In the past cars weren't as complex as today but they also weren't as efficient, convenient, and safe as today's cars. This is largely thanks to the closed circuit inside cars that powers every electrical system and component. This circuit has grown bigger and bigger with now there being more electrical systems in cars than ever before.
Batteries and fuses may be the essential components of your car's circuit but there's the AC, power windows, power mirrors, electronically adjusted seats, heated seats, heated steering wheel - the list goes on. But all of these components give you something to control via electrical signals. Instead of levers, we use switches that work according to the function we want to perform.
Types of Switches by Design
Push-Button
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Depending on what you want to do, there will be a different switch in use. For example, push-button switches are going to be used in places where you need to use something like a horn. The design of these auto electrical switches makes them operate when pushed in and only then.
Momentary-Push Button
Similar to the above switch, a momentary-push button switch is different in that it has an exposed button that sticks out from the surface on which it's mounted on. Usually, these types of car switches are used for the “start” and “stop” functions of your vehicle.
Rotary
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A rotary switch is operated by turning a dial either to the left or right. This type of switch is used when you need to be able to select between different positions. Hence why rotary switches are mainly used for the operation of the headlights.
Toggle
A more traditional car switch that is being used more in modified cars nowadays is the toggle switch. This is a manually activated switch that typically uses a lever. The use of toggle switches is mainly to turn something on and then off without the need for two separate car switches.
Rocker
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Similar to toggle switches in how they work but with a more modern design, rocker switches can illuminate too. Rocker auto electrical switches have also been less popular with modern-day vehicles but they serve the same purpose as toggle switches.
Slide
With a slide switch, you get an actuator that goes in one direction or the other. Slide switches are popular nowadays when it comes to selecting between different two positions or options. Although these can be quite larger than other types of switches, slide switches are low-power switches that are mounted with a through-hole.
Types of Switches by Mechanism
SPST
With SPST or single pole single throw car switches you get the simplest mechanism found in a switch. This makes for a simple on and off switch that has one input and one output contact. SPST switches are able to switch on and off only one circuit.
DPDT
DPDT or double pole double throw switches are the most complex since they have six terminals. These switches come with 2 input contacts and 4 output contacts which makes them usable as either on-on or on-off-on auto switches. The best example of a DPDT switch is the turning signal in your car.
SPDT
Single pole double throw or SPDT switches have half the terminals of DPDT switches. That's one more than the simplest SPST switches which come with 2 terminals. SPDT switches have one input contact and two output contacts. This makes them have two ON positions and one OFF position. The majority of slide switches nowadays make use of an SPDT mechanism as they need to change over between two outputs.
NO vs NC Switches
Normally open and normally closed switches differentiate themselves by their resting positions. NO or normally open switches have an OFF resting position, which when you press the button, the switch comes in an ON position. Because of this, NO switches have the button sticking out a bit. NC or normally closed switches, on the other hand, have an ON resting position which means they are depressed. When you press the button, they come into an OFF position and thus the button is sticking out again to signify that.
Momentary vs Latching Switches
With a momentary switch or a double pole double throw switch, you need to have it pressed or continuously held in the ON position in order for it to do its thing. Once the switch is released, meaning it goes to its OFF position then it ceases to operate. These auto switches are not as common in cars as they are in computer peripherals. Latching switches are much like your regular light switch as they stay on until you change their position and vice versa. You don't need to hold the switch in the ON position, it stays there until you decide to change it.
Summary
No vehicle is complete without switches, as small and hidden as they may be. Without a proper set of switches and proper mechanisms that they rely on, no vehicle will allow you to operate even the simplest of tasks as easily.
