A foot switch symbol on an electrical schematic represents a foot-operated electromechanical actuator used to control machinery, welding equipment, or medical devices. Because these switches are often subjected to harsh environments, heavy vibration, and accidental impacts, reading the exact symbol variant—specifically whether it is momentary, maintained, or shielded—is critical for safe machine operation and troubleshooting. Below is the complete reference for identifying, wiring, and testing these components across global standards.
The Complete Foot Switch Symbol Reference Table
The table below maps the most common foot switch symbols to their IEC 60617 (International/European) and IEEE 315 / NEMA (North American) designations. Use this as your primary lookup when reading schematics or replacing failed contact blocks.
| Switch Type & Actuation | IEC 60617 Symbol Features | IEEE 315 / NEMA Symbol Features | Terminal Pinout (IEC EN 50013) | Typical Application |
|---|---|---|---|---|
| Foot Switch, NO, Momentary | Standard switch with a downward-pointing arrow and a foot/pedal line; NO contact. | Standard switch with a pedal lever drawn above the contact; NO contact. | 13 (Input), 14 (Output) | Press brakes, spot welders, sewing machines. |
| Foot Switch, NC, Momentary | Downward arrow/pedal line; NC contact (line intersecting the path). | Pedal lever above; NC contact. | 11 (Input), 12 (Output) | Emergency stop circuits, safety interlocks. |
| Foot Switch, Changeover (SPDT) | Pedal line with both NO and NC contacts drawn from a single common terminal. | Pedal lever with a double-throw contact symbol. | 11/12 (NC), 14 (NO), Common is 11 or 14 depending on block. | Reversing motor controls, dual-speed machine tools. |
| Foot Switch, Maintained (Latching) | Pedal line with a small mechanical latch symbol (a hook or detent) next to the actuator. | Pedal lever with a mechanical latch indicator (usually a small square or hook). | 13/14 (NO) or 21/22 (Second NO if DPST) | Conveyor belt start/stop, continuous-run lathes. |
| Foot Switch with Protective Guard | Standard pedal symbol enclosed in a half-circle or inverted 'U' shape representing the shield. | Pedal lever enclosed in a semi-circle shield outline. | Matches internal contact block (usually 13/14). | Guillotines, hydraulic presses (prevents accidental drop-actuation). |
Regional Standards, Numbering, and Wire Colors
Knowing the symbol is only half the battle; wiring the foot switch correctly requires understanding the regional terminal numbering and control circuit color codes. A miswired foot switch on a 400V press brake can result in immediate, uncommanded machine actuation.
Terminal Numbering Conventions
Modern industrial foot switches predominantly use IEC 60947-5-1 / EN 50013 numbering for their contact blocks. The first digit identifies the contact sequence, and the second digit identifies the function:
- 1 and 2 (e.g., 11, 12, 21, 22): Normally Closed (NC) contacts. Used for safety interlocks and stop circuits.
- 3 and 4 (e.g., 13, 14, 23, 24): Normally Open (NO) contacts. Used for start and run commands.
- 5 and 6 (e.g., 15, 16, 17, 18): Changeover or timed contacts (less common in basic foot pedals, more common in relays).
In older North American NEMA-style panels, you may instead see sequential numbering (1, 2, 3, 4) or letter designations (C for Common, NO for Normally Open, NC for Normally Closed). Always verify with a multimeter if the terminal block lacks stamped numbers.
Control Circuit Wire Colors (NEC vs. IEC)
When wiring the foot switch back to the PLC or motor starter, the wire insulation color must match the regional control standard. According to NFPA 79 (Electrical Standard for Industrial Machinery) in the US, and IEC 60204-1 internationally, the colors differ significantly:
| Circuit Function | IEC 60204-1 (International / EU) | NFPA 79 / NEC (North America) |
|---|---|---|
| AC Control Circuit (General) | Black | Black |
| DC Control Circuit | Blue | Blue |
| Interlock Circuit (External to Cabinet) | Orange or Yellow (varies by revision) | Yellow |
| Safety / E-Stop Circuit | Red and Blue (or Red/Yellow for specific safety relays) | Red (often with yellow tracer for safety) |
Rows People Get Wrong and Faded Marking Protocols
When troubleshooting or replacing a foot switch, schematic misinterpretation and degraded physical labels are the most common sources of downtime. Here is how to navigate the edge cases that trip up even experienced technicians.
The 'Rows People Get Wrong' Notes
- Confusing Momentary with Maintained (Latching): The most frequent schematic error is missing the tiny mechanical latch symbol (a small hook or square detent) next to the IEC pedal arrow. If you wire a standard momentary NO contact block into a circuit designed for a maintained switch, the machine will only run while the operator's foot is physically on the pedal, which can cause severe process errors in continuous-run applications.
- Ignoring the Protective Guard Symbol: The half-circle shield over the pedal symbol is not just a mechanical suggestion; it is a safety requirement. If a schematic calls for a guarded foot switch (common on shears and press brakes), installing an unguarded open pedal violates safety standards (like OSHA 1910.217) and risks accidental actuation from falling debris or a slipping foot.
- Assuming DPDT means Dual-Pedal: A Double-Pole Double-Throw (DPDT) symbol on a single foot switch means one physical press actuates two isolated circuits simultaneously (e.g., engaging a clutch AND dropping a safety brake). It does not mean there are two physical pedals.
Safe Interpretation When Markings Are Faded or Missing
Industrial environments are brutal on labels. If the actuator housing is stamped with a faded legacy prefix (like an old 'FS-1' NEMA tag) or the terminal block numbers are worn away by oil and metal dust, do not guess the pinout. Use this bench-test protocol:
- Isolate the Switch: Disconnect all wiring from the foot switch terminals. Lock out and tag out the machine control panel.
- Set Your Meter: Use a digital multimeter (like a Fluke 117 or 87V) set to Continuity or Ohms (Ω).
- Find the Common (C): Probe the terminals in pairs. On a standard 3-pin SPDT block, the common terminal will show continuity to one pin in the resting state (NC), and continuity to the other pin when the pedal is depressed (NO).
- Verify the Travel: Press the pedal through its full mechanical travel. A healthy NO contact should read < 1 ohm when fully depressed. If it reads > 5 ohms, the internal contacts are pitted or carbon-fouled, and the contact block must be replaced, even if the mechanical pedal feels fine.
- Check for Ground Faults: Measure resistance between every terminal and the metal chassis of the foot switch. It should read 'OL' (Open Loop). Any reading below 1 MΩ indicates moisture ingress or insulation breakdown inside the pedal housing, requiring immediate replacement.
For deeper study on graphical symbols and schematic reading, the All About Circuits reference library provides excellent visual breakdowns of IEEE and IEC symbol variations. Always cross-reference the machine manufacturer's specific wiring diagram, as proprietary PLCs may map physical inputs differently than standard hardwired relay logic.
