First of all, the video of my switch working can be found here. Thanks to Mariko for filming the clip. My switch works as follows. A sheet of flexible material is suspended between two level structures. This spanning piece has a wire, soldered to a piece of copper tape fixed to the bottom. Underneath this there is another structure, at a lower level than the two holding the spanning piece, which has another wire/copper combo fixed to it. When the wire on the lower structure and the flexible span meet, they complete the circuit, making the lights turn on. Instead of pressing on the flexible sheet with my body, I instead placed a bucket on top of the spanning sheet and filled it up with water until the sheet flexed enough to complete the circuit. In practice, the two structures that held the spanning sheet were two tables in the IM lab. The third, lower structure was an adjustable height chair, and the spanning piece was a sheet of translucent plastic (covered on both sides with some paper covering) I found at one end of the lab. Below are a few close-up pictures illustrating different parts of the setup. The first shows me pressing down on the plastic spanning piece, completing the circuit. The second shows the underside of the plastic spanning piece, and the chair mounted part of the circuit. The third shows off my sick nasty soldering skills. The fourth is the circuit diagram for this project I made using this Python module.
