pcDuino Crowdsource Kiosk

Contributors: Nick Poole
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The Chocolate Dispenser

I started in on this project by designing a gravity fed hopper that can dispense Hershey's Minis one at a time. I chose Hershey's Mini bars because they're small and relatively uniform in size.

Whenever I'm designing a piece of hardware, I start by playing around in SketchUp. Here are the drawings I made:


This drawing shows the dispenser stepping through one ejection cycle.


Here's an exploded view, this helped me when building the physical object.

A servo driven solution seemed to be the most robust approach. My design incorporates a card-shaped pusher moving inside a channel to eject the bottom chocolate bar on the stack. As the servo sweeps counter-clockwise, the push-card slides a chocolate bar through an opening in the front of the hopper. When the servo sweeps clockwise, the card returns to its home position behind the hopper, and the stack of chocolate is allowed to fall in the hopper, thus resetting the mechanism.

It seems straight-forward enough, but before I invested any material in it, I built a prototype out of cardboard. There were some hiccups in translating from cardboard to a more rigid material (in this case: acrylic) but it worked great! Here's a picture of my cardboard prototype and my final acrylic components side-by-side:


The acrylic mechanism turned out larger because the material is thicker and also in order to increase capacity. Note the mounting tabs on the final mechanism!

The servo based mechanism ended up being extremely reliable. Unfortunately, because of operating system restrictions, the same cannot be said of the pcDuino servo library. To remedy this situation, I decided to take the burden of pulsing the servo off of the pcDuino and incorporated a SparkFun RedBoard into my dispenser. The code on the RedBoard is really simple: As soon as a particular pin was pulled low, it would sweep the servo one direction, delay a few milliseconds, and return the servo to its start position. All the pcDuino needs to do now is pull that RedBoard pin low to dispense chocolate!

Before we jump into the pcDuino side of things, let's talk about how this whole thing will be enclosed...