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RFID Based Vending Machines

I've procured two vending machines to use for this project:

The plan is to add an RFID interface to these machines so that members can deposit funds into their personal account, then use their RFID card to buy drinks and food (or whatever else I manage to fit into the machines).  

Drinkbot - Dixie-Narco Pepsi Stack 501 Magnum Circular Door (Parts Manual)

Foodbot - Snackshop 4000 (Manual)


Non-food things to put in foodbot:
AA / AAA / 9V battery packs
Electronic components such as Arduino boards (once RFID is up and running)

Planning

Drink bot operates on a single set price for all drinks.  This can be changed once the RFID system is in place by having the system debit a users account for one amount (say, $2 for a Redbull), then tell the machine $0.75 was deposited and allow it to vend.  This would involve a few changes to the machine.  "Control Board" (CB) refers to the one I will be building.  My current plan is to have the machine operate normally with change and dollars, with all drinks the same price, and special drinks (more expensive, beer, etc.) disabled by the CB by making the machine think they are sold out.  When someone uses an RFID card on the machine, it will activate all selections and debit the account accordingly.  In the future I may have the control board totally replace the current control system and handle all transactions.  Plans needed for this stage are in blue.

Inputs to CB:
  • Coin sensors x 3 ($0.25, $0.10, $0.05)
  • Dollar Bill changer (I believe this outputs a simple high/low signal based on if it detects a valid bill has been inserted.  Need to determine for sure.
  • Coin Return/Cancel Transaction
  • Selection Buttons x 8
  • Change Availability x 3
  • Drink availability x 8
  • Temperature sensor (will need to provide one)
  • Misc sensors that may be present in original machine.
Outputs from CB:
  • Coin Sensors x 3
  • Drink availability x 8 (this will be a pass-through with the machine seeing it as normal, but the control board governing certain special selections.
  • Text Display to give users instructions and show remaining credit on accounts.
Operation:

Normal Mode -
  1. CB reads Drink Availability status and passes info on to machine.  CB tells machine special drinks are sold out, so that user can not buy them.  Text display has some sort of welcome message and machine internal temp.
  2. User inputs bills or coins as normal.  Text display updates with amount deposited.
  3. User presses button and product vends.  If sold out, display tells user so.
  4. Machine grants change if needed
  5. If user hits coin return, display clears balance and money is returned as normal.
RFID Mode -
  1. CB reads Drink Availability status and passes info on to machine.  CB tells machine special drinks are sold out, so that user can not buy them.  Text display has some sort of welcome message and machine internal temp.
  2. User swipes RFID card.  Display shows name and available balance.  Coin return switch will cancel transaction at any time.
  3. CB unlocks special selections if appropriate.
  4. User presses selection button.  Display informs user of price, or if sold out, and asks them to press same button again to confirm.
  5. Display debits account, then actuates coin sensors to make the machine think money was put in, then actuates button press to vend product.
  6. Display shows remaining balance then returns to welcome screen.