Behind...

Getting a little behind here...anyway.  No pictures in this one, it's late.  A little while ago, my friend and I boosted the assemblies on Duplo bricks and added ramps to divert the coins.  Later, I rebuilt both of the modules.  I put care into making the mechanism that moves the touch sensor shorter, shortened the coin slot and connected the two together.  Seemed like it worked pretty well (the assembly on the touch sensor felt like it made it more easily into the bucket).  Then, I rebuilt the coin-holding and dispensing mechanism.  Ended up pretty well, although wider than it needed to be.  Unfortunately, I don't have any pictures of this version....because inspiration struck.

I realized that I could stack the "coin slot and touch sensor mechanism" on top of the "change holding and dispensing" mechanism.  The "bucket" could simply turn 180 degrees one way and deposit the coins.  So, I did so.  I added some sloped bricks on top of the linear moving assembly to divert the coins into the holders.  The result is a much more compact machine, with the coin-dispensing location much more accessible.

After that came a slope to divert the coins down from the dispensing location.  Then a second slope to divert the coins from the "bucket" rotating in the opposite direction (to return the coin being analyzed).  Then, disaster.

Unfortunately, I forgot to put in a light sensor to sense the coins coming out of the dispensing location.  And I don't want to lengthen the slope, so I pulled the RCX light sensor out of the coin slot and put it in.  After a lot of programming employing just about every possible method to detect the coins consistently, it won't work like I want it.  I'll have to lengthen the coin slot and change chute.  (Or something else.  How about twisting the change chute....?)

Project Update

I suppose that recharging the batteries was the right idea, because it works now.  However, there are a few things to remember to fix in the final version:

• The attachment on the touch sensor that contacts the coin tends to get stuck on the "holding tank" if it is not in the perfect position.  Possibly, I could fix this using a troubleshooting part of the program?  Must make the entire money manipulating mechanism easy to access.
• The connecting ramp between the coin detecting and coin dispensing modules is not steep enough.
• The place where the coins come out is very hard to get to.  Must make ramp that connects to front of machine.
• There is no ramp for the coin return.
• The "walls" that hold the coins in their stacks jump over the wheel that dispenses the coin.  (I don't think that it is harming it, however)
• No bill feeder or bill reader
• Coin dispensing motor is not electrically run

As you might notice, most of these will likely be able to be remedied without much brainwork.  The bill reader/feeder may never be built.  However, I think that I am done with it for now.  I think that I will be able to fix these problems in the final version.

On a different note, I had an idea for the product dispensing mechanism.  If I do not implement the bill feeder (which have been considering not to implement for a white now) then I can spare two motors for the product dispensing mechanism and use only two NXT Intelligent Bricks without my RCX or Power Functions.  And how would I be able to use two motors?  Well, using a mechanism inspired by here, I can run four functions in forward only off of two motors.  And not having backwards is not detrimental since the products need only to be dispensed by the machine, not taken back in by it since I'm planning to load it from the top or front.

Change Mechanism and Combining Modules

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).

Another Project....

Well, after this project did not preform so well, I decided to find a better way to have a machine output food when a user inputted money. So, even at that time, I decided to make a vending machine.

I had quite a few goals to achieve:

• Proper coin differentiation between the dime, penny, nickel and quarter.
• Several products
• Change dispensing
• Bill analyzer
  

I saw a video online in which the robot moved a mechanism down on top of a coin until the mechanism activated a touch sensor. I decided to use the same idea on my coin differentiation device.

Here's the second version. The coin goes in on the right until it is detected by the blue light sensor. It then falls into the black "bucket." The "bucket" could be rotated to let the coin go to the vault/change mechanism or to the coin return. The motor on the left moved a setup on the touch sensor into the "bucket" until the touch sensor was pressed. The rotation sensor in the left motor was then read to detect how far it had moved, and therefore, how big the coin was.

Here's the current version. It works pretty consistently if everything is in the right position before hand and the coins are placed in one at a time.

So now for the change-dispensing mechanism. I currently have a rotating design, based off of the coin holders on this project. However, it's not working that well....it's hard to get a solid construction that can hold each of the four coins and they keep on coming out when the device rotates. I'm hoping to switch to a linear design using bricks (just hope it'll work)