HomeRoast Digest


Topic: Controlling air popper heat (35 msgs / 944 lines)
1) From: Dave
I have a variac I thought I would use, but it's not beefy enough (3.75A). So
I'm trying figure out what to use instead. I can buy a variac from Tom for
~$130 and have a 25 lb hunk of copper and iron to lug around. I googled -
1500 Watt rotary dimmer - and found a Lutron T-1500 for ~60 bucks. Any
reason not to use this? I know I'll have to enclose it etc.that's no
problem. It seems like if it will work, the end result would be much more
convenient.
Any other ideas? Suggestions?
Thanks!
-- 
Dave
Some days...
It's just not worth chewing through the leather straps

2) From: Michael Dhabolt
Dave,
Dave  wrote:
<Snip>
Don't get rid of the small variac. If you find a Poppery 1 (original) it'll
come in handy.  When you find one large enough to deal with the heat, you
can use the small one to control the fan speed - - resulting in total
control.
Mike (just plain)

3) From: Peregrine38
While poking around on the internet, I found that people have used  
the big dimmers with their poppers.  Sorry I don't have the links.   
We put a 600W dimmer (through a 25V transformer) on the fan and a  
switch on each of the heating coils.  Details for this are also out  
there and require some internal rewiring.
During a roast we normally switch the lower heat coil and the fan  
leaving the "big heater" on all the time.  We want to try a 600W  
dimmer on the low heat coil since this may be all we need for fine  
control.
HTH, Roger
On Mar 15, 2007, at 8:50 PM, Dave wrote:
<Snip>

4) From: miKe mcKoffee
Main reason for variable transformer (aka variac) over dimmer is 'most'
variacs come with 10 or 20% voltage increase capability while a dimmer will
have only lowering voltage capability AND the max voltage will be slightly
below line voltage do to loss in the dimmer itself. With wider min AND max
voltage better able to control profiles and compensate for low ambient
temps. That said a 10A or better variac will run a 1500w roaster all day no
problem. And can be found on eBay relatively not to bad. I got a new
industrial grade US made Powerstat 10A for under $50 few years back, runs
the heater side of Frankie. Took a bit of time to get the right auction, but
will last virtually forever.
Kona Kurmudgeon miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/	From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of Dave
	Sent: Thursday, March 15, 2007 5:50 PM
	
	I have a variac I thought I would use, but it's not beefy enough
(3.75A). So I'm trying figure out what to use instead. I can buy a variac
from Tom for ~$130 and have a 25 lb hunk of copper and iron to lug around. I
googled - 1500 Watt rotary dimmer - and found a Lutron T-1500 for ~60 bucks.
Any reason not to use this? I know I'll have to enclose it etc.that's no
problem. It seems like if it will work, the end result would be much more
convenient. 
	Any other ideas? Suggestions?
	Thanks!
	-- 
	Dave
	
	Some days...
	It's just not worth chewing through the leather straps

5) From: Sean Cary
ditto that - Mike built me a roaster last year when I got home from Iraq,
and he splits the fan and power in a project box, I added a small variac to
the fan, and can ramp up the fan to 110% and really get the beans moving.  I
use it to keep the beans moving at the beginning of the roast, and to ramp
up the heat by decreasing the fan speed later in the roast.
 
I have not added a variac to the heat side, but one of these days I will...
 
Sean M. Cary
Major USMC
Tempus Fugit Memento Mori  
From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of Michael Dhabolt
Sent: Thursday, March 15, 2007 9:18 PM
To: homeroast
Subject: Re: +Controlling air popper heat
Dave,
Dave  wrote: 
I have a variac I thought I would use, but it's not beefy enough (3.75A). 
Don't get rid of the small variac. If you find a Poppery 1 (original) it'll
come in handy.  When you find one large enough to deal with the heat, you
can use the small one to control the fan speed - - resulting in total
control. 
 
