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Embedded Components - Design Considerations

LED: A LED (light-emitting diode) is a semiconductor which produces light when traversed by an electrical current. It is a diode which has the characteristic to emit light (not all diodes emit light). In our membrane keypad applications, we use SMT LED (surface-mount technology) components which means that the LEDs are mounted on the surface of the circuit substrate. GGI International offers a variety of LEDs, available in mono-color, bi-color and tri-color versions.

  • Characteristics:
    • Polarity: a LED is bipolar. One of its poles is called anode and other cathode. The LED will function if the power is on from the anode towards the cathode.
    • Basic colors (monocolor): yellow, green, red, orange or amber, blue and white.
    • Basic colors (bicolor): red/green, yellow/green, yellow/red
    • Luminosity: expressed as millicandela (mcd). LEDs are designed to function optimally under a 20 mA current, at approximately 2 volts.
    • Typical mechanical specifications:
      • Monocolor 3215 (LxLxH) = 3.2 x 1.5 x 0.5 +/-0.1 mm (0.126 x 0.06 x 0.020" +/-0.004")
      • Bi-color 3226 (LxLxH) = 3.2 x 2.6 x 0.5 +/-0.1 mm (0.126 x 0.102 x 0.020" +/-0.004")
    • Minimal mechanical specifications:
      • Monocolor 1608 (LxLxH) = 1.6 x 0.8 x 0.75 +/-0.1 mm (0.063 x 0.031 x 0.029" +/-0.004")
      • Bi-color 1615 (LxLxH) = 1.6 x 1.5 x 0.7 +/-0.1 mm (0.063 x 0.060 x 0.028" +/-0.004")
    • Other mechanical specifications: Non-standard sizes and types of LEDs can also be integrated into the membrane switch keypads designed by GGI International. In this case, a specific feasibility study is then carried out by the team of engineers of GGI International.

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  • Various considerations:
    • GGI International makes it possible to proceed to the embossing of the LED windows of the graphic overlay, which can improve the angle of vision up to 180 degrees.
    • The LED windows can be printed with a translucent colour in order to improve light diffusion.
    • If all the LEDs must or can be lit at the same time, GGI International recommends a maximum of 5 LEDs per circuit trace.
    • If the LEDs are not powered according to the recommended electrical specifications, the light output and the emission colour can be affected.

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Overview  |  Design Considerations