Be careful not to do what I did and use LOW or HIGH instead of FALLING or RISING!
From Brian Schmalz:
attachInterrupt(COIN_COUNTER, intHandle, LOW);
needs to be changed to
attachInterrupt(1, intHandle, RISING);
and then it will work.
The reason for the two changes:
1) Even though you call "pinMode(COIN_COUNTER, INPUT);" with COIN_COUNTER being 0 (a pin number), you need to use the "interrupt number" (i.e. INT1, or "1") as an argument to attachInterrupt(). I don't know why, that's just the way it is.
2) We don't have code right now to do LOW or HIGH level interrupts, we only support RISING or FALLING as edge types (second parameter).
If you make that change, it will work as you expect. If RISING is not the right value for your coin mech, use FALLING.