Remember the old days, when you had to insert a coin into a machine and twist the handle to get a tasty treat, or better still, just twist the handle? Well, we've bought that bit of nostalgia to the 21st Centuary with the mbed Snack-o-tron, replacing this :

With :

.. you'll just have to wait :-)

All you have to do is send a text message saying either "SNACK 1" or "SNACK 2".

If sending a text is too much hassle, just use your smartphone to read the QR code, and send the text message for you!

How it works¶

The handles have been replaced with Dynamixel AX12 servos. These have been programmed to wind the handle forward 60 degrees each time a snack is ordered, delivering precisely one portion of deliciousness - just make sure you have a tub ready.

Of course, the servo motor isn't the novel bit, it is the ordering system on the back end. The QR code will instruct a smart phone to send a text message, or you can send the message manually. A mobile messaging service, Txtlocal, will send the contents of the message to python script we installed on a web server, which makes a note of the orders. The mbed microcontroller then polls the web server to see if any snacks have been ordered, and if so, dispenses as needed.

The code¶

More details¶

The hardware setup for the Snackotron is :

• mbed + Snack dispenser
• Ethernet connected via an RJ45 connector
• AX12 servo motor(s), driven on a half-duplex serial port
• LCD for the useful status information
• 9v power supply for the servo motors (900mA each!)

The software components were all sourced from the cookbook :

• HTTP-Client
• Ethernet
• Dynamixel-AX12-Servo
• Text-LCD
• SerialHalfDuplex