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Thread: No Luck With Arduino Popper Roaster. Tried Everything and always sour/vegetal/green.

  1. #1
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    No Luck With Arduino Popper Roaster. Tried Everything and always sour/vegetal/green.

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi guys

    I'm at my witts end with my roasting endeavors. I spent a great deal of time modifying a target popcorn machine using a solid state relay, motor controller, Arduino and Artisan Roast to get a PID controlled roaster which actually does work and I think is a decent roaster but I have yet to make a decent coffee.

    The problem I am having is green/vegetal/acidic or some kind of taste that seems to over-power everything else. I have tried the following:

    3 different types of beans. Columbian, Ethiopian Yirgacheffe and Peru Ceja (which I bought thinking it would be forgiving). Two were from bean bay, one was from an old italian man who had green beans in his shop.

    I have tried multiple profiles, short roasts, long roasts hot roasts cool roasts, long dry, short dry I have pushed the beans to near ash, with up-to 17 minutes roast time (with the development phase at 230C for about 12 of that) and I still can't shake this flavor. The closest I have got came from upping the heat right at first crack and turning it into a rolling crack but it still didn't fully eliminate the problem.

    My beans also seem to sweat a lot in the days after roasting, and sometimes this shows up as they are coming out of the roaster.

    I can tell you the following about my setup:

    There are no issues with lack of power, at 100% the beans become burnt very quickly, but at around 60-70% power it seems to do fine.

    I usually run a 70g batch, any more and the beans over-flow even on a low fan setting.

    Beans usually come out looking fairly consistent but some of the shorter roasts have a bit of a spectrum.

    Given I've had this problem with almost all of my roasts, I feel like there must be something simple I am doing wrong.

    The vegetal/green etc taste seems to come from the core of the bean.

    Anyone who has experienced this please get in touch if you found a solution.

    Cheers,

    Mark

  2. #2
    CoffeeSnobs Owner Andy's Avatar
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    green/vegetal/acidic = underdone.

    I think you have complicated it way more than you need when starting.

    Grab another unmodified popper, 80g of beans and roast them.
    Once too light, one too dark then once in the middle. Taste each and you will get a better grounding on what you like and how to get there

    Then you can go back to the world's most complicated popper and fine tune the results.

    Keep it simple and you'll be fine.
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  3. #3
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    Thanks I will try that but I did start off that way but my machine was burning the coffee before it was at first crack even with stirring which led to the upgrades. Since the mods I have run a lot lot of my roasts at a set power level too which would be no different from an unmodified popper and have the same results. I don’t see how a roast that’s been past second crack and roasted for over 17 minutes can be underdeveloped but as you’ve pointed out I’m very new to this.

  4. #4
    CoffeeSnobs Owner Andy's Avatar
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    If you have to stir, you have too much in there. The 80g is an average. The beans should turn slowly when you start and get more agitated as they lose water.
    To little or too much agitation is no good.

    Popper is a great proof of concept, it will prove that you can roast and then you can tweak.
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  5. #5
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    So this morning I ran an experiment taking your advise on-board.

    I set my popcorn machine to 85% power and made 3 batches of beans 50g each.

    The first hit FC @ 3:24 (204C) and drop was at 6:04.
    The second hit FC @ 3:21 (208C) and drop was at 6:16.
    The third hit FC @ 3:32 (207C), FCe @ 6:13 (229C) Sc@ 7:14 (232C) and drop at 9:32 (232C).

    Because the third hit a temperature plateau I pushed the power to 100% and did one roast to a darker level.

    This one was 100% power throughout, FC @ 2:10 (241C), runaway first and second cracks, with no gap. Drop @ 3:35 (260C)

    In the image I have linked, the roasts go from the lightest 85% to the final one at 100% which roasted to a darker level.

    It should be noted that the temp probe is slightly above the bean bed due to dropping from 70g to 50g, so it's not an exact bean temperature, more of a post-bean environmental temperature.

    I have put all four beans in sealed jars (loose lids) to rest and will taste them in 1 week and 2 weeks time.

    I did try all 4 in a french press and all had the same vegetal/green sour taste that I have been finding which in my experience hasn't gone away with aging.

    I will buy a new completely unmodified popper from the good guys today, (the sunbeam CP4600) and try a few runs with a standard machine.

  6. #6
    Senior Member deegee's Avatar
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    I've been roasting very happily with modified poppers for several years now, but I can't give you a simple answer to your problem. However, I can tell you what works for me with my gear, and hope that maybe you can adapt my methods to work with your setup.

