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Low-cost Variac alternative for PopperyI fan speed boost (15V boost transformer)
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Chocolate_Dog_Kona
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Posted Fri Apr 13, 2007, 11:43am
Subject: Low-cost Variac alternative for PopperyI fan speed boost (15V boost transformer)
 

I know that a lot of us are still using the venerable Poppery I (and original Pumper) for our home-roasts.

Recently, a link was posted here for a REALLY good 15Vac boost transformer.  This, in combination with a cheap $6 fan speed control (similar to a light dimmer switch) available at any hardware store, works just as well as a high dollar variac to boost the voltage to the fan so you can roast more green beans per batch.

This link was buried in another thread, and I really think it is worthwhile to post it again, so here it is:

9$ Heavy-Duty Boost Transformer

You can order up to three without really changing the shipping cost if you select ground shipping (shipping is ~$10 for 1-3 units).

These transformers are really designed to boost line voltage in places such as old buildings.  I bought several, and they are VERY good, heavy-duty units.  They're rated for over 6A (~750 Watts), so they are more than capable of boosting the voltage to the Poppery I's fan without any worries of failure.  They're not small; they weigh about 5 lbs each, and are about 3" x 3" x 5", but they're made to last.

In my experience, with a good 120Vac line, I get right at 140Vac using the boost transformer.  Using one of these at full power for roasting, I can do 210g of green per roast without tilting the popper.  If I tilt the popper (I set the front on a ~1 high ledge), I can get about 235g of green per roast without having to shake or otherwise touch the roaster.  If you wanted to do a more hands-on roast, I imagine you could do slightly over 250g per roast.

The fan speed control comes in handy later in the roast once the beans are really moving.  I find that after about 350 degrees, I turn the fan down to about 120Vac for the rest of the roast.  My roasts are running about 13 minutes on average to a rolling 2nd crack (what I use for espresso) at an ambient temperature of 70 degrees.  Once Im done with the roast, I turn the heater off and crank the fan back up to full to cool the beans.  For the record, Im using a soup can (or in my case mixed vegetables) to extend my roast chamber and hold my temp measuring devices.

Hope this post can help a few people out!!!  I am sure happy with this set-up!

 
"Engineers don't idle well."
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PJK
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Posted Fri Apr 13, 2007, 1:01pm
Subject: Re: Low-cost Variac alternative for Poppery I fan speed boost
 

That transformer with a switch will almost get a USA Silvia up to Euro steaming power.  It is a bit on the small side - ~750 Watts vs. 1100 watts but for about 1 minute to get to steaming temp. it may be OK.

Phil

Chocolate_Dog_Kona Said:

I know that a lot of us are still using the venerable Poppery I (and original Pumper) for our home-roasts.

Recently, a link was posted here for a REALLY good 15Vac boost transformer.  This, in combination with a cheap $6 fan speed control (similar to a light dimmer switch) available at any hardware store, works just as well as a high dollar variac to boost the voltage to the fan so you can roast more green beans per batch.

This link was buried in another thread, and I really think it is worthwhile to post it again, so here it is:

9$ Heavy-Duty Boost Transformer

You can order up to three without really changing the shipping cost if you select ground shipping (shipping is ~$10 for 1-3 units).

These transformers are really designed to boost line voltage in places such as old buildings.  I bought several, and they are VERY good, heavy-duty units.  They're rated for over 6A (~750 Watts), so they are more than capable of boosting the voltage to the Poppery I's fan without any worries of failure.  They're not small; they weigh about 5 lbs each, and are about 3" x 3" x 5", but they're made to last.

In my experience, with a good 120Vac line, I get right at 140Vac using the boost transformer.  Using one of these at full power for roasting, I can do 210g of green per roast without tilting the popper.  If I tilt the popper (I set the front on a ~1 high ledge), I can get about 235g of green per roast without having to shake or otherwise touch the roaster.  If you wanted to do a more hands-on roast, I imagine you could do slightly over 250g per roast.

The fan speed control comes in handy later in the roast once the beans are really moving.  I find that after about 350 degrees, I turn the fan down to about 120Vac for the rest of the roast.  My roasts are running about 13 minutes on average to a rolling 2nd crack (what I use for espresso) at an ambient temperature of 70 degrees.  Once Im done with the roast, I turn the heater off and crank the fan back up to full to cool the beans.  For the record, Im using a soup can (or in my case mixed vegetables) to extend my roast chamber and hold my temp measuring devices.

Hope this post can help a few people out!!!  I am sure happy with this set-up!

Posted April 13, 2007 link


 
Philip J. Keleshian
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CraigA
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Posted Fri Apr 13, 2007, 2:27pm
Subject: Re:Lowcost Variac alternative for PopperyI fan speed boost 15V boost transformer
 

Chocolate_Dog_Kona Said:

Recently, a link was posted here for a REALLY good 15Vac boost transformer.  This, in combination with a cheap $6 fan speed control (similar to a light dimmer switch) available at any hardware store, works just as well as a high dollar variac to boost the voltage to the fan so you can roast more green beans per batch.
This link was buried in another thread, and I really think it is worthwhile to post it again, so here it is:

You can order up to three without really changing the shipping cost if you select ground shipping (shipping is ~$10 for 1-3 units).

Hope this post can help a few people out!!!  I am sure happy with this set-up!