Mike (just plain)

6) From: Dave
I had this one apart to see what made it go. I'm pretty sure the fan runs on
110. I'm planning to use Mike's transformer boosted then dimmer circuit to
control the fan. I'll check for sure before I actually do the hack.
I didn't open the heat chamber, but from the wiring external to that I think
this unit uses only one heating element. Mike pointed out that using a
variac would allow me to boost the voltage to the heater a bit as well as
reduce it. With a 1500 watt unit, I'm not sure that is any really an
advantage, just an extra capability.
Anybody know how much voltage I drop across a dimmer turned to full-on?
Thanks for the help!
-- 
Dave
Some days...
It's just not worth chewing through the leather straps

7) From: Michael Dhabolt
Dave,
Dave wrote:
<Snip>
I tried it once, I would imagine different dimmers have different voltage
drops at maximum.  The one I tried had about a 3% voltage drop.  With the P1
it changed the max green bean load substantially.
Using the boosted voltage of a Variac increased the green bean load approx.
30% above that of an un-modified P1 fan.  And as Sean indicated, the ability
to control air flow has other advantages.
Mike (just plain)

8) From: Rich
The actual voltage drop across the electronic dimmer at full on will be a function of the forward 
resistance of the device and the current flow through it.  Figure that it will be 2.5% of the applied 
voltage as a nominal value.
Rich
--Original Message Text---
From: Michael Dhabolt
Date: Fri, 16 Mar 2007 09:34:53 -0700
Dave,
Dave wrote: >Mike pointed out that using a variac would allow me to boost the voltage to the heater a bit 
as well as >reduce it. With a 1500 watt unit, I'm not sure that is any really an advantage, just an extra 
capability. 
<Snip>
I tried it once, I would imagine different dimmers have different voltage drops at maximum.  The one I 
tried had about a 3% voltage drop.  With the P1 it changed the max green bean load substantially.
Using the boosted voltage of a Variac increased the green bean load approx. 30% above that of an un-
modified P1 fan.  And as Sean indicated, the ability to control air flow has other advantages.
Mike (just plain)

9) From: Dave
I'm planning to use separate fan and heat controls, with a boosted fan
voltage. Will reducing the heater voltage be a problem? It doesn't seem like
it should be.
Thanks!
-- 
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, Michael Dhabolt  wrote:
<Snip>

10) From: Dave
I think I found just what the Dr. ordered:http://tinyurl.com/qs574Variable voltage & bypass for $25.
One of these for the heater, a $4.00 dimmer + transformer for the fan
A few parts for mounting it all
I should be in good shape.
-- 
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, Rich  wrote:
<Snip>

11) From: Douglas Strait
Dave, in a typical triac based dimmer powering a *resistive load* you 
only have a couple of volts drop across the dimmer at full on. The 
motor, however, is not a simple resistive load and in fact can look 
weird as far as the dimmer is concerned. If your popper has a 
commutated series wound universal motor like the Poppery P1 or 
Wearever 1400W Pumper,  the motor when rotating can creat "back 
voltage" which may affect the point in the applied AC input waveform 
that the dimmer triac turns on. Due to the very non-sinusoidal nature 
of the residual drop across the dimmer, the measured drop is not the 
reduction of RMS voltage that the motor sees. What I think you care 
about is how much is the voltage to the motor reduced. The best way to 
determine this is to measure the motor voltage with the dimmer full on 
and then again with the dimmer jumpered out of the circuit. These 
measurements should be made with a True RMS reading meter.
Doug

12) From: Rich
You want to use an RMS RESPONDING meter not an RMS READING meter.  All of the current crop of 
commonly available DVM types are calibrated to read RMS.  Some are RMS responding and some are 
not.  You will have to check carefully.
There is minimal value in this lab experiment anyway.  The fan will fan slower with the dimmer in the 
ckt with the same line voltage applied.  If you have no use for the full speed fan then the dimmer will do 
the job.  If you need all of the air the fan can produce then it is transformer boost time into the dimmer.
Rich
On Fri, 16 Mar 2007 13:41:50 -0400, Douglas Strait wrote:
<Snip>

