The proximity sensor on the button legends allows the user to find the switch and turn on the legends, even in the dark. The lighted legends provide him or her with basic instructions for the use of the system. If we also add a software lockout on the button-and-slider controls, such that these cannot be activated within two to three seconds of initial proximity detection, this should prevent the accidental setting change if the user brushes past the interface.
We also minimised power and cost, because we can use a less expensive power supply to only supply the energy for backlighting the legend for the 10-20 seconds the user will need to set the lighting level. Our interface also minimises cost because the capacitive proximity and touch-sensor design can be implemented using a low-cost printed-film sensor.
Now, some may ask, why not make the complete interface capacitive-proximity based? For example:
1. If the user moves his or her hand from left to right, this could turn the light on, and right to left to turn it off.
2. Moving the hand up/down past the sensor could control dimming of the light.
While this is possible with the technology currently available, the question becomes how does it affect user experience? How will the user find the interface in the dark without potentially turning the lights on at full brightness? What happens if the user brushes past the sensor and turns off the lights? Or, what happens when the family dog brushes its tail past the sensor?
While these may sound somewhat contrived, the designer does have to keep in mind that capacitive touch is susceptible to this kind of environmental noise, and should consider how sensitivity of a capacitive-proximity system can affect operation. It is also possible to handle problems in this kind of system using a more robust gesture-recognition system. However, processing requirements for implementing even a simple two-to-three gesture pattern-recognition system are typically beyond the capability of small, low-cost microcontrollers. So there is a cost trade-off to be considered.
Some things to keep in mind
Capacitive proximity and capacitive touch are exciting new technologies, but the designer must remember that these bring not only new freedom in design but also new challenges that have to be considered when designing a UI. Noise-susceptibility, both electrical and environmental, as well as complexity of the UI experience, has to be considered in design. Remember, it is not just a case of substituting one switch for another. Instead, it is a completely new technology with its own set of advantages and challenges. After all, the novelty of a new interface fades quickly if it is difficult to use and is susceptible to new factors from which the previous system was immune.
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