HomeRoast Digest


Topic: HotTop profiling (10 msgs / 788 lines)
1) From: John Abbott
John,
I don't really know the answer to that but think its a combination of slow
roast, drum and then profile. This isn't too far off the shark-fin curve
that an uncontrolled FR runs. What ever it is I'm content with it at the
moment; but in my tinkering with it I've already determined how to hack the
system and make it laptop controlled. Maybe next year.
Roast On!!
John - the old Texas variety
--

2) From: John Abbott
Dan,
I've been hacking my Fresh Roast for a long time now. Started with a switch
and now has progressed to an application board that I've just reworked. I
had been using SCR switches but they are current limited. So I've switched
to relays and now the little beastie behaves well. I have an A/D interface
and the relay control mounted on the board. The temp probe goes into a small
signal conditioning and then the A/D. The computer checks the output of the
A/D every 5 seconds. If the reading changes and is stable (no LSB wobbling)
then the reading is converted to a temperature and the program checks the
dwell time and makes the appropriate decision (do nothing, stop the heat,
start the heat or change the step). The program is a series of steps, each
step has a dwell and temperature.
I have loaded about 20 bean profiles - but I still mess up the ending time
from time to time and manually over-ride and stop the heat (small toggle on
the board). It wasn't nearly as easy as I had envisioned! But its almost
working. I think when its finished I'll post all the schematics and software
- I used BASIC to program because I can make changes and use a run-time
package without having to compile. When I'm finished I'll convert it to C++ 
Its a fun project - keeps my mind working (to figure out what I just did
wrong). 
John
--

3) From: John Abbott
Dan,
NO NO!!  I'm not switching every five seconds.  I'm taking an A/D reading
every five seconds for the decision process.  I probably switch them 8 ti=
mes
during the roast.  For $400 I can buy a LOT of relays :O)  I understand
ladder logic - I replaced a TON of it in lumber mills with digital logic.=
   
Did you realize that the PAL chips are a copy of ladder logic? We made a
BUNCH of those at National.   My reason for going with hardware and my ow=
n
software is that I control it all.
John
--

4) From: John Abbott
Well I control it all except for ........ GUILTY!!
--

5) From: AlChemist John
Sometime around 19:15 9/4/02, John Abbott typed:
<Snip>
I note from this that the longest portion of the roast is getting it up to 
first crack.  From what I recall of Black Bear and the various variac 
profiling done here is that the long "step" is  between first and second 
crack.  With all the raves the HotTop is getting, any thoughts if it is the 
different profile or the drum roasting that is giving the wonderful roasts?
Likewise, are any of you with Variac (MM?) up to a  little experimenting to 
see if matching the HotTop profile makes a significant difference?
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

6) From: Dan Bollinger
But in my tinkering with it I've already determined how to hack the
system and make it laptop controlled. Maybe next year.  John
I've thought about this, too.  What would you use for software?  I/O?
Here's my thoughts, there are a number of less complex methods that don't
require a dedicated computer.
I think a simpler approach would be to use a Programmable Logic Controller
(PLC).  There are $99 units with 8 inputs and 8 outputs that can certainly
handle the most complicated roasting machine and profile.  You can adjust
the profile by using input selectors (rotary switches or pots) or upload a
specific profile from any PC.  In my shop are two, new PLC controllers I'm
building that will control the vacuum tank 'profiles' I need at work.  They
have 6 inputs and 4 outputs.
Even cheaper or 'smart' programmable relays.
Finally, you could use three banks of thermostats and timer relays to
control  for the 'drying',  '1st crack' and '2nd crack' profile times and
temperatures.  Just twiddle the dials to change the profile.
Dan
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

7) From: Ed Needham
"I control it all!!!!!!" 
Haaaaaaaaaaaahahaaaaaaaaaaaaahaaha Haaaaaahaaaha Haaaaaaaa!!!!!!!!!!   The
new mantra for CSA.

8) From: Dan Bollinger
Aah...  BASIC, I remember it well!  You'll find your relays don't last long
switching high current every 5 seconds.  The 50A relays on the ovens at work
sample every 40 seconds and they last about a year if I'm lucky.  Of course
these are used 8 hours a day.
You'd like PLCs.  They use 'steps', too.  It is called Ladder Logic, much
like what you are using.  The software is Windows. I'm a novice; this is my
first attempt.  I've done a lot with relay logic over the years.  But for
this project the PLCs are more cost effective and more adaptable.  The basic
controller + software is $400.  The same progarm in relays and timers would
have been almost $1000 and require an enclosure 4 times the size.  See:http://store2.automationdirect.com/cgi-bin/ncommerce3/ExecMacro/plcdirect/storefront.d2w/report
Dan,
I've been hacking my Fresh Roast for a long time now. Started with a switch
and now has progressed to an application board that I've just reworked. I
had been using SCR switches but they are current limited. So I've switched
to relays and now the little beastie behaves well. I have an A/D interface
and the relay control mounted on the board. The temp probe goes into a small
signal conditioning and then the A/D. The computer checks the output of the
A/D every 5 seconds. If the reading changes and is stable (no LSB wobbling)
then the reading is converted to a temperature and the program checks the
dwell time and makes the appropriate decision (do nothing, stop the heat,
start the heat or change the step). The program is a series of steps, each
step has a dwell and temperature.
I have loaded about 20 bean profiles - but I still mess up the ending time
from time to time and manually over-ride and stop the heat (small toggle on
the board). It wasn't nearly as easy as I had envisioned! But its almost
working. I think when its finished I'll post all the schematics and software
- I used BASIC to program because I can make changes and use a run-time
package without having to compile. When I'm finished I'll convert it to C++
Its a fun project - keeps my mind working (to figure out what I just did
wrong).
John
--

9) From: Ed Needham
That appeals to my sense of visual reference.  Want to ramp up for a few
seconds at point 'g', give it a bump.  I can see it now though....scissors,
tape, glue...creating templates for the disks.  A Sulewesi disk, a Burundi
disk, St. Helena...
Geesh...maybe a thermometer and a stopwatch will do for now.
Ed Needhamhttp://www.homeroaster.comed
****************************************
**********************************************

10) From: Dan Bollinger
This is a multi-part message in MIME format.
John,  I understand now.  You are using the relays to switch power =
occasionally, not for logic or temperature control (switching often).  =
They ought to last the life of the machine at that rate.  I'm found of =
the enclosed relays that plug into sockets. It makes maintenance a snap. =
Are PAL chips the ones used in PLCs?  I'm a newbie to digital controls. 
A controller that no one has talked about yet, but is good for process =
temperature profiling like roasting, is a cam temperature controller.  =
Before digital came out this is what the most sophisticated ceramic =
kilns used for precise controlling of temperature over time for exotic =
glazes like crystal growing.  
It is quite simple.  A slow-rpm clock drive turns a cam.  A feeler =
follows the edge of the cam and controls the process temperature.  The =
cam starts as a disc. It is marked around the circle for your time units =
and along the radii for temperature.  You cut the disc to the =
temperature you want at the time you want.  Imagine the roasting =
profiles on Ed's website.  Now, just rotate these into a circle and =
you'll get the cam shape you want. Like a profile?  Just save the disc =
and re-install when you want to use it again.  
Dan


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