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Seeking variac opinions/advice for Poppery I
CoffeeFishingBeer
I have a moderately modded Poppery I:

-Fan and heat circuits seperate
-Enlarged the fan holes to get more air flow
-Removed the "fin" so I can just stick a soup can in it
-Drilled a hole through the for a thermometer

Generally, my roasts have gone way too fast (6 minutes or less); my Poppery seems quite hot. Expanding the air holes to the fan seems to have helped more than my first approach, which was a router speed controller from Harbor Freight; after a few roasts, the magic smoke escaped from it in the form of the plastic around its outlet receptacle melting.

I did some roasts today (ambient temp 100, it was a hot one in San Jose), and reached the begnning of second crack in 7 minutes.

My fan slows down *a lot* when I plug the heat circuit in and I'm thinking I may need a variac on one or both of those. I took some readings with my multimeter and got these numbers:

Popper not plugged in:

116 V at outlet
116 V at end of 20 foot 14-gauge extension cord

Fan circuit plugged in:

Voltage jumps around very rapidly from 106 - 130; average is probably still around 116

Heater circuit plugged in:

Voltage smoothes out and drops about 10 volts, to average 106

Today's roasts:

Ambient temp: 100 F
First crack started 4:15 into the roast @ 400 degrees.
Second crack started at 6:45 - 7:00 @ 450 degrees

There wasn't a lot of audible cracking in first crack, but maybe this is normal for the bean I roasted (first tme with this one, Sumatra Lintong Tano Batak, so I don't know), so I can't really say when FC ended.

I'd prefer a longer roast time, but that's probably hard to get when the ambient temp is so high, but I really feel like I need higher fan speed; I have to tilt the popper way over and hold it by hand to get good air flow even with only a 3.2 ounce load. Thus, I feel lke I probably need a variac on the fan side to boost it back up to 116 or maybe even 120. Do you think I might also need to use one to reduce the voltage on the heat circuit, or should I just get a much heavier duty router speed controller than the one I wrecked?

Thanks!!
 
yamhill
I'm not sure that you'd get much benefit from a voltage boast on the blower side. It sounds to me like your initial attempts to control the heat with the router control were in the right direction. I'm running a harbor freight control on the heater side of my 72000 pumper and a dimmer control for the fan speed control. I've run maybe 25 roasts without problem so far. I believe the guts of my 72000 and your poppery I are very similar. My experience with the 72000 is that it cranks out a lot of heat. I can't imagine roasting success without heat control. On the other hand, my 72000 will move 130 grams cold - without any any modification to the fins.

With bean movement as you described, it sounds like you've already pressed the limited of slowing the roast with a larger load. Less heat seems like the best way to go. I don't think that 5-10 volts more line voltage is going to give you much more air.


John
 
CoffeeFishingBeer
Thanks for that informtion, Yamhill.

Just to clarify something that looks less clear to me when re-readin my own words, with the heat and fan both on, line voltage is 106, and the fan slows waaay down when I plug in the heat circuit. I'm thinking of using a variac to push the fan speed up to 125, which would be a 19V boost over what I get now with the heat on.

FWIW, it also just crossed my mind that I have a 100 foot extension cord. The next time I roast, I'll put that on the heat circuit to see what improvement I can get from that. If that is helpful enough, I may just go with that on the heat side. If I need more, I can get a better speed controller than the Harbor Freight one I fried :-)

I can see there's gonna be a PID in my future at some point, which in turn will be a way point on the road to a Hottop, which will probably be a waypoint on the road to a commercial roaster :-)
 
oldgearhead
A couple of varible-autotransformer things to think about.
1) The new inexpensive ones from China only provide a 10% boost. Therefore, your 106V would become 117V, tops.
2) The Staco brand units go up to 17% boost, at a much higher cost.
3) The $180 you invest in the varible-autotransformer will pay for a good part of a bigger roaster.
4) If you buy a varible-autotransformer are you going to get one big enough (20A) to use with your Hottop, later? In this case, cost might exceed $200.00..
No oil on my beans...
 
JackH
You can get the fan plugged into a wall outlet directly and get full fan speed to move the beans. Then use your long extension cord on the heater alone to reduce the voltage to the heater and hopefully increase the roast time.

I was assuming that you had both heater and fan plugged into the long extension.
 
JackH
I have a poppery II and used an AC dimmer on the fan's transformer to vary the fan speed instead of using a variac. The variac would be more useful on the heater and you could use one of the Harbor Freight units instead.
 
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