Tactile Switch: What It Is, How It Works & Pinout Guide

A tactile switch is a push-button switch that provides the tactile feedback of a click when activated. It's the little button found on remote controls, routers and microcontroller boards and electronics, and they also refer to it as a tact switch.

This is the term you are searching for, likely to find a definition, to learn about the pins or to know how to distinguish this part of the keyboard from the "tactile" part which people refer to when talking about the keyboard switches. This is a guide to all three in simple terms.

This guide answers the following questions:

A tactile switch is not the same as a tact switch or a push button?
What occurs within when it "clicks"?
Which one of the four pins do I put in?
What is the meaning of "tactile dome switch"?
What should I choose for me and why is mine not working?

The answer is provided in the first line in each section, followed by an explanation of how to use it.

What Is a Tactile Switch (and Is It the Same as a Tact Switch)?

A tactile switch is a switch that you can feel. It is typically small, attached to a circuit board and connects a circuit when pushed. You'll know the press has been made by clicking or by feeling a soft bump under your finger.

The term "tact switch" is synonymous with "tactile switch". The two are used interchangeably by manufacturers and some manufacturers use their own names. For instance, Panasonic sells the same type of part as a "Light Touch Switch.

Momentary is also the term for tactile switches. They remain whenever the button is pressed, making them ideal for reset buttons, or menu and wake buttons. For a switch that remains energized when not depressed, you will need a latching switch.

Need Keyboard Switches? The other term for keyboard fans is "tactile switch," which refers to a key switch that has a bump during part of the keypress. That is another component. Proceed to the part of the document that is dedicated to the keyboard.

How Does a Tactile Switch Work Inside?

When the button is pushed, it pushes the small domed metal contact down until it snaps, which completes the circuit. The dome will bounce back when released, and the circuit will again be closed.

Manufacturers count the parts a bit differently, typically 4 or 5. This is the same as in practice:

Actuator: the part you press (button).
The part that snaps to form the click sound is known as the dome contact.
The fixed contacts: the pads the dome in contact with when the dome collapses.
Base and pins: the housing and legs which solder to the board.

The buckling of the dome is what you feel when you click. It's also useful in your design, as it ensures the user that the press was completed.

How Do You Read a Tact Switch Pinout?

It is only logical that a basic 4-pin tactile switch only has two connections. The four pins are connected internally in a pair and pressing the button connects the pairs.

Suppose that there are two wires, with a tiny distance between them. When pressed, this button will close the gap. This also implies the need for only a single pin of each pair, typically.

Which pins are paired?

The two pins on one side are connected to the other, while the two pins on the other side are connected to the other. Not all parts do though. Other sections use pins diagonally, however, so don't rely on memory when it comes to pin layout. Refer to the datasheet or test the part.

How to find the pairs with a multimeter

Set the meter to its beep setting (also known as continuity setting).
Press the two probes to two pins when not pressed. A beep indicates that they are in the same pair.
Repeat until both pairs are found, #3. Either of the pair of pins can be wired to.
Press the button and cross the two pairs. You should now get a beep between them.

Wiring to a microcontroller

Take one of the first pair of pins and wire it to an input pin, and take one of the second pair and wire it to ground. Most microcontroller come with a built-in pull up, so external resistor is not always necessary. Switches are not polarized, meaning it doesn't matter which way it is connected. It is the connection between two pairs that is important, not the twisting itself.

Other pin counts

In 2pin switches there is no pairing to do.
There are five-pin versions available for the compact joystick-style control.

A note for PCB designers

There are many times when there are four pins in the many footprints and two in the schematic symbol. Your design software might complain about the unrouted connection; the two numbered pins are already connected within the switch. The footprint can be edited to use 4 separate pins, and mark the ones connected internally not to be connected by a trace. The method of soldering all four pins to the board is still used by some designers, since this ensures that the solder joints are more resistant to repeated pressing.

What Is a Tactile Dome Switch, and How Is It Different from a Membrane Switch?

A tactile dome switch is a small dome-shaped spring (typically made from metal) which is snapped down when pressed. The dome is located in the housing of a PCB tact switch. It is located under a flat membrane layer in a keypad. The dome makes the click and the build up around it determines the type of switch.

