This Piggy Bank Is Our Stock Broker


[Johna and Justin] are working to take the emotion out of playing the market. They built this piggy bank which automatically purchases stock when your coinage totals the cost of a single share. That’s right, just turn the selector to one of your three chosen stocks (Google, Facebook, and Apple are used in this example) and plug in some coins. The bank counts your money, compares it to the current online stock price, and pulls the trigger if you have enough dough. You can check out a demo clip after the jump.

The hardware is rather simple thanks to Adafruit’s programmable multi-coin acceptor. It handles the cash and it’s pretty easy to interface with the Arduino which handles the rest of the work. It connects to a computer via USB, depending on a PHP script to poll the current price. We dug through the code repository just a bit but didn’t find the snippet that does the actual stock purchase. Whether or not they actually implemented that, it’s certainly an interesting concept.

42 thoughts on “This Piggy Bank Is Our Stock Broker

  1. Ugh, I am so tired of seeing projects where people obviously never bother to measure anything or even make an effort to cut a square, well aligned, straight hole! I know some of these things are just “fleshing out” ideas, but dang guys! Try working on those fabrication skills will ya? You never know when your prototype is going to end up being the end product. Working on getting it right the first go will only help build those skills.

    1. I would like to see less jerry-rigged and more complete looking projects. It is a visual display of pride and the effort put in. Imagine if this looked like you might buy it in a store? I would probably call it a cool hack and overlook that I am fairly certain when you buy or sell a stock there’s a flat commission. So buying one stock at a time would most likely be worse than using an ATM with a $3 transaction fee to withdraw 200 dollars in separate 20 dollar transactions.

      ps, I’m quarter Jerry.

  2. They most likely didn’t implement an auto buy feature since regulations require a human in the loop to make the purchase. The human in the loop can be as simple as pressing a button though, so it would be simple enough to get rid of by explaining that the placing of the coin or pressing of some button is the consent to purchase.

    Either way, very interesting project!

      1. Yup, to the point where they’re building offices closer to the stock exchange, so the light pulses don’t take so long travelling down the fibres to get there. Nanoseconds now = $$$. Machines salami-slice trades thousands of times a second, to make big money out of a million slices of uncertainty, while humans try find routines so the machines can anticipate each other while knowing they too will be anticipated.

        From the days of “If you all chip in to buy me a new plough, I’ll give you a share of the profits from my corn”, to this, one can’t help but feel something’s gone horribly wrong.

        It doesn’t help that the nature of competition drives each of them faster and faster. Every MHz opens another little window for Chaos to get in through. Mathematical chaos, obviously. The stock markets are well past the point of human understanding even in theory now.

        It’s kindof a bummer, and as usual it’ll be the poorer people who didn’t have any stock to start with who’ll suffer when it collapses. So buy stock in whoever makes dried food and shotgun shells!

        1. I don’t disagree with that. 80% of fund managers under-perform basic market averages, lol……..with more banking/finance jobs than manufacturing, what do you expect from this shit bag country….

  3. Smee is right. Love the build, but actually using this to buy is a real, real bad idea. In many cases the stock price would have to double or triple just to break even. Set it up to buy in lots of several hundred shares, and it’d be a different story. But I LOVE the idea and the build! Very creative.

    1. When I was a kid (centuries ago), my mom had me in some cheapo stock program for kids where you really good buy in small volumes without huge transaction costs. I’m sure there were serious limits on what you could do with, when compared to a proper brokerage account.

      But it was a good learning tool. I’d ride my bike to the library and look through pages and pages of historic and current stock prices before telling my mom what I wanted.

      So I’d like to see this as an educational tool that does the same. Parents load one of those accounts with $100. The kids save their chore money, allowance, lemonade proceeds, etc. They can track and choose stocks from a list and punch them in the machine. It could even track their gains/losses for them, and then make purchases as described.

      This would make for a brilliant widget to go with a service like that, if they still exist.

        1. With my original comment I was half baiting in hopes someone knows of a small volume percent based fees broker….to answer your question, the best thing I know of that could help you out would be share builder – though it is for long term investment and reinvestment of specific stocks and is not for trading.

          1. Smee, sharebuilder was actually one of my first thoughts too. You’re right though, it doesn’t seems like this build would work with that, as I seem to remember that was a an automatic investement program of some kind.

            But may companies do have direct purchase programs where you pay zero transaction fees. Some of them use an outside company that acts a little like a broker, and only charge (something like) $1 to buy. In addition, you can do DRIP programs for automatic dividend reinvestment.

            That would be more likely for something like this, except that you wouldn’t be buying at the 3pm market price for a share. I believe (you’ll have to check this) that those work such that you’re purchasing at the days closing price. I also don’t know if direct purchase programs allow you to purchase through an API or web form.

