It wasn't too hard to make that linear change mechanism. Here it is. I'm worrying that the dimes will not stack correctly with what I have here. I decided that nickels are the easiest to work with since they are thick in relation to the other coins and just about perfectly fill a 3X3 brick space. Stacks of coins are moved on top of a wheel that is in the little "hole" to the left of the ramp in the picture. The mechanism is "refilled" through the ramp, the upper motor moving the correct coin stack into place.
So, I then had to combine the two modules, so I did the cheap way and just stacked the coin detection mechanism on top of the change mechanism. I had some problems with the connecting ramp, and I had to shift the entire coin detecting mechanism, and the ramp still isn't quite steep enough. Not to mention that the place where the coins are dispensed is way underneath....but I think that I'll be rebuilding this later. I'm hoping to make the entire thing more compact and sturdier. I'm hoping to steepen the connecting ramp and build two other ramps, one from the change mechanism, one from the coin return, to give coins to the machine user. Now, I must figure out why the light sensor doesn't seem to be working (I'm recharging the NXT's batteries, I hope it will help).
