Coffee Roasting with Modified Popcorn Poppers
F e l i x  D i a l
f e l i x d i a l  at cox dot net

Update 20 Sept 2003: I've added photos of the inside of the 1400W WearEver Pumper that I modified.
Update 19 Nov 2003: I've modified and have begun roasting with a 1500W WestBend Poppery1. Look Below ...
Update 04 Sept 2004: A lot has changed since Nov 2003. Not long after the last updated I started using a Variac on the heat circuit. There's more info below. Also, I've PID'd my setup ... click here.

I guess I should start off with a disclaimer.  Everyone seems to have one of these.


The following photos and text on this web page are for informational purposes only.  If you choose to open up your popper, you might ruin your popper, get shocked, burn off your fingers, burn down your house, burn down your neighborhood, AND, ruin all of your tastebuds rendering any coffee you roast, grind, and brew, to taste like swamp water.

1250Watt WearEver Pumper

Figure 1 is a photo of one of my 1250Watt WearEver Pumpers.  It has been modified to roast coffee via a control station that utilizes two dimmers to moderate the fan (DC fan motor) and the heat generated by popcorn poppers. Please see Figure 0 below.

Figure 0: The control station has been updated.
Please see section below on the 1400Watt Pumper.

For more info on this control station, click here. The 1250Watt WearEver Pumpers and the 1200Watt WestBend Poppery II's have the same design. The color of the wires might differ as well as the housing and the size of the roasting chambers, but the innards are essentially the same.  Please see Dick Hegg's web site for photos of the insides of a later model 1200Watt WestBend Poppery II.

Figure 1

Note the two cords and the color of tape on each cord.  The cord with the blue tape is for the fan and the cord with the red tape is for the heat.  Each cord plugs into the appropriate receptacle in the control station.

Figure 2

Figure 2 is a photo of the inside of the pumper and the wire connections that I made from the two cords to the fan motor and heating elements.

Figure 3

Figure 3 is a closeup of the connections to the fan motor.

Figure 4

Figure 4 shows the heating element and the connections to the cord with the red tape.

Compare figure 4 to the photos of the heater section of Tan and Black Poppery II at Jeff Mielke's  web site. Jeff Mielke has a web page discussing the modifications that he's made to popcorn poppers to use as coffee roasters.  He has also created his own custom control box. There are photos and circuit drawings of this control box as well as circuit drawings of the popper's unmodified heater section. The color of the wires in figure 4 don't completely match the color of the wires in this circuit drawing, but they are easily converted:

Figure 4 Wire Colors    Circuit Drawing Wire Colors
        White                                         Black
        Red                                            Red
        Black                                         White
Before I rewire the heater section of any popcorn popper, I always disassemble the heater section and follow the wires to make sure that I'm connecting the correct wires together. I do not rely on wire colors. In figure 4, I connected the white wire on the heater section to one of the wires on the cord with the red tape. The white wire in figure 4 is the wire that is directly connected to the thermal fuse. I connected the red and black wires to the second wire on the cord with the red tape.

1400Watt WearEver Pumper

Dick Hegg's excellent web site has photos of the insides of a WestBend Poppery 1.

Figure 1

Figure 1 shows the modified 1400Watt Pumper. Just like the 1250Watt Pumper, I split the heat and fan circuits with this popper.  I removed the On-Off switch and use the opening for the two cords. The fan motor with this pumper runs on AC.  However, I still use a transformer to boost the voltage to the fan motor.  Thank you Mike McGinness!

Figure 2
There are three screws that fasten the white plastic top in Figure 1 to the yellow plastic bottom. Figure 2 shows the top of the roast chamber.  The two white wires are connected to the thermostat. I've done only two roasts so far with this popper, and in both cases, had no problems reaching final temperature of 450°.  I'll bypass the thermostat later if it becomes an issue. To do this, all I would have to do is remove the two white wires from the thermostat and connect them together. The little skinny black wire is connected to the fan motor.

Update 19 Nov 2003:  Maybe two or three roasts after I wrote this section, I went ahead and bypassed the thermostat.  I could still reach final temps of 450°, but I was noticing that I was having a difficult time keeping temperatures increasing at the appropriate rate from about 420° on.

Figure 3
The roast chamber in Figure 2 lifts out of the yellow plastic container. Figure 3 shows the original wire connections.  If you can, trace the skinny black wires connected to the fan motor to see where they end up.

Figure 4

Figure 4 is the top of the fan motor.  Again, it runs on AC.

Figure 5

Here's a nice close-up of the fan motor. The little silver barrel wrapped in plastic and held in place with the gold colored tab is, I'm pretty certain, the thermal fuse. Maybe there's enough info here to tell me what year this popper was produced?

Figure 6
Figure 4 shows only 2 of the three screws holding the roast chamber together. Removing all three of these screws allows access to the fan blades, the bottom of the roast chamber (note the bump found on all WearEver Pumpers), and the heating coil. See Figure 6.

