First I tried just bypassing the thermostat on a Poppery II, and that worked very well, but in order to use the fan independently of the heaters, it was necessary to add a transformer and some other parts. I found it helpful to make some diagrams of the Poppery II circuit in its unmodified form to get a picture of how to go about modifying it.
Here are scanned images of the heater section of a tan and black Poppery II, and here is a PDF file that traces the circuit seen in the scanned images.
This diagram, in PDF format, shows the original and modified wiring of a tan and black Poppery II. The only part of the modification that involves the heater section is bypassing the thermostat, and possibly the thermal fuse. The rest of the modifications inside the popper involve only the three wires that are attached to the heater section and the wires attaching to the motor. The power cord attaches to the control box. Originally I left the thermal fuse intact. For poppers on which I only bypassed the thermostat, I have been replacing the 213- and 216-degree Celsius thermal fuses with 228-degree fuses from Radio Shack. However, manipulating the fan speed can cause the temperature around the fuse to be high enough to blow the fuse, so I bypassed the thermal fuse in the popper I modified to use with the control box. Keep in mind that this is the last line if defense against a fire or meltdown, but if you do this modification, you should be attentive enough during roasting to notice if a problem is developing...
Salton's popcorn popper is similar to the Poppery II, and much easier to open up and modify. The wires inside the Salton are different colors from the Poppery II. If modifying the Salton, it is necessary to change the wire colors on the diagram as follows (some of the connections are also made in slightly different places):
Poppery II -> Salton
black -> blue
red -> black
white -> red
light blue -> white
Here are the parts I used and where I bought them:
1 25.2 volt 2 amp transformer (Radio Shack)
1 600 Watt dimmer (hardware store)
3 illuminated 10 amp (at 120V AC) switches (Radio Shack)
2 DIN jacks (Radio Shack)
2 DIN plugs (Radio Shack)
1 plastic box (Radio Shack)
nuts and bolts (hardware store)
wire (cut up 13-amp extension cord) (Radio Shack)
solder (Radio Shack)
heat shrink tubing (Radio Shack)
Some of these things are optional, such as the DIN plugs and the master switch. They don't actually increase performance; they are conveniences. And I have been informed that they might be potentially hazardous. They are bottlenecks in the circuit, and there is a lot of current involved. So if you don't need to switch poppers and don't mind unplugging the unit to turn it off (or turning everything off individually), it is safer and easier to to leave these things out. Most of my soldering effort was spent on the DIN plugs and jacks, because the wire I used is very thick, considering what the plugs are intended for: data, not house current.
Here are some pictures of my control box, a modified popper, and the cable used to connect them.
Obligatory Disclaimer: If you intend to try this or anything similar at home, do so at your own risk. Be aware of the dangers of electrical shock and fire. Neither I nor any of the people or companies mentioned on this page are to be held responsible for any harm that may result from attempting to duplicate what is described here.
E-mail me at mielke@ling.ohio-state.edu.
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