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Topic: Caffe' Rosto profiling >was Re: +Puerto Rican Yauco Selecto City Roast (5 msgs / 118 lines)
1) From: Mike McGinness
From: "EskWIRED" 
Yes, but without pictures. In brief I use a 20amp variac to control the
voltage which is monitored with a DMM. I use a Weber BBQ thermometer to
monitor the bean temp, thermocouple soon rigged. Main 'City' profile 230f
@2min, 350f @3:30min, 400f @7min, 435f @10min. Example roast for Central
or Island green: at ambient 70f  90v to 230, 125v to 350, 106v to 400,
108v to 420, 110v to 435 (YMMV.) I need to rig the thermocouple to monitor
the heated air in the roast chamber at the inlet on the Rosto. I also plan
on disconnecting the fan from the variac controlled main plug on my older
Rosto (out of warranty) and have the fan run constant 120v. Oh, this profile
was modified from Black Bears... Seems to keep the brightness with increased
body and complexity.
Home Ju-Ju Variable Variac Rockin' Rosto Roasting in Vancouver, WA USA
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2) From: EskWIRED
Do you have a good source for well-priced variacs?
I also plan
I have the fan on my 1250w Popcorn Pumper on a dimmer switch, with the two
heaters on one switch, with a second switch for the main on/off function.
Everything is built into the case, including the transformer.  It looks nice
and clean, and I have only one piece to schlep outside.
 I can manually lower the temp by turning the heater on and off, and I can
raise the temp enough to melt down the whole mess by decreasing the fan
speed. (I'm thinking about how to modify the dimmer so that it has better
resolution, and as a safety precaution, so it will be incapable of turning
the fan down TOO slow.)
 I greatly increased the size of the air inlets, so the fan MUST be turned
down later in the roast, in order to get enough temperature to reach second
crack.  I can easily roast 3/4 cup, and with initial stirring I can roast a
full cup of beans at a time using this setup.  I can get them to roast very
evenly, but would really like to have direct temperature control (built into
the case) so I could more easily roast smaller batches.  As it is, the heat
is either on or off, with me acting as a manual thermostat.
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3) From: Dan Bollinger
function,... but would really like to have direct temperature control (built
Two heaters?  Are they both the same wattage? You could wire the larger one
so it is 'always on' and put the other one on a 500W or 750W incandescent
light dimmer switch, whichever is required to safely handle the power.  That
way you'd have good control of everything.  Dan
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4) From: EskWIRED
That's an interesting idea.  The two are of very different sizes.  I don't
know the wattage of either of them.  It is not outside the realm of
possibility that the larger one could go on a heavy-duty dimmer switch.
What's the failure mode for dimmer switches?
The smaller heating coil is used, in a stock popper, to reduce the voltage
going to the motor.  The motor gets about 20 volts and, I am told, sucks up
2 amps. I use a 1.5 amp transformer in my modified Popcorn Pumper, because
it's the biggest one I could fit into the case.
Some people use three switches, and put each of the heating elements on
their own switch.  I treat the two of them as one, having them wired in
Your idea is going into the hopper for v. 2.0.
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5) From: EskWIRED
You are referring to the winding in the motor, I assume.  I measured 20
volts or so myself, but relied on somebody else's measurement for the 2 amp
draw.  Now that the motor is supplied by a 24v transformer, it runs at more
like 22v or so, without the dimmer in the circuit.  I didn't measure it
after inserting the dimmer.  I assume the dimmer reduces the voltage on the
secondary side slightly, even when turned up all the way.
Again, I assume you are talking about the motor.  Don't forget that the
transformer is powered through a 600w dimmer switch, which is of less than
100% efficiency.  And during much of the roast, the power to the motor is
reduced anyhow, to slow down the fan and keep the heat in the beans, instead
of blowing it out the top too quickly.
Will do.  But given that I'll be sitting right there, and given that this is
a labor of love and a vehicle for experimentation, a meltdown would not be
the end of the world.  I'm thinking of installing a fuse in the popper
itself, and it is still protected by a thermal fuse, so it is likely that
any real problems would result in a blown circuit breaker or a blown thermal
fuse. So long as nothing explodes into a big shower of sparks, like in the
movies, I should be fine :)
But!  If you are correct in your assumptions about current draw, a 1000w
dimmer should be adequate (almost?) to control the heating elements.
Has anybody ever tried this?
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