HomeRoast Digest


Topic: [Roasting_Data] Re: Howdy (8 msgs / 218 lines)
1) From: gin
<Snip>
 needs it's own coffee academy. Wouldn't that be nice...<<<
yes, and a whole hell  of a lot more...
yes, I will step off of my soapbox.
ginny

2) From: Bruce Carlisle
Ben, Thanks for the response!!! Gary was right when he said this 
group would be a good resource.
<Snip>
simulink. 
<Snip>
take 
<Snip>
I'm curious mostly about your "user interface" and what parameters 
you consider necessary to control the roast.
I can see three TCs. Not sure about 4 unless you want 2 in the roast 
chamber. (Maybe a TC on the triac to prevent damage?)
What kind of safety precautions do you intend to include in your 
design? I'm thinking about sensing the airflow so that the heater 
isn't run without airflow. Anything else I should be considering?
Thanks
Bruce
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3) From: Deward Hastings
Bruce:
The four useful measures (apart from "time", of course) when "managing" =
an
air roaster are:
   Inlet (to the roast chamber) air temperature,
   Exhaust air temperature,
   Bean temperature,
   Air flow.
A fourth temperature measurement, which might be of some modest help in
heater control, is ambient temperature . . . but ambient has no effect =
on
the roast itself.  As a practical matter (assuming adequate airflow and
available heat) inlet air temperature and bean temperature are =
sufficient to
"define" the roast (determine and control the roast profile), and only =
inlet
air temperature needs to be controlled.
Difficulties arise measuring bean temperature because the beans are =
embedded
in a (typically much) hotter fluid which makes direct (contact) =
measurement
imprecise.  Insofar as possible the measurement must be taken outside =
the
primary heating (airflow) area of the roast chamber, while still =
accurately
sampling the bulk of the bean mass.  IR measurement is complicated by =
the
thermal vulnerability of the sensor, and compromised by the differential
between surface and interior bean temperature, especially during periods =
of
rapid heating.  IR thus reads "high" during heating, though not as much =
as
does a contact probe in the air stream.
I have not found an inexpensive and reliable sensor for measuring =
airflow in
a 500 degree (exhaust) air stream.  The inexpensive flow meters I have =
found
are plastic, and would fail at that temperature.  Measuring airflow at =
the
inlet requires the additional complexity of an inlet plenum/flow guide . =
. .
(the exhaust will typically already be contained to allow chaff =
control).
The value of a flow interlock (except for power control . . . i.e. never
turn on the heater without at least power to the fan) is probably small =
. .
. the inlet air temperature probe is probably enough to protect the =
heater
in all but the most extreme circumstance, and replacement heaters are
inexpensive compared to the protection device itself (although perhaps a
simple vane on a microswitch could be rigged as a go/no-go for the =
heater).
At one time I was actively experimenting with all of the above =
(dataloging
digital thermometer, "homebrew" TC probes, IR windows, flow diverters =
etc.),
but at some point I realized that I was managing to roast acceptable =
coffee
whether the "gadgets" worked or not.  It has been a while since the toys
came out of the box and I've used anything more complicated than a Rosto =
and
a variac (or CVT), supplemented by eyes, ears and nose and a simple =
kitchen
timer.
Maybe next year, when all the other "projects" are done . . . .  =
Always
available for "advice", though . . . .
Deward

4) From: Gary Townsend
You know, this place has the best classroom available anywhere, and
it's free. I learned more here in 4 months, than I ever did in school.
Really. I do more coffee related research on the web, than I ever
thought about doing on any other subject, ever. Methinks this country
needs it's own coffee academy. Wouldn't that be nice...
 Deward Hastings  wrote:
<Snip>

5) From: Pecan Jim Gundlach
I've taught at a university for over thirty years and I wish the 
university could be as effective at teaching as this list and the 
internet resources that it links to is.
        Jim Gundlach
On Dec 2, 2004, at 10:35 AM, Gary Townsend wrote:
<Snip>

6) From: Les
Jim,
I think it has something to do with motivation!
Les
On Thu, 2 Dec 2004 12:39:32 -0600, Pecan Jim Gundlach
 wrote:
<Snip>

7) From: AlChemist John
It is indeed a great resource.  On that note, I am looking for stocking 
stuffers for some *$ drinkers and need some help.  OK, not really, but I am 
looking for a place to get some coal.  Does anyone actually use it? or have 
some around locally?
And I too have learned more on this list about practical applications of 
technology that any class ever gave me.
Sometime around 10:39 12/2/2004, Pecan Jim Gundlach typed:
<Snip>
--
John Nanci 
AlChemist at large
Zen Roasting , Blending & Espresso pulling by Gestalthttp://www.dreamsandbones.net/blog/http://www.chocolatealchemy.com/

8) From: Ben Treichel
Bruce Carlisle wrote:
<Snip>
ambient inlet temp, roast chamber inlet/bottom, middle of bean mass, air 
above bean mass.
<Snip>
I have an interlock that prevents heater voltage w/o fan voltage 
present, but no air flow sensing.
<Snip>
-- 
Ben Treichel
Program Manager
S.E Michigan
SwRI
248-232-7365 (o)
248-935-6845 (m)


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