Cash-Caching Automaton

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Revision as of 20:26, 2 January 2013 by Jimshoe (Talk | contribs)

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Implementing v0.1
Born On:
23:34, 18 October 2012 (CDT)
Last Updated:
20:26, 02 January 2013 (CDT)


The Cash-Caching Automaton, or "CasCA", is a machine designed to dispense coins to Makers for use with the drink, candy, and snack machines. Many people don't carry around cash or change, but the vending machines at the shop currently only accept coins or dollar bills. This machine will make use of personal accounts assigned to Makers that may be funded by PayPal, Bitcoin, and other manual forms of payment, like checks or cash. Below is the current list of desired features:

  • The machine should be able to reliably dispense a user-selectable number of quarters (not too few, or too many)
  • It should be able to offer multiple forms of user-authentication:
    • Username + password
    • Makers door-authentication thumbdrive (plus optional pin number/password)
    • (Possible) Smartphone authentication via QR displayed on screen
    • (Possible) Other smartphone authentication: NFC, Bluetooth, WiFi?
    • (Possible) RFID tag
    • (Possible) Google Authenticator
  • Accounts should be automatically fund-able at the machine via PayPal or Bitcoin
  • Accounts may be manually funded via check or cash
  • Can show account balance on screen
  • MUST have secure connection to a secure database for transactions
  • Easy to physically refill with quarters
  • Automatic email notification when low on quarters
  • Display a message on a screen when low on quarters
  • Able to dispense coins without an account when using PayPal or Bitcoin
  • Physical and account-based intrusion detection and notification

v0.1. Requirements

  1. Only dispense $0.50
  2. Determine amount in machine
  3. Dispense change
  4. Don't charge if there isn't any money.
  5. USB Member Authentication
  6. Manual Deposit
  7. Red empty light
  8. Remove dollar acceptor



We've purchased a old change machine from a guy out in Trinity. It is a small, tabletop unit that should work quite well for the quarter dispenser, since it already handles giving out quarters and checking for low levels. It is also already lockable and theft-resistant. The machine's dollar acceptor did not work, so we will not be able to retain the bill-to-quarters functionality.

A previously proposed design for the dispenser was to use a tall 1" i.d. pipe (PVC) to store the quarters to be dispensed. The bottom of the pipe would have small slot where a single quarter may slide though and a sensor to detect whether there are any quarters remaining. A servo would move forward to push a quarter out of the slot, and move back to let the stack of quarters slide down.




  • method of data entry for account usage and USB drive usage
    • Raspberry Pi?
  • NFC and some RFID
  • Tiny combined USB BT and WiFi card?


Cost Analysis


Progress Log

22:57, 5 November 2012 (CST): The small desktop change machine has been acquired and tinkered with. Jimshoe has hooked up a switch that will manually trigger the dispensing of up to four quarters at a time. This switch will be replaced by a transistor or relay that will be controlled electronically.

22:57, 21 November 2012 (CST): Code has been written that interprets commands over serial and calls different functions based on the commands and inputs. This code has been committed to the new CasCA git repository on GitHub.

23:17, 16 December 2012 (CST): Successfully tested relay board with some coin-dispensing Arduino code additions. Added some simple money-tracking to the Arduino code: it can now be refilled, quarters can be dispensed, coin levels checked, and no attempts to dispense coins will be made if not enough coins are in the machine.


= Database

  • user
  • transaction

Design Files