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I am trying to find a way of determining the colour of an LED without an electrical connection to it, i.e a sensor pointed at the LED. I can place the sensor quite close to the RGB LED I intend to measure, but i'm struggling to come up with something that will do what I need.

I will be using the sensor with a micro controller of some kind, probably an arduino, or the ti myRIO.

I found this Colour sensor however it looks like it might be overkill for my requirements.

Many of the other sensors I have come across work by shining RGB LED's on the object and measuring what is reflected back. I don't think they would work when the object I am measuring is a light source in itself. Am I correct here? For example

Are there any other solutions that I am missing?

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    \$\begingroup\$ How about a set of photoresistors or other light sensors with color filters? Can you arrange it so the LED is in front of three different sensors? \$\endgroup\$ – Austin Nov 6 '15 at 11:16
  • \$\begingroup\$ You are trying to determine the color of the plastic LED housings, right? Not the color of the LED or LEDs with clear plastic housings? \$\endgroup\$ – Robert Stiffler Nov 6 '15 at 11:18
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    \$\begingroup\$ What is overkill? I would say, overkill is if you put too much effort and too much money into something. The sensor costs <3GBP and outputs a frequency which can easily be measured by a microcontroller. The sensor may technically be overkill, but not practically. There may also be a cheaper solution for mass products. But if you build one device, this should be fine, shouldn't it? \$\endgroup\$ – sweber Nov 6 '15 at 11:37
  • \$\begingroup\$ Use another RGB LED as sensor and measure the components for each color (requires some A/D component). Also your requirements aren't very clear - so I can't really comment if the RGB sensor you linked is "overkill" or not cutting your specs. I'd just use a full digital RGB sensor, but mainly because I have not much analog design experience and trust that people at Vishay, Avago and others provide better solutions than I can come up with in my spare time. \$\endgroup\$ – Arsenal Nov 6 '15 at 13:00
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You can use multiple light sensors, block one with a filter that only lets through green light and block the other with a filter than only lets through red light, another for blue. You will be able to tell the colour by the brightness. This will give you a rough idea, it will not give you an extremely accurate colour measurement though.

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  • \$\begingroup\$ Note that each color in your RGB LED has a fairly narrow spectrum so you need to match the filter colors to the LED. If you use the wrong blue filter, for example, it may not pass much light from the blue LED chip. \$\endgroup\$ – DoxyLover Nov 6 '15 at 18:49
  • \$\begingroup\$ Since the LEDS are monochromatic you would simply need a band that allows the colour of the LED to pass. A very specific blue filter may be problematic, but a wide band blue filter would work better for example. \$\endgroup\$ – HighInBC Nov 7 '15 at 1:43

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