HomeRoast Digest


Topic: Adding Thermal Probe to iRoast2 (8 msgs / 501 lines)
1) From: raymanowen
Just remember that the sensor has to obey the laws of physics, and even the
digital readout giving 6 decimal places is at least 5 places of fiction if
you think it is any particular temperature. The numbers you read are only
<Snip>
reading bean surface temperatures with a color corrected infra red (IR)
probe.
The IR probe can only "see" the surface of the bean, while the majority of
the roasting takes place beneath the surface. If it's at the exothermic
threshold, the interior could be hotter than the roaster's Hellfire at the
bean's surface.
Enter "Thermocouple probe" in your search engine, and look for a 1/16"
stainless steel sheathed grounded junction type K probe. The grounded
junction is pretty rugged and fast-responding, although not as fast as the
bare junction supplied with the SM digital meter.
Get it with as much Teflon insulated lead wire as you need, with a miniatur=
e
male plug for the connector and it will just plug in to the SM meter. A 12i=
n
probe length should be plenty to allow you to be creative.
You can bend the thermocouple probe like a coat hanger and install it so it
doesn't move in the roaster. Bend it so the tip is in the downstream volume
of the bean mass. The measurement junction of the thermocouple is at the ti=
p
of the probe, but keep the probe in the heat for a few inches away from the
tip, otherwise the heat will rapidly flow away from the tip to the cooler
zone if you mount it on an iceberg.
In a 3000 furnace, everything outside the flame box was extremely cold- =
a
heat sink.
Three probes in the roaster with three meters will read differently.
Location, Location, Location. Don't move it at all!
Do not gauge the roast by the temperatures you read.
Cup the roast and correlate the temperatures and times with the taste. The
correlation will be lost if you move the probe from roast to roast.
Cheers -RayO, aka Opa!
If your only tool is a hammer, everything pretty much looks like a nail...

2) From: Justin Marquez
On 6/28/07, raymanowen  wrote:
<Snip>
endpoint (i.e. not to "3rd crack") is ever truly exothermic.  Exothermic
means heat is generateddue to some chemical or physical change - "3rd crack"
would be a fine example of that. I suspect that when the temperature seems
to rise rapidly the reason is that the reaction just became LESS ENDOTHERMIC
and with a constant heat input, the temperature of the air rises. If you
remove the heat source, the system begins to cool - a good example that it
is not truly exothermic.
As you remove the moisture and the beans get "dry", there is likely to be
less energy sucked up as the water has been vapoized out already.  Boiling
water takes a lot of energy. Water gone = less endothermic.
It may be that the sugar carmelization reactions generate heat - I am not
sure exactly what is happening chemically there.
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)

3) From: Dan Bollinger
This is a multi-part message in MIME format.
I did some research on this a few years back at the coffe research =
institute ASIC. http://www.asic-cafe.org/index.phpOne study did a calorimic study of coffee by separating the solubles and =
insolubles. I summarized it on this webpage. It may help.  =http://www.claycritters.com/coffee/calorimetric_study_of_coffee.htmDan
  On 6/28/07, raymanowen  wrote: 
    The IR probe can only "see" the surface of the bean, while the =
majority of the roasting takes place beneath the surface. If it's at the =
exothermic threshold, the interior could be hotter than the roaster's =
Hellfire at the bean's surface. 
    Cheers -RayO, aka Opa! 
  I still remain unconvinced that the roast process taken to some =
reasonable endpoint (i.e. not to "3rd crack") is ever truly exothermic.  =
Exothermic means heat is generateddue to some chemical or physical =
change - "3rd crack" would be a fine example of that. I suspect that =
when the temperature seems to rise rapidly the reason is that the =
reaction just became LESS ENDOTHERMIC and with a constant heat input, =
the temperature of the air rises. If you remove the heat source, the =
system begins to cool - a good example that it is not truly exothermic. 
  As you remove the moisture and the beans get "dry", there is likely to =
be less energy sucked up as the water has been vapoized out already.  =
Boiling water takes a lot of energy. Water gone = less endothermic. 
  It may be that the sugar carmelization reactions generate heat - I am =
not sure exactly what is happening chemically there.
  Safe Journeys and Sweet Music
  Justin Marquez (CYPRESS, TX) 

