How to make a coin selector for Making a piggy bank?

Hi.
I'm interested in making a piggy bank, but not how to make a cheap currency setector.
Thank you for contributing ideas

A piggy bank is usually a container with a slot in the top. I'm guessing that you want some way to determine the value os a coin being pushed into a coin slot. I think the cheap toys use a spring-loaded arm that turns a pot and the peak value of the pot is a rough measure of coin diameter.

Look out for a cheep electronic money box and salvage the coin mechanism.

The one I have seen uses a spring loaded arm and several small infrared sensors, each coin is a different size and will cover a number of these sensors, the numer or order these sensors are covered is the value of the coin.

All that it looks at is the diameter of the coin.

Using Eddy Current coin detector

http://arduino.cc/forum/index.php/topic,97925.0.html