Posted April 13, 2007 link

Awesome & excellent Jared!
Low cost alternatives like this & any & all useful helpful informative info is always needed & certainly appreciated, reposted 2, 3, whatever how many times! {;-D

 
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ronnie_b
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Posted Sat Apr 14, 2007, 5:02am
Subject: Re: Low-cost Variac alternative for PopperyI fan speed boost
 

I burned out 2 Radio Shack transformers boosting my P1 before I found that transformer at The Surplus Center and posting it here. Since it seems to be catching on now I ordered 2 for backups before they go out of stock. :-D
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dBndbit
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Posted Sat Apr 14, 2007, 5:06am
Subject: Re: Lowcost Variac alternative for PopperyI fan speed boost 15V boost transforme
 

Great Idea instead of an expensive variable transformer.

---snip, cut---

Sorry, I confused myself on this one!  I definitely need another cup of caffeine.  This boost transformer is a one-piece step-up.

 
Jim
http://www.ReeferDoor.com
  (Home-roasting and fair trade)
  Website is a work-in-progress.  I hate HTML.
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ronnie_b
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Posted Sat Apr 14, 2007, 3:22pm
Subject: Re: Lowcost Variac alternative for PopperyI fan speed boost 15V boost transforme
 

2 pieces, you still need a dimmer.
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Chocolate_Dog_Kona
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Joined: 21 Jun 2005
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Espresso: SD3C PID Rancilio Silvia!
Grinder: Solis Maestro Plus
Vac Pot: Bodum Press Pot
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Roaster: Boosted Poppery I
Posted Mon Apr 16, 2007, 10:44am
Subject: Re: Low-cost Variac alternative for PopperyI fan speed boost
 

All by itself, the transformer is a one piece step-up, and plenty usable.

However, with the addition of a $6 fan dimmer, you get all the control you need over the fan.  Through the dimmer, I measure up to 17v boost, and as low as 48v of buck (without load).  This gives you a range of 72v-137v to control the fan speed if desired, and at the low end the fan is barely moving.  I would say this set-up does just as good as any variac could.

Having said all that, I took some measurements this past weekend during a couple batches.

Under load (with the heating element on), I get about 15v of boost through the dimmer and 17v straight out of the transformer (due to internal losses in the dimmer).  However, because the heater is pulling so much current, line voltage tends to sag under the load.  I measure about 110 - 112 Vac on the line with the heater turned on.  Adding the 15v of boost from the transformer/dimmer only puts you at 127Vac, so you're really only boosting the fan motor 7v.  In practice, this does make a huge difference though, as a 210g batch of green coffee in 10 - 12 minutes is no trouble.  The motor should be able to handle the extra 7v without any problem.

Also, ronnie_b, nice find on the transformer!!!  I bought 3.  I burned up my first rat shack one right away, and haven't bothered with trying again since.  When I saw this transformer for such a good price, I couldn't resist!

 
"Engineers don't idle well."
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ronnie_b
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Posted Mon Apr 16, 2007, 4:07pm
Subject: Re: Low-cost Variac alternative for PopperyI fan speed boost
 

I can't measure the way you did, but I can roast 240 grams by tilting the roaster, 250 gram roasts are a little too uneven.
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kuban111
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Posted Fri Apr 20, 2007, 5:36am
Subject: Re: Low-cost Variac alternative for PopperyI fan speed boost
 

Great find and thanks for passing on the info.

Question ???

Im not using a Poppery 1. Im using a UFO/TO roaster would this work on this combination as well. I roast 12oz - 1lbs

This, in combination with a cheap $6 fan speed control (similar to a light dimmer switch) available at any hardware store, works just as well as a high dollar variac to boost the voltage to the fan so you can roast more green beans per batch.

Any more detail info on this light dimmer switch please.

Do I connect in series (Voltage booster, Light dimmer switch, UFO/TO)  

Ive been having a lot of fun & great success home roasting with my UFO/TO
Sure would appreciate any new info that would held me continue learning.

Thank you,

 
What ever machine you choose...Enjoy and have fun...Learn and share the experience.
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PJK
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PJK
Joined: 21 Jan 2002
Posts: 2,319
Location: Shingle Springs CA
Expertise: I love coffee

Espresso: Rancillo Silvia, Tonic...
Grinder: Modified Rocky, Elma side...
Vac Pot: Old Silex
Drip: Melitta BCM 4  +Some old...
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Posted Fri Apr 20, 2007, 8:55am
Subject: Re: Low-cost Variac alternative for PopperyI fan speed boost
 

Hi Michael,

I am not sure what you are going to do with the transformer.  If you are controlling the heating element you will probably need a bigger transformer and a heavy duty dimmer.  If you are controling the motor this setup should be fine.

An argument can be made for either putting the transformer before the dimmer or the dimmer before the transformer.  The argument for putting the dimmer first is that it will be operating at its design voltage.  I believe that the triacs used in the dimmers are rated for 400 volts so I wouldn't worry much about this.

I would put the transformer first since any lack of symety in the dimmer could put DC into the transformer primary.  This may cause core saturation and in turn overheating.

A good illustration of this transformer / dimmer setup by the "frankenformer" guy himself is here:

http://mdmint.home.comcast.net/coffee/fancontrolproto.htm

Phil



kuban111 Said:

Great find and thanks for passing on the info.

Question ???

Im not using a Poppery 1. Im using a UFO/TO roaster would this work on this combination as well. I roast 12oz - 1lbs

This, in combination with a cheap $6 fan speed control (similar to a light dimmer switch) available at any hardware store, works just as well as a high dollar variac to boost the voltage to the fan so you can roast more green beans per batch.

Any more detail info on this light dimmer switch please.

Do I connect in series (Voltage booster, Light dimmer switch, UFO/TO)  

Ive been having a lot of fun & great success home roasting with my UFO/TO
Sure would appreciate any new info that would held me continue learning.

Thank you,

Posted April 20, 2007 link


 
Philip J. Keleshian
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