Studies of elite athletes have shown that a faster running cadence leads to increased speed and endurance as well as less injury caused by things like over-striding. Many articles quote a magic cadence number of 180 strides per minute (90 per foot) as being the perfect target. The 180 target is not without debate, but the focus on this project is not on finding the perfect number. Instead we are concerned with how to measure cadence in real-time so that one can actually target whatever number is right for them.
Sports watches exist that can sound an alarm when cadence is above or below a pre-defined threshold and/or show the average cadence after a run is complete. These are nice features, but what you really want to know is what is your cadence right now so that you can adjust in real-time to hit your target.
Sparkfun Pro Mico
This is a very small micro-controller. It fits neatly inside our watch enclosure. It is not an official Arduino board, but it is Arduino compatible. That basically means you have to do a little extra setup before you can program it via the Arduino IDE. The process is pretty straight foreword.
850mAh Lithium Ion Battery
110mAh Lithium Ion Battery
Power Cell (Lipo Charger/Booster)
Our battery outputs 3.7V. The Pro Micro board requires a 5V power source. The power cell is used to boost the 3.7V output to 5V for the Pro Micro. The battery hooks into the power cell using a standard JST connector. The power cell provides a convenient micro-USB connector that can be used to charge the battery. We expose this connector on the side of the enclosure so that the watch can be recharged without removing the lid.
SPDT Mini Power Switch
The on/off switch exposed on the outside of the watch enclosure.