Next in our closer look at the reference model is the Rfish reader. It should be able to distinguish swimmers by reading their personal ID. In principle, the reader could be designed to work as a stand-alone lap counter but as you’ll see soon, connecting it to the internet makes it a lot more useful. Therefore, we design the Rfish reader to pass the data it reads on to a web server.
In the near future, web-enabled special purpose devices and even individual sensors will each have their own direct connection to the internet over one of today’s mobile phone networks (an example of such a device is the Amazon Kindle). But right now, GPRS modules required for such a connection are still a little pricey. Fortunately a cheap alternative is readily available, because of the abundance of Bluetooth-enabled mobile phones. All we have to do is to wire our reader to a cheap Bluetooth hardware module and use a standard mobile phone as a gateway to the web. A further advantage of this setup is that we can connect multiple readers through a single gateway, reducing the cost per lane.
Since Bluetooth data transmission works without wires and doesn’t consume too much energy, it should be possible to put the reader, the Bluetooth module and a battery together in a relatively small, water-tight case. In terms of energy use, low-power ZigBee radio would be even better, but current mobile phones do not support it.
There is at least one supplier selling an RFID reader with Bluetooth in a palm sized form factor for around $300. Assembling a custom reader might lower the cost, given the actual price of RFID readers and bluetooth hardware. Still, the prototype will be considerably above $100. And yes, this is an optimistic estimate by someone who never before designed a hardware product. So, if you know better please drop me a note.
Photo by Thomas Hawk
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