General Electrical Terms
Current (Amperage) Rating: The amount of electrical current that will flow through the circuit will determine the amperage rating required for the switch and cable. The current rating for the switch must be higher than the current rating of the circuit, and a safety factor is typically required. The current and voltage rating for input (mains) power for a device should be available on the equipment’s rating plate. You can also compute the current required for a circuit if you know the power and voltage required by the circuit.
Voltage Rating: The working voltage at which a device is designed to be used; may be either AC (alternating current) or DC (direct current). Typical voltages in the US for AC input power are 120 and 240 VAC. Typical voltages for DC circuits are 3, 6, 12, 24, and 48 VDC.
Variable Resistance: Variable resistance devices use a potentiometer to provide a control signal for the equipment that they are attached to. They are not connected directly to mains or input power, but rather to a reduced control circuit used only for variable signal input. If all three terminals of a potentiometer are used, the foot control can act as a voltage divider circuit for motor speed control. If only two terminals are used (one side and the wiper), the foot control can act as a variable resistor. Note: Potentiometer foot pedals cannot be hooked up directly to a motor; a variable-speed motor drive must be used (contact an electrician or the motor drive manufacturer to determine the requirements of a motor drive circuit).
Consult a certified electrician if you have any questions to determine the amperage, voltage, and electrical requirements for your application.
Foot Switch Pedal Action
Momentary Action: Press and hold pedal to turn on, release to turn off (like a car horn). The user must continue to hold the pedal down to keep it on. As soon as the user lifts his or her foot, the unit will turn off.
Maintained Action: Press pedal once to turn on, press again to turn off (like a light switch). The foot switch will stay on and the user can remove his or her foot from the foot pedal until the user presses the pedal again to turn it off.
Anti-Trip Safety Feature (G-Series only): The user must press forward a safety latch inside the hood before pressing down on the pedal lever to turn it on. These foot switches then have a momentary action; the user must keep the pedal pressed down in order to keep it on.
Switch Circuit and Contact Terms
SPDT Contacts: Most SSC foot switches with one switch in them have SPDT (single-pole double-throw) contacts, which have terminals including common, normally open, and normally closed. Also called “Form C” contacts. Typically, foot switches with cables on them have SPDT switch contacts that are wired to the "normally open" (or N.O.) and common terminals, which means the foot switch is off (no current will flow) until the pedal is pressed.
SPST-NO Contacts: These contacts close when the foot switch is pressed. This is the most common foot switch circuit, one in which the circuit is “off” until the foot switch is pressed, at which point it turns on. Also called “Form A” contacts.
SPST-NC Contacts: The opposite of SPST-NO, this circuit is closed in the at-rest position, and will open or turn off only when the foot switch is pressed. Also called “Form B” contacts.
DPDT Contacts: Equivalent to two SPDT contacts operated by one control.
Double Break Contacts (SPDT-DB): Double break contacts open and close at two separate places in the circuit. Because they make contact at two points, instead of just one, DB contacts dissipate heat more readily, providing longer switch life, enabling the switch to have improved performance in DC circuits, and typically handle higher voltages. A SPDT-DB switch must be used on circuits of the same polarity. Also called “Form Z” contacts.
Number of Poles: The Number of Poles determines the number of circuits that will be switched. For example, a single pole (SP) switch will make and break one circuit, while a double pole switch (DP) will make and break two circuits.
Common (C): The Common terminal provides a path to the N.C. or N.O. terminals for a SPDT switch. This terminal must be used for the foot switch to work, as it will direct the current to either the N.C. or N.O. terminals.
Normally Closed (N.C.): The N.C. terminal is connected to the common terminal in the at-rest position of the foot switch, and will open (or turn “off” if wiring is connected) only when the foot switch is pressed.
Normally Open (N.O.): The N.O. terminal is not connected until the foot switch is pressed, at which point the contacts close and allow current to flow from the common terminal to the N.O. terminal and complete the circuit.
Number of Throws: The Number of Throws is the number of separate wire paths the switch can direct for each pole. Most SSC switches have double throw (DT) contacts, meaning there is a common wire, one that can be wired normally open (N.O.), and one that can be wired normally closed (N.C.). Most SSC foot switches are shipped with the wiring set to Normally Open, meaning the switch is open or “off” until it is pressed, at which point the circuit closes and current can flow.