Don't worry, I am not calling for tethered, wired remote controls for the TV; the IR remote is a marvel of low cost and overall reliability (and RF ones are coming on strong, see our recent article, RF in Action: Consumer Remote Controls). But I will admit there are times when a basic, simple wire is a pain, and is better replaced by a wireless link, even if the cost is higher.

My example: the basic speedometer on a bicycle. These consist of two units: a magnetic sensor on a spoke, which opens/closes a switch (reed or Hall-effect) on the fork, and a handlebar-mounted readout. Placing the cable is no problem, since everything is out in the open, and there are no tolerance issues, no complex cable runs.

But at the same time, that cable can be a pain, It can get snagged by branches or when you put the bike in a car, for example. It has to be properly dressed to the fork and frame with lots of tie-wraps. And if you need to take the front fork or handlebars off the bike (for maintenance or shipping the bike in a box), it another thing to remove and then have to reattach.

So the wireless bike speedometer is a great improvement, despite its drawbacks, which include the need for a battery at the sending end (where the sensor pickup is) in addition to the battery in the readout; and higher cost (typically abut $10). [As an aside, both the sender and receiver of the bike speedometer are real low-power design challenges, admittedly helped by the low data rate, low duty cycle, and modest turn-on time requirements of the application.]

The point is that you sometimes have to put your biases aside and look at the application needs versus the pros and cons the solution, to make an honest engineering assessment of what is the "best" approach in an application, given the priorities and constraints. Just because it was a good idea to do something one way before doesn't mean that it is a good idea to follow the same path again, without checking things out.

As always, feel free to contact me by email or phone (no Twitter, please) with your comments, suggestions, gripes, whatever.

Bill Schweber, Site Editor
RF DesignLine
bschweber@techinsights.com
781-738-0389