13) From: miKe mcKoffee
IMNSO router controller may work for some/many desired profiles and ambient
temps, BUT it's a mistake. There are times/segments/ambients were I'll
briefly push my full available 132v at the heater. (mine only has 10% boost
heater side of Frankie, wish I'd been more patient and gone 20% at times)
Full heater power seldom needed, but without the boost capability you'll be
hamstringing yourself. OTH I do routinely use up to 125v or higher during
some early segments. You'd be much much better off with variable boosted
voltage capability to the heater. And if you take your time won't spend much
more. Something along these lines would work marvelously:http://tinyurl.com/2egovyNo case model like I used in Frankihttp://tinyurl.com/2h66m3Etc. etc. etc. Lots of 'em out there just takes some patience to get a good">http://tinyurl.com/yog6w9http://tinyurl.com/2yz3o8http://tinyurl.com/2egovyNo case model like I used in Frankihttp://tinyurl.com/2h66m3Etc. etc. etc. Lots of 'em out there just takes some patience to get a good
price. BTW, those URLs to 7.5A variacs were not a mistake. They'll handle
non 24x7 roasting duties no problem. (I can send you the equations for safe
duty cycle if you're concerned:-)
But what ever, it's your decision!
Kona Kurmudgeon miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/	From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of Dave
	Sent: Friday, March 16, 2007 10:28 AM
	To: homeroast
	Subject: Re: +Controlling air popper heat
	
	I think I found just what the Dr. ordered:
http://tinyurl.com/qs574	Variable voltage & bypass for $25.
	One of these for the heater, a $4.00 dimmer + transformer for the
fan 
	A few parts for mounting it all
	I should be in good shape.
	-- 
	Dave
	
	Some days...
	It's just not worth chewing through the leather straps
	
	On 3/16/07, Rich  wrote: 
		The actual voltage drop across the electronic dimmer at full
on will be a function of the forward resistance of the device and the
current flow through it. Figure that it will be 2.5% of the applied voltage
as a nominal value.
		
		Rich

14) From: Dave
OK. I just opened it up to look again and do a little measuring. I'm not
familiar with motor terminology, but from looking Douglas's name for it
"commutated series wound universal motor" sounds just right. Power comes
into the motor, and powers the field coils and the moving part, (commutator?
armature? through the brushes) in series. I used an analog meter (no
question, definitely RMS) and measured 75VAC across the brushes.
The power comes from the wall through the switch, then through what appears
to be a safety thermostat, then to the motor and the heater (heater & motor
are in parallel after safety device). There also apears to be a thermal
switch of sort fastened to the field coils. Is this likely to be an issue? I
guess I'll find out.
So with a nominal 115VAC to the fan motor, I guess I'm gonna try Mike
McCoffee's circuit for the fan:http://tinyurl.com/qs574for the heater.">http://tinyurl.com/32qhqeAnd the router control:http://tinyurl.com/qs574for the heater.
I'll let you all know how it comes out.
Thanks for the help!
-- 
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, Rich  wrote:
<Snip>

15) From: Rich
If it is an analog meter then it is peak respomding and calibrated to read rms.  As long as the 
waveform is a true sine wave ther is no appreciable error.  If the waveform is distorted then there is a 
large error.
--Original Message Text---
From: Dave
Date: Fri, 16 Mar 2007 11:30:11 -0800
OK. I just opened it up to look again and do a little measuring. I'm not familiar with motor terminology, 
but from looking Douglas's name for it "commutated series wound universal motor" sounds just right. 
Power comes into the motor, and powers the field coils and the moving part, (commutator? armature? 
through the brushes) in series. I used an analog meter (no question, definitely RMS) and measured 
75VAC across the brushes. 
The power comes from the wall through the switch, then through what appears to be a safety 
thermostat, then to the motor and the heater (heater & motor are in parallel after safety device). 
There also apears to be a thermal switch of sort fastened to the field coils. Is this likely to be an 
issue? I guess I'll find out. 
So with a nominal 115VAC to the fan motor, I guess I'm gonna try Mike McCoffee's circuit for the fan:http://tinyurl.com/qs574for the heater. ">http://tinyurl.com/32qhqeAnd the router control:http://tinyurl.com/qs574for the heater. 
I'll let you all know how it comes out.
Thanks for the help!
-- 
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, Rich  wrote: You want to use an RMS RESPONDING meter not 
an RMS READING meter.  All of the current crop of
commonly available DVM types are calibrated to read RMS.  Some are RMS responding and some are
not.  You will have to check carefully. 
There is minimal value in this lab experiment anyway.  The fan will fan slower with the dimmer in 
the
ckt with the same line voltage applied.  If you have no use for the full speed fan then the dimmer will 
do
the job.  If you need all of the air the fan can produce then it is transformer boost time into the 
dimmer.
Rich
On Fri, 16 Mar 2007 13:41:50 -0400, Douglas Strait wrote:
<Snip>

