Electrical Lab - how a 4-pin momentary tactile switch works

UpdatedUpdatedJune 12 - 2017June 12 - 2017

Momentary tactile switch (normally open) pin configuration


A tactile switch may have 4, 6, 8 or even more pins. Here we will discuss about a simple tactile switch which has 4 pins.

We will use jumper wires to build our own tactile switch from scratch. Then it will become clear to us how a normal tactile switch works and how we can use it as a pushbutton.

Let's first take two jumper wires (red and yellow) and place them on a breadboard to create our 4-pin tactile switch which basically has 2 terminals.

So normally when we don't press the button, it looks just like the above image. When we press the button, then terminal 1 + terminal 2 become short (in image green wires are used to denote short circuit).

Now Connect terminal 1 VCC (+5V).
Terminal 2 10K resistor GND (ground).
LED anode (+ve) terminal 2.
LED cathode (-ve) 220 Ohm resistor GND (ground).
The green wires are not connected which means the tactile switch is not pressed and LED is OFF.

The green wires are connected which means the tactile switch is pressed and LED is ON.

When the button is not pressed, the circuit is incomplete so current does not flow from VCC (+5V).
When the button is pressed, current flows from terminal 1 (VCC) to terminal 2. Since we have a very high resistance (10K) between terminal 2 and ground, current flows through the LED.

External link

Hint: Click on Start Simulation, then activate LED by pressing the tactile switch. When you release the switch or button, LED will be deactivated.

For a normally closed momentary tactile switch, it works in the opposite way. So by default terminal 1 and 2 are connected. When the button is pressed, the terminals become open so no current flows.