HomeRoast Digest


Topic: PID for a poppery (10 msgs / 330 lines)
1) From: Aaron Boothe
I have been using a dimmer switch in my poppery to control the temp.
However, I have been trying to concentrate more on the low temps of the
roast, and the dimmer is just not holding up.  So I'm contemplating getting
a variac, but using a PID sounds like fun too.  If I get a PID, what kind
should I get?  Is there one that works especially well for air roasting?  Im
am in the process of building a 1-2# air roaster and I would like to be able
to use it on that one when it is finished.  I am just looking for input on
whether I should go for a variac or a PID, and if a PID, what kind?  Thanks
for all the help in advance.
Aaron B

2) From: raymanowen
a PID is what? I understand that in common vernacular usage, it does have
some meaning. By itself, you have no use for a PID. Without a Triac gated by
a Diac and associated circuitry, better known as a SSR, you'll blow up the
1/16 DIN PID.
Call one of the application engineers at Omega and pose your question. If,
however, you already have made some definite assumptions or have some
unstated qualifications for your setup, gather them all together and write
them down.
For example, the heat capacity and power requirements of your heater, and
the power you have available should already be known. If you bring up a
continual shanges and caveats as you talk to their application people, it's
doubtful they can help you over the phone.
In that case, I hope you like to read, because Brown will be arriving with a
wheelbarrow load of free books and manuals related to your project.
The Omega controllers used to be made by Love Controls, and we had many
controls and strip chart recorders in the instrument shop at CSM Research
Institute. Leeds and Northrup made an analog curve tracer that would
generate heat profiles by controlling a fuel gas valve or electrical power.
Cheers -RayO, aka Opa!
Got Cooler?

3) From: John Moody
You will need high current or 240V to air roast 1-2lb. Around 2000 - 5000W
depending on design.
From your message, it sounds like you are not too sure how this stuff
connects together, which can be very dangerous and we would not want to see
you hurt or burn down the house.
Buying an uber-P1 from Mike (just plain) could save you huge amounts of
trial and error time, and probably money as well from not destroying things
along the way.  From there you can work towards your 1-2lb roaster with a
better confidence.
John

4) From: Aaron Boothe
<Snip>
Very true.  I have very little experience in this area.  I am in school for
Chemical Engineering, and it is the chemical aspect of roasting that
intrigued me so much.  I do understand that this stuff is dangerous (the
electricity, not the coffee...well maybe that too...) and so I have an
electrical engineering grad student working with me so I don't kill myself.
Buying an uber-P1 from Mike (just plain) could save you huge amounts of
<Snip>
I also wasn't aware that Mike sold his P1's.  How do I go about checking
them out?
As far as what I mean by a PID, I'm looking at one on the McMaster-Carr
catalog (Auto Tuning PID with fuzzy logic) and my EE friend tells me that we
have to run it with a solid state relay.  At least, I think thats what he
said.  Actually he said a lot of things most of which I didn't understand.
As I type this email, I am struck by the fact that maybe this part of
roasting should be left for people with some background in electrical
stuff.  If trying to get started with a PID controller is this difficult, I
dont think I could ever figure out how to use it right.  This would only
further slow my ability to roast.  So, I think I will just get a variac.
Thanks for your help.
PS does mike (just plain) have a website?

5) From: John Moody
Modifying the Poppery 1 articles by Mike (just plain)http://www.homeroasters.org/php/forum/viewthread.php?forum_id2&thread_id=269http://www.homeroasters.org/php/forum/viewthread.php?forum_id2&thread_id=282">http://www.homeroasters.org/php/forum/viewthread.php?forum_id2&thread_id=270http://www.homeroasters.org/php/forum/viewthread.php?forum_id2&thread_id=269http://www.homeroasters.org/php/forum/viewthread.php?forum_id2&thread_id=282
The Fuji PID is very popular; in the above articles.
Other various pages.http://members.shaw.ca/espressomio/COFFEEMENU.HTMLJohn">http://homepage.mac.com/dparham_is/PhotoAlbum31.htmlhttp://members.cox.net/felixdial/popper.mods.shtmlhttp://members.shaw.ca/espressomio/COFFEEMENU.HTMLJohn

6) From: Michael Dhabolt
John,
There is a certain amount of information that may be of help to you
at:http://www.homeroasters.org/php/forum/viewforum.php?forum_id2.
Several threads are titled "Modifying a Poppery 1 (articles 1 thru 3),
as well as other threads that contain some information that may be of
interest to you.  If you have any specific questions that aren't
answered in one of those threads, email me off-list and I'll try to
answer them (or direct you to someone that can).  This is definitely
not an imposition.....if the questions aren't answered in the threads
- I should edit to add the information.
Mike (just plain)

