Rocker switches vary slightly from standard push buttons. These switches are typically a three-position switch and can either stay in the last pressed position, or spring back to the neutral or middle position. There are many ways to implement this type of switch and three of these are shown in the figure below.

Figure 3-11 Tri-State Switch Implementation Examples

Implementing this type of switch can be done with different technologies. Designers can incorporate this method with electro-mechanical contacts similar to the encoder or button applications. The same problem of wear and tear applies here as in those other applications. Designers can use a magnetic Hall sensing based design or an inductive sensing based design for a contact-less rocker switch. Designers can implement the Hall-effect sensor design using either linear, latch, or switch sensors. For more information on how to use Hall to implement these tri-state switches, see the HMI Rocket Switch With Hall-Effect Switches, application note. For the inductive sensing application, this is similar to the touch button or encoder design. Depending on the mechanical motion of the switch, a metal target can pass over two different sensor coils depending on the state of the switch.

Figure 3-12 Inductive Tri-State Switch Concept

Alternatively, each active state can have their own metal target that moves closer to the inductive sensor coil when that active state is chosen. There is freedom of design to match the mechanical motion required because the only components required are the sensor coils and the metal target.

In comparison of the implementations, the mechanical design is cheap and simple, but the design is more prone to wearing down over time. The Hall based design is easy to implement and does not have the same wear and tear concerns, but this design requires a magnet and can be susceptible to external magnets. The inductive sensing implementation also removes the wear and tear concern while being immune to DC magnetic fields, and this option can use any conductive metal as the target. This option does require additional design effort, however, to create the sensor coils.