Picking up where Synthesis Studios left off, EETimes has posted a detailed look at the Nike+iPod Sport Kit’s internal components, and their findings reveal some very clever — and very surprising — engineering inside.
Now, I’m not an engineer by any stretch of the imagination — in fact, sewing a piece of velcro onto my shoe is about as close as I’ve ever come — but since the announcement of the Sport Kit, I’ve been fascinated by how such a small, inexpensive device could accurately measure everything that it does. I became even more fascinated after discovering that there’s nothing special about the Nike+ shoes in terms of aiding the Kit’s functionality.
From everything in Apple’s marketing materials, plus the fact that the sensor doesn’t need to be “stepped on” to work, many of us assumed that the internal accelerometer mechanism measured the movement and velocity of the foot. But the EETimes made a surprising discovery:
Perhaps the most amazing finding was related to the sensing element used to detect runner action. Apple’s FAQ states that “a sensitive piezoelectric accelerometer monitors your footstrike when you walk or run and determines the amount of time your foot spent on the ground. This contact time is directly related to your pace.” In the transmitter implementation, this equates to a low-cost stroke of genius in the form of using a piezoelectric disk speaker–common to inexpensive toys and greeting cards–in reverse mode. By allowing some travel in the plate of the speaker, the piezoelectric effect causes the transducer to function as the pickup of foot action. About the size (and cost) of a dime, the speaker isn’t driven to make sound, but rather monitored for motion-induced electrical signals.
This information may help us diagnose the cause of accuracy problems that some people are having with their own improvised methods of attaching the sensor to their shoes. For instance, any rustling or noise produced by the sensor moving around inside the tongue of the shoe, or in an attached shoe pouch may “confuse” the sensor. Likewise, if the “motion induced signals” are too muffled due to the way it’s attached t the shoe, the sensor may not be able to give an accurate reading. That all being said, I had no trouble using the sensor in a Nike Shoe Wallet, but it may be time head back to the lab and do some more investigation. Surprisingly, the folks at EETimes don’t seem to consider that the transmitter might work when worn outside of the shoe:
While Nike sells special shoes with an insole pocket for the transmitter, the device could conceivably be used with other footwear. But it may feel like a sizable pebble if not installed thoughtfully.
Another interesting piece of the EETimes article is their cost estimate and analysis:
The $30 package probably costs less than $7 to manufacture, so profit margins are good, but it’s on a small base. A once-every-few-years revenue of $20 or so is about the most that might be expected in follow-on Sport Kit hardware. Far bigger profits, however, lurk in the prospect of the twice-a-year (or more) $100-plus purchase of specialty running shoes. Similarly, the iPod ecosystem gets a boost with possible player and iTunes sales.
Accompanying the article is a really nice photo of the Sport Kit’s internal components, all labeled for easy identification. I’m hoping that all of this research inspires some “outside the box” uses for the Sport Kit… and for iPods in general. Clearly, the iPod has the potential to be much more than a music/video player.
Thanks to Ho John Lee for the link.
Read the full EETimes article.
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I’m very interested in some sort of RSS/XML access to that Nike data for my runs. There is some real potential for community activity around that, moreso than what they are providing through that Flash site.
You have to have hidden files disabled in either windows or mac to see the information. In a mac disable the option for itunes to automatically open when your ipod is connected. Then when your ipod is mounted on the desktop go iPod_Control/Device/Trainer/Workouts/Empeds/0A0000AAAA(FOLDER NAME VARIES)/latest or /synched (depending on if you already synched to nike +)
You also have to have the iPod set to use disk mode. I needed to access those files on my wife’s iPod to move the XML file from synced to latest because the data was not actually syncing to the Nike site, but it acted like it did and moved the latest file into synced each time. It turned out to be an issue with the Nike site that Nike admitted in a support response, but by that time we had already made up another account that worked instantly.
I’ll have to see what I can do with this!
I’m considering getting one of these, but I primarily run on trails at a park, where the length of my stride is often very inconsistent (up and down hills, over terrain). Does anybody know how accurate it is in such a situation?
I have just added a quick hack on how to add runs that are recorded when you forget to attach the receiver:
http://www.walkjogrun.net/blog/index.cfm/2006/9/6/Hacking-the-Sport-Kit
[...] The article doesn’t specifically mention the Nike+iPod sensor as a beneficiary of this technology, possibly because its implimentation is a bit different, but it does mention that motion sensing technology has already shown up in portable computers and cellphones: Nokia this year launched a “sports” cell phone, the 5500, with an accelerometer that not only controls a game, but works as a pedometer as well. Other potential uses for such a chip in a phone include managing the user interface: pat the phone or flip it over to send a call to voicemail, Vigna suggested. [...]
I already have a sansa mp3 player. Does anyone know if a compatible sport kit is coming or will I have spend the bucks for an ipod?
John: Since the Sport Kit was co-developed by Apple, it’s unlikely they’ll release one compatible with the sansa player.
Thanks Thought I’d ask before spending the bucks on an ipod. My sister recently got the sport kit, it seems to really motivate her running.