What is a switch?
An electrical switch is use to turn power on or off to a device. This occurs when the switch opens or closes a set of contacts within the switch. The contacts act as a bridge to allow electricity to pass through the switch.
Terminology you will see, hear and need to know…
Open: The contact points of the switch are not touching thus no power can pass through.
Closed: The contact points of the switch are touching thus power can pass through.
Normally Open (N.O.): With the switch in the default position the contact points for the switch will be open, thus no power can pass through. You have to move the switch to the other position to close the contact points.
Normally Closed (N.C.): With the switch in the default position the contact points for the switch will be closed, thus power can pass through. You have to move the switch to the other position to open the contact points.
Momentary: The switch will only change the contact position as long as the switch is held in. Once it is release it will go back to its default position.
Maintained: The switch stays in that position when pressed and released.
Poles: Describes the number of contact sets a switch has.
Throw: How many positions the switch lever has to control the contact points.
Load Rating: How much current can flow through the switch safely. You can figure out the load by dividing watts by voltage.
VAC: Volts Alternating Current. Such as the power coming from an outlet in your home.
VDC: Volts Direct Current. Your Power supply produces this, other sources are automobiles or batteries.
Switches come in all shapes and sizes, but they basically all work the same way. When a lever or button is moved in the opposite direction it will either open or close a set of contacts. This is how the power is controlled. These contacts are located within the switch itself. Some switches have more than one set of contacts and they will allow you to control one or more devices at the same time.