Wednesday, 19 October 2011

Seeing playing cards with an LDR and RGB LED

It didn't take long after posting about our intelligent poker table for the emails to come in pointing out a few mistakes on our colour-block image.

We'd tried to come up with at least 52 unique combinations of colour blocks, using only primary (red, green, blue) and secondary (magenta, cyan, yellow) colours. We thought we'd done a pretty good job until Matt from BuildBrighton pointed out -

Looking at the top-left block of colours, it's easy to see that we've two red, one green and one blue block. Let's write this as 2R-1G-1B.

Now on the top row, look at blocks three and five.
Block three has two red, one magenta and one green.
Magenta is made up of equal parts (1:1) red and blue.
So block three is 3R-1G-1B

Block five is made up of two red, one yellow and one blue.
Yellow (as most people who paid attention in physics class will tell you) is made up of red and green light (yes, when mixing paint, yellow+blue = green, but when mixing light, red+green = yellow. Just accept it!)
This makes block five also 2R + 1R+1G + 1B = 3R-1G-1B

So although we'd used unique combinations of colour pigments for our blocks, we've actually repeated intensities of light for a lot of the colour combinations. In fact, looking through the image, we can see we've actually repeated ourselves quite a few times!

Back to the drawing board....