Switches

Switch Basics

A switch is often to turn something on or off. In the simplest case it is just a wire that is connected or not. Unplugging an appliance is one way to switch it off. A switch is usually a mechanical device where some sort of handle connects or disconnects conductors inside the switch. Another way of thinking of a switch is that it is like a resistor that sometimes has infinite resistance and sometimes has 0 resistance. A computer keyboard is made of a large number of switches. Some switches stay in the on or off position, others only stay on or off while you switch them, these are called momentary switches. A light switch is normally not momentary, a doorbell switch normally is momentary.

Uses:

• On Off control
• Range change, as in a meter
• Data input

Links

• Switch From Wikipedia,the free encyclopedia ( inc. Schematic and Picture )
• Switches

Relays

A Relay is a switch that is turned on and off by an electro-magnet ( actually there are new forms that do not use an electro-magnet ). Like other switching devices it allows a small amount of power to control a large amount of power. A nice feature of relays is that there is no electrical connection between the control circuit and the circuit connected to the switch. ( this is called electrical isolation ). They are often used to let low power digital circuits control normal 110v power in a home.

Uses:

• Turn on several circuits with one control circuit.
• Control motors.
• Isolate a low voltage circuit from power line.
• Reverse current ( double pole double throw relay )

Links

• Relay From Wikipedia, the free encyclopedia
• Controlling Big, Mean, Devices
• Relays

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varc4tb Switch Terminology _P_T - SPST - SPDT - DPST - DPDT - 3PDT - ....

Relays - Use these to control large power sources that a microcontroller cannot do alone