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Modded popper sample roaster
I've been lurking around and commenting sparsely for the last month now, and I can't even begin to thank you all enough for how much I've been able to learn here. This is one of the most supportive, friendly forums I've ever seen.

So, after much experimentation and trial and error, I finally have what I want out of my popper. It was time to stuff all the bits and pieces into the original housing and complete the unit!

The things I wanted:
-Glass RC.
-Adjustable fan speed.
-At least some kind of simple adjustment of temperature. But not so far as to PID it.
-Ability to do 120g loads. This results in two days of coffee in our house.
-For all of this stuff to fit in the original base, so I can take it out of the cabinet, plug it in, and be roasting.

Here's the story:
I started with some no-name popper from wal-mart that was shaped like a basketball. My Dad no longer needed it, so I took it home and propmptly scorched my first batch of beans. It ran too hot. So I completely took it apart. The first things I did were remove the ridiculous basketball shape from the top, de-activate the thermal bi-metal switch, and put the fan on its own circuit.

After this, I could extend roasts by switching the heat element on and off during the roast, but that got old pretty quickly. During this time, I dove into every possible way I could think of to control the heat element for less than $10, infinity switches, big resistors and switch banks, finding a free variac, using a repeat cycle timer and a SSR, but none of these things worked out. Then I turned to controlling the fan speed instead.

So the final mods were, opening up the vents in the bottom of the RC, making bigger holes in the chassis, getting a dimmer circuit and transformer for the fan, and putting on a glass RC (hurricane lamp globe). I now had the problem of not enough heat at the end of a roast if I was doing 120g of green.

My heating circuit is two coils, like most poppers, in series with each other. In between them, a wire comes out to bring roughly 20v to the fan (originally). I simply wired a switch to either run power to both coils, or just the larger one. This now allows me that extra 40 degrees to finish out a dark roast, if I so desire. And it met the criteria of being cheap and simple. I think it's great.

So enough talking, here are the pictures from today's final assembly:
This is the heater coil with a power on/off switch (on the left) and the heat selector switch for the coils.
In the depths of project mode. Yes, my workspace is a board clamped to the deck railing. I'm not sure why one of my socks is out there.
Everything jammed into the base. I'm amazed it all fit! You can better see my dimmer circuit here. It originally came with a cheap 500k pot, but my fan barely used a 1/4 turn on it, so I switched it out for a 100k, and now I have nice even adjustment across the top 30% or so of my fan speed. I like it much better.
The base with all the goodies inside. Left to right is: Transformer backpack, fan power switch, fan speed knob, heat power switch, heat selector switch.

The transformer is so heavy, it tips backwards without the glass on it.
Everything together! And she works!

In action! I'm sure most of you know what a popper looks like, but I wanted to post it anyway :D
That is a novel assemblage of parts. I like your use of the lamp chimney.

PS: You must be very good with darts, otherwise you wouldn't hang your water hose so close to the board!
1 pound electric sample roaster, 3 pound direct-flame roaster, both handmade; modified Mazzer Mini grinder, LaSpaziale Vivaldi II automatic espresso machine. When the electricity goes out I make vacpot coffee from beans ground on my Zassenhaus hand grinder, and heat the water with a teakettle on the gas range.
Very cool. This rig will be able to keep up with any of the big boys in regards to control and quality of roasts. In looking over the assembly of parts into the base I'm reminded of some magic acts where a myriad of things are pulled out of one hat. Grin

Dan, maybe that's a dripper/mister hose?

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Yeah, that dartboard was here when we moved in. I thought it's location was a little odd too.

We don't have any darts though, so we throw knives at it.
Nice work getting everything into the base!

Popper roasters are a lot of fun and you learn about the roasting stages easily.
I would watch the fan speed and not get it too low with the heating element on full.

Running the fan full (heater off) for a while when you are done and letting the roaster cool off will extend the life of the heater too.


KKTO Roaster.
I like to look of your modded popper, it looks like a little robot, especially with the "transformer backpack" and "potentiometer arms"

Hopefully it roast's as good as it looks!
"Grind it like it did you some great injustice!"D.L.Clark
It's been roasting fantastic coffee recently! The ambient air temperature recently has been perfect for a nice 10 degree/min ish roast. I'd like to put a SSVR in it though to have real control of the heat.
Do you toggle the large and small heating elements on now to length the roast? Or just one on in the beginning and both on in the end?
"Grind it like it did you some great injustice!"D.L.Clark


Airhan wrote:

Do you toggle the large and small heating elements on now to length the roast? Or just one on in the beginning and both on in the end?

So unlike a Poppery II, my popper was set up with two coils in series that were both pretty warm. One had a resistance of about 14 ohms and the other about 4 (or something like that). When they're getting 120v in series, they are on what I call the LOW setting. Then I put all 120v through just the 14 ohm side and it heats that coil up a lot. That's my HIGH setting.

When I use those is sort of random. The HIGH setting has been handy on the really cold nights we've been having recently. I do most of my temp control with the fan speed.
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