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  • Dimal
    replied
    Originally posted by gonzob View Post
    Well, after spending the afternoon farting around with PWM on the Raspberry-Pi, I got the variable fan speed working, however I discovered that the fan motor was overheating my servo driver, and slowing the fan down even a bit really made the heating coils glow red.
    Yep, you can't control one without the other. You'd need to ensure that heater output was maintained within an acceptable range, either by cascading air flow and thermal output together or setting thermal output limits to the air reaching the bean mass. The fun is in working it all out...

    Mal.

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  • MrJack
    replied
    You could find a way to redirect some of the flow between the heating element and the roast chamber. Could aim to maintain approximately the same total flow (so no change in air temperature).

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  • gonzob
    replied
    Well, after spending the afternoon farting around with PWM on the Raspberry-Pi, I got the variable fan speed working, however I discovered that the fan motor was overheating my servo driver, and slowing the fan down even a bit really made the heating coils glow red.

    I decided to leave well enough alone.

    Gonzo

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  • MrJack
    replied
    What, an actuated valve isn't automated enough?

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  • gonzob
    replied
    Originally posted by Dimal View Post
    G'day Gonzo...

    If you wanted to do anything with the fan output, would probably be better to pulse the output from a low of say 50% to a high of 80-90% (only guessing) during the latter stages of the roast and then leave on high between 1st and 2nd-Crack. Experimentation would would confirm what the optimum duty cycle would be. This would allow you better control of moisture retention whilst still allowing for the exhausting of chaff.

    Some of the up-market pro roasters (equipment) allow for it to be done this way, so might be worth thinking about...

    Mal.
    Ooooo... "up-market pro roasters". Sounds like a challenge. I like the idea of 50%+

    And yes, I like automation.

    A bit.

    Well, no, a lot.

    Gonzo.

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  • Yelta
    replied
    Originally posted by Barry O'Speedwagon View Post
    You manually switch the boiler on and off Yelta? I'm impressed.
    Was under the impression we were discussing roasting Barry.

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  • Barry O'Speedwagon
    replied
    You manually switch the boiler on and off Yelta? I'm impressed.

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  • Yelta
    replied
    No good talking to me then, I'm a control freak, no machine is going to make decisions for me, hands on all the way.

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  • Dimal
    replied
    I think Gonzo loves the idea of automation, just the impression I get...

    Mal.

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  • MrJack
    replied
    You could always control the airflow the old fashioned way - with some kind of slide/louvre/butterfly valve. You could even actuate it with a stepper motor controlled by the pi.

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  • Dimal
    replied
    G'day Gonzo...

    If you wanted to do anything with the fan output, would probably be better to pulse the output from a low of say 50% to a high of 80-90% (only guessing) during the latter stages of the roast and then leave on high between 1st and 2nd-Crack. Experimentation would would confirm what the optimum duty cycle would be. This would allow you better control of moisture retention whilst still allowing for the exhausting of chaff.

    Some of the up-market pro roasters (equipment) allow for it to be done this way, so might be worth thinking about...

    Mal.

    Leave a comment:


  • gonzob
    replied
    Thanks for the replies.

    The reason I asked was that my Roast-Pi runs the heat gun fan flat out all the time, and PWM adjusts the heating coils. I was wondering if I would be better off ramping the fan speed as well, so as to "cook" rather than "dry". It sounds as if I am in the right ball-park, so I don't think I'll bother.

    Gonzo

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  • Yelta
    replied
    Originally posted by Steve82 View Post
    Around the start of rolling second crack I would expect around 18% loss. So you are looking pretty good.
    Second crack around 16%, rolling second crack! never been there so cant comment.

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  • evelynr
    replied
    The first line was really needed as I thought it is something about weight loss through coffee

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  • Steve82
    replied
    Around the start of rolling second crack I would expect around 18% loss. So you are looking pretty good.

    Leave a comment:

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