crazy computer

Discussion in 'Cycling Equipment' started by Robert Strickla, May 13, 2003.

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  1. Help! My bike computer (Sigma Sport BC800) seems to have flipped its lid. I took the spoke magnet
    off briefly and now after I've put it back on, the computer is giving me at least an extra 5-10
    miles/hour. I know I didn't suddenly become really fast and I can't imagine why this would be
    happening. I didn't remove or adjust the receiver unit or change anything on the computer itself.
    Any suggestions why this would happen? Thanks in advance.

    Rob Strickland
     
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  2. Don Holly

    Don Holly Guest

    Perhaps you've managed to position the magnet just right so that it sometimes teases the sensor into
    switching twice per revolution. Try adjusting your wheel magnet a little.

    Robert Strickland wrote:
    > Help! My bike computer (Sigma Sport BC800) seems to have flipped its lid. I took the spoke magnet
    > off briefly and now after I've put it back on, the computer is giving me at least an extra 5-10
    > miles/hour. I know I didn't suddenly become really fast and I can't imagine why this would be
    > happening. I didn't remove or adjust the receiver unit or change anything on the computer itself.
    > Any suggestions why this would happen? Thanks in advance.
    >
    > Rob Strickland
     
  3. Rb

    Rb Guest

    I have the same model. I've had two times where the odometer went backwards, counting down mileage
    instead of up. I got it to work properly by pressing the function select button and going through
    the functions a few times. In your case, could your cyclometer gotten itself somehow into measuring
    kph instead of mph? Look at the calibration setting to make sure. I can't see how taking the magnet
    off and back on could cause this, since only movement of the magnet past the sensor triggers the
    electrical signal input to the cyclometer. One pass equals one impulse.

    r.b.

    "Robert Strickland" <[email protected]> wrote in message
    news:<[email protected]>...
    > Help! My bike computer (Sigma Sport BC800) seems to have flipped its lid. I took the spoke magnet
    > off briefly and now after I've put it back on, the computer is giving me at least an extra 5-10
    > miles/hour. I know I didn't suddenly become really fast and I can't imagine why this would be
    > happening. I didn't remove or adjust the receiver unit or change anything on the computer itself.
    > Any suggestions why this would happen? Thanks in advance.
    >
    > Rob Strickland
     
  4. dennisg

    dennisg New Member

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    I've had weird things happen to computers when water somehow seeped underneath the computer and managed to cause a short between the connecting terminals.

    If the other advice you're getting doesn't fix the problem, take off the computer and wipe down the terminals.
     
  5. Jobst Brandt

    Jobst Brandt Guest

    Robert Strickland writes:

    > Help! My bike computer (Sigma Sport BC800) seems to have flipped its
    > lid. I took the spoke magnet off briefly and now after I've put it back on, the computer is
    > giving me at least an extra 5-10 miles/hour. I know I didn't suddenly become really fast and
    > I can't imagine why this would be happening. I didn't remove or adjust the receiver unit or
    > change anything on the computer itself. Any suggestions why this would happen?

    First off, it seems the magnet is not positioned correctly. That is the first place to look.
    However, for it to give a higher than accurate reading, it would have to give a double trigger to
    the pickup, at least now and then. I can only imagine that the magnet is out of place. Did you check
    your calibration number to see if it is still the correct one?

    The pickup on these units is a reed switch whose closure, by the passing of the magnet, draws
    current from the speedometer. To prevent draining the battery in the event the magnet is parked in
    next to the pickup, a high impedance circuit is used (with a large resistor and capacitor). If the
    mounting bracket becomes wet and the water is not distilled water, the contacts can be effectively
    shorted so that the capacitor charge is leaked out and only a few or no pulses are detected. Since
    this interface is not easily kept dry, the next best method is to spray it with Armor All, or some
    such hydrophobic liquid, so that a continuous water film cannot produce a short. Although the
    opposite from your predicament, it is something to be aware of.

    Other than that, you could have a goofy unit. Did you drop it?

    Jobst Brandt [email protected] Palo Alto CA
     
  6. "I have the same model. I've had two times where the odometer went backwards, counting down mileage
    instead of up."

    Now THERE'S one I have never heard before ROTFL!!!

    May you have the wind at your back. And a really low gear for the hills! Chris

    Chris'Z Corner "The Website for the Common Bicyclist": http://www.geocities.com/czcorner
     
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