Stokes' ProjBlog

Further work on the Soda Machine Hack September 18, 2009

The W&B soda machine continues its march towards the Internet. Yesterday, Sam Gerstein (another W&B member) and I spent a couple of hours investigating its treacherous inner workings, figuring out specifically where the credit-emulating relay needs to go and testing the selection detection board.

Despite a couple of brief setbacks, the afternoon was a success. Virtually everything in the machine worked more-or-less as predicted. The CONTROL BOX did contain a couple of mysteries: a switch fixed in one position in by a steel plate and a couple of screws, a relay not connected to anything whatsoever, and color-coded wires that didn’t seem to match the schematic. Apart from those, however, it was fairly spacious and tidy inside. The machine had apparently been modified modified so that every item is the same price, so only one of the four circuits that denote credit is actually in use, and shorting this with the ‘hot’ connection registered as money having been deposited. The relay board will be easy to integrate.

The selection detection board also went through its first full test. Nervous that it might explode or catch fire, I asked Sam to plug it into the wall. My fears were unfounded, however: no explosion, no fire, and not even a wisp of smoke. One of the seven optocoupler circuits didn’t work correctly, however; it almost seemed to be working in reverse, outputting a ‘high’ signal when AC power wasn’t applied and a slightly lower voltage when it was. Eventually, Sam noticed that one optocoupler’s transistor’s base and collector were shorted; I never spotted it, probably because the transistor’s base isn’t used in the circuit.

Now, I need to reinstall my TINI/1-Wire development environment and start trying to get the software side started.


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