One of the most unexpected differences between Los Angeles and New York has been the number of places here that only accept cash for payment. In the age of Square, PayPal and a multitude of other credit processing services, I don't really buy that it's too expensive or difficult to accept credit cards. Whenever possible, I buy things using my credit card or debit card, because it's easier to automatically quantify expenses (using

Coin Jar

In LA, almost every retailer & restaurant took card and I often wouldn't have any cash. Here, carrying cash is a requirement. And one of the side effects of paying with cash is collecting change in the form of coins.

It was so rare to pay cash and get change in Los Angeles that I didn't even have a change jar. While I do have one now, I have a terrible tendency not to actually put the coins in it.

A change jar is a decent indication of how the money 'adds up'. But it still lacks context. Obviously, a jar full of pennies is not nearly as useful as one full of quarters. But when all the coins are mixed, it's more difficult to guess the value.



Goal: Put loose change in context of things you care about.

Physical Experience

The existing coin sorters do a decent job counting your coins and giving you a number. They come in two basic forms, one you dump your coins into for sorting & a toy that is supposed to teach kids how to save money.

[caption id="attachment_558" align="aligncenter" width="568"] Old collectors don't put change in context.[/caption]

These devices work fine for counting coins or to teach children about their corporate overlords. However, they don't give you a good reason to convert your change into 'useful money.'

Coins in the context of things you buy & the ways you give (with help from the series of tubes)

This device will automatically count the amount of change you put it in context of the things you are planning to buy or ways you can donate to help others. My original concept planned for data scraping from an Amazon Wishlist. Thinking about tangibility, I thought there may be a better way to select items than using buttons to cycle through things on an LCD display.


How it works

  1. Drop coins daily: when you get home for the day, you place your coins in the collector. It activates and automatically adds the amount of coins to a database. (On a day to day level, this is all you need to do)
  2. Scan a trinket to see how it adds up: Pre-registered (at this point) trinkets such as a heart or a toy are encoded with a serial number. When you place them on the platform, the coin collector checks your total savings and the cost of the item and posts to the LCD display.
    • item trinket for something you want to buy: How much more money you need to buy the item (ex. You need to save another $3.00 to buy Perry the Platypus)
    • donation trinket for something you care about: How many people you could help (ex. Your change could buy 5 people meals for a week)


  • off-the-shelf coin counter mechanics (will save time by providing the basic mechanics)
  • sensors to detect each type of coin being added (optical, microswitch?)
  • arduino + ethernet shield (already own)
  • adafruit NFC/RFID shield
  • trinkets (preferably 3D printed)
  • NFC/RFID tags
  • box/case so it's not an ugly off-the-shelf coin counter

Web Software

  • database for trinkets
  • database for storing the saved amount of money (providing some permanence when the Arduino is unplugged, perhaps could also be saved on an SD card)

Potential Challenges

This project has a number of moving parts and components that likely won't play well together when they are first setup.

  • Internet / database problems: it's possible it will take an inordinate amount of time to go off and check the database, perhaps I could keep the  total change on an SD card & the tag values either on the tag or the card.
  • Ethernet Shield + NFC/RFID shield may not work together
  • Method for setting goals / things you want to save might not be ready for the final:  Ideally a method that allows an organization to set up how change could benefit them or automatic scraping of things you are interested in would be cool
  • It would be awesome to try out that newfangled raspberry pi but I don't think it's worth the risk on a condensed timeline


I already own a large majority of the components.

  • $25 (approx.) Coin collector for parts
  • $10 (approx.) Additional RFID tags
  • $10 (approx.) Sensors to read coins
  • $30 (approx.) Wood or Plexi for enclosure
  • $25 LCD Shield (text only)
Approximate total: $100




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