basic light sensor for project

hello everybody,

I am making a simple project for school that demonstrates a bunch of different sensors. my project is sorting change. I was wondering if anyone knew of an Arduino sensor that will give me an analog output that I can then use to see how much light is being reflected there for knowing the size of the coin. quarters are the largest diameter, therefore, reflecting the most light.

many thanks, Connor

What if you use a dull quarter vs. a shiny nickel? Dull nickel vs. shiny penny?

If all quarters (or other coins) were bright, shiny and new, that may work. In the real world they are not. Some are shiny (reflective) and some are tarnished and old (not reflective) and some in between. And I don’t see how you would differentiate between a shiny penny and a dirty quarter.

Maybe a vertical slit along the center line of the coin with a light shining through the slit. A small coin would let more light through and a large would block more light. Then use a Light Dependent Resistor (LDR) to measure how much light is allowed by the coin?

dougp: What if you use a dull quarter vs. a shiny nickel? Dull nickel vs. shiny penny?

luckily because I get to hand pick what kind of change I'm putting through it and its only demonstration ill get to hand pick the quarters nickels etc. I get to put through it.

Well then, I guess you could use a plain old CdS photocell sensing reflected light.