I’m a novice to coffee roasting, and a debutante’ to
electronics. While my initial experience roasting
coffee with a popcorn popper was wonderful, I quickly
became frustrated because I didn’t really have control
of the process and didn’t want to sink a lot of money
into a commercial roaster. Also, while I’ve read
various approaches to modifying WestBend Poppery IIs
(WB IIs), none gave control over both air velocity and
heat flux. Below, is my experience developing an
inexpensive way to achieve control of both factors. I
am much happier with my roasts and have enjoyed the
process of developing the system. I don’t know how
long the components will last yet, but I can say the
board circuit design is rated at 120 V and 10 Amps –
far above that used here.
Controlling the Heat
I followed others’ lead and used a 1500 W dimmer
(Lutron C-1500) available from Home Depot or Lowes.
Keep in mind that the WB II has two heaters. One
carries most of the load, the second reduces the
voltage for the motor. You want to connect both of
them to the dimmer or you won’t get enough heat.
Controlling the motor
The motor is controlled using a custom circuit built
according to a designer, (whom I assume is Randy
Linscott). I found it difficult to Purchase an AC
motor controller anywhere. Most people say a simple
Triac or “dimmer” will work – it doesn’t since the
motor function interferes with the Triac unless you
filter the gate supply. This is explained more fully
at Randy’s url:http://home.maine.rr.com/randylinscott/aug99.htm. I
also found that one needs a wirewound resister with a
5 W rating in this circuit. Continuous control is
obtained using a potentiometer.
Be careful not to turn on the heat when the fan isn’t
running. The AC motor controller puts out more
voltage than an unmodified WB II – so it’s easier to
move 4 Oz of green beans. Later in the roast, you can
turn it down to keep the beans in the WB II and
increase the rate at which the beans heat. It’s very
easy to stall the roast after first crack if you want
to try it. I purchased a simple bimetallic
thermometer (uncalibrated) to monitor my roasts. A
Sample roast profile is appended.
Enjoy this project! If you’re not up to the board,
you could possibly switch the fan between a 12 and 15
V transformer– but this gives much less control.
I can email you an RTF with more detailed instructions
including where to get the major parts.
My apologies to those that are tired of the
engineering thing. Please don't try this if you aren't
comfortable with electronics. You do this at your own
Brazilian Auction Lot Winner (SweetMarias) 4 Oz
Min Temp Comment
0 80 --
2 310 --
3 350 "Yellow"
7 415 First Crack Starts
9 440 First Crack Ends
11 460 Second Crack's first Snaps, Stall to 425
13 460 Second Crack Starts
14 475 Second crack more regular, Stop.
Remember, my thermometer in uncalibrated. I stalled
the second crack with the dimmer.
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