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IoT Application: Road Biking Fitness

IoT Application: Road Biking Fitness
by Daniel Payne on 08-10-2014 at 8:00 pm

Eleven months ago I started a fitness kick in order to lose some weight, get healthy and have more energy, so I picked a familiar activity, road cycling. Being an engineer I have always loved measuring things, like my speed and distance, however I had an old-fashioned cyclocomputer called the Cateye Velo 2. This device connected to the handlebars and a wire went down the front fork to a sensor that picked up the magnetic signal from a spoke-mounted magnet.

Being some 10 years old, there was no mechanism for the Cateye Velo 2 to transfer the cycling data to a computer or the Internet, so I went searching for something high-tech that would connect my ride data to the web. My first approach was to use an Android-based cell phone with GPS enabled and a free app called Strava.This worked pretty well to show me a map of the route, speed and elevation.

The Strava app worked fine on my Samsung Galaxy Note 2 phone, and I just had to be patient waiting for the GPS signal to lock before starting a new ride. When the ride finished I pushed one button in the app to sync my ride data by WiFi to the Strava web site.
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Somehow I wasn’t content with just velocity, because I wanted to know my cycling cadence and heart rate too. My next approach was to buy a wireless device and I looked at several companies:

Garmin was too expensive for my budget, Trek was possible, Sigma was a brand not familiar to me, so I ended up with the Cateye Stealth 50. This device uses GPS to capture my location, along with wireless sensors for: speed, cadence and heart rate.

Being curious, I took the device apart to see what was inside, which of course voided my warranty.

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To the right is the lithium ion battery, separated from the main PCB by a black plastic housing. The PCB on the left has four main chips on it, none of them had corporate markings. From the Cateye website I learned that one of those chips is a 4-bit micro-controller. I can guess that this device has chips for:

  • 4-bit micro-controller
  • LCD display driver
  • ANT+ protocol
  • USB connectivity

The four shiny posts on the bottom of the PCB are the connectors to dock the Stealth 50 to a USB cradle, used after a ride to load your data to a computer, then upload to Strava or Cateye’s web site for analysis. The retail price of this device is $150.00, so I’ll also guess that the margins are also quite high with such a small Bill of Materials. Since were talking about making measurements a few times per second, the chip technology could probably be a mature process node like 180nm, so you don’t really need bleeding edge technology to make a successful IoT device.
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All four companies listed above support the ANT+ protocol for ultra low-power wireless device monitoring, and there’s even an industry association to promote it for a diverse set of uses: runners, swimmers, cyclists, exercise equipment, hiking and medical.

For my bike I added a Garmin sensor to monitor both speed and cadence, it attaches near the rear wheel, and uses the ANT+ wireless standard.

While at the Bike Gallery in Beaverton I purchased an ANT+ compatible heart rate sensor from Bontrager (Trek brand).

Since Cateye is a Japanese company their user manuals take some interpretation, so it was much easier for me to visit the USA web site and watch a how-to video to get all my gear talking and working together.

The fun part is actually going for a ride and being able to view in real time my: Speed, Cadence and Heart Rate. After the ride I can see all of the numbers or graphs in Strava:

The above graphs show the elevation of my route, speed, estimated power, heart rate and cadence. For the time point at the cursor I was gliding down a hill at 40.7 mph, while not pedaling so the cadence was 0, and a heart rate of 156 bpm. On that ride I averaged 90 rpm for cadence, 153 bpm for heart rate, and 20.7 mph for speed. Now that’s a lot of data for a cyclist to consume. The only other technology gizmo that I could add would be either a power meter crankset or pedals, but at prices between $995 and $1,995 that’s way too rich for my budget.


The IoT as a cyclocomputer and wireless sensors has many vendors to help you measure your fitness level and achievements. Standards like ANT+ make a lot of sense for both consumers and vendors, instead of taking a proprietary approach and you really can mix-and-match between them like I did. On the software side the two main web-based providers are Strava and MapMyRide, I started with MapMyRide and then moved over to Strava where the more competitive road cyclists hang out. All of this is made possible at an affordable price because of our semiconductor ecosystem powering the electronics.

Hopefully I may have inspired some of you to get fit too. I’ve lost 30 pounds in 11 months, and am at 170 pounds today because of my cycling fitness efforts. I’ll never go back to my old, sedate lifestyle again.

My son and I just finished the Portland Bridge PedalRide
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