DPDT Momentary Switch

DPDT momentary switch is one of essential small devices for any kind of simple or complicated circuit controlling, which is widely used in a single circuit or two totally different circuits according to the actual need. To better understand what a DPDT momentary switch is, it needs to figure it out from two aspects – DPDT and momentary action. In terms of DPDT switch, it comes a few different types, including DPDT toggle switch, DPDT rocker switch, and DPDT transfer switch and so on. When it comes to momentary switches, there are momentary push button switch, momentary toggle switch, momentary rocker switch, momentary key switch, and momentary contact switch and so on.

DPDT switch

Types of switches

According to the number of poles and throws, switches can be classified as mainly three types.
SPST (Single Pole Single Throw);
SPDT (Single Pole Double Throw);
DPDT (Double Pole Double Throw).

Comparing between SPDT and DPDT, you will find that SPDT has a public contact of COM, a contact for “push-to-make” (or normally-open or NO) and a contact for “push-to-break” (or normally-closed or NC). However, DPDT is with dual outputs when working, which won’t disturb and affect each other as there are no public terminals.

What is DPDT?

DPDT is the abbreviation for Double Pole Double Throw. Actually one DPDT switch is the combination of two SPDT switches, which are arranged in parallel. If you compare a SPDT toggle switch to DPDT toggle switches, you will understand their relationship well.

The wiring of DPDT is exactly the same to that of SPDT. The two poles of both of them are connected by an insulating plastic and shared by a handle. Each side of a DPDT switch is the equivalent of a SPDT switch. In other words, a DPDT momentary switch can be used as two sets of SPDT momentary switch. What’s more, for a DPDT switch, every two adjacent poles on the same side is the equivalent of one SPST switch. That is to say each of them can be used as four SPST switches. Due to different wiring configuration between A’, B’, A, and B, it can achieve different tasks, such as changing the direction of current or voltage and switching electrical component location. For more information about SPST, please refer to another post about SPST momentary switch.

How does a DPDT switch work?

Since DPDT means Double Pole Double Throw, namely the relay that has two sets of changeover contacts. The principle please refers to the following diagram. When the circuit is not energized, the two poles connect to their NC respectively. When the circuit is energized, the two poles change to NO at the same time.

DPDT momentary switch

Given that DPDT momentary switch is one type of momentary switch, the momentary action has to be mentioned here. Simply put, momentary action, to some extent, is equal to hold-to-run or hold-to-stop. That’s to say, the circuit stops working when releasing while resumes working when pressing.

Since DPDT momentary switch is the combination of DPDT and momentary action, its characteristics has been widely used in many industries that require a variety of flexible alarm settings. For example, when a device needs to be monitored, the signal during working process such as temperature, pressure, level or flow should be closely watched. Once abnormal conditions occur and signals that are too high or too low compared to the alarm setting value are detected, it would immediately send out the signal to open or close the control, or trigger an emergency stop. Or when problems occur, the alarm will just trigger the warning light, alarm bell or buzzer. All this process has to rely on a DPDT momentary switch, which render a single alarm relay has two independent outputs. If the two nodes on DPDT toggle switch simultaneously change the state, DPDT toggle switch can have two functions, such as closing valves or the opening of the ventilator.

Of course, there are many other kinds of applications about this DPDT switch. So long as you know the secret of how to control a DPDT momentary switch, it can help solve a lot of problems about circuit controlling.