Sensing object sitting on surface

Hi!

I've got a question regarding feasibility for a project I'm thinking about. All hypothetical right now.

It's fairly complex project, but I'll try to simplify it to get to the core of my question.

Imagine I have a board with four squares on it, a similar board next to it with five LEDs in each square (1 blue, 1 green, 1 red, 1 yellow, 1 white), and four blocks (1 blue, 1 green, 1 red, and one yellow).

Now, this is what I want to do; If I put the blue block on the first square on the board, the blue LED should light up in the corresponding square on the other board. If I put the green block on the second square, the green LED should light up in the second square on the other board, and so on. If there are no blocks on one of the squares, the white LED should light up on the second board in the corresponding square.

If I'd move the blue block from the first square to the third square, the blue LED in the first square would turn off, and the white LED would turn on, the white LED in the third square would turn off and the blue would turn on.

So, in essence, what I want to do is be able to identify an object that is sitting on top of a surface and carry out a command as a result of it.

Is this at all feasible? I think NFC/RFID technology could possibly solve this. What are your thoughts? Are there other options?

Many thanks for your help and thoughts!

For a very limited number of blocks you may also use strategically placed electrical contact.

The Pixy camera can automatically track several different colored blobs.

You could put a simple color sensor under each square. Often this is just a light sensor and a set of color LEDs. Turn on each LED and sample the light sensor. This could be done with four of the six analog inputs and three outputs for Red Green and Blue LEDs.

In the Arduino Projects Book, there's an experiment in chapter no. 4, color mixing lamp which uses red, green, and blue 'gels' (little colored sheets of plastic) to filter white light onto photoresistors to in turn set the color of an RGB LED. Maybe they'd work.

dougp: In the Arduino Projects Book, there's an experiment in chapter no. 4, color mixing lamp which uses red, green, and blue 'gels' (little colored sheets of plastic) to filter white light onto photoresistors to in turn set the color of an RGB LED. Maybe they'd work.

Note that three photoresistors for each of four squares would require 12 analog inputs which would require an Arduino Mega or an external multiplexer.