I have a Cateye Urban Wireless computer on my road bike. I commute to work sometimes, and I use a Light & Motion brand Urban 800 model light. I started noticing that speed and miles were not being recorded on the computer for about the first mile or two after I leave home. I thought the batteries were the problem so I replaced them. Same problem. I pulled the urban wireless instructions out of the box, and sure enough, it indicates that 'interference may occur...or certain battery-powered lights. I had a different light on for awhile before the Urban 800 and never experienced this problem.

Are there certain brands or models that do this? Anybody else experience this? Don't really have many options for mounting the light away from the computer on road bike handle bars.

Thx,
Mark

Yes, and it's REALLY annoying. I have a very old Lupine Tesla that interferes with wireless computers, but since it was made before the latter became really popular I wasn't too surprised. However, I was quite disappointed when a brand new NiteRider Lumia 750 also interfered with it. In the end I replaced the wireless computer with a Cateye wired one.

Interestingly coded computers don't seem to suffer from this problem. My Garmin Edge, for example, continued to pick up the signal from the cadence/speed sensor regardless even though it was mounted much further away.

That just proves that wireless isn't always the best way to go.

Jon

How close is the light to the computer? Do you have an option to move them to opposite sides of the handlebars? Or mouth the light lower, like on the stem or the head tube?

If there is interference I am guessing the light needs to be very close to the computer to cause it. Even if the light is between the computer and the wheel sensor it should be okay. It's likely that the light is too close to the computer itself.

Another option is to create a Faraday Cage. (It will help disperse rouge electromagnetic signals) Wrap the sides of the light in aluminum foil or a piece of metal window screen (has to be metal, not vinyl). See if that fixes the problem. If it works you can do it carefully so it looks nice. It might not work but it's a very cheap thing to try.

It probably will. But then again, moving the light a couple of inches away will also probably fix it.

I have the same problem with my light/speedo. My light is a Nite Rider 500 something, the computer is a Catseye wireless unit. What I have noticed is that if the light is on high or pulse the speedo works fine, low or medium causes the speedo to quit. I've come to the conclusion that it is a elector-magnetic field caused by the light causing the problem. Unlike a "nromal" light, LEDs are pulse width modulated to achieve "low light" settings which sets up the interference. As mentioned shielding the light with foil or such should stop it but it looks like kaka. The other option is to move the two as far apart as possible which worked for me.

fasthair

I have a Light & Motion Urban 900 mounted to the left of my stem. The cycling computer was mounted at the forward-most part of my stem, so the rear of the L&M light sat along the side of my CatEye computer. When the light was on, I lost computer sensor reception.

Moving the computer aft a couple inches, to the rear of the stem was enough to make the difference. Perfect reception now that they aren't directly adjacent to each other.

So yes, LED lights do interfere with wireless cycling computers. I believe the reason is that the lights strobe at super high speeds to regulate brightness, and this oscillation has some RF leakage.

It might also help just to swap sides. If the light is on the left and the computer is on the right, just swap sides. The computer's sensor could be on the same side of the unit that the light is on. Simply putting the light on the other side, an inch and a half further from the computer's sensor, could solve it.

(But the Faraday cage idea was more fun in a nerdy way. I like to take a "Damn you, physics! I'll put my stuff where I want to!" approach to life.)

I'm not sure the Faraday cage will make any difference. Most of the better bike lights and flashlights are already inside one, in the form of their aluminum housings. Leakage paths for stray RF would likely be the switch, the battery compartment door, the charger port, if it has one, and of course, the lens/reflector assembly. And, that RF might be bouncing off the handlebar or something else. About all you can do is try moving the comp and light to different locations.

Do write to the manufacturers of both the comp and the light to inform them of the problem; they can at least look at design improvements for their next round of products.

Very interesting topic. Never occurred to me that there could be issues like this. I've got a Garmin Edge 520 computer and Cygolite 450 Streak front light. They are mounted within an inch of each other. I haven't seen any interference problems, but I don't run the light very much right now. I'll have to watch for problems as the days get darker heading out of the summer months.

Mark

Is there any way to shield the computer from picking up RF interference? It seems that my wireless computer gets along ok with my light, but it seems to pick up signal from whatever outside sources; for example, it doesn't work when a tram is nearby, or sometimes it shows going at crazy speeds while resting on my desk at the office.

I doubt you'll have a problem. This only seems to affect the cheaper computers which are not coded to a specific transmitter. I have a Garmin Edge 705 and the lights never bothered it at all, even though it was right next door. I had to move the Cateye computer to the other side of the bars to let it work with my NiteRider light. It's a shame that wireless computers are now so prevalent.

I assumed a plastic housing. If it's an aluminum housing then yeah, your'e probably right.

I switched to ant+ computer/sensors to work with lights that Cateye wireless computers were not compatible. No problems since.

That is because uncoded one tend to be analog, so any RF spike, like from power lines or apparently a lighting system, will trigger them.

Coded ones tend to be digital, so they don't pick up the interference because it does not match the "code".