16) From: Dave
On 3/16/07, miKe mcKoffee  wrote:
<Snip>
Just when I make up my mind someone tries to confuse me with facts;-)
Ambient temps should help me reduce the need for boosted heater voltage.
It's not likely to be much below 70 degrees around here 'til October, even
in the winter 40 is really cold here.
Etc. etc. etc. Lots of 'em out there just takes some patience to get a good
<Snip>
There was poster when I was in high school, 2 buzzards are sitting in tree
looking at a skeleton, and one says to the other: "Patience my ass! I'm
gonna kill something"
BTW, those URLs to 7.5A variacs were not a mistake. They'll handle
<Snip>
I'd like to see those. I believe you, but yeah I'm a little concerned.
But what ever, it's your decision!
<Snip>
Thanks! I really appreciate the help.
-- 
Dave
Some days...
It's just not worth chewing through the leather straps

17) From: Dave
I'm thinking about things I hadn't considered in years... I just opened the
meter and there is no filter capacitor to cause it to hold a peak. I'm
pretty sure that was one of the advantages in sticking with good old analog
meters, what you measure is always RMS. I don't  have a way to generate a
known waveform to test this with though.
-- 
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, Rich  wrote:
<Snip>

18) From: Michael Dhabolt
Dave,
I regularly roast in my kitchen (installed ventillation fan and ducting for
exhaust) with a household temp normally around 68F.  The added facility of
increased voltage to the fan and heat control via PID allows me to roast 1/2
pound net weight roasts as my norm.
If you are going to go the route of major modifications to a P1.....you will
be real happy if you build something that gives you maximum flexibility,
you'll be living with it for a loooong time (these things virtually never
wear out).
Mike (just plain)

19) From: miKe mcKoffee
Here's a cut & paste of what I posted Feb 06 (found searching the searching
archives:-)
"From: miKe mcKoffee
Yes, 10A is fine for heater side control. The US made variable transformers
10A rating is for 24x7 continuous use. Mine doesn't even get warm running
Rosto roasts back to back. Using a 10A Powerstat no problem. From the
Superior Electric Company spec sheet for my 10A the rated *safe* overload
use formula rating is: actual current divided by rated current squared minus
one equals off time divided by on time. For only a 5A rated under 120v
roasting with a 1100w FR (pulling 9.166A @120v) with 10 minute roast time
the *safe* operational off time would be: (9.166/5)(9.166/5) - 1 = X/10min
with X being safe time off between roasts. Solving for X=.236min = 16sec for
1100w FR on 5A variac. For a 1300w Rosto 52.85sec. off time same 5A. Much of
the above I cut & pasted from my List posts discussing use of 5A variacs and
over fusing from April '03.  
End cut & paste. 
Bottom line even a 5A could safely handle the Rosto (or P1) with about 1min
off for each minute on. The only variac cooling time I give is while beans
cooling in Rosto fan motor (on other control circuit) running and heater
off. (It's way more than enough for the 10A variac to not even get the
slightest warm.) Then immediately start next roast. I'll leave doing the
math for various roast/duty times solving for required safe off time with
7.5A and your popper to you!
Kona Konnaisseur miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/	From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of Dave
	Sent: Friday, March 16, 2007 12:40 PM
	
	Just when I make up my mind someone tries to confuse me with
facts;-) 
	Ambient temps should help me reduce the need for boosted heater
voltage. It's not likely to be much below 70 degrees around here 'til
October, even in the winter 40 is really cold here. 
		BTW, those URLs to 7.5A variacs were not a mistake. They'll
handle
		non 24x7 roasting duties no problem. (I can send you the
equations for safe 
		duty cycle if you're concerned:-)
	I'd like to see those. I believe you, but yeah I'm a little
concerned.

