Wacked Out Wireless World

When on, LED lights may generate weird errors on some bike computers. Welcome to the wacky world of wireless.

What’s wrong with the above photo? Note the speed – 59 mph. The bike isn’t even moving. It’s not trickery, but I wish it were. It’s the result of radio frequency interference (RFI), also called electromagnetic interference (EMI) between the light and bike computer.

My bike computer is wireless. The light has light emitting diodes (LEDs), which are tiny die cut from a semiconductor wafer. Apply a small current and they light up. And therein lies the problem. These highly efficient LEDs need power for an integrated circuit (IC) to make the LED light up. In addition to batteries, the light’s power module needs an inductor, basically a small wound copper coil.

This coil creates a magnetic field and you know that means. Magnetic fields generate electric currents that oscillate at radio frequencies. The printed circuit board design and the kind of power IC (switching regulator) can also come into play generating more errant signals.

The bike computer relies on a radio frequency that’s generated by the small magnet attached to the front wheel spoke and transmitted to the unit on my handlebar.

We experience EMI interference all the time, especially noticeable with cell phones as they encounter radio frequencies generated by our TVs, toasters, computers, most anything electronic, Bay Area Rapid Transit (BART) included.

Unfortunately, my bike computer is low frequency analog. Some bike computers are digital and digital signals typically transmit at higher frequencies where there’s less interference.

I can’t give advice on which devices have conflicts. You have to find out for yourself. Short of moving the devices farther away from one another, or wrapping them in lead, there’s nothing you can do. (I moved the computer onto the handlebar but it didn’t fix the issue entirely.) Some cyclists choose to run wired computers to avoid this issue.

I’ve used wired bike computers and they have their own problems. Technology rules, but not without some minor inconveniences.

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2 Responses to “Wacked Out Wireless World”

  1. Murali Says:

    Out of curiosity, what problems have you experienced with wired computers? This is one application where I thought wireless has very limited utility.

    I have a wireless on my Ritchey Breakaway, because when I take it apart, I do not want to disconnect the computer (because the wire is connected to different parts).

    However on my other bikes I have wired computers and have no problems. The wire gives me no drawbacks. The wireless is yet one more thing to keep in tune.

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