The DPDT push switch

The DPDT Push Switch(Double Pole Double Throw), more commonly known as 6 Pin Push Switch, is nothing but a combination of two switches placed together in a single unit. Unlike momentary or tactile switches, these switches maintain there switching state, that is ON or OFF until they are triggered again.
For example, if I push it once so that it’s turned on, it will remain in the ON state until I push it again. That’s why these switches are mostly used for switching low-current power supplies ON and OFF.

Construction #

Its construction is rather simple, just two SPDT(Single Pole Double Throw) switches placed together inside a box independently. Here, what I mean by independence is that no connections between these two SPDT switches exist.

The gist of the lingo is:

• Pole: common pin.
• Throw: the number of pins the pole can switch to. Therefore, SPDT switches have 1 common pole and 2 switching states, ON and OFF.

For example, those small sliding switches we’ve all used are actually SPDT switches.

Working #

The key difference in using DPDT switches rather than their SPDT counterpart lies in the fact that, in DPDT switch, the common pins of both the sub-switches, COM1 and COM2, are to linked to each other. This construction results in both the sub-switches having the same switching states when the DPDT switch is pushed.

ON state	Off state
The trigger is pushed down.	The trigger is restored.

For example, referring to the pinout above, the typical states of a DPDT switch would be:

• OFF state: COM1 -> NC1, COM2 -> NC2
• ON state: COM1 -> NO1, COM2 -> NO2

Here, NO refers to Normally Open, and similarly, NC refers to Normally Closed pins of the switch.

Usage #

Though this miniature switch may seem simple, which it is, still its smart implementations simplify many complex schematics.
One such example is using this switch as a commutator.

Some of the projects where I’ve exploited the commutating action of this switch are:

• Convertendo: Solves the issue of incompatibility of earphones with your phone using a mini-sized adapter.
• Boggler: Allows you to toggle between the serial and parallel outputs of multiple batteries on the push of a switch.