A portable rgb led light source with color control mechanism for backlighting application
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Date
2016-09-01
Authors
Saiful Azrul Saarif
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Abstract
This thesis presents the development of color control mechanism for Red, Green and
Blue (RGB) Light Emitting Diode (LED) light source. The additive mixing by the
primary LED requires a control mechanism since a color produced is subjected to
variation. This is due to the influenced of elevated ambient temperature and selfheating
of the LEDs. The color point will vary because the individual LEDs output
radiant intensity degradation is not the same. A microcontroller is proposed as a
central unit to obtain an initial set point of the color mixing thus controlling each
LED when the difference of new color point exceeded tolerance. The method relies
on the forward voltage prediction to the individual LEDs and the radiant intensity
measured by an optical sensor. The developed color control mechanism can
effectively maintain the mixed color point when it is subjected to an accelerated
ambient temperature test through heating the heat-sink attached to the LED. The
system is tested on two types of RGB LED. The system is able to reduced 83% of
relative error for the first type LED and 78.6 % of relative error for the second type
LED. The relative error is obtained during the measuring process with the closedloop
control mechanism reducing the open-loop control system error from its initial
set point. The ambient light disturbance is also successfully eliminated during the
sensor in operation.