            Either way, this is a great way to buy stock in a company, for someone that doesn’t want or need the full features of a typlical brokerage account, doesn’t care about buying at the 1pm price instead of the 3pm price, and is only interested in longer term holdings… since you won’t be selling your shares quickly.

  4. Smee and Dougmsbbs are correct. Even through a company like sharebuilder you are looking as a per buy/sell transaction cost of anywhere from $4.99 – $9.99 or more depending on what service you use to purchase your stock. So if the share of stock has a purchase price of $28.99 you must factor in a transaction cost of lets say $4.99 to that purchase which would equate to a cost of $33.98. To sell that share would cost an additional $4.99. So the total transaction cost for that share / buy sell is $9.98, and at $28.99 for the share you would have to sell the share at $38.97 to break even. Not to mention any capital gains tax you would have to pay.

    The device is really cleaver, but as a banker and stock buyer, I shudder at the concept of buying one share at a time. This think is a money put as you are in the hole $9.98 to even do anything with the share (buy and sell).. Only way this could really be cool is if it let you store funds, and buy a number of shares at a time so it spreads the cost over the number of shares, decreasing your buy/sell cost per share.

    1. I like that idea. Use it as a piggy bank for your spare change, then when the amount you’ve put in it equals the total cost for, say, 20 shares, then fire off the purchase order. The only thing I don’t get is once the purchase has been made, what do you do with the coins? Take them to your bank for deposit to cover the debit from the purchase?

    2. Things sure must be different in the USA. In Australia, the minimum buy / sell is a “marketable” parcel, value $500. Plus broker’s fees.
      So I suppose our version would count the change up to $500, AND monitor a stock, to tell you how many shares you’ll get [once you go over $500].

    1. But then you can hedge those shares against a money market mutual fund, then re-invest the earnings into foreign currency accounts with compounding interest aaaand it’s gone.

  5. Why don’t banks have a machine like this, where you can come, put your bank card in and throw the contents of your coin jar down a chute and have the money deposited into your account?

    1. They have them in supermarkets. Pour your change in, it counts it pretty quickly, then prints out a voucher. You take the voucher to Customer Services who redeem it for cash. This saves having to fill the machine with high-value currency. Anyone who robs it can have as much pocket change as they can carry away.

      The machine keeps 7% of the money. I suppose for the supermarket it’s another source of change, which they sometimes have to pay for from a bank. Presumably the machine’s owner pays the supermarket rent, or gives them a cut.

      They’ve been in UK supermarkets for years now. I’d be surprised if it was only us.

        1. As far as I can remember, it’s 7% in the one round the corner. Maybe it varies, but I don’t suppose it’s a service with a lot of competition. 7% of pocket change isn’t too bad to get rid of the trouble of carrying it. Tho I’ve sometimes bought tobacco with a heap of pennies and 2p pieces on the day before payday.

        2. Time to upgrade that memory.

          Coinstar basically OWNs the coin-to-cash market (big Green machines in every grocery store and walmart)

          9.8% in the US and 11.9% in Canada

          But (and it’s a good but) you can get a Amazon voucher for 100% of your coins (other vendors too, but who cares, has pretty much everything).

      1. I thought I remembered seeing some from specific banks (in supermarkets) that offered no fees if you were a customer of that bank, otherwise the ~10%. Coinstar is pretty prevalent, but there are others too, right?

    1. You loose before you even start playing, transaction costs. Creative, but worst piggy bank ever.

      Also the 3 stocks that you choose from will likely take a long long time to re-earn you that transaction cost from single purchases, if ever. I don’t even do stocks and this makes sense to me.

  6. Maybe if the stock goes up enough they could afford to buy a carpenter’s square (or teach their seeing eye dog to bark two times when something is square or level).

    //dead Amish people the world over are spinning in their graves over that build//

  7. As far as I can tell, it never claimed to buy the share for you. It just counts the coins and lets you know when you have reached enough to buy a share. Correct me if I’m wrong…

    1. FTA

      “When the piggy bank’s value equals that of the stock price, StockBank automatically purchases a share of the selected stock.”

      Consider yourself corrected.

  8. “Your $22.00 of actual currency has been changed to stock which has dropped in value due to single share purchases and has been maligned to penny stock. You now owe the machine $14.00 for the difference in price due to market fluctuation during the amount of time it took you to pour in your next jar of coins”..
    Rinse/repeat until you owe them your first born lol.

  9. wooow awesome, so that piggy thingy has some sort of teleport thingy that transfers magic coins to whoever offers stocks, and in return, prints them back as bacon!! yummy!

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