My LED lights seem to be causing my wireless cycling computer to not pickup the signal (suggested by the manufacturer and verified through tests at home).

What strategies/options are there for reducing the interference outside of repositioning the computer (since I've tried all available positions)?

  • I would be interested in hearing what the tests were. – Gary.Ray Oct 13 '10 at 23:04
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    I moved it around spun the tire then turned on the light. It kept reception better if the light was on solid but still dropped. If the light was flashing it dropped right away. – curtismchale Oct 14 '10 at 2:09
  • What cycling comp was it? What kind of LED lights were these? Also what colour lights were they? I have 2 white LED lights normally in "flashing" mode and haven't seen any interference. That's not to say they don't interfere but I'd appreciate if you had some more information. You can see my lights and where they are placed in relation to the comp here: flickr.com/photos/runningwithbulls/6978622804 – Bernard Tyers Apr 29 '12 at 15:18
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    Might get better answers over at www.electronics.stackexchange.com. – mattnz Apr 10 '14 at 3:31

Because the items are going to have to remain in close proximity, it's unlikely that there is anything that will completely solve your problem, but there are a couple of things you can try.

If the lights are wired, it is possible that the wire is working as an antenna, and you can use a Ferrite Choke or two on the wire.

ferrite choke

Tape one near where the wire leaves the battery, and another to where the wire lead plugs into the light. The can be found at stores like RadioShack for a few bucks.

If the lights are wireless, aluminum and tin foil is an excellent reflector for this kind of Electro-Magnetic Interference (EMI).

The first step would be to see if foil will help. Try wrapping the outside of the lights with foil and repeating the tests you did before. I doubt you can add foil to the computer because this will interfere with it picking up the wireless signal from the sensors.

If that reduces the interference you can tape the foil to the lights, carefully cutting away the foil around mounting brackets and buttons and see if the EMI is still reduced. If the lights can be easily disassembled you can try taking them apart and lining the interior with foil as well; take care not to short out the internal electronics.

Good Luck.

  • It'd also be intertesting to see if the OP tried using the suggested ferrite choke. If you can't find/don't want to spend the couple of bucks to buy one, they can normally be found on some electronics equipment (like your broadband router, or a house telephone) as they are sometimes susceptible to RF interference. – Bernard Tyers Apr 29 '12 at 15:20
  • Might as well got to Halogen lights given the weight of an effect choke. – mattnz Apr 10 '14 at 3:19
  • @mattnz there are much smaller chokes than the one pictured, and ferrites may be more effective if you pass the wire through them a couple of times in a loop. – Chris H Apr 10 '14 at 8:36

The problem is the current controller built into the LED bulb has no or ineffective EMC suppression. This is extremely common in cheap equipment from unbrand named suppliers, who save costs by not going though the rigourous CE or FCC testing requirements. They also cut costs by not placing components (usually a small cap is all thats needed), and lay out the board poorly so it radiates noise.

I have heard of people successfully soldering a small tantalum cap onto the LED board. Best palce is as close to the control IC as possible, across the power input wires. If that does not work, another across the LED itself would help. (Careful, they are polarised)

Alternately wrap it in a conductor (Tin foil is good), and tie it to ground to create a Faraday cage. Problem is with it tied to ground, its hard to ride far, and you need a hole to let the light out, but that lets out the RF noise.

A better option is to buy a light that meets CE or FCC EMC standards, but they tend to be more expensive.

  • Unfortunately on a bike there's no ground to connect to, but a Faraday cage might help even without and depending on the frequency of the wireless you could have quite a big hole without spoiling that. But it's certainly worth adding capacitors - I'd probably put a scavenged ceramic (non-polarised) across the battery leads where they meet the PCB and across the LED lines as close to the LED as possible. I know on 1/2 power my front light uses PWM, and I suspect that it regulates the current in the same way even on full power. – Chris H Apr 10 '14 at 8:45
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    I would second the recommendation for lights that meet standards. They also will pay attention to light intensity and wavelength standards that cheap ones won't. – JohnP Apr 10 '14 at 15:33
  • The Faraday cage (aluminum foil) is a good idea. It need not have 100% coverage to be reasonably effective, and simply "grounding" to the handlebar should be sufficient. And if one is a real fanatic about it, you can buy fine aluminum screening that would let most of the light out while shielding the lens opening. – Daniel R Hicks Oct 24 '16 at 21:18

I too had major interference problems between my 700lumen Smartlight (no, not the Garmin one, just a brand called Smart) and VDO M6 wireless computer with all 3 sensors (speed, cadence, HRM) stopping when light was on. I tried wrapping the light in normal, household aluminium foil and hey, it works! Not too pretty but no need to spend time making a bracket to mount the light away from the computer. By the way, it also started working, without the foil hack, when I held the light more than 12cm from the computer.

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    Nice work - a rare case where a tinfoil hat is useful and effective. – Criggie Sep 28 '16 at 23:51
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    @Criggie - I dunno, I've lined my helmet with tinfoil and since then, the aliens have stopped speaking to me. I do have to wear the helmet 24/7 though. :-) – RoboKaren Jan 2 '20 at 5:56

When wrapping your light with tin foil, remember high power means maximum ventilation is required. They can chuck out some heat. On the computer side, when was the last time you changed the battery in the sender unit attached to the fork? Does the problem only occur when your light is on flash or pulse? If so try switching to a steady light instead.


Another thought is to disassemble the light, and paint the inside of it with electrically-conductive paint.

Downsides are that the light is more capable of shorting should anything go wrong with the internal wiring, and you might damage the light by disassembling. You could also paint the outside of the light, but it would suffer from wear.

Note the paint used MUST be electrically conductive, not just silver-coloured. These paints are expensive, probably more expensive than a new light.


For me, foil allowed the computer to operate only if I covered the entire light, cord, and battery with foil, including the lens. So, I got a new computer that uses signals from GPS satellites rather than pulses from a magnet on the wheel to measure speed and distance. This solved the problem. My light is a Nite Rider MiNewt. It has a cord: it is not the wireless version. My old computer was a Specialized Sport. My new computer is a Garmin Edge 25. I had used the MiNewt with other wireless computers without problems.


A wired Cateye fixed the problem for me

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    Well you're not wrong, but a super short answer like this makes the SE quality bot sit up and flag it. Can you use Edit to add further information? Did you try any other solutions? Do please read the tour to learn how StackExchange works. – Criggie Dec 30 '18 at 0:05
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    Unfortunately, wired units are hard to find. – Daniel R Hicks Dec 30 '18 at 1:52

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