StarLeaf Touch 2035 VOIP Phone

Capacitive Touch Interface with Selective Dead Fronted Lighting

Project Description

StarLeaf LTD, a leader in cloud and video conferencing techniques, wanted to create a modern and easy to use capacitive touch interface for their video endpoints. Based on their research, they wanted their interface to contain:

  • A fully backlit dial pad
  • A Backlit, dual-color, mute key
  • A Backlit, dual-color, video mute key
  • A Backlit volume keys
  • A Backlit make call and hang up keys
  • A Backlit home key for easy navigation

Starleaf contacted us and presented their requirements. Based on their requirements, we proposed a PCB type capacitive touch interface that uses our custom FORE LIGHT™ technology.

There are several challenges involved in designing and manufacturing a capacitive touch interface. One of them is responsiveness. Consumers expect an instantaneous reaction when they touch a button.
We made sure this was possible by:

  1. Ensuring a scan rate of 80 scans per second was possible
  2. Proposing that the interface communicates with their main controller via a full duplex UART link. This means that the interface will communicate button press and release information as soon as they were available and need not wait for a query from the main controller

Another challenge is the robustness.

The keypad is expected to work in all conditions that it may encounter during operation. Generally, this is performed by testing labs such as UL. Some of the tests performed on this interface by UL were:

  • Subjecting a fully assembled interface to sparks from an 8KV ESD test gun on the glass interface, screws and the stand.
  • Subjecting the unit to a sweep from 150kHz to 80MHz of an 80% modulated AM carrier, 1kHz modulation frequency, of sufficient strength to cause a 3V RMS noise signal on the wires.

Our design for Starleaf was subjected to such tests and passed them comfortably!

The biggest challenge in this project was the lighting. Since this is a backlit panel, it was important for the customer to ensure that the various selectively lit regions had uniform brightness. Several factors such as variations in the LED brightness, alignment issues, etc. could cause the various regions to have a different brightness.

A test was developed based around a camera and some image processing software. This test worked by taking the average brightness of the keypad module and failing modules which have keys outside a particular limit. Results from this test were then used as inputs to tweak our production processes.

The result of all this hard work is the StarLeaf’s Touch 2035.

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