermocouple in the top left corner of the cabinet near the roof.




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    Re: Behmor modded

    hello Brettly

    nice work on the mod

    im still a mug roaster, i dont use anything to monitor my roasts and im always stuffing around opening the door a little up to first crack and then jam the brush handle in at first crack, real hit and miss stuff .

    There used to be a thread where Andy and his dad were in the early stages of a prototype mod on the Behmor.

    thanks for sharing

    Darren

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    Brett would you consider something like this for a Behmor mod by any chance? I've only had a quick look but with some changes to the program it appears to me that a number of custom PID'ed profiles could be pre-programmed into the roaster, and manual control added as well, for little additional cost compared with the multimeter USB logging upgrade so worth exploring?

    Other forums are discussing the Behmor "built-in safety features" but I am yet to locate some more details around what these are and how they interfere with the heating elements. Can you point me to any resources around the construction and internal workings of the BM? Such information would be very useful even without applying any mods.

    What are the four switches for in your mod, can you please explain? The idea I'm starting from would be to run the roaster in either standard or PID'ed mode. When run in PID'ed mode, you would just run the BM on P1 - is this feasible?

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    Senior Member brettreaby's Avatar
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    Hi Rumo

    Actually Rumo there are available on ebay etc "ramp/soak"pids which look like the one i fitted but have provision to do what is described in the reflow oven example for arduino.

    Search Auber- they also do specific units as well.

    Regarding modding the BM, it is somewhat a can of worms so before i answer there are 2 questions, 1. what level of electronic/electrical experience do you have, 2. you may terminally damage your BM are you prepared for that?

    And yes the BM has lots of safety features which need to be bypassed for the PID to work properly.

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    Great thanks Brett, will have a look @ ebay

    Re your questions, personally I have quite a bit of experience, I am not sure if all those who might be reading this thread do. As far as the chance of bricking the BM is concerned, I am hoping it is inversely proportional to the degree of experience; that being said, anyone attempting a mod of anything is or should be aware of this risk.

  6. #6
    Senior Member brettreaby's Avatar
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    ok rumo here is my preferred modification to the behmor. as a pdf.

    Note: i have not specified how to do the volt detector circuit here but there are a few options ; simplest is using a 5V (N/O) and 12V ( N/C) DC relay in series. The idea is only to allow the SSR drive from the PID to activate the main SSR when the main fan speed is "normal".

    There is no reason or need to control anything else

    Also in this scenario you need to "start" your ramp soak pid at the same time as you start the behmor.bm pid control.pdf

    Again i stress that only those who are used to mixing elv and lv voltages should go near this AND make sure all control and power wiring you use is high temp silicon wire. AND use 1.0 mm2 minimum for the heater wiring
    Last edited by brettreaby; 18th February 2013 at 12:41 PM. Reason: add.

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    After playing with the Behmor a bit more I have decided that overall I am quite happy with what the roaster does using mainly P2, but it's too fiddly and imprecise so I'd love to be able to use P1 / P4 and vary the elements' heat output manually during first crack. I am just not 100% happy with the door opening trick (at least on my machine) & wonder if the heat radiated by the elements is still too strong even with the door open.

    I might end up just installing a simple dimmer and running the beast with manual override on P1/P4. Based on your previous experience modding it, can you see any problem with this approach?

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    Coffee Nut fg1972's Avatar
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    Not sure about using a dimmer, it may rob some power but another simpler option is to install a switch to cut power to the elements instead.
    The only problem with either of these methods is you can't ramp up the power when the preset profile is running the elements at lower power but at least gives you some control.

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    Just want to verify my understanding here, is the low power mode achieved by switching the elements on and off, only during the low power stages of P2, P3, P4 and P5? I'm asking because if that were the case, then running the BM on P1 only would essentially ensure that the system is trying to run at full power from start to finish - thus leaving scope for manual control of the power fed to the elements.

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    Coffee Nut fg1972's Avatar
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    Hi Rumo,

    I don't have details on the Behmor controller but I suspect the power modes are controlled by PWM (pulse width modulation).
    Ie; Switching the elements on/off at various frequencies to control the output.
    In theory, the P1 profiles drive the elements at 100% power for the entire duration leaving some scope for limited manual control.

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    Quote Originally Posted by fg1972 View Post
    Hi Rumo,

    I don't have details on the Behmor controller but I suspect the power modes are controlled by PWM (pulse width modulation).
    Ie; Switching the elements on/off at various frequencies to control the output.
    In theory, the P1 profiles drive the elements at 100% power for the entire duration leaving some scope for limited manual control.
    I would question that logic: I suspect the P1 profile holds the temperature at "maximum" for the entire duration, rather than keeping the elements on 100% of the time (although I have yet to test and confirm this).

    Based on other profiles, the 100% power-periods do NOT mean the elements are all on: they still switch on and off according to the inbuilt temperature probe of the Behmor. I'd be very surprised if the P1 profile is any different because I don't think the Behmor can withstand full power throughout a roast profile.

  12. #12
    Senior Member brettreaby's Avatar
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    the main heater elements are controlled via a relay switching 240VAC onto them; so yes, that qualifies as "PWM" except at a very slow rate. The more common usage of the term PWM would usually involve using an SSR ( solid state relay) which can switch at up to 50 times per second. A dimmer control uses phase control switching to delay the switch on of the power in each sine wave, effectively giving a continuous power level.

    To observe when the power is being used, connect the behmor via a cheap power meter and watch the current - it goes from 0- 5A (main elements, no afterburner), 7.2A ( main elements +afterburner), 2.2A (afterburner only). In the final stages of a roast using P2, you will see current switching from 2.2 to 7.2A as the main heaters cycle on and off.

    In P2 mode the main leements stay on until the last stages of the roast and then cycle- i presume on some kind of temperature limit.

    I don't use P1 but you could observe to see how this works.

    Quote Originally Posted by fruity View Post
    I would question that logic: I suspect the P1 profile holds the temperature at "maximum" for the entire duration, rather than keeping the elements on 100% of the time (although I have yet to test and confirm this).

    Based on other profiles, the 100% power-periods do NOT mean the elements are all on: they still switch on and off according to the inbuilt temperature probe of the Behmor. I'd be very surprised if the P1 profile is any different because I don't think the Behmor can withstand full power throughout a roast profile.

  13. #13
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    Behmor Coffee Roaster
    Yeah brettreaby, I keep my Behmor running through a cheap power meter, so that's where I got the idea. I might try the P1 profile to confirm it works the same.



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