Interference on wireless computer readings when using flashing LED front lights

Discussion in 'The Bike Cafe' started by Wrightstuff, May 10, 2005.

  1. Wrightstuff

    Wrightstuff New Member

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    Hi has anybody else noticed that some wireless computers can be affected by their flashing LED front lights.

    I had a Sigma wireless kit and I found that when I used a single flashing LED front light, the speed readings would go crazy when I turned the light on. I told my local LBS this and they couldnt believe it. However with a similar light and a new specailized wireless computer (still in the plastic packaging and nowhere near a bike) turned the light on and then the speed readings went haywire (from zero to 22-28 km/h). My newer 5 LED front light didn't seem to affect the computer.

    Are wireless computers also affected by other stray effects ?
     
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  2. wackydeirdre

    wackydeirdre New Member

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    I'm not sure but it may explain my cadence computer failure
     
  3. MountainPro

    MountainPro New Member

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    your wireless computer uses an infrared diode and photo transistor as an emitter/detector. The ir diode is basically an led that emits light in the ir wavelength that us silly humans cannot see. The transistor will pick up stray infrared radiation from any source. Your light LEDs shouldnt emit radiation at any other wavelength other than red/white/blue (depending on the colour of the diodes) but unfortunately due to impurities in the semiconductors the wavelengths arent very narrow and they do start flashing in infrared wavelength as well. There is nothing you or the manufacturers can do about it.

    your flashing light LEDs frequency is being interpreted by your cycle computer and converted into speed. The computer thinks the light is coming from your ir led on the wheel and the speed of your flashing LEDs will equate directly with the speed of a wheel for the speed being diaplayed on your computer....pretty clever really.
    If you stop using leds and use halogen or krypton bulbs instead this should reduce ir radiation.
     
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