    My Breville popper has separate heater and fan circuits. The fan is now powered by an old laptop charger with a PWM to vary the speed. It had good airflow originally, but it now runs about 20% faster than before. I can roast up to 120g of greens with little or no stirring
    The heaters run on mains power with the voltage controlled via a variable SCR.
    I adjust the heater voltage and fan speed manually during the roast.

    I usually aim for 14 - 15 minute roasts, but have had good results from as low as 12 min and up to about 16 min.
    Normally start with the fan running at about 90% speed, and an initial heater voltage of 150v. At one minute intervals I increase the voltage by 10v until it reaches max after 9 min. From that point I reduce the fan speed in small steps, again at one minute intervals, until I reach my target temperature, or until I hear the start of second crack if that's what I'm aiming for. Then I cut power to the heaters and crank fan speed up to max, which cools the beans within a couple of minutes.

    This routine gives the beans a gradual drying phase at first, followed by a fairly steady rate of rise up to first crack, and tapering off slightly until the end.
    Frankenpopper 2.JPG

    This is a pic of one of my poppers in action. The roast chamber is extended with a tall slightly tapered can.
    Voltmeter at the top , a cheap timer, laptop charger, digital thermometer and control box.
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    Hi deegee, thanks for that! Your system looks very similar to mine, except I control my motor speed and heat with sliders in Artisan. I use 2x 12v wall warts, which I have been told is terrible practice but they work in series to produce ~22v after the motor controller I use to control the heat. My popper unfortunately had integrated fan and heater circuits, as the cheap Target popper utilized the heater elements as a voltage divider but in the end I got it separated. My heating element is controlled with an SSD, which uses PWM to control heat as opposed to your SCR.

    Andy, today I went to Good Guys and bought the Sunbeam roaster. I just turned it on with 50g of beans, and got flashbacks to why I modified mine in the first place due to some beans not moving off the heater inlets and lots of unevenness in the start. That said with some stirring and manual agitation I got it to first and second crack pretty quickly, I would say under 3-4 minutes, and ended up with a dark roast. The taste isn't awful, and probably as good as any I have done with my more complex set-up so that says a lot to my abilities. I am a bit confused though as to what the difference is between my two roasters given that both are now on constant fan and constant heat. It may be possible that my first roaster was somehow contaminated during the initial trials I made (where coffee beans got caught in the outlets and turned to ash, there is also a lot of residual oil). Perhaps the roaster itself is imparting a bad flavour on the coffee.

    I will provide an update in 1-2 weeks, once it's had a chance to age off a bit. Hopefully I can share some pictures of my set-up too, when I figure out how images work on this site

    Regards,

    Mark

  8. #8
    Senior Member Yelta's Avatar
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    Crikey! sounds like an extremely complex way to roast enough beans for about 4.5 cups of coffee.

    Have you investigated a Coretto setup Mark? tried and proven.
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    I have seen the Coretto setup. I probably spent less on this setup though than I would have on the Coretto, and tbh I really wanted to learn a bit about Arduino as well. It does work very well too, it does exactly what you tell it to do in terms of profile, but when you are as green as I am that's probably a bad thing.

  10. #10
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    Mark, have you split a bean and look closely? If it's really underdone on the inside and overcooked on the outside, it should be fairly obvious.

    How long do you let your beans rest before tasting? If I taste my own roasts at anything less than 4-5 days post-roast, I get this signature grassy flavour that indicate too fresh roasts, regardless of the coffee origin. It subsides and is gone completely after 5-7 days rest.

    p/s: Sorry, just saw your later post indicating a week rest. No idea what went wrong for you then.

    Deegee, a really neat modified popper btw!
    Last edited by samuellaw178; 1 Week Ago at 10:21 PM.
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  11. #11
    Senior Member deegee's Avatar
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    Mark, I wrote my reply to your original post a few hours before I posted it, so I had not read your post #5 at the time. Now that I have, I believe that you need to slow down the early and middle stages of your roasts. Suggest you try for an overall roast time of at least 10 to 12 mins, with FC starting at about 75% of the total time.
    I can only guess at how do this with your gear, but maybe you could try applying say 50/60% power for the first couple of minutes, then increasing it by 5% per minute or 10% each 2 mins to find a pattern that works for you.

