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Topic: Arduino-roast (6 msgs / 206 lines)
1) From: Allon Stern
I've been meaning to do this very thing for some time...someone beat  
me to it. Ah well, I can crib their stuff :)http://hackaday.com/2009/11/05/automated-coffee-bean-roaster/Except that I have a thermocouple amplifier and thermocouple I was  
going to use. It looks like they use a much less-precise device.
And I was going to drive an iRoast with it.
And use solid state relays.
Okay, at least they actually built one :)
In theory, you should be able to adapt the control electronics to most  
any device that supplies heat, and have some way to control it, and  
probe the bean temperature.
Pretty much any off the shelf PID can do this, of course. The next  
steps are profile control aimed at roasting, and automating other  
aspects, including logging.
-
allon
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2) From: Tom Parkin
2009/11/5 Allon Stern :
<Snip>
Me too :-)  I have a half-assembled version of this very thing sitting
on my desk at the moment.  Thanks for the link !
One thing I have been pondering on as I've been experimenting with
roasting in a popcorn maker is how the speed of the roast changes the
quality of the roasted beans -- my roasting cycles are rarely longer
than about seven minutes, and some have been so fast that the first
crack has segued into the second almost without pause.  Yet most of
the sources I've read in books and on the internet tend to refer to
roasting cycles in the region of fifteen minutes.
Can any of the old hands comment on this ?  Is a slower roast likely
to yield a better final result ?
Thanks,
Tom
-- 
Tom Parkin
www.thhp.org.uk
The worst moment for the atheist is when he is really thankful and has
nobody to thank /Rossetti/
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3) From: Allon Stern
On Nov 5, 2009, at 12:36 PM, Tom Parkin wrote:
<Snip>
When you do larger batches, you have a lot more thermal mass to move  
around, and can get slower roasts more easily.
Rushing to the finish line isn't always the best approach; roasting is  
more than turning green beans brown. when you fry eggs, do you turn  
the heat all the way up?  Roasting is COOKING. You might change the  
amount of heat applied at different stages in the process.
Also, depending on the target level of roast, you might go faster or  
slower at different stages. For a light roast, you'd probably go easy  
on the heat, and gradually approach your City roast. For a dark roast,  
you might be a bit more aggressive to reach 1st crack, then slowly  
head towards 2nd. One rule of thumb is that from 1st to 2nd shouldn't  
take more than, say, 5 minutes.
You always want the temperature to climb, never dip until the cooling  
phase of the roast.
The beans do have thermal mass, and the roast does have momentum.
-
allon
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4) From: Joseph Robertson
Allon ,
A lot of what you say here sounds like it is coming from my instructors
lips. I can tell you have spent many hours with your roasters. I spent a
bunch of $ and went to a major roasting school and learned way more in a
week than my brain could retain. I do remember rule of thumb about the 5
minutes between 1st and 2nd c. Kind of depends on what your target is. miKe
M. on this list could and might elaborate on this.
Allon, when you say,"The beans do have thermal mass, and the roast does have
momentum."
It brings back terms like 1 phase of roast is endothermic and 2 phase till
finish is exothermic where the bean create there own heat and in my case I
have to back off the heat for the rest of the roast to compensate...
Great thread, Thanks Allon, Tom and any others not showing in this thread,
Happy roasting to you,
JoeR
On Thu, Nov 5, 2009 at 11:50 AM, Allon Stern  wrote:
<Snip>
-- 
Ambassador for Specialty Coffee and palate reform.
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5) From: Tom Parkin
2009/11/5 Allon Stern :
<Snip>
That's an interesting analogy.  As a keen home cook I have followed
the path from "poor tools, poor ingredients" to "slightly better
tools, reasonable ingredients", and it has been enlightening to
observe how e.g. a decent, thick based pan can help turn a decent
hotpot into a really good hotpot.  Thinking of coffee roasting from
the same perspective seems useful.
<Snip>
That makes sense.  Presumably each roaster would have their own
subjective opinion of what is suitable for a specific bean and
specific roast target, and that's one of the things I'm interested in.
<Snip>
Good tips, thanks.
As you'll probably have realised, I'm a bit of a clueless newbie, but
I'm enjoying the process of learning.  Having spent a year roasting
various beans I feel confident that I should be able to achieve a
better end result than I currently do (not that it's /bad/, but
there's always room to improve).  An obvious place to start would seem
to be my current lack of control over the roasting process, hence the
interest in the arduino project.
Thanks,
Tom
-- 
Tom Parkin
www.thhp.org.uk
The worst moment for the atheist is when he is really thankful and has
nobody to thank /Rossetti/
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6) From: Doug Hoople
"One rule of thumb is that from 1st to 2nd shouldn't take more than, say, 5
minutes."
In my limited experience, I've had more trouble getting the duration between
1st and 2nd crack to go longer than a minute or two.
But lately, I've managed to get a decent interval in, and now am getting
between 3 and 5 minutes between cracks.
When working with the iRoast, it seems very difficult to slow down the roast
in general, and particularly difficult to control the curve once 1st starts,
and holding it back without inducing a stall is a major challenge. I think
projects along these lines to control the voltage are dead on track for
getting all that under control.
But back to the cracks for a moment.
One of the problems is simply in determining terminology. Does first crack
start with the first outlier? From the initial crack of what might become
rolling 1st? Smack in the middle of rolling 1st? Same for 2nd, although
identifying the start of 2nd crack seems a lot more manageable.
Also, how do you know you've actually gotten 1st underway? My 1st cracks
seem to dawdle along, a few cracks here and there all the way through. I
don't seem to get a defined rolling 1st crack. There does seem to be a pause
between the peak activity in 1st and the start of 2nd, but there are always
a few straggler popping 1sts mixed in with the starting snaps of 2nd.
That's kind of the shape of my profile these days, and I've liked the
results. My roasts generally take no less than 13 minutes and no more than
16. Not on the iRoast, either. I use HG/DB, mostly because the roasts on the
iRoast were running too short, and I don't have the mechanical or electrical
engineering skills to do the mods required to slow it down.
When roasting on shorter cycles, I tried to push the roast toward a short
and defined rolling 1st crack, which might be forcing things unnecessarily.
As often as not, rolling 2nd would follow directly on the heels of rolling
1st, and I often couldn't tell when one started and the other left off. I
was rarely satisfied with the roasting results when the cracks were so
tightly compressed.
My $0.02.
Doug
On Thu, Nov 5, 2009 at 11:50 AM, Allon Stern  wrote:
<Snip>
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