San Francisco Bay Area Home Roaster Get-Together June 2003

San Francisco Bay Area Home Roaster Get-Together June 2003
(Robin Kibby & Brian Donaldson house, Berkeley)

It was a funfilled Sunday afternoon. The coffee was plentiful, the food was delicious and the house was clean! (a joke, Robin – your mom was amaze). Zara looks on

David Lewis and

Brooding engineer with HotTop envy

Well, everyone had HotTop envy, because the star of the event was Jeffrey Pawlan’s CCR roaster … meaning PC Computer Controlled.

A better view

Interior of the roaster sans drum. You can see the 2 custom made thermocouples

From the top, the termocouples slotted on either side of the bean chute(where you dump coffee into the drum), glued in place with a high temp expoxy.

The experimentor, programmer and machinist, Jeffrey

The control screen with real time graph plotting bean temp and environment temp as the roast progresses

The left side of the same control screen showing all the “segments” (you simply add or subtract segments to control roast stages) and temperature meters.

Not bored, somewhat bewildered. Jeffrey actually did a manual roast, contolling the heater and fans with simple mouse-clicks, responding to the temperature readings and making adjustments on the fly. But you can also have the computer make all the determinations according to your presets.

The results, an even Mandheling roast with very little erratic bean expansion (puff that you get with air roasts) or divots (from rapid outgassing).It was extremely lively as espresso with zero rest, not pleasant, but hey, no rest! It showed great potential as espresso when rested a real 48 hours. I brought a sample home – can’t wait until it is rested…

Of course, Maria knit most of the time. Unforunately, I forgot to eat and drank too much coffee. Oh well, how often do we see eachother?

7.4 Meg AVI Movie of the HotTop

Some more notes on the CCR from Jeffrey – posted to the homeroast list on 6/27/05 … he explains the CCR a lot better than I can …

I saw a real need for being able to accurately control a complex roasting profile and also be able to achieve identical results with multiple roasts. I know that some of you prefer zen roasting and /or dog bowls. That is fine and I respect that we all have different tastes, preferences, and styles. I have both a Hearthware Precision and also a HotTop. I have done perhaps 600 roasts so far and I have temperature logged some and taken notes on others. I have determined the best roasting for my particular taste and it requires complex profiles and good accurate control. The prototype computer controlled roaster (CCR) is based on a modified HotTop as Tom and others have written today. You can see some photos on his webpage:

I will try to make a webpage regarding my roaster and will let you know when it is ready. I have my electronic engineering consulting webpage at and I will put the roaster page under that one when it is ready. Some details and answers to questions:

1. The thermocouples are both high accuracy and both are kapton covered wire with a kapton sheath. If you are using anything other than kapton in your roaster, you are risking serious poisoning and possible death (except for stainless steel sheath but that is very SLOOOOW responding so not recommended.)

2. The user first sets the roaster preheat temperature and the time you want it to stay at that temperature to stabilize before the Ready light illuminates. You click on a button called Begin Preheat when these are set.

3a. The user can choose Manual roast and use the mouse cursor to slide a control up and down which linearly controls the heat. The user can manually turn on and off the drum, the fans, the bean dump, and the cooling tray motor, all with a single mouse click on four buttons on the screen.

OR: 3b. The user can choose Automatic roast and then select how many “segments” you want in your profile; from 2 to 6 segments. You then set each segment goal temperature and the amount of time you want the ramp to take to reach that temperature. If you were to select an unrealistically short segment time, then the segment continues until the goal temperature is reached using the maximum permissable heater power.

4. You begin the automatic roast by pressing a button labelled “Beans in; begin roast”

5. You can see the air temperature and the bean temperature and the difference between them (differential) all simultaneously being updated at less than 1 second intervals.

6. You see the slope of the air temperature and the bean temperature displayed both on two slope meters and also as numeric readouts. This is in degrees F per minute. This is updated once per second.

7. By pressing a button, you can initiate a realtime plot of both the air and bean temperatures on a moving graph, updated every second.

8. By pressing another button, you can simultaneously save the data for logging the roast. At the end of the roast you press another button to actually transfer the data to the file and it asks you for the name you want to use.

9. You can either let the roast complete by itself or you can terminate it and dump the beans at any time.

10. Unlike the unmodified HotTop, there is no waiting before running another roast. You are not expected to cool it down unless, of course, you want to.

11. My hardware interface and my program can be modified for almost any roaster and I intend to make a special version for air roasters which I will use three thermocouples so the air inlet temperature and the outlet temperature can be monitored as well as the approximate bean temperature.Brief answers to questions: Yes, I am willing to make your roaster into a CCR and sell you a complete system ready to plug in and roast. I should be done with all of my programming within a month. This will work on a P3 notebook computer and does not require that latest high speed computer (speed and memory tbd).

Depending on how many people want one, I will either make them one at a time (very expensive) or redesign for manufacturing. I also intend to partner with others to design a brand-new roaster but that is down the line. I am a very experienced engineer and will be able to do all the electronic design and manufacturing drawings myself. My complete contact information is on my webpage. Regarding roast profiles and double roasting: I will send this list a separate reply regarding double roasting as that is a
different subject thread.

Jeffrey Pawlan

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