Tactile / Push Button
Switch
A small momentary push button that closes only while pressed. The standard 'click' button for boards, keypads and resets.
Schematic symbol
Switch (SPST)
How tactile / push button appears in a circuit diagram.
Types & variants
Key specs
Type
-Normally-open momentary (closes while held).
Actuation force
gfHow hard you press; affects feel.
Current/voltage rating
mA / VSmall: e.g. 50mA at 12V - logic level, not power.
Lifetime
cyclesRated presses, often 100k-1M.
Markings
Usually unmarked. On 4-pin parts the two pin-pairs are internally joined; pressing connects the pairs.
Standard values
6x6mm THT 4-pin (most common), 3x4mm and 3x6mm SMD, various heights.
How to choose
Pick size/mounting (THT vs SMD), button height, force/feel, and sealing if exposed. For switching power, drive a transistor/relay - the button only carries logic current.
Pinout & package
4-pin THT: pins on the SAME side are NOT connected; opposite/diagonal pairs are. SMD usually 2-pin. Add a pull-up/down + debounce.
Example circuits
- MCU input with pull-up (active-low)
- Reset button
- Menu/navigation buttons
- RC or software debounce
Common failures
Bounce (multiple reads per press), intermittent contact from dust/wear, stuck or broken plunger.
How to test
Continuity mode: across the correct pin pair it's open normally, ~0Ω while pressed. Wrong pins read open always (pick the diagonal pair).
Substitutes
Any momentary NO button with the same footprint/height; rating is rarely the limit for logic use.