HomeRoast Digest


Topic: Seeing first crack (12 msgs / 229 lines)
1) From: Allon Stern
So, in my quest to build a roaster (someday), I have thought, how useful would it be to be able to detect the cracks?
Well, that remains to be seen, but the other day, I was at a party and ran into a friend (and fellow homeroaster) who showed me an app for his iPhone, that I immediately went and downloaded. It is an audio spectrum analyzer which gives a waterfall display. Now, the accuracy of the iPhone's built in mic leaves much to be desired, but it's an interesting tool nonetheless.
Anyway, here are some spectrograms of my HG roast of 250g of Oriente:http://www.radioactive.org/pix/First.jpgMore cracks are visible. Again, on the right is where I shook the basket.http://www.radioactive.org/pix/Coasting.jpgHere I turned off the heat gun and coasted a little bit before starting cooling.">http://www.radioactive.org/pix/Outlier.jpgBlue is low level, red higher level, and white is higher still. There is a frequency scale on the right which is largely obscured, but more visible in other spectrograms I took. The first crack is shown in the middle, to the left and right is where I was shaking the fry basket and bowls that I use to roast in. The red background is the noise of the heat gun.http://www.radioactive.org/pix/First.jpgMore cracks are visible. Again, on the right is where I shook the basket.http://www.radioactive.org/pix/Coasting.jpgHere I turned off the heat gun and coasted a little bit before starting cooling.
For the uninitiated: See:http://en.wikipedia.org/wiki/Spectrogram-
allon
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2) From: Bruce Garley
Which ones are the cracks?
Bruce Garley
Plant Whisperer
San Juan Capistrano, CA
 
Vivir con miedo es como vivir a medias.
 
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3) From: Bruce Garley
What was the name of the app? 
Bruce Garley
Plant Whisperer
San Juan Capistrano, CA
 
Vivir con miedo es como vivir a medias.
 
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4) From: raymanowen
Wow, the Cracks are really outstanding and obvious!
Now, for the metal drum roaster with the sound of tumbling beans and the
drive mechanism whine- Notch filters with Twin-T r-c fb on voltage follower
op-amps? You wouldn't need all that if you custom built some instrument
microphones a la stethoscope.
Maybe not- electronics is cheaper than mechanics, and you don't need a Hi-Fi
pickup -ro
-- 
Persist in old ways; expect different results - suborn Insanity...
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5) From: Allon Stern
On Dec 13, 2009, at 11:56 PM, Bruce Garley wrote:
<Snip>
The cracks are the vertical blips that stand out by themselves.
It's a scrolling chart, which scrolls from right to left; most recent sounds are on the right, older sounds scroll out on the left. The vertical blip in the middle ofhttp://www.radioactive.org/pix/Outlier.jpgis a crack.
The app ishttp://pocketchirp.com/spectrogramThere are apparently better spectrogram programs available. Looking into it :)
-
allon
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6) From: Jim Gundlach
This is really interesting.  With my rather bad hearing having this  
application on my iPhone would be really nice.  Really another way to  
delay hearing aids.
       pecan jim
On Dec 13, 2009, at 10:45 PM, Allon Stern wrote:
<Snip>
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7) From: Seth Grandeau
I wonder if it's time for the BehmorThing app on the iPhone... (hint hint)
It could not only do BehmorThing tracking, but also sound an alarm when it
hears 1st crack (and record it).  Add in a thermocouple and this may finally
force me to buy an iPhone!
On Mon, Dec 14, 2009 at 9:10 AM, Jim Gundlach wrote:
<Snip>
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8) From: Rich
Android 2.0 ..
Seth Grandeau wrote:
<Snip>
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9) From: Mike Koenig
Allon,
This is fascinating..  I work in the Pharmaceutical industry, and there have
been a number of efforts to monitor production processes by putting a
microphone on the side of various types of equipment, and characterizing the
process by sound.  It's mainly been done for tablet coating and fluidized
bed granulation (which is remarkably similar to an air roaster).  Usually it
involves expensive software, so being able to do this on an iphone is
impressive.
I'm wondering if it's possible to get enough detail that you can see any
changes that happen shortly BEFORE first or 2nd crack?  I know in my HotTop
the sound of the rolling beans changes slightly during the roast as the
roast proceeds, but I'm not able to identify any specific markers for when
the cracks are approaching, and do it by the seat of my pants.
--mike
On Sun, Dec 13, 2009 at 11:45 PM, Allon Stern  wrote:
<Snip>
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10) From: Yakster
This would be very interesting to be able to identify and anticipate first
or second crack.  In my Behmor, I've noticed whooshing noises that precede
first crack.  I'm not sure if it's part of first crack or just something
leading up to it.  It sounds like gas jets expelling from the beans, but not
like cracks.
-Chris
On Wed, Dec 16, 2009 at 5:33 AM, Mike Koenig  wrote:
<Snip>
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11) From: raymanowen
"Blue is low level, red higher level, and white is higher still.
There is a frequency scale on the right which is largely obscured, but more
visible in other spectrograms I took.
The first crack is shown in the middle
The first crack is shown in the middle
The first crack is shown in the middle"
On Sun, Dec 13, 2009 at 9:56 PM, Bruce Garley wrote:
<Snip>
-- 
Persist in old ways; expect new results - suborn Insanity...
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12) From: raymanowen
"I've noticed whooshing noises that precede first crack.
I'm not sure if it's part of first crack or just something leading up to it.
It sounds like gas jets expelling from the beans, but not like cracks."
[Prior to 1st Crack, the beans are being heated and lose most of the
moisture. I have no Behmor roaster, so haven't heard the sound. I will hear
it as soon as I get the RK Drum rolling. Nearly roasted beans around 400=
 F
can't hold much moisture, compared to green. As the beans dry they get
progressively harder.]
We're roasting by sound now, not time/ temperature profile? Me too.
The cracks don't occur all at once- BANG! But they progress with a sound
like pouring water in a cup of ice cubes.
Combining a shallow temperature ramp with the ability to stop the roast
exactly where you want it to stop should be more effective than watching for
some precise mile marker, then be Unable to actually Stop the damn roast
until you've coasted a mile down the road. Sounds + + Ungood.
-ro
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