Tuesday, November 12, 2013

Nike Glow v2

Its been a year and a half since working on my first revision of what I have termed "Nike Glow" so I decided to finally revisit the idea and see what I could improve. To figure out what I wanted to do in the new revision, I made a list of issues with v1.

  1. Impractically large controller box.
  2. Complex accelerometer wiring.
  3. Using an accelerometer allowed more flexibility but created complex code.
  4. 9v battery did not create stable enough output causing instability in the micro-controller when the LED switched on
  5. Arduino board was too large and required additional power
  6. Battery was not rechargeable and inconvenient size.
Next, how would I address these issues?
  1. Main cause was the Arduino board size and battery. I needed to go with a smaller board and a better suited battery. The smallest Arduino is the Pro Mini which is 0.7" x 1.4", small enough to fit in the Nike + adapter slot in my shoes. It is more difficult to program since you need a separate USB controller but it is worth it to save the space. For the battery I went with a LiPo 3.7v 850ma battery. The dimensions of the battery would allow me to mount it inside the shoe somewhere, the voltage was enough to power the LED and Arduino, and it was rechargeable allowing me to just plug it in each time it needed to charge.
  2. In place of an accelerometer, I went with a Force Sensitive Resistor (FSR). It is simply a sensor that increases in resistance when pressure it put on it. This would allow me to sense if someone had their weight on the heel of the shoe, which typically means they are standing still. When weight is removed, resistance drops, and I can switch the LED green. The best part of this is that I went from 8 wires running from the Arduino to the sensor, to two wires from the Arduino sensor. On top of that, all I had to do in the code was read the analog input from the FSR and determine what number corresponded to the appropriate pressure in the shoe.
  3. See above
  4. 3.7v 850ma LiPo battery created power the spare since it can provide up to ~3.1watts and the LED only pulls up to 1watt when each color turns on. In addition I went with the 3.3v 8MHz model of the Arduino Pro Mini which uses little to no additional power. 
  5. I went with the smaller Arduino and battery :-)
  6. See #4
Look at this, all my parts showed up!

In the first revision of my shoes, I was able to fit the accelerometer in the Nike + adapter slot in the shoe. My original plan was to put the Arduino in this same slot but as you can see, this would not work.

Guess I have to remove the plastic holder ¯\_(ツ)_/¯

For the LED, I need to drill a hole in the heel of the shoe so it can light up the bubble. Once again, in my v1 shoes, this worked perfectly but since I am using a lower voltage this time around, I ended up cutting out the foam of the shoe so I could place the LED as close to the bubble as possible.

This is how I originally planned on laying the sensor and LED out. The sensor data sheet states the ideal location to attach it is a hard surface where the back will not deform. The back of the LED would have been perfect for this if I didn't end up burring it in the shoe.

The FSR sensor is very simplistic in its setup. You just have to provide a voltage to one side, and a pull down resistor to the other. Connect a wire from the pull down side and connect it to an analog input on the Arduino. 

Next, I had to make my own harness for the battery to connect to the Arduino since one did not exist.


Now that I had power, I could wire up the LED and connect it to the Arduino. Since I am only using red and green, I didn't bother with connecting the blue line.

Hey, look at that, I did something right the first time! I'm skipping over the code writing and uploading section since thats pretty anticlimactic. Essentially when the pressure on the FSR is above a certain amount, the LED changes red. When its under a certain pressure, it stays green for 3 seconds minimum (longer if the pressure is still below the value I set.

The following pictures show the installation of the electronics into the shoe along with testing the LED.

I tucked the battery away in a spot inside the wall of the shoe. 

So this is Nike Glow v2. Its a bit of a step forward compared to my v1 in many ways. Smaller, lighter, faster, more efficient, etc. I truly believe the technology exist to manufacture a shoe like this that is better integrated. The potential to have a shoe that is visible at night and lets others know if you are moving or not is something I love having. For now, I will see where this tech goes and maybe revisit it if something new comes up.

Don't forget to view and thumbs up my ad I made!

-Daniel Spalding

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