Wireless Cycle Computers and Interference

Today a customer came into the shop complaining that his cycle computer was giving wild readings whenever he turned his LED headlight on in flash mode. "Yep," I said, "it's RF interference. I've seen wireless computers freak out under power lines and by the anti-theft scanners at store doorways as well. The internet knows about it." The customer had tried his own search plugging in the names of his cycle computer and light together with the word "interference" and had come up empty but a quick "RF interference cycle computer" brought up pages of results showing a variety of lights and computers exhibiting the problem.

The customer was less than thrilled with my initial idea of making a little foil shield but Mike managed to make the computer behave by moving it to a location on the handlebars further from the light. Poking through a few of the pages revealed by the internet search revealed a few interesting tidbits.

• Wired computers pretty much don't have this problem.
• The newer, fancier cycle computers using the ANT+ digital protocol don't seem to have this problem.
• There are still idiots on the internet and a lot of wrong info.

The final bullet point is illustrated by the page at:

http://uk.answers.yahoo.com/question/index?qid=20090221044009AA3z7oF

The question asked is:

Is it true that wireless bike computers don't work if you have LED lights?

and the group wisdom is:

No it doesn't happen and the logic seems to be: I've never seen it, therefore it doesn't happen. My favorite is the guy who adds "Source(s): 6 years as professional bicycle mechanic."

We could apply this "logic" elsewhere. For example, I've traveled for 30 years and never been to Portugal, therefore Portugal does not exist. Or, I've ridden a thousand miles and never had a flat tire, therefore flat tires don't exist.

So, doing my bit to add a bit of signal to the noise that is our beloved internet, I'm posting these words:

Some LED lights when flashing do interfere with some wireless cycle computers. I've seen it. If it happens to you, try increasing the distance between your computer and your light or maybe work up a shield or switch to a different cycle computer.

And remember, no matter where you are or what time it is, someone is wrong on the internet.

Keep 'em rolling,

Kent "Mountain Turtle" Peterson

Issaquah WA USA