What is a DPST Switch : Working & Its Applications

In an electric field, a switch can be defined as an electrical component that is used to connect or disconnect the conducting lane within an electrical circuit, Generally, switches are made in several configurations which include different sets of contacts that are controlled through the similar actuator or knob & the contacts may function sequentially, alternately or simultaneously. There are four types of switches available SPDT, SPST, DPDT, and DPST switch. So this article discusses one of the types of switches like DPST switch – working with applications.


What is a DPST Switch?

The switch which has two inputs and two outputs where every input includes one corresponding output is known as the DPST switch. In this switch, every terminal can either be in the ON/OFF position. The DPST switch symbol is shown below.

DPST Switch Symbol
DPST Switch Symbol

In this switch, the DP stands for the double pole and ST stands for the single throw. In this switch, Pole refers to the number of circuits controlled through the switch whereas throw refers to the extreme position of the actuator.

DP switches simply control two separate circuits and ST switches simply shut a circuit at only a single position because the other position of the handle will be in the Off position.

How Does DPST Switch Work?

The working principle of DPST or a double pole single throw switch is to control two different circuits simultaneously; either both circuits are OFF or ON using simply a single actuator like a pushbutton, toggle, etc. These switches include four terminals like two inputs & two outputs. But, it is possible to have different voltages from different sources connected to a single DPST switch. This switch accepts two inputs that are capable of driving two different outputs within a circuit. These are fundamentally two SPST switches built as one, affecting separate circuits however controlled by the same actuator.

Specifications

The specifications of the DPST switch include the following.

  • The type of terminal is 4.8mm × 0.8mm quick connect solder tail.
  • The contact gap is ≥ 3mm.
  • Spacing for insulation is ≥ 8mm.
  • Contact Resistance < 20 mΩ initially.
  • Dielectric Strength up to 3.5 kV.
  • Insulation resistance is > 50 MΩ.
  • Mechanical life is ≥ 100,000 Cycles.
  • Electrical life is ≥ 20,000 Cycles at full load.
  • The minimum thickness of the panel is 1mm.
  • The cut-out size is 19.3mm × 13mm.
  • The thickness of the panel maximum is 3mm.
  • Cut-out size is 19.5mm × 13mm.
  • Double-Pole (Max) : 10.
  • Single-Pole (Max) : 7.
  • The button or Body is made with Nylon 6/6.
  • The illuminated button is made of Polycarbonate.
  • Copper alloy terminals.
  • Silver alloy contacts.

DPST Switch Circuit Diagram

The circuit diagram of the DPST switch is shown below. To understand the working of this switch, the following circuit is explained.

DPST Switch Circuit
         DPST Switch Circuit

Any electrical load or electric power supply includes a minimum of two terminals. As this switch permits two inputs as well as two outputs, then you can control a single load by using a single power supply, otherwise two different types of loads with two different power supplies. In the above circuit, Here, in the above circuit, two different loads are connected with two different power supplies.

Here we can observe that load1 like lamp1 is connected to the first battery and load2 like lamp2 is connected to the second battery. Here, you can consider battery1 as source1 and battery2 as source2. Similarly, you can consider Lamp1 as load 1 and Lamp2 as load 2. Whenever we enable the switch, then both Lamps will be activated together. Similarly, once we turn off the switch then both lamps will be deactivated together. Like this, the DPST switch controls the lamps within the circuit.

Advantages

The advantages of the DPST switch include the following.

  • By using this switch, two independent circuits can be opened or closed simultaneously.
  • It functions with two independent circuits.
  • Both the input-output pair functions simultaneously.
  • This switch is equivalent to 2- SPDT switches

Disadvantages

The disadvantages of the DPST switch include the following.

  • The switching function provided by this is either on or off.
  • This switch is a somewhat more complicated on-off switch where it connects or disconnects two circuits simultaneously.
  • Once this switch is ON then the current starts flowing throughout two loads when it is turned OFF then two loads will be turned OFF.

Applications

The Applications of the DPST switch include the following.

  • This switch is very helpful in switching mains supply because it can change both the neutral & live connections.
  • These are used in breaker control logic circuits and also used as Industrial selector switches.
  • This switch simply controls two circuits together; either both circuits are ON/OFF.
  • This switch is used to isolate power from a load.
  • Two independent power sources can be switched simultaneously.
  • This switch is used in any 240V application.
  • This type of switch is mainly used to control an appliance that includes both supply lines & a neutral wire.
  • These switches are frequently used in controlling electric heating loads which have a temperature detecting component to let them open or close the contacts automatically through a change in the external temperature. When this switch is used for this purpose, then we can call it a thermostat.

Thus, this is all about an overview of a DPST switch. This kind of switch from the outside is similar to a typical SPST switch however it interrupts two current-carrying conductors inside instead of only one. So, this makes it suitable for controlling as well as isolating loads that use two ungrounded conductors & work at 240V single-phase. Here is a question for you, what is a DPDT switch?

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