4) From: stereoplegic
sorry, i don't have an iRoast2 (or 1 for that matter). as far in the 
bean mass w/o reading the heat source as possible is what works for me. 
i would follow RayO's advice as far as SS sheath is concerned. once you 
learn to decipher RayO's posts, they can be quite helpful. i found a 
very cheap 12" analog deep fry thermometer (much more than you should 
need) from a local hardware store which i just cut open w/ my trusty 
hacksaw. such a thermometer should provide all the sheath you need, 
should you opt for a bare thermocouple digital thermometer such as the 
one Tom sells.
robotyonder wrote:
<Snip>

5) From: Michael Wade
This is a multi-part message in MIME format.
Robert:
Looks like the guys are off and running on some serious thread creep.  =
To get back to your original request for some help:
There was a link to someone's instructions that I used to install mine, =
but I can't find it now.  I found this fragment in a thread on the =
archives.
*********************************************************
...I have 24 roasts on my iRoast 2, and 17 of those have been done with  =
a semi-permanently mounted K-type bead thermocouple. The wire snakes  
through the bottom of the roasting chamber between the housing and  
the insulating O-ring. The tip appears to be 3/4" from the wall of  
the roasting chamber and about the same distance from the bottom.  
*****************************************************
My own thermocouple (Fluke) has very thin teflon insulation on the leads =
and it is installed as above.  Very(!) briefly, you have to take the =
bottom off of the glass roast chamber, remove the rubber gasket, mold =
the TC lead around the edge of the glass, replace the gasket and =
reassemble.  Note that the little plastic plunger that acts as a detent =
and presses down the safety switch on the base unit is spring-loaded and =
will launch itself into oblivion if it senses that you are the least bit =
inattentive...
If you are handy at disassembling things and paying attention to how it =
came apart, you should be able to figure this out easily.
The other method that I have seen pictures of is to obtain a TC with a =
rigid metal probe and drill a hole through the chaff collector at the =
right angle to put the tip about even with the lower edge of the central =
tube, and about half-way between the central tube and the glass.  That's =
where my probe is located also.
Minor variations in the probe location are not an issue.  No two =
iRoast's roast the same anyway, and your temperature readings are only =
relative to your own experiments, though my temperatures are reasonably =
close to the ones shown in Tom's pictorial guide.
I got frustrated at the iRoast's limited temperature control points and =
my inability to hear the cracks, parked the thing and went to HGDB for a =
year or so.  It was the best thing I ever did; taught me more about =
roasting in the first few roasts than I had learned in several years =
with a Precision and then the iR2.  I got it out again recently and was =
able to roast some decent coffee with it, but I've just gone and =
splurged on one of Jeffrey Pawlan's last CCR's so it's all moot now.
Good luck with getting your TC mounted.  If you can't find one of those =
links and you need more help feel free to contact me.  I can go into =
more detail and shoot a picture or two of mine if it would help.
Go for it,
Michael Wade

6) From: stereoplegic
the "rigid metal probe" is the same thing RayO and I mentioned-the 
sheath. we mention this for the sake of durability. see Tom's notes on 
this own bare TC digital thermometer.
mlwade wrote:
<Snip>

7) From: stereoplegic
correction: HIS, not THIS
stereoplegic wrote:
<Snip>

8) From: Dave Ehrenkranz
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I remember this topic being discussed much earlier. I found a link  
(with pictures) to doing what you want to an iRoast1 which is I  
believe similar enough to the iR2. The link is:http://jbensen.home.mpinet.net/leisure/coffee/iroast-1/probe/
iRoast-1_Temperature_Probe_Mod.html  orhttp://tinyurl.com/yrq2jvAlso here is another email from the past:
	From: 	  dcschooley
	Subject: 	Re: +iroast2 thermocouple
	Date: 	December 30, 2006 9:41:08 AM PST
	To: 	  homeroast
	Reply-To: 	  homeroast
I ran my thermocouple wire in through the bottom. You will need to
take apart the roasting chamber by removing the screws at the bottom
of the chamber. The wire first goes down on the outside between the
glass and the plastic and then back up on the inside of the chamber.
The wire then bends in toward the center and down a bit to always be
in the bean mass. If you do it right, the wire does not contact the
metal reflection plate. (I think there is an o-ring.) This is a
semi-permanent mod, in that it is easy to undo (no drilling), but you
do not need to mess with the wire every day. The wire does not move
around, so your temperature measurements remain consistent from one
roast to the next.
On 12/29/06, Mike Garfias  wrote:
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