Switch
A switch makes or breaks a circuit on demand. Push, slide, toggle, or rotate — the result is a clean electrical connection or open.
Inside, two metal contacts sit a tiny gap apart. Mechanical action presses them together or pulls them apart, sometimes with a snap-action mechanism for crisp tactile feedback.
In plain terms
A drawbridge for electrons. Lower it and current crosses; raise it and the path is broken.
Also called: pushbutton, toggle, DIP.
Why designers use it
- Capture a deliberate user action.
- Configure jumpers and DIP switches at assembly.
- Provide an emergency-stop or interlock.
- Interrupt power for service or transport.
Best for
- User input
- Configuration jumpers
- Power switches
- Limit switches
When not to use it
- When mechanical contact bounce has not been allowed for in the input circuit.
- When the selected switch's contact, voltage, current or mechanical-life ratings do not suit the application.
Common mistakes
- Reading a button without debouncing — every press fires three times.
- Picking a tactile rated for 10 k cycles in a daily-use product.
Where you will find it
- A push-lock/turn-reset emergency-stop button with normally closed safety contacts opens those contacts when pressed and holds its actuated position until reset. Safe machine stopping and restart prevention require the complete safety-control system, not the button alone.
A short history
Switches differ in both their mechanical action and electrical contacts. A momentary switch returns when released; a latching mechanism holds its state until reset. For example, Omron's cited emergency-stop button uses push-lock/turn-reset action and a normally closed contact. The button's physical position and the contact's electrical state are different things.
Good to know
- 'Normally closed' describes the contact before actuation. Pressing the switch opens that contact.
- A button can stay physically pressed while its electrical contact stays open. Mechanical latching does not mean electrical closure.