Test 1
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Test 1: Array 6 x 6

A small circuit board was designed with space for three sets of 12 LEDs, one each for red, green and blue types. The LEDs are arranged in diagonal rows for testing only. A real larger LED panel probably would have triads of RGB LEDs.


Initial Tests

The figure to the left shows the 36-LED test array under full power. The LEDs were mounted on very ‘long’ legs such that they can be reused later. The camera looks at the lights at an angle. Looking directly into the LEDs would blind the camera.


The next three figures show the array with only a single color being powered.

The array was aimed at a white poster board some 32 inches away as the result was photographed.

Several shortcomings of this test setup showed up immediately. While the green and blue LEDs have a radiation pattern with a nominal spread of about 15 degrees, the red LEDs, according to the manufacturer’s specification, have a 20 degree beam spread. The latter claim is debatable.

All three color LEDs supposedly have a similar light flux per specifications. This is difficult to judge with this setup since the projected beams cover different areas for the different colors. No matter how the relative power for each color is controlled, no white light is achievable over the entire beam width.

You may recall, that the goal of this test was to obtain relationships between the input power for each color to obtain white light. The test did not produce any tangible results.

What’s Next?

It appears that the total output of the Red LEDs is lower than produced by the green and blue ones. Maybe the red LEDs are being badmouthed since their energy is spread over a wider angle.

Plans: Set up another test with ‘bunched’ clusters of LEDs.


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