This is how I built a coffin that has sound, fog, lights, and a motion activated lid. To watch a video see my photobucket site.
Step 1: Building the coffin
I started by cutting a piece of plywood to the shape and size of the bottom of the coffin. From there I built a simple frame out of 2x4s. I attached 1x4s to make the exterior of the coffin.
Step 2: Building the coffin lid
I started in the center and worked my way out. I made four cross beams to hold the 1x4s in place. After the entire coffin was covered by the 1x4s I cut it to shape with my table saw.
Step 3: Adding sound, light and fog.
I decided to use a power strip for electricity so I mounted it to one of the 2x4s. Then I mounted the fixture that held my two lights and plugged it in the strip. Ater that I mounted the PC speakers in the coffin and plugged them in. The audio was provided by a cd player. All the way to the foot of the coffin I mounted my fog machine which was hooked to a timer.
Step 4: Adding pnuematics
I used a motion detector to activate my screen door closer air cylinder. To send air to the cylinder I used a washing machine solenoid. To add more movement I activated the solenoid with a 12volt car flasher and a relay.
Step 5: Weather the wood
I used watered down grey paint and black spray paint to weather the wood on the coffin.