20) From: Rich
Brain lock.  An analog meter is an average sresponding device.  There is a rectifier in there somewhere.  
It has been many years since I taught basic electronics.....  Anyway for what you are doing it does not 
make any difference...
--Original Message Text---
From: Dave
Date: Fri, 16 Mar 2007 11:52:44 -0800
I'm thinking about things I hadn't considered in years... I just opened the meter and there is no filter 
capacitor to cause it to hold a peak. I'm pretty sure that was one of the advantages in sticking with good 
old analog meters, what you measure is always RMS. I don't  have a way to generate a known waveform 
to test this with though. 
-- 
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, Rich < rich-mail> wrote: If it is an analog meter then it is peak respomding and 
calibrated to read rms. As long as the waveform is a true sine wave ther is no appreciable error. If the waveform is 
distorted then there is a large error. 

21) From: Dave
Yep a diode, so if the waveform isn't symmetric about ground, readings would
be screwed up.
Like you say, for this purpose, it doesn't matter a hill of beans, not even
a hill of Tom's Goo Goo muck beans;-)
On 3/16/07, Rich  wrote:
<Snip>
-- 
Dave
Some days...
It's just not worth chewing through the leather straps

22) From: Dave
On 3/16/07, miKe mcKoffee  wrote:
<Snip>
I'll leave doing the
<Snip>
Thanks! It looks simple enough. I'll see what the numbers tell me.
-- 
Dave
Some days...
It's just not worth chewing through the leather straps

23) From: miKe mcKoffee
Ditto. I've never regretted doing it "right" but have regretted doing on the
"cheap". The pain of waiting and or paying a bit more lasts a short time
while the use satisfaction lasts forever versus the monetary savings glow
transitory while the dissatisfaction knowing something is not as good as it
could be returns with each and every use and never leaves.
Kona Kurmudgeon miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/	From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of Michael Dhabolt
	Sent: Friday, March 16, 2007 1:17 PM
	
	Dave,
	 
	I regularly roast in my kitchen (installed ventillation fan and
ducting for exhaust) with a household temp normally around 68F.  The added
facility of increased voltage to the fan and heat control via PID allows me
to roast 1/2 pound net weight roasts as my norm. 
	 
	If you are going to go the route of major modifications to a
P1.....you will be real happy if you build something that gives you maximum
flexibility, you'll be living with it for a loooong time (these things
virtually never wear out). 
	 
	Mike (just plain)

24) From: Dave
On 3/16/07, miKe mcKoffee  wrote:
<Snip>
Now that's dirty pool! That's the same argument I use when buying tools!
-- 
Dave
Some days...
It's just not worth chewing through the leather straps

25) From: miKe mcKoffee
Yup, we're talking about a tool. A coffee roasting tool.
miKe
	From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of Dave
	Sent: Friday, March 16, 2007 1:53 PM
	On 3/16/07, miKe mcKoffee  wrote: 
		Ditto. I've never regretted doing it "right"
	Now that's dirty pool! That's the same argument I use when buying
tools!
	-- 
	Dave
	
	Some days...
	It's just not worth chewing through the leather straps

26) From: Douglas Strait
Dave,
Another means of raising the maximum heat input is to lower the 
resistance of the heater coil by shortening it. I have removed as much 
as 25% of the length on 1400W Wear Ever Pumpers with no problem at 
all. I then use triac based control for the heat. This gives you the 
maximum heat boost without the bulk and expense of a variac.
Doug

27) From: Dave
 I may look into that. I believe this is a re-badged Wear Ever pumper:http://tinyurl.com/yoku49 I like the weight savings that would result. It would sure help
portability, if that ever matters.
Thanks!
-- 
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, Douglas Strait  wrote:
<Snip>
-- 
Dave
Some days...
It's just not worth chewing through the leather straps