7) From: Justin Marquez
Aaron -
   Depends on what your goals are in this venture as to how you should
proceed. If you just want the best, freshest coffee you can drink, get a
HG/DB setup and buy the greens from SM. That'll limit you to "zen roasting"
by sight, smell, sound and time. But good results are very easy to get.
Exact repeatability is harder to achieve. But not necessarily required
either.
   Now, if you want "tinker" (and apparently you do), be prepared to drop a
LOT of your time and possibly a chunk of your money into it.
  If you want "repeatability" and more exact control over a roast profile,
then you have a few choices.  You could buy one of Jeff's Computer
Controlled Roaster setups.  You may blanch at the upfront cost, but you will
very possibly spend as much "rolling your own".  There are a few roaster
widgets out there whch do have profile capabilities and cost less. The
HotTop ($500 for a 1/2 lb) is an example.  The soon to be available Behmor
1600 will  also have it ($300-$400 for up to a 1lb batch). There are some
popper-looking roasters that do too about a 1/4 lb roast and those are less
in cost.
[ OLD MAN MODE *ON* ]
  Having been in school for a ChE degree, my suggestion to you is this
(which you probably won't like very much) - get a simple roasting
arrangement for now - a popper, or a HG or maybe even the Behmor. Enjoy
*great* coffee while you get that very important degree.
  When you get out, get a job and get a life  - THEN do the tinkering thing.
You probably don't really have time for it right now. (Heck - you don't
really have time to read this list during the school term!)
[OMM *off* ]
BTW - once properly attached to the right equipment, the PID controls are
not hard to adjust.
PID stands for Proportional, Integral, and Derivative.  A fancy way of
saying that the three modes of control are:
Proportional - the correcting output from the controller is PROPORTIONAL to
the error (the process measurement compared to the setpoint)  (GAIN or
proportional band sets how strong the applied correction will be.)
Integral -  the correcting output from the controller is related to the how
LONG the error has existed
Derivative - the correcting output from the controller is related to the
how FAST the error is changing. (This sounds like a great idea, but often
leads to process instability.)
Usually the "P" and "I" are all that is needed.
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)
BS ChE Miss. State Univ 1969
On 7/26/07, Aaron Boothe  wrote:
<Snip>
--

8) From: Aaron Boothe
Mike and John, thank you very much for the links.  They are very helpful.
Justin,
My goal is to start a specialty coffee shop after I get out of school.  I
don't really want to be a ChemE.  So, the reason I am doing all of this
coffee stuff on the side is so that when I get out of school, I wont have to
start at ground zero to figure roasting out.  I really want to learn exactly
what roasting is doing to the coffee.  The really sweet part is that I am
actually doing this for school.  One of my ChE professors is sponsoring me
for an Undergraduate research project, in coffee roasting.  Specifically:
the flavor chemistry of coffee and how the time vs temp roast variables
change the chemical make-up.  I am also partnering with the Chemistry
department, in hopes of using their Gas Chromatography stuff to figure out
more about the additional flavors compounds in coffee (ie berries, chocolate
etc).
So...I do want repeatability and accuracy.  After all, its for an upper
division ChE requirement. :)
Aaron
PS- I think that was just a really creative way of saying that i don't like
your suggestion of sticking to school. :)

9) From: Justin Marquez
Hey - in that case, tinker away!  If you want real repeatability and
accuracy, you should probaly compare notes with Jeff Pawlan as a starting
point... op. cit., and all that...
I hope you get to fulfill your dream of the Left Brain Coffee Shop.  It is
important that we really like what we do in our daily jobs because we will
be doing it for quite a while!
Best of luck to you.
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)
p.s. - See, I warned you that you would't like it!
On 7/26/07, Aaron Boothe  wrote:
<Snip>
--

10) From: raymanowen
"The Fuji PID is" a temperature controller.
Justin well points out the P-I-D functions. Just imagine yourself at the
control of a King sized 100lb 3Kva Variac feeding the heater element. You
can light it off by cranking up the Variac to 1.4X the normal to make the
heat jump up quickly to roasting  temperatures.
That does three things:
1.) applies 1.4X potential to the heating element (Duh- what you wanted!)
2.) with 1.4X potential applied, the restive heative element draws
1.4Xnominal current, hmmm-
     As a result of (2), high resistance electrical connections will make
themselves known, whether the connection can take the heat or not. (Easy to
locate, smoke and sparks mark the spot)
3.) If the heater drew 10 amps nominally, the Variac draws 20 amps to
1.4Xboost the heater V.
If you thought the Variac would compensate for weak wiring, that's Fiction,
it exacerbates the problem.
Cheers -RayO, aka Opa!
Not a EE, just high school Physics and grade school math...
On 7/26/07, Justin Marquez  wrote:
<Snip>


HomeRoast Digest