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Topic: Variable Rosto Roasting (11 msgs / 232 lines)
1) From: Randy Roy
This is a multi-part message in MIME format.
I just did my first 2 roasts with my freshly hacked Rosto, now with heat =
controlled by Variac,  and a variable speed fan with votage boost via =
transformer to give me an extra 12 volts. 
The extra voltage gives me enough fan speed so that a 150 gram batch =
does not require any rocking of the Rosto for proper agitation early in =
the roast.  I'm just using a standard rotary dimmer switch to control =
the fan speed.  What's nice is that I can now control the roast profile =
by heat variation and fan speed/airflow.  Both batches were roasted to =
440 deg./12-13 minutes and were very uniform in color,  much more so =
than usual.  I attribute that to the better agitation during the early =
stages of the roast.
I also notice that first crack occurs at a slightly higher temperature =
with the extended roast profile.  With my popper or even the stock =
Rosto, it started around 385-390.  Now it's more like 400-405.  I'll see =
how/if this affects the taste after they rest a bit.
All in all, I really like this set-up.  The Rosto fan seems to tolerate =
the extra voltage quite well, so far.  Time will tell...
Randy    
 

2) From: Mike McGinness
From: "Randy Roy" 
<Snip>
controlled by Variac,  and a variable speed fan with votage boost via
transformer to give me an extra >12 volts.
Cool, you're one step ahead of me! What current rating transformer did you
use and what voltage jump, 12v or 24v or ?
<Snip>
not require any rocking of the Rosto for proper agitation early in the
roast.  I'm just using a standard rotary dimmer switch to control the fan
speed.  What's nice is that I can now control the roast profile by heat
variation and fan speed/airflow.  Both batches were roasted to 440
deg./12-13 minutes and were very uniform in color,  much more so than
<Snip>
the roast.
Just standard light dimmer or other potentiometer? The extra fan speed
during early stages is what I'm looking for too. It's better with fixed 120v
fan than was before with heater/fan both variac but still not there. Even
so, early equalization stage is more even with 120v fan lower heat. You're
route probably cheaper than the $30 I'll end up paying for a second raw
variac. (Though it will be 5amp rated) Think I'll check out transformers and
pot' before I'm comitted. (though maybe should 'be' comitted:-)
<Snip>
the extended roast profile.  With my popper or even the stock Rosto, it
started around 385-390.  >Now it's more like 400-405.  I'll see how/if this
affects the taste after they rest a bit.
Fascinating that you should mention that. I wasn't sure if it was my
imagination or what. I seem to be getting very very similar results, C1 now
coming higher temp.
<Snip>
the extra voltage quite well, so far.  Time will tell...
The Rosto does seem to be tough. I pushed 135v into heater/fan tied together
Rosto emulating a FR French in 4min roast! Don't think I'd want to do it on
a regular basis though:-) Rosto still going strong. It's the two year old
I've already separated input voltage.
MM;-) aka Kona Konnaisseur miKe mcKoffee
Variac Rockin' Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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3) From: Mike McGinness
From: "Mike McGinness" 
<Snip>
Duh, you said extra 12 volts...
MM;-) aka Kona Konnaisseur miKe mcKoffee
Variac Rockin' Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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4) From: Randy Roy
Mike, I got a 12v, 3 amp transformer from Radio Shack for $10, $6 for a
project box and $4 for the dimmer.  The transformer actually puts out almost
14v,  so I have about 134 volts available for the fan.  It's just what the
doctor ordered for early roast agitation.

5) From: dewardh
Mike:
<Snip>
use and what voltage jump, 12v or 24v or ?
The fan draws less than 1 Amp., so that's all the current rating you need.  24V 
might be pushing your luck (given that you have a full 120V supply voltage to 
begin with), although it might work out fine.  But a 12V 1A transformer is all 
you need.  It's nice to know that a standard "dimmer" works . . . but those 
"router speed controllers" are under $15 at Harbor Freight, and they are sure 
to work and keep working  (this is exactly the application they're designed 
for . . . speed control on AC/DC "brush" motors).
Deward
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6) From: Mike McGinness
Thanks Randy & Deward for the input. (Rick too for wiring directions
earlier.) Of course, I just got home with parts before receiving these
replies. As it turns out I picked up the exact same $9.99 12.6v 3A
transformer at Radio Shack and a 5A rated continuously variable ceiling fan
control from Lowe's ($9.95). Now to see if I can wire it correctly:-) No
fear of flying, but do have a fear of frying! But then, if I get it wrong
just right I'll do both:-)
MM;-) aka Kona Konnaisseur miKe mcKoffee
Variac Rockin' Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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7) From: Ken Mary
<Snip>
The router speed controller that I bought did not work properly, neither did
its replacement. The maximum speed is about 50% of uncontrolled, far too low
to be useful. I have not taken it apart to inspect for problems or check it
on the scope. It is the same as Harbor Freight no. 43060.
--
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8) From: dewardh
Ken:
If I recall correctly you were attempting to control not just the fan but the 
whole roaster . . . and that's what burned it (them) out.  Am I mistaken about 
that?  btw . . . the 43060 can be had for $12.99 when ordered as 43060-2VGA 
(web order) . . . I'll get one and see how it performs on a Rosto fan . . .
Deward

9) From: Ken Mary
<Snip>
No, just the fan on a Poppery I. I do not know if the router controllers are
defective or just poorly designed. I tried them on a variety of small ac
brush motors, no good as received.
I checked the website, no -2VGA, only -0VGA for $24.99. How did you find the
lower price?
BTW another Poppery I has just joined my roaster family. It is completely
disassembled and washed, drying as I type this. $3.99 at a thrift, yes I
paid too much, but did not want to go back another day for a tag sale price
and risk losing it.    8^)
--
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10) From: dewardh
Ken:
<Snip>
lower price?
Click on "order from printed catalog" and enter the whole part # . . . the 
reduced price will appear in the "shopping cart".  For laughs "delete" the item 
and do the routine again using "1VGA" . . . the whole system works like that. 
 If you're looking at an expensive item, or "seem to recall" seeing a lower 
price in the not-to-distant past, doing a quick scan like that can be a real 
money saver . . . (the highest number is not always the lowest price, btw).
It'll be a week or two (probably) before the one I ordered gets here (and I've 
had time to test it) . . . I'll post results ASAP . . .
Deward
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11) From: David Westebbe
<Snip>
 Even
<Snip>
miKe -
Where do you get a "raw" variac for $30?  I've only seen ones in cases which
cost at least 3 times that amount.
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