28) From: Rich
That will work with the open wire type of heating element.  Beware that reducing the resistance will 
raise the current and also raise the operating temperature of the heater.  Heater service life is 
inversely proportional to operating temperature.  You will shorten the service life by doing that.  Have a 
spare on hand.  As it will fail in the middle of a roast with the last of the premo beans....
--Original Message Text---
From: Dave
Date: Fri, 16 Mar 2007 15:04:16 -0800
I may look into that. I believe this is a re-badged Wear Ever pumper:http://tinyurl.com/yoku49 I like the weight savings that would result. It would sure help portability, if that ever matters. 
Thanks!
-- 
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, Douglas Strait < dougstrait> wrote:Dave,
Another means of raising the maximum heat input is to lower the 
resistance of the heater coil by shortening it. I have removed as much
as 25% of the length on 1400W Wear Ever Pumpers with no problem at
all. I then use triac based control for the heat. This gives you the
maximum heat boost without the bulk and expense of a variac. 
Doug
-- 
Dave
Some days...
It's just not worth chewing through the leather straps 

29) From: Dave
On 3/16/07, Rich  wrote:
<Snip>
I would bet there is even a square factor in there somewhere.
You will shorten the service life by doing that. Have a spare on hand. As it
<Snip>
Probably a desperation roast of the last beans in my stash, swept from the
corners, cleaned out from under the fridge...
If wasn't for bad luck, I wouldn't have any luck at all;-)
Thanks,
-- 
Dave
Some days...
It's just not worth chewing through the leather straps

30) From: raymanowen
There's no sense in having the Variac carry the entire current load of the
roaster.
My suggestion would be to have the fan wired for Low, Normal, High speeds-
three switch selected power levels.
The heat output of the heater varies radically with fairly small changes in
the input voltage to the heater element. It's not necessary to vary the
input from 0 - 140% of the line voltage.
You would have absolutely no use for the 0 - 85% of line voltage input (way
too cool to be of any use), and above 120% input would be very hot and
destructive of the heater, at almost 200% max heat output. So (0-85 +
120-140)/140, or (105/140)% = 75% of the variac's output range is a total
waste. Expensive paper weight that I'll need to wake up my Thunderbolt
linear one day soon.
You could leave the heater wiring alone, save for a series buck/ boost
transformer driven by your small Variac. A 120v/12v 10a transformer could be
fed by a 1a Variac and a DPDT phase reversal switch, for a total heat range
in excess of 75% - 120%. If that doesn't work- Back to the Drawing Board
with it. The problem is elsewhere. You might be working with a 20% current
overload at max settings.
Over a period of time you'd learn the difference between electrical smoke
and coffee roasting smoke. Deal with it. It might happen at continuous full
throttle...
Cheers -RayO, aka Opa!
Remember Sylvania's flashbulbs- Blue Dot for sure shot? Say Cheese!

31) From: raymanowen
PS- Since heat is related directly to power, and P=Vē / R watts, you ge=
t
surprising heat changes for small voltage changes. -ro

32) From: miKe mcKoffee
Ray,
I almost agree and do agree in principle, don't need to lower heater voltage
variably down to zero! However my initial warming profile targets 150f @
30sec then 200f @ 1min, 250f 2min, 300f 4min. Depending on ambient I'll
start anywhere from 120 to 130v then as approaching 150f slam down to 96 to
104v. That's only 80% voltage applied to heater warm ambients (talking 90f
or so) so 85% too high;-) Today's morning roasts started 126v dropping to
102f, about 45f ambient in the garage. Did another batch this afternoon with
ambient 65f 123v dropping to 99v.
For the average person a single 10A or so variable transformer much easier
to implement than a large fixed boost transformer controlled by second
variable unit of choice. And cost wise like I said, work eBay and easily
done for under $50 including s/h. I got a 10A Superior in case for just
under $40 inc. s/h thinking to dismantle and use in Frankie then realized
much more difficult than anticipated so sold it and paid a bit higher for a
sans case brand new 10A Superior unit, also eBay.
Kona Kurmudgeon miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/	From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of
raymanowen
	Sent: Friday, March 16, 2007 5:41 PM
	
	There's no sense in having the Variac carry the entire current load
of the roaster.
	