    I'm not a fanatic believer in the DTR theory, but when I first heard of it, a quick check showed most of my better roasts did hit FC at around 75-80% of total roast time. But there were some exceptions where it happened earlier or just a little later.

    To clear up a possible misconception in my previous post, Breville poppers have integrated fan/heater circuits. I had to rewire mine to split them.
    So anyone interested in modding a popper should NOT rush out and buy a Breville because they think it will be easier to work with.
    They are good quality (by popper standards), but one of the more difficult brands to work with.

    Cheers, deegee.

  12. #12
    Senior Member Yelta's Avatar
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    Quote Originally Posted by mfwar1 View Post
    I have seen the Coretto setup. I probably spent less on this setup though than I would have on the Coretto, and tbh I really wanted to learn a bit about Arduino as well. It does work very well too, it does exactly what you tell it to do in terms of profile, but when you are as green as I am that's probably a bad thing.
    Morning Mark, don't take this the wrong way, however I guess it depends largely on whether your a coffee freak or a technophile.

    My ultimate goal is quality in the cup and achieving it the simplest way I can.

    I roast 750 grams of green beans (very successfully) about every week to 10 days, and have been doing this for many years.

    The only reason I'm explaining this is to give you some insight as to where many of us on Coffee Snobs are coming from.

    There are certainly those among us who are into the technology as well as quality, however I suspect the majority are aiming for quality in the cup in the simplest/easiest way it can be achieved, I know I am.

    FWIW here's a pic of my first roasting efforts, pretty low tech but the result was good, from this I graduated to a Coretto, and, have stuck with this method to the present day.

    DSC_7631_resized.jpg
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  13. #13
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    Quote Originally Posted by deegee View Post
    Mark, I wrote my reply to your original post a few hours before I posted it, so I had not read your post #5 at the time. Now that I have, I believe that you need to slow down the early and middle stages of your roasts. Suggest you try for an overall roast time of at least 10 to 12 mins, with FC starting at about 75% of the total time.
    I can only guess at how do this with your gear, but maybe you could try applying say 50/60% power for the first couple of minutes, then increasing it by 5% per minute or 10% each 2 mins to find a pattern that works for you.

    I'm not a fanatic believer in the DTR theory, but when I first heard of it, a quick check showed most of my better roasts did hit FC at around 75-80% of total roast time. But there were some exceptions where it happened earlier or just a little later.

    To clear up a possible misconception in my previous post, Breville poppers have integrated fan/heater circuits. I had to rewire mine to split them.
    So anyone interested in modding a popper should NOT rush out and buy a Breville because they think it will be easier to work with.
    They are good quality (by popper standards), but one of the more difficult brands to work with.

    Cheers, deegee.
    Hi deegee, thanks again for your insight, having the closest setup to mine, I think I will try your method. I have tried extended dry times before, but with no luck. I am working on mk. 2 of my roaster now and I might hold off until I have that one set-up problerly in-case my current machine is causing the poor taste.

    Morning Mark, don't take this the wrong way, however I guess it depends largely on whether your a coffee freak or a technophile.

    My ultimate goal is quality in the cup and achieving it the simplest way I can.

    I roast 750 grams of green beans (very successfully) about every week to 10 days, and have been doing this for many years.

    The only reason I'm explaining this is to give you some insight as to where many of us on Coffee Snobs are coming from.

    There are certainly those among us who are into the technology as well as quality, however I suspect the majority are aiming for quality in the cup in the simplest/easiest way it can be achieved, I know I am.

    FWIW here's a pic of my first roasting efforts, pretty low tech but the result was good, from this I graduated to a Coretto, and, have stuck with this method to the present day.
    Hi yelta, I get what your saying. I was hoping for a similar result (i.e. good quality with a simple method), but starting with my popcorn machine that quickly burnt some beans and left others green, I started down the path of customizing what I had rather than exploring other simpler options. Coming from the other direction I have enjoyed the process of setting up my machine enough to make it worthwhile for me but I am ready to start producing acceptable quality coffee now so looking for advise on how to get there. I think I will stick with the popcorn machine for now, and if things don't improve after trying the suggestions in this thread I may graduate to a Coretto.

    Cheers guys,

    Mark

  14. #14
    Senior Member Yelta's Avatar
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    Don't think its a case of graduation Mark, simply another way of skinning a cat.
    Skin a cat.jpg

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    Behmor Coffee Roaster
    I've had oily beans from loading into too hot a roaster, so maybe you're using too high a heat setting early on?



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