Feasibility of 16mm metal push button switches with dual NO/NC contacts

16mm metal push button switches can be configured with both normally open (NO) and normally closed (NC) contacts—a common design for versatile control scenarios (e.g., motor start-stop, alarm reset, or dual-circuit monitoring). The most typical dual-contact configuration is 1NO+1NC , though some industrial-grade models offer 2NO+2NC for complex dual-load control. These switches integrate a shared "common terminal" (COM) that toggles connection between NO and NC when the button is pressed: in the unpressed (normal) state, COM is closed to NC (NC circuit conducts) and open to NO (NO circuit cuts off); when pressed, COM disconnects from NC (NC circuit cuts off) and connects to NO (NO circuit conducts).

Key Wiring Considerations for Dual-Contact Designs

Terminal Identification FirstAlways reference the switch datasheet or physical markings to distinguish COM, NO, and NC terminals (misconnection causes functional failure). COM is the "bridge" terminal—never connect power directly between NO and NC (risk of short circuits).

Load & Current MatchingEnsure the switch’s rated current/voltage matches the total load of both NO and NC circuits (e.g., a 10A switch cannot power two 8A loads simultaneously). For inductive loads (e.g., motors), select switches with anti-arc contact materials (e.g., silver-nickel alloy) to prevent contact burn-out.

Polarity & Circuit Isolation

For DC circuits: Connect the positive power supply to COM; NO/NC then link to respective load inputs (negative load terminals connect to power ). Reverse polarity may damage illuminated switches (if equipped).

For AC circuits: Polarity is not critical, but isolate NO and NC circuits (e.g., avoid sharing neutral wires between loads) to prevent cross-interference.

Safety Compliance

Ground the metal switch shell (via dedicated ground terminals if available) to avoid electric shock from insulation failure.

Maintain minimum electrical clearance (≥3mm for AC 220V) between NO/NC terminals and adjacent components to prevent arcing.

Illuminated Switch WiringIf the switch has an LED indicator, its power supply (often 12V/24V DC) must be wired separately from the NO/NC control circuit. Include a current-limiting resistor (e.g., 1kΩ for 24V LEDs) in the indicator loop to avoid LED burnout.