MAKE - Mercury Switch Doorbell ~ Dons Deals

A Very Cool Door Bell!:)

Don

By Nick Normal
Posted February 27th, 2013
Category Electronics

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I have held on to this custom doorbell switch and re-installed it in various places for nearly a decade now. It was originally fabricated by engineer and artist Brian Matthews, aka Pirate Brian. You can see more of his work here. It is a fantastic contraption and includes an interesting example of a mercury switch, a traditional type of tilt switch now somewhat harder to find owing to our improved understanding of the toxicity of mercury.

An animated GIF of the switch in motion. The glass container has been wrapped with tape where the metal clamps hold the container, to reduce the possibility of the glass cracking at either of those points.

Though toxic, mercury has some unique attributes that make it intriguing for switch applications. Like all other metals, it is a conductor of electricity; unlike all other (pure) metals, it is a liquid at room temperature. In the image above, you can see the liquid mercury housed inside a sealed glass container, and copper ring terminals (background) on the ends of the switch wires, which are encased in ceramic insulators connected to the container’s two contacts.

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http://blog.makezine.com/2013/02/27/mercury-switch-doorbell/