	My suggestion would be to have the fan wired for Low, Normal, High
speeds- three switch selected power levels. 
	
	The heat output of the heater varies radically with fairly small
changes in the input voltage to the heater element. It's not necessary to
vary the input from 0 - 140% of the line voltage. 
	
	You would have absolutely no use for the 0 - 85% of line voltage
input (way too cool to be of any use), and above 120% input would be very
hot and destructive of the heater, at almost 200% max heat output. So (0-85
+ 120-140)/140, or (105/140)% = 75% of the variac's output range is a total
waste. Expensive paper weight that I'll need to wake up my Thunderbolt
linear one day soon. 
	
	You could leave the heater wiring alone, save for a series buck/
boost transformer driven by your small Variac. A 120v/12v 10a transformer
could be fed by a 1a Variac and a DPDT phase reversal switch, for a total
heat range in excess of 75% - 120%. If that doesn't work- Back to the
Drawing Board with it. The problem is elsewhere. You might be working with a
20% current overload at max settings. 
	
	Over a period of time you'd learn the difference between electrical
smoke and coffee roasting smoke. Deal with it. It might happen at continuous
full throttle...
	
	Cheers -RayO, aka Opa!
	
	Remember Sylvania's flashbulbs- Blue Dot for sure shot? Say Cheese!

33) From: raymanowen
You're right-
The single, self-contained 0 - 140v, 20a Variac is by far, easier to
implement than a Rube Goldberg Jury Rig. I know first hand that the fruits
of your efforts are Top Notch! Methinks that was the occasion of my getting
the Mazzer fire hydrant that grinds coffee!
I'm thinking of the commodious junk box I accumulated over the years- it's
all electrical stuff, including a few big vacuum tube filament transformers,
and much larger fork truck battery charger transformers, etc.
I used to have some spare 208v 3.95Kw Chromalox heating elements for a
client's screen printing ink curing dryer. I thought of building a fluid bed
roaster scaled up from the Fresh Roast, using a Kirby vacuum blower for air
flow. I ran out of "wherewithal" before I could order the 4 inch dia 48 inch
long Pyrex glass tube.
Without heater power, and a carpet tube mockup with the air blowing into two
tangential ports in the base, I achieved quite a cyclone in the carpet tube
"roasting chamber."  The dried green peas blew right out, into the chaff
collector/ cooling cyclone with the blower at full blow-(120v and waste gate
closed).
As a wintertime roaster using the basement fireplace flue, it Could work.
Being clumsy and butter-fingered, I thought twice about the Pyrex tube...
Not- Not! I resolved not to commit big bucks items to the junk box or worse
yet- the trash pile!
Far cheaper and half the power would be electric cooktop elements. Both they
and the Kirbys seem to run forever, so no longevity issues but the glass
chamber!
Cheers -RayO, aka Opa!
"The indisputable truth is that no coffee is fresh if it isn't fresh
roasted." - - Martin Diedrich

34) From: Scott Marquardt
On 3/16/07, raymanowen  wrote:
<Snip>
I'll have to dissent on that, myself. Without my lightweight Variac's
minute control over blower speed (boost to 140), I wouldn't have
anywhere near the level of control I do. I don't PID, so with manual
experience I've gotten to where, for a given bean (geez they vary --
with morphology, density, general shape, moisture content . . .) I can
tell when I'll need to tweak the Variac a hair to achieve something
two minutes later. A switch with even five or six levels would really
freak me out.
But anyone able to control heat, I'd think, might be able to live with a switch.
As for the e-bay popper Dave found, yeah, it's a good OEM. I picked
one up a while back too, and its slated to be modded using Douglas's
superb plans -- though, Doug, our exchange of many weeks ago may be a
bit stale in case you've refined things further. Have you URL'd all
that?
- S

35) From: Dave
Thanks Ray. That's an interesting idea. But I'd still have to get all the
parts besides my undersized variac, and it wouldn't be as straightforward to
use. I think I'm deciding to go ahead and get a beefier variac, that looks
like the simplest, and most flexible option.--
Dave
Some days...
It's just not worth chewing through the leather straps
On 3/16/07, raymanowen  wrote:
<Snip>


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