How to choose a right switch for your appliance?

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How to choose a right switch for your appliance?

There are three important features to consider when choosing a switch:

· Contacts (e.g. single pole, double throw)

· Ratings (maximum voltage and current)

· Method of Operation (toggle, slide, key etc.)

Switch Contacts
Several terms are used to describe switch contacts:

· Pole - Number of switch contact sets.

· Throw - Number of conducting positions, single or double.

· Way - Number of conducting positions, three or more.

· Momentary - Switch returns to its normal position when released.

· Open - Off position, contacts not conducting.

· Closed - On position, contacts conducting, there may be several on positions.

· Size : The length,height and width for the rocker switch

ON-OFF
Single Pole, Single Throw = SPST

    A simple on-off switch.
    This type can be used to switch the power supply to a circuit.
    When used with mains electricity this type of switch must be in the live wire, but it is better to use a DPST switch to isolate both live and neutral.

(ON)-OFF
Push-to-make = SPST Momentary on

    A push-to-make switch returns to its normally open (off) position when you release the button, this is shown by the brackets around ON
    This is the standard doorbell switch.

ON-(OFF)
Push-to-break = SPST Momentary off

    A push-to-break switch returns to its normally closed (on) position when you release the button.

ON-ON
Single Pole, Double Throw = SPDT

    This switch can be on in both positions, switching on a separate device in each case.
    It is often called a changeover switch.
        For example, a SPDT switch can be used to switch on a red lamp in one position and a green lamp in the other position.
    A SPDT toggle switch may be used as a simple on-off switch by connecting to COM and one of the A or B terminals
    A and B are interchangeable so switches are usually not labeled.

ON-OFF-ON
SPDT Centre Off

    A special version of the standard SPDT switch.
    It has a third switching position in the center which is off.
    Momentary (ON)-OFF-(ON) versions are also available where the switch returns to the central off position when released.

Dual ON-OFF
Double Pole, Single Throw = DPST

    A pair of on-off switches which operate together
    A DPST switch is often used to switch mains electricity because it can isolate both the live and neutral connections

Dual ON-ON
Double Pole, Double Throw = DPDT

    A pair of on-on switches which operate together
    A DPDT switch can be wired up as a reversing switch for a motor

Dual ON-OFF-ON
DPDT Center Off

    A special version of the standard DPDT switch.
    It has a third switching position in the center, which is off.
    This can be very useful for motor control because you have forward, off and reverse positions.
    Momentary (ON)-OFF-(ON) versions are also available where the switch returns to the central off position when released.

Size :
The standard size is 9.2*13.6mm, 13*19.2mm ,11*30mm ,22*28MM,22*30MM,

∅12mm,∅15,∅20,∅22,∅25, so on