Figure 7

The heating coil, like the Poppery1, is mounted in ceramic.

Figure 8

Figure 8 shows the inside of this pumper with the modified wiring. Again, I just split the heating coil from the fan motor.

Figure 1

Here once again is figure 1 to show us the final result.

Figure 9

Figure 9 is a crummy photo (will update soon) of the control station.  I've added a second transformer, another 600Watt dimmer and another receptacle. It's heavier now.

If you have a 1400Watt Pumper that you modified to roast more than 170 grams (which is about 1 cup or about 6 oz volume) of green beans, please let me know what you did.  I would love to be able to make this pumper roast about 8 oz at a time.  This pumper was used when I bought it, and with normal wear and tear on the fan motor, it might not be possible for this pumper to roast 8oz. However, I still welcome suggestions.

I lucked into a mint, never been used 1400Watt pumper that's sitting in its original box in my garage, but I'm reluctant to start hacking it.  I'm more inclined to start tweaking the Poppery1 that I also own.


1500Watt WestBend Poppery 1
Again, please see Dick Hegg's excellent web site for more information on the WestBend Poppery 1.

Figure 1
Figure 1 is a photo of the Poppery1 (WBP1) that I currently use for roasting.  I have two spare WBP1s, and I found all three in local thrift stores.  Like the other popcorn poppers that I use, I disabled the thermostat and split the fan and heater circuits on the WBP1 in figure 1.  But I've also done some other mods.

Figure 2

Figure 2 shows the wire connections.  Again, I split the heater and fan circuits.  I replaced the stock cord with two higher gauge computer power supply cords.
Figure 3
I had a difficult time taking a photo of the fan motor. Figure 3 is the best of the bunch.  Note that this fan motor is manufactured by the same company that manufactured the fan motor in the 1400W Pumper (WEP1) above.  The fan in figure 3 is rated at 0.84A while the previous fan motor for the WEP1 is rated at 0.95A.  However, I can still roast more with this modified WBP1 than the WEP1. Using my control station with the voltage boosted fan circuit, with a little shaking and tilting at the begining, my WBP1 can roast about 7.5oz or 212grams while my WEP1 can roast about 6oz or 170grams.
Figure 3
I've removed the thermostat and replaced the mechanism with, of all things, a paper clip. The thermostat is in figure 3 just below the two metal leads.  Click here to view the thermostat in its original position.

Update 08 January 2004: The paper clip was not a good solution. Look closely at Figure 3 and at the previous link, you'll see a little tiny screw that is used to adjust the temperature threshold.  To disable the thermostat, I removed that little screw.  There is also small porcelain cylinder (I think porcelain) that is part of this mechanism and is held in place by that tiny screw. The thermostat for the 1400W Pumper discussed above has the same mechanism.


Figure 4a and 4b

Figures 4a and 4b are photos of the bottom of the WBP1. I did a few experiments with the plastic and metal bottom plates and found that there is better bean movement when both plastic and metal bottom plates were not attached to the WBP1.   I removed the metal plate and cut a hole into the plastic bottom. The metal screen is from a small colander and keeps chaff and other debris out of the WBP1.  I place the WBP1 on a cooling rack (see figure 1 above) to also increase air flow.  I suppose it helps, but I never really tested this.  Note the color coded cords in figures 4a and 4b.
Figure 5

I used wire clippers, a file, and finally a Dremmel tool to remove the entire bakelite fin in the roast chamber.  See figure 5. I read somewhere that removing the fin improves bean movement (makes sense).  An added benefit is that the the glass chimney that I use with my pumpers now fits into the WBP1 roasting chamber.

Figure 6
Figure 6 was taken looking down through the glass chimney towards the bottom of the roasting chamber.  I notched the bakelite (see figure 5) so that I could place a thermocouple between the glass chimney and the bakelite.  Note the oil buildup on the thermocouple's sheathing.

Figure 7
The WBP1 and the WEP1 take about 4-5 minutes to cool from 450° to about 100°.  I instead use the fan and frying basket in figure 7 to cool just roasted beans. The fan is the Honeywell HT804H (~$8).  The frying basked I purchased from a restaurant supply store (~$12). With this setup, it takes about 1-2 minutes to cool 7-8oz of beans from 450° to about ambient temperature.

Update 04 September 2004: Sometime in December of 2003 I started using the variac below. I won it on eBay for $32 with $16 s&h. It's quite heavy. I don't know when it was manufactured but it's a "Powerstat 3PN116C". It works really well on the heater circuit. With the 1500W dimmer, small nudges on the dial often caused undesirably big temperature changes. With the variac, the dial isn't so sensitive. Also, if I'm roasting big loads in the heavier poppers, it's easier to follow a 30°F/min ramp because the variac can exceed 120V output. The 1500W dimmer can't do this.

Figure 8

click here to view my coffee links page

last modified: 04 September 2004