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Switch Circuit Symbols: Guideline on Circuit Switch Designs

Undoubtedly, you are bound to find switches in a wide variety of electronic circuits and devices. Whether it’s applications in motors, lamps, TV, or cookers, you will often apply on and off switch circuit symbols. 

There are a variety of switch circuits, each with different symbols indicating their type, structure, and function. Thus today, we are going to show you the various electrical characters along with a simple description. In the end, you’ll make an informed decision on the type of switch circuit that suits your needs. 

1. What is a Switch?

A switch is a simple electrical device that breaks or closes a connected circuit. It does so by disrupting the current path hence connecting or disconnecting any appliance it serves. In doing so, there’s also an interruption of electrical current between a device and a power source. Moreover, you can operate it as a sensing element (like the ones in a thermostat) or manually by pressing (like a momentary switch). 

Some specialized forms or types of switches include;

Further, there are four main methods of operation of the switch circuit. They include;

  • DPDT (Double pole double throw switches),
  • DPST (double pole, single throw),
  • SPDT (single pole double throw), and 
  • SPST (single pole single throw switch).

We will give out more details as we proceed.  

2. Switch Circuit Symbol Introduction 

The examples listed below are some types of switches that majorly fall under mechanical and electrical controls. Furthermore, they are physical switches, and you can activate them by pressing, releasing, or even touching their contacts. 

Limit switch 

Limit switch

(Limit switch )

A limit switch functions by any machine’s mechanical part that controls the systems. In addition, coming into contact with its actuator leads to its activation by machine parts or other electric objects. 

Switch DPDT

Switch DPDT

(Switch DPDT)

It consists of two SPDT switches conjoined with a standard lever and can switch two different circuits simultaneously. Sometimes, it is equivalent to a simple on-off switch of 2 SPDT switches.

Generic switch symbol

Generic switch symbol

(Generic switch symbol)

It’s simply a generic switch when in an open condition.

Telegraph key 

Telegraph key

(Telegraph key )

It is a switch symbol with a special designation for the transmission of text messages in the form of Morse codes. It achieves transmission by disconnecting or connecting the circuit switch. Then, it makes pulses of different lengths termed ‘dits’ and ‘dahs.’ 

Closed switch 

Closed switch

(Closed switch )

The symbol shows a closed switch that denotes a complete circuit that allows current flow. 

Differential switch 

Differential switch

(Differential switch )

A difference between a neutral line current and a phase line current contributes to the operation of the differential switch. Thus, any difference in current that occurs because of fault current breaks the circuit. 

Open switch 

Open switch

(Open switch )

An open switch stops the flow of current by breaking the circuit. 

Pulse counter switch 

Pulse counter switch

(Pulse counter switch)

A pulse counter operates the actuator in the pulse counter switch. When the pulse counter reaches a specific fixed value, it activates the button that triggers the circuit. 

Thermal magnetic switch 

gnetic switch

(Thermal magnetic switch )

A thermal-magnetic switch uses both thermal and electromagnetic braking, and the electromagnet instantly breaks the circuit in case there’s a high current surge. Then, if there’s an excess of the current limit, a bimetallic strip component offers a delay. 

DIP (Dual Inline Package) switch 

DIP (Dual Inline Package) switch 

DIP (Dual Inline Package) switch 

A DIP switch is commonly applicable in printed circuit boards because of its small size. Also, their manufacturing process involves packing together multiple switches in a DIP. 

Timer switch 

Timer switch

(Timer switch)

When a timer runs out, the timer switch makes and breaks the circuit contact. Also, it creates a time delay in some applications. 

Float switch

Float switch

(The Float switch)

Float switches detect liquid level and turn off or on depending on the liquid fall and rise.

NO (Normally Open) push button

(NO (Normally Open) push button)

(NO (Normally Open) push button)

Often, it’s in a constant OFF (open) position. A pushbutton switch puts the switch ON (close place), whereas releasing the button retrieves it to its initial OFF position. 

Rotary open switch 

Rotary open switch

(Rotary open switch)

The symbol signifies a rotary switch in its OFF/open position. 

Switch SPDT

Switch SPDT

(Switch SPDT)

It consists of three terminals, with a common terminal and two others. Then, one of the two terminals has a connection with the common terminal. Also, it is recommendable in three-way circuits like turning a light off or on in two separate locations.

Switch DPST/ Dual ON-OFF switch

ual ON-OFF switch

(Switch DPST/ Dual ON-OFF switch)

It can accommodate two different circuits since it has two poles and switches them OFF and ON instantaneously. Moreover, due to its one throw, it has a single closed-loop/ON position. And, it majorly regulates appliances with 240V. 

Switch SP4T

Switch SP4T

(Switch SP4T)

It has four throws and one pole. Its four positions enable it to switch a circuit after connecting the switch with one of the four terminals. 

Pushbutton Single pole double throw 

Pushbutton Single pole double throw

(Pushbutton Single pole double throw)

A pushbutton SPDT has no open position but is in the ON state in the two conditions. 

NO thermal switch 

NO thermal switch

(NO thermal switch)

The switch operates at room temperature and gets activated when there’s a temperature rise. 

NC thermal switch

NC thermal switch

(NC thermal switch)

Its state at room temperature is at a closed/ON switch. However, when the temperature increases above a particular level, the switch becomes open/OFF. 

Foot-operated switch 

Foot-operated switch

(Foot-operated switch)

They often drive heavy machinery.

Selector switch 

Selector switch

(Selector switch )

It can switch a single circuit or more but at different times. 

Mercury switch 

Mercury switch

(Mercury switch)

Its tilting motion can open and close up a circuit. 

Joystick switch 

Joystick switch

(Joystick switch )

It has a stick or lever connected to its base. In addition, you’ll find it in applications such as industrial trucks and cranes, and gaming controller pads. 

ON delay switch 

ON delay switch

(ON delay switch )

The ON delay switch postpones the time it takes when switching the circuit from OFF to ON. 

NC push button 

(NC push button )

It’s always constant at the ON/ closed position. If you press the NC push button switch, it gets into an OFF/open position, whereas releasing the button returns it to a closed state. 

Switch SPST/ Toggle Switch

(Switch SPST/ Toggle Switch)

It is the simplest form of an electrical switch with only one output and one input. Therefore, the single pole switch is a common type in most electric circuit software.

Summary 

In conclusion, it is imperative to know about switches and pushbuttons symbols when setting up electrical projects. In this way, you’ll learn how to easily interrupt electric current or divert it from one conductor to the other in your circuit operation. The billions of operations can comprise devices like audio amplifiers and motor drives. 

Finally, this article has given you a variety of switch circuit symbols plus descriptions. And since we’re always open for questions or clarifications, you can reach out to us

Hommer
Hi, I am Hommer, the founder of WellPCB. So far we have more than 4,000 customers worldwide. Any questions you can feel free to contact me. Thanks in advance.

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