Tilt Switches

Tilt switches are used to detect a change in angle.

The basic design of a tilt switch is a mercury switches. A mercury switch is made up of two electrical wires and a ball of mercury positioned inside a contained cylinder.

Mercury is a liquid metal - it flows like water, but it conducts electricity like a solid metal. In a mercury switch, one wire (wire A) goes all the way across the bottom of the cylinder, while the other wire (wire B) extends only part way from one side. The mercury is always in contact with wire A, but it may break contact with wire B.

When the cylinder tilts one way, the mercury shifts so that it comes into contact with wire B. This closes the circuit running through the mercury switch. When the cylinder tilts the other way, the mercury rolls away from the second wire, opening the circuit.