What is DPDT Switch : Working & Its Applications

A DPDT switch (double-pole, double-throw) is an electromechanical switch that can be formed by adding a pole to the SPDT switch. This is very easy to install because it is available with a locking system that can lock & unlock the switch directly in a remote cabinet without using any Nut-Bolts or screw for fitting. This article discusses an overview of a DPDT switch and its working with applications.


What is DPDT Switch?

A DPDT or Double Pole Double Throw switch includes two inputs & four outputs where every input has two equivalent outputs. This switch is very versatile because each terminal in this switch can be either in one of two positions. The inputs of this switch can connect to four different outputs, so it can redirect a circuit into two different modes of operation. This switch is the combination of two SPDT switches. The schematic symbol of the dpdt switch is shown below.

DPDT Switch Symbol
DPDT Switch Symbol

This switch is very helpful in changing the polarity of the voltage applied. So it is used where we require dissimilar outputs. This switch has three states like ON, OFF & ON but the main disparity between the two ON states is the polarity which is quite opposite to each other.

How does DPDT Switch Works?

DPDT or Double pole, double throw switches will break or make the two conductors connected to two separate circuits. In this switch, DP switches control two independent circuits whereas DT switches close a circuit in the up & down position. These switches have six terminals like two inputs and four outputs which are available in both momentary & maintained contact versions.

This is a dual ON-ON type of switch that is derived from the SPDT characteristics. Generally, this switch has 2 (ON-ON) positions or 3 (ON-OFF-ON) positions. The set of SPDT switches operates mutually through four circuits with two independent circuit systems.

These circuits can be activated at the same time. So, in this condition, both appliances within similar circuits will be power-driven once the switch is ON. Meanwhile, for the four circuits within a DPDT switch, only two circuits can be energized simultaneously. This switch uses polarity reversal that permits it to switch two energized circuits simultaneously.

DC Motor Control using DPDT Switch

The DPDT switch circuit diagram is shown below which is used to control a DC motor. To control a DC motor, first, we need to connect the motor to a switch. Generally, DPDT has six terminals whereas DC motor has two terminals. Here, the switch terminals are represented with A, B, C, D, E, F &G. The connection of this circuit is as follows.

PCBWay
DPDT Switch to Motor Connection
DPDT Switch to Motor Connection

First, we need to connect a wire in between two terminals like A & F  through soldering as shown in the above circuit. Connect a wire between two terminals like B & E. The DC motor is connected in between A & B terminals whereas the battery is connected in between C & D terminals.

Working

The working of this motor can be done in two ways like forward rotation and reverse rotation. Once the switch is pressed in forward direction then terminal-A is connected to terminal C whereas terminal B is connected to terminal D. Therefore, the DC motor rotates in forward direction because the battery is allied in forward connection toward the motor.

Forward Rotation Connection
Forward Rotation Connection

Once the switch is pressed in the reverse direction, terminal-C is connected to terminal-E & also terminal-D is connected toward terminal-F. Therefore, the DC motor rotates in the reverse direction because the battery is allied in reverse connection toward the motor.

Reverse Rotation Connection
Reverse Rotation Connection

DPDT Toggle Switch

This DPDT toggle switch is available in On-Off-On configuration which is rated at up to 6A & 125VAC. By using this switch, you can switch two different circuits or two loads simultaneously. The dpdt on-off-on switch diagram is shown below.

DPDT On Off On Switch
DPDT On Off On Switch

This switch is used in Jeeps, RV’s & boats. This switch is a Marine-grade toggle switch and sealed with waterproof. The operation of the DPDT toggle switch is, it acts like two separate SPDT switches which are connected to a similar switch bat. This switch includes two separate ordinary terminals where each of these terminals can be connected to one or two terminals on a similar face of the switch. The dotted line within the toggle switch illustrates that the switch includes two SPDT switches within one package through one switch bat.

What will happen if you wire a light switch wrong?

If a light switch is wired wrongly then a short circuit may occur or the switch will not work properly. If this switch wiring creates a short circuit, then the switch gets damaged so these errors can lead to fire, electric shock, etc.

Why do we use electric switches?

An electric switch is used to interrupt the electric current flow in a particular appliance. The devices which use these switches are torchlight, table fan, etc.

How do you reverse polarity in a circuit?

The polarity can be reversed by providing signal voltage. If the polarity is reversed in a circuit, then both the neutral & hot wires get switched, which causes the current to supply backward and flow into the appliance using the neutral terminal rather than the hot terminal, which strengthens the appliance even it is turned off.

Advantages & Disadvantages

The advantages of the DPDT switch include the following.

  • It carries two independent signals
  • They work with high voltages & currents
  • Failover capabilities
  • High switching current allows the device to drive motors, pumps, and control relays.
  • This switch can be used in different applications
  • By using this switch one can control an appliance at the same time through one flick.
  • This switch is not expensive
  • Less weight

The disadvantages of the DPDT switch include the following.

  • As compared to bridges, these are expensive.
  • Network connectivity issues cannot be traced using this switch.
  • Broadcast traffic may be difficult on a switch

What is a DPDT Switch used for?

The applications of DPDT switch or DPDT switch uses include the following.

  • A DPDT switch is used where an open and closed wiring system is used.
  • This switch is frequently used for simultaneous switching of two independent signals that should work in tandem.
  • This switch is frequently used for switching mains’ electricity as it can separate both the neutral & live connections.
  • A DPDT switch can be connected like a reversing switch for an electric motor.
  • By using the DPDT switch, reverse polarity can be achieved in a more controlled way.
  • This switch is used to control the robot.

Thus, this is all about an overview of a DPDT switch and its working. Here is a question for you, what is the difference between DPDT & SPDT?

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