There are three types of domes you will encounter:

Type	Feel	Where you see it
Metal dome	Sharp, crisp snap	Tact switches, control panels, keypads.
Polydome	Smoother and quieter, embossed in a layer of polyester	Low-cost membrane keypads
Rubber dome	Soft, cushioned response	Most everyday keyboards

There's a compromise that needs to be understood. Metal domes provide the most feedback - but are more expensive and smaller in size. Polyester membrane designs may be bigger in size and also require less energy to trigger.

There is no click on a plain membrane switch without dome. It is only when you check that it works that you know it does. Put a dome under and the same one is then tactile.

How Do You Choose the Right Tactile Switch?

First, see how it attaches, then size and force. Supplier catalogs allow you to sort by these very qualities.

Factor	What to check	Why it matters
Mounting	Can be installed through-hole, SMD or panel-mount.	Determines the footprints and assembly processes
Size and footprint	The spacing between the pins on the body and the size of the body itself.	Must be compatible with your board and enclosure
Actuation force	The amount of force you exert before it snaps into place	Allows affects to feel and accidental presses affect.
Actuator height and style	The amount the button protrudes from the capsule	Should be the same as your case or button cap
Sealing	Standard or sealed	Sealed types are suitable for dust or moist environments
Electrical rating	The datasheet includes voltage and current information. Volts and amps are listed in the datasheet.	Tact switches are designed for low power signals.

On ratings: Tactile switches are designed for low power devices and the ratings are dependent upon the individual part. Do not connect anything but a logic level signal unless you have read the datasheet first.

Tactile Switches on Keyboards: Same Word, Different Switch?

A tactile switch is a mechanical switch that has a small bump that appears part way into the press that lets you know that the key has been pressed on a mechanical keyboard. It's in the middle of smooth linear switches and clicky switches. Cherry MX Brown has been mentioned quite a bit.

This component is a small board mounted button that will open or close a circuit. Both have "touch" feedback, but they cannot be interchanged. If your here to select the keyboard switches, make sure to check the bump, actuation force and travel of the switch you're thinking about.

Why Isn't My Tactile Switch Working?

The vast majority of problems are due to wiring the wrong pins or to taking the wrong wiring layout.

It always reads "pressed". You might have crossed two wires – one is always connected. Use one pin for each of the pairs.
It never registers. Ensure that the two connections are on different pairs and verify the pairs using a meter.
When a press refers to "several", it means one. This is called contact bounce and is a characteristic of mechanical switches. Use a short software delay or small capacitor to handle it.
It feels loose or cuts out. Check your soldering. Over time, the joints can become stressed from repeated pressing.

FAQ

What is the difference between a tactile switch and a push button?

Tactile switch: One type of momentary push button. It's small, fits a circuit board and clicks when you press it! Other push buttons might be panel mounted or may latch or may not click.

Are tactile switches polarised?

The current in a tactile switch can be either in the forward direction or the reverse direction. It doesn't matter which pins to connect, but which two pairs, you connect across it.

Is a mains/tactile switch suitable for mains or high power loads?

No, not really; in small electronics, the signals are at low power, and this is the type of switch they are built for. Look at the ratings in the datasheet, and if you need to use a relay or switch for anything other than a logic-level signal, use a relay or switch rated for the load.

Why does my tactile switch show more than one press?

This is “contact bounce”. The metal contacts open and close for a few milliseconds when they touch each other. A brief software delay (or a small capacitor across the switch) filters this out and provides one clean press.

The Short Version

Tactile Switch A small momentary switch that clicks when it completes a circuit. The "tact switch" is the same part, and the dome on the inside is the small metal spring which makes the click.

When your project doesn't work, it's most likely a problem with the pins. Use a multimeter to determine the two pairs that are connected together, and then wire one pin from each of these pairs; before trusting any pin diagram you have memorized, refer to the datasheet. If you purchase one, the first thing you'll need is the mounting type, size and the amount of force required to activate it, and the rest is a breeze.