What Is Double Pole Single Throw Switch – Working & Its Applications

Hello friends welcome to the new post. In this post, we will have a look at the Double Pole Single Throw Switch. Double pole single throw switch comes with two inputs and two outputs, every input has its resultant output. In this post, we will cover the different parameters of this switch like working, construction, and uses. So let’s get started DPST switch.

What is a Double Pole Single Throw Switch?

• The DPST or double pole single throw switch comes with a different terminal and is used for connecting two source terminals with respective output terminals. The DPST switch can used in an ON or OFF state, where its terminals are connected ON or OFF.
• Suppose its 4 terminals are denoted as 1, 2,3 and 4
• Terminals 1 and 3 are the first pair of terminals and are isolated from terminals 2 and 4.
• 2 and 4 is another pair.
• If the switch is ON State, it makes the connection between terminals 1 and 3, making circuit 1.
• Terminals 2 and 3 are connected to completing isolated circuit 2.
• This switch configuration is like the SPST switch from the extern design but internally instead of interrupting one current-carrying conductor, it interrupts two. it is best for controlling and isolating loads that use two underground conductors and work for 240V single-phase.
• The schematic symbol of the DPST switch comes with a dotted line connecting two moving switch parts that is a mechanical interlock. That means if one switch moves other will also move with it.It makes sure that working the external handles will connect or disconnect line conductors.
• These switches are used to control electric heating loads and come with temperature sensing parts that help to automatically open or close contact with changes in external temperature.  IF used for this working use these switches are thermostats.

Construction of DPST Switch

• This switch comes with a structure like an SPST switch externally, and inner side instead of interrupting one current-carrying conductor it interrupts two. So it is best for controlling and isolating loads that use 2 underground conductors and work at 240-volt single phase.
• The symbol of DPST is a dotted line connecting two moving switch components defining a mechncal interlock, which means when one switch moves, the other also moves with it. It makes sure that operating outer handles will either connect or disconnect both line conductors.
• This switch is used to control electric heating loads and comes with a temperature sensing component helping them to open or close contact with temperature change.

Working Principle of DPST Switch

The electrical power supply or load comes with a minimum of two terminals. As the DPST switch has two inputs and 2 outputs, we can operate a single load with a single power supply or two loads with 2 different power supplies.

We will make a circuit with the connection of two different loads with 2 different power sources.

Related: What is a Double Pole Switch? How its Work

Types of DPST Switch

• Two main types of DPST switches are commonly used in circuits

Toggle DPST Switch:

The DPST comes with 4 different terminals and is used for connecting two source terminals to the corresponding output terminals

Rocker DPST Switch:

This switch works with the use of a rocker or button that is pressed to switch circuitry OFF and ON

Advantages of DPST Switch

• The basic advantage of a DPST switch is that both circuits are completely isolated from one another. This configuration can be circuits where different voltages are used.
• The common example of a DPST switch is when the status light circuit shows the connection of high high-voltage load circuit

Disadvantages of DPST Switch

• The switching function of this switch is either on or off.
• This switch complicated design on/off switch where it connects or disconnects two circuits at the same time.
• When the DPST switch is ON state current flows through 2 loads when it is OFF then 2 loads will be off

Applications of DPST Switch

• DPST switches are mostly used in thermostats to control electric heating loads by automatically opening or closing contacts and detecting a temperature change.
• This switch is also used in industrial instruments for controlling multiple power circuits at the same time

Read also: What is Double Pole Double Throw (DPDT) Switch

Difference Between, SPST, SPDT and DPDT

DPST vs SPST Switch

• SPST switches come with a single input and output, the circuit is in the open or closed state and is best for ON/OFF switching. it maintained or has momentary action.
• DPST switch turns two circuits ON or OFF with the use of a single actuator. With two poles and one throw for every pole, the DPST switch comes with 4 terminals, two inputs, and two outputs. They are 2 SPST switches made with each other, control separates circuits but controls with the same actuator.

DPST vs DPDT Switch

DPDT is a double-pole double-throw switch. The 2 isolated circuits can switched, in two possible configurations.

DPST is a Double pole single throw switch, two independent circuits can switched, but they can only one connected with one single remote location, or disconnected

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How to wire a Single Pole Double Throw (SPDT) switch.

Standard 3-Way Switch Wiring (3 Wire Control)

If you are wiring a standard 3-way switch, use the 3-wire control method. In this process, common nodes of both switches connect.

For easy configuration, the Common terminal is A, the left terminal is B and the right terminal is C. Terminal B on both switches can connect the AC supply line through a hot wire.

The 2 C terminals connect one point of the light bulb. With that other light bulb terminal connected with a neutral wire on the AC supply.

Through toggling switch, wecan on or off light. If both switches are in the same state, both common terminals are connected with B or C terminals. Through flipping one we can on the light since we vary the closed circuit from A-C to A-B.

How Does an SPDT Switch Work?

• The SPDT switch comes with one input terminal and 2 output terminals. It used to connect input terminals with one of two output terminals at one time and not both at same time.

DPST Features

• Contact Dimensions= 4.8mm × 0.8mm
• Dk=3.5 kV.
• Insulation resistance: 50 MΩ.
• Mechanical life = 100,000 Cycles.
• Electrical life = 20,000 Cycles
• Contact gap=≥ 3mm
• Insulation spaceing= 8mm.
• Contact resistance=20 mΩ
• Panle thickness= 1mm.
• cut-out size = 19.3mm × 13mm..
• Double-Pole (Max): 10.
• Single-Pole (Max): 7.

 Uses of SPDT Switches

SPDT switches come with features to activate or deactivate devices such as relays, and light control circuits.

In audio instruments, SPDT switches are used for selecting between many signal paths or switching between different effect

What is Single Pole vs Double Throw?

Single pole and double pole switches can be either single or double throw. The pole is a number of separate circuits switch can control, a single pole switch can control one circuit and a double pole switch can control two circuits. The throw defines how many states can activated with the switch

 Advantages of SPDT Switches

• it is a low-cost switch
• that is reliable for different applications.
• it can work with high voltae and currents.
• High switching current helps devices to control, and relay, devices like pumps

What is an example of a Single Pole Double Throw switch?

• A simple example of a single pole double throw switch is ACS 550 or 800 VFD’s output terminal relays. In this circuit relay switch can be made like one input with two different outputs.

FAQs

1. Write the maximum current rating of a DPST switch.

• The highest current rating is based on the design and application of DPST. its  NC  rating is  30A max and for  NO 15 A maximum

2. Is the DPST switch control the flow of electricity in 2 circuits?

• The working of DPST comes with controlling 2 different circuits from a single actuator, which can be a toggle, lever, or push button. Every switch has 4 terminals, like a set of contacts (two poles) and two throws (the position these poles acquire).

3. Is a 4 way switch a DPST?

• The common uses of DPST are 4-way switches, that used in conjecture with two 3-way switches that help Lamp to control from 3 or more points.

4. Write applications of DPST switches?

• The use of a DPST switch is to control two different circuits at the same time, either circuits are off or on with the use of a single actuator such as a pushbutton, toggle, etc. These switches come with 4 terminals two inputs & two outputs.

5. What is the difference between DPST and DPDT switch?

• The DPDT switch comes with 2 inputs, each has two outputs. Since with DPST switch, there are 2 independent circuits, every of which is operated through a single switch. The DPDT switch is best for controlling many devices at same time, either in domestic environment or industrial control.

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