The work principle of tact switch can be divided into the following four parts:
- Tact Switch’s Core Structure Composition
The tact switch consists of a button, an elastic element (metal dome/spring), a contact piece/welding piece, a base, and a pin.
1> Button: The operating part to which the user applies external force, triggering the internal mechanical movement.
2> Elastic element: Provides restoring force to restore the switch to its original position when there is no external force.
3> Contact piece: The key component of the conduction circuit, usually located on the base.
4> Pin: Connects to the external circuit; the standard configuration includes two sets of two-by-two conduction pins (four pins) and one ground pin (five pins). - Tact Switch’s Workflow
1> Pressing phase: When external force acts on the button, the elastic element (metal spring or spring) deforms, pushing the contact piece to contact the solder piece on the base, completing the circuit path.
2> Holding phase: The circuit conduction state lasts until the external force exists.
3> Release phase: After the external force is removed, the elastic element returns to the initial position by its own restoring force, separating the contact piece and the solder piece, thus disconnecting the circuit. - Tact Switch’s Main Part Functions
1> Metal shrapnel: It has the dual functions of deformation conduction and circuit conduction. Its material properties directly affect the contact resistance (usually less than 0.05Ω) and operating life (up to 100,000 times or more) of the switch.
2> Base structure: It ensures the accuracy of the shrapnel deformation trajectory and prevents false triggering caused by contact offset. - Tact Switch’s Circuit Characteristics
1> Transient signal output: In digital systems such as FPGA, each press generates a level flip (high→low or low→high), restoring the original state when released, making it suitable as a pulse signal source.
2> Conduction logic: When pressed, the four pins are connected in pairs (such as 1-2, 3-4 pins), and the fifth pin is an independent ground terminal.
Note: Compared with micro switches, tact switches lack a quick-action mechanism and rely entirely on mechanical deformation to achieve on and off. This results in a shorter operating stroke (0.3-0.7mm) and smaller trigger force (160-350gf).
