Tesis ini mengemukakan pembangunan mekanisme kawalan warna untuk sumber cahaya oleh Diod Pemancar Cahaya (LED) Merah Hijau dan Biru (RGB). Pencampuran secara penambahan daripada LED asas tersebut memerlukan
mekanisme kawalan kerana warna yang dihasilkan tertakluk kepada variasi. Ini adalah disebabkan peningkatan suhu ambien dan pemanasan sendiri oleh LED tersebut. Titik warna akan berubah kerana penurunan keluaran keamatan sinaran tiap-tiap LED adalah tidak sama. Pengawal mikro dicadangkan sebagai unit pusat untuk mendapatkan set titik permulaan pencampuran warna seterusnya mengawal setiap LED apabila sisihan titik warna baru berubah melebihi had. Kaedah ini
bergantung pada jangkaan voltan ke depan terhadap setiap LED dan sisihan ukuran sinaran oleh penderia optik. Mekanisme kawalan warna yang telah dibangunkan boleh mengekalkan gabungan titik warna dengan berkesan apabila tertakluk kepada
ujian suhu ambien terpecut menerusi penenggelam haba yang dilekatkan pada LED. Sistem ini diuji pada dua jenis LED RGB. Sistem ini berupaya untuk mengurangkan 83 % ralat relatif untuk LED jenis pertama dan 78.6 % ralat relatif untuk LED jenis kedua. Ralat relatif diperolehi semasa proses mengukur dengan mekanisme kawalan tertutup mengurangkan ralat sistem kawalan terbuka daripada set titik permulaannya. Gangguan cahaya ambien juga berjaya dihapuskan semasa penderia beroperasi.
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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.
A portable rgb led light source with color control mechanism for backlighting application / Saiful Azrul Saarif