HomeRoast Digest

Topic: Wandering John's Computerized FR [was RE: +Advise on buying a home roaster.] (12 msgs / 351 lines)
1) From: Rick Farris
Don't you have a computerized FR?  Would you mind describing your setup?
PIO card?  SSRs?  A/D? Feedback?
-- Rick
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2) From: John Abbott
Sorry for the LONG delay in get to this - went to a play and then dinner.
Carolyn is still the best date around!
I broke the control wiring away from the timer, also split the wiring on the
motor/heater.  I use an LM339 temp probe running back to a 12 bit A/D
converter. The wiring is brought out to a pair of relays (bang bang) after
giving up on noisy circuit using SCRs.  The application board contains I/O
for the A/D and the switch latches.  There are mechanical override switches
on the system so I can manually control it (didn't trust the computer for
awhile).  I use a constantly changing profile for the roast cycle and the
last cycle for a specific bean is stored for the next such roast.   It
works, but I'm REALLY not impressed with the system or the results.  I pull
it out and reassemble it every couple of weeks to try a new idea. The rest
of the time I use the HotTop or the unmodified FR+

3) From: Rick Farris
John wrote:
[a description of his computerized FreshRoast]
So, it seems to me all you're lacking is either a motorized variac or a
solid state AC power source...  With variable AC control you should be able
to duplicate your Hot Top profile, yes?
-- Rick
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4) From: John Abbott
	I'm not sure.  I've been able to get a fairly extended roast cycle with the
computer, but the coffee isn't as bright as it seems to be from the HotTop.
It IS however, better than the standard 5 minute cycle from the standard
FR+.   I have considered using a Variac, but that represents 20# of coffee
for the HotTop :O)

5) From: Ben Treichel
John Abbott wrote:
My Variac is on order so that I can get away from the standard 5 minute 
cycle. We could roast and trade to see how a variac'ed FR compares to a 
HotTop. Of course I need to get it first, and then get a little experience.
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6) From: John Abbott
OUCH!! Just came back from Mexico and having a root canal started, so I'm a
little slow in responding.  Sounds like a plan to me.  I don't use the FR
other than to play with the computer interface, so I'll do a roast on the
HotTop & FR so you can get a real comparison.

7) From: Ben Treichel
John Abbott wrote:
Dentists are against my religion! I'm a devote coward!! I hear that they 
are cheap and good however.
How about after the 1st of the year. I've got  3 & 1/2 weeks of travel 
between now and then. Ohio for thanksgiving, 1st week in Dec for work in 
San Antoinio, and Christmas in AZ.

8) From: John Abbott
Thanks for the URL Tom.  Yes, the noise on the control line was causing the
SCR to lock on. NOT a good design. I didn't really put enough thought into
the schematic and deserved what I got.  The fastest fix was to drop in a
couple of heavy relays (have a box of them) and they work well - but I do
want to go solid state before I put it all in a new box. Zero Crossing
switches are the safest I'm sure - but a tad bit more expensive.  My current
search is for DC stepping motors, Pan motors etc.  Any ideas there?

9) From: John Abbott
Super - just drop a line when your ready to go.
You're right about good and cheap.  My root canal, post and crown will come
in at $380  The last one I did here in Texas came in at $850 - a noticeable
difference.  A great many of the dentists (mine) have AMA licenses.  The
offices are very small, but very clean and modern.  After one gets past the
lack of concern over exterior aesthetics of buildings down there - it is a
very pleasant experience. The only problem is the 80 minute trip over the
bridge and through security on the return - but nobody complains.
I hope your using a frequent flyer plan :O)
Have an extraordinary Thanksgiving!

10) From: Rick Farris
Wandering John wrote:
Errr...a few more pounds than that.  20# of coffee for the Hot Top
represents a manual hand-adjusted variac that defeats the purpose of your
computer automation.
A motorized variac or a GPIB-controlled solid-state AC power inverter is
gonna set you back somewhere between 100# and 500# of coffee.  :-)
And then you'd need a flow-rate sensor so you could know how much heat
energy you were pumping into the beans...
Maybe I should look for a job in a test engineering lab, so I could have
access to old junk stuff again...
-- Rick
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11) From: John Abbott
Yeah, I know the feeling - I keep wishing I still had my lab at Boeing
Aerospace.  I could order up test equipment for anything and nobody ever
asked why.  My lab was in a secured screen room so nobody had access
either - I could have developed a real roaster and told people it was for
the Rover.

12) From: jim gundlach
On Tuesday, November 26, 2002, at 09:24 AM, John Abbott wrote:
Now that would have been a real beneficial spin-off of the space 
Jim Gundlach
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