Remove the piezo transducer from its casing using pliers and a small knife. Be careful not to damage the transducer when doing so.
The piezo transducer works in the same fashion as a microphone; however, instead of picking up sound, it reads shock waves. This is the device that will respond when you hit your drum or drum pad.
Strip the ends of the two wires attached to the piezo transducer and solder them separately to the phone jack's wiring contacts. Your drum trigger can now be attached to a 1/4-inch instrument cable, which is a very common format used among musical devices.
Connect your drum trigger to the drum module using the 1/4-inch inputs. Any standard drum module will work; Roland, Alesis, Yamaha and a variety of other companies make and sell these for anywhere between $300 and $1000.
Glue the jar lid to the piezo transducer to increase the surface area of your drum trigger. If you are using the trigger with a drum kit, you will still be hitting the drum head, not the trigger itself.
Cut two pieces of poly foam rubber big enough to encase the jar lid. Drill or slice a small hole in one of the pieces big enough to fit the transducer's wires through. The rubber piece with the hole will be used for the bottom, the other for the top.
Pull the transducer's wiring through the hole in the bottom rubber piece. Glue around the outer edge of the top rubber piece and quickly press the jar lid to it, then press the bottom piece to it.
This has created a protective surface for your trigger. Placing the piezo transducer directly on a drum head can send too strong a signal and damage it; the shock wave can now travel through the foam and onto your trigger.
Place the trigger on your drum head, near the outer surface. This will prevent you from accidentally hitting the trigger with your drum stick. Attaching the trigger and a portion of the wiring to the rim of the drum with a small amount of duct tape should hold it in place.
Glue the piezo transducer to a small wood block, just big enough to snugly fit into the PVC pipe. This will create distance between the pipe itself and the transducer, again minimizing contact between the trigger and the surface being hit by the drum stick.
Push the trigger into the PVC piping. What you use will depend on how long your pipe is; if short enough, use your finger. If not, a pencil or screwdriver will suffice.
Glue the mouse pad around the outside of the PVC pipe. Padding the pipe will add some resistance to the "drum," creating a more realistic feel than simply hitting the pipe with a drum stick.
Close the PVC pipe off by drilling a hole into the cap, pushing the 1/4-inch insert on the phone jack through it and attaching the cap to the pipe.