Chandelier lit well Chandelier under black light
Falling Chandelier

When a visitor steps through the front door, a 16" chandelier in the foyer falls about a foot making a loud thump, and then rocks violently back and forth. The lights on the chandelier flicker. It then slowly raises and resets itself.

This is a totally automatic effect and the single most mechanically complex. Despite the complexity, it was one of the most reliable. It had to be because it can't be worked on during Halloween night: it's screwed into an overhead light fixture box. The box containing all the control electronics, three motors, three sensors, two 12 volt power supplies, flicker sequencer, and cord take-up mechanism is only 3" by 5" by 9". It's made almost entirely of discarded surplus parts, some taken from broken dollar bill changers recovered from a dumpster behind a commercial electronics repair shop!

A mat switch under the carpet made of poster board and aluminum foil triggers it. Another mat under the chandelier, which we call the "not pad," prevents the chandelier from falling when someone is standing under it. The cord holding the chandelier is held by a ratchet-like catch attached to a lever. When someone steps on the trigger mat, a motor turns an off-center wheel which pushes the lever to the side and releases the chandelier. We made this motor continue rotating until it's out of the way by simply adding a couple of capacitors in parallel. The chandelier falls and hits bottom, and its lights are made to flicker by a motor-driven rotor/brush setup. A motor then winds the chandelier up until it hits the top sensor and an epoxy bead on the cord passes the catch. The motor then reverses and lets out the cord which is taken up sideways by a spring around two ball-bearing turn posts until another sensor is hit. This take-up mechanism allows the chandelier to fall fast and free when it's released from the catch.

When the chandelier falls, it's made to rock from side to side by having the cord attached to a lever spring which is attached to the chandelier. The spring bends when the chandelier hits bottom causing it to move sideways, but allows it to hang level normally.

Chandelier mechanism The chandelier makes a deep thumping sound when it hits bottom using the whole ceiling as a sounding board. It has about 2 pounds of lead weights in the top. The chandelier is made of cardboard so if it were to hit someone, it would just crumple rather than transferring the force of the weights to the person's head. In case the cord which is wound up by the motor breaks, there's a second safety cord attached to the chandelier which normally doesn't bear any weight. This cord first proved it's necessity recently when the spring broke while we were demonstrating the chandelier to a friend.

We discovered a design flaw after the first or second year: if someone walked under the chandelier while the motor was raising it, there was insufficient power to click down the relay which responds to the "not pad." So if someone were also standing on the trigger mat, the chandelier would fall as soon as it reached the top and let out its cord even though someone was standing on the "not pad." We fixed this by adding a second 12 volt power supply.

I have three versions of a stereographic 3D photo of the chandelier mechanism.



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