The pedal switches are mounted on the pedal inside the car, through a connection that can be threaded or through coupling.
By operating the brake pedal (or clutch pedal), the electrical circuit in which they are inserted is opened/closed.
Some switches, referred to as hydraulic pedal switches, are driven by liquids as they’re mounted in the hydraulic circuits.
Constitutive elements and operating principles
The closing system of the contact may be sliding or front.
The variation of the state of the circuit (circuits) from normally closed (N/C) to normally open (N/ O) or vice versa, takes place operating a tip.
The switches with normally open circuit and sliding closing circuit system are equipped with a permanent sliding tip and are fixed to the pedal through a threaded connection.
The type with snap coupling is divided into three types:
- circuit normally closed (N/C) with front closing and self-regulation tip.
- A combined circuit (N / O - N / C)
- normally open or closed circuit with an electronic locking system and target of soft iron.
Some newer models of pedal switches include spark suppressor systems made of a capacitor and a resistor or an inductor in series. The reactive components of the filter at the opening/closing of the circuit charges and then discharges slowly, without creating sparks. This is necessary to avoid subjecting the switch contacts to excessive wear.
The device block ferrule serves to adjust the position of the tip during assembly on the pedal.
In the delivery condition, the device is armed and the tip can have a limited movement, not enough to make the exchange.
The disarming of the tip block device can be implemented in two ways, depending on the type of the switch:
- through a rotation that locks the switch on the pedal and, at the same time, makes the tip free to move, allowing the exchange
- through insertion of the vehicle harness
Major causes of failure
- Thermal stress
Effects of failure
- Switch degradation in dynamic prolonged operation at room temperature, low and high
The pedal switches can be either electromagnetic or electronic (electronic switches are proximity sensors, typically of Hall Effect type, of brake pedal or clutch).
In electromechanical switches, when the foot pedal has not been pressed, the switch has the tip pressed, at pedal pressed the tip is at rest.
In the electronic switches, when the foot pedal is not pressed, a Hall Effect sensor detects the presence of a plate of soft iron, integrated with the pedal, called "Target".
The switches operated by pressing the pedal can be of 2 types:
- circuit N/O normally open: normally open with pedal pressed, they close when the pedal is open
- circuit N /C normally closed: normally closed with pedal operated, close to the pedal closed