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Description
2 Pin Push Button Switch in Karachi
What is a Switch
A switch is a component which controls the open-ness or closed-ness of an electric circuit. They allow control over current flow in a circuit (without having to actually get in there and manually cut or splice the wires). Switches are critical components in any circuit which requires user interaction or control.
A switch can only exist in one of two states: open or closed. In the?off?state, a switch looks like an open gap in the circuit. This, in effect, looks like an?open circuit, preventing current from flowing.
In the on state, a switch acts just like a piece of perfectly-conducting wire. A short. This closes the circuit, turning the system on and allowing current to flow unimpeded through the rest of the system.
Defining Characteristics
Actuation Method
In order to change from one state to another, a switch must be actuated. That is, some sort of physical action must be performed to flip the switch’s state. The actuation-method of a switch is one of its more defining characteristics.
Some examples of switch types.?Push button,?rocker,?slide, and?magnetic.
Switch actuation can come from pushing, sliding, rocking, rotating, throwing, pulling, key-turning, heating, magnetizing, kicking, snapping, licking,?any physical interaction which can cause the mechanical linkages inside the switch to come into, or go out of, contact.
Momentary vs. Maintained
All switches fall into one of two distinct categories: momentary or maintained.
Maintained switches like the light switches on your wall stay in one state until actuated into a new one, and then remain in that state until acted upon once again. These switches might also be called toggle or ON/OFF switches.
Momentary switches only remain active as long as they re actuated. If they re not being actuated, they remain in their off state. You ve probably got a momentary switch (or 50) right in front of you keys on a keyboard!
Semantic alert! Most of the switches we refer to as ?buttons? fall in the momentary category. Activating a button usually means pressing down on it in some manner, which just feels like a momentary control. There are such things as a maintained button, but for this tutorial when we slip and talk about buttons, think momentary push-down switch.
Mounting Style
As with most components, the termination style of a switch always comes down to either surface mount (SMD) or through-hole (PTH). Through-hole switches are usually larger in size. Some might be designed to fit in a?breadboard?for easy prototyping.
SMD switches are smaller than their PTH counterparts. They sit flat, on top of a PCB. SMD switches usually require a gentle touch, they?re not built to sustain as much switching force as a through-hole switch.
The?Arduino Pro?has two SMD switches: a?slide switch?for power control, and a?push-button?for reset control.
Panel mount switches ? designed to sit outside an enclosure ? are a popular mounting style as well. It?s hard to flip a switch when it?s hidden inside an enclosure. Panel mount switches come in all sorts of termination styles: PTH, SMD, or heavy-duty solder lugs for soldering to wires.
Poles and Throws, Open and Closed
A switch must have at least two terminals, one for the current to (potentially) go in, another to (potentially) come out. That only describes the simplest version of a switch though.
More often than not, a switch has more than two pins. So how do all of those terminals line up with the internal workings of the switch? This is where knowing how many poles and throws a switch has is essential.
The number of?poles*?on a switch defines how many separate circuits the switch can control. So a switch with one pole, can only influence one single circuit. A four-pole switch can separately control four different circuits.
A switch?s?throw-count defines how many positions each of the switch?s poles can be connected to. For example, if a switch has two throws, each circuit (pole) in the switch can be connected to one of two terminals.
Knowing how many poles and throws a switch has, it can be more specifically classified. Commonly you?ll see switches defined as ?single-pole, single-throw?, ?single-pole, double-throw?, ?double-pole, double-throw?, which are more often abbreviated down to SPST, SPDT, and DPDT, respectively.