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I see the Philips Hue and LIFX led bulb can generate the millions of colors, I can find enter image description here.

can anyone tell me how this light works to generate millions of colors, what is the yellow LED light and white LED light, are they all the RGB led lights ? is each LED individually controlled by the circuit, and use all of them to make a color combination and is each LED controlled by simply opening/closing or dimming in different levels.

Thank you

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  • \$\begingroup\$ Although technically correct, no sane person would be able to tell the difference between most of these million colors, especially as at any single moment in time only one color is mixed and emitted by the whole bulb. But it sounds good from a marketing persepective. \$\endgroup\$ – jippie Apr 19 '15 at 16:32
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Imagine you have three LEDs (red/green/blue "RGB").

Each LED primarily stimulates a corresponding type of "cone" in the human eye as described here.

enter image description here

So a perceived color is created by a combination of the intensities from the three LEDs. If we include intensity of color as a discrete color, then for 1,000,000 colors we would need log2(10^6)/3 bits per color or about 7 bits per 'color'.

Most likely they are using 8 bits PWM intensity per color (about 0.4% steps in intensity), giving 16,777,216 or 16 million 'colors'. In reality you are not going to be able to visually distinguish anything like that many, and many of the 'colors' are just different intensities of a color that is visually the same.

White LEDs look yellow when not on- also some sources use a yellow component to the light to make the color appearance better for sensitive things like flesh tones and food (so they're RGBY rather than RGB).

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can anyone tell me how this light works to generate millions of colors, what is the yellow LED light and white LED light, are they all the RGB led lights ?

The white LEDs are individual red, green, or blue LEDs as indicated by their silkscreen. The yellow LEDs are white LEDs; the yellow part of the LED is a phosphorescent material that absorbs high-energy photons (e.g. blue light) and emits lower-energy photons (e.g. orange-yellow light).

is each LED individually controlled by the circuit, and use all of them to make a color combination and is each LED controlled by simply opening/closing or dimming in different levels.

It is very common to use PWM dimming in order to have fine control of a LEDs output; I have no proof that it is used here but that is very likely the case.

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The connector in the center has four leads labelled "R", "G", "B" and "W".

So it's safe to assume that all red LEDs controlled by one signal (they work in unison). Same for the blue, green and white LED groups.

The traces seem to indicate that the LEDs for each color are connected in series.

Dimming LEDs by PWM is patented in some countries, so the dimming for each color could be achieved by by a very similar method, which is however sufficiently different from patent lawyer's perspective. Analog dimming is, most likely, not used as it would produce more heat in the driving electronics (and make them more complex; the controller circuit is digital anyway).

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