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Cadence sensor data is being used to show speed on Edge 500

I've just purchased new non-magnet cadence and speed sensor twin pack to replace my GSC10 which stopped working, to use with an Edge 500 and I've got a bit of an odd problem happening.

If I pair only the cadence sensor and rotate the cranks then I see a reading for cadence on my Edge display, if I pair only the speed sensor then I see a speed reading when I spin the back wheel, now if I choose to pair as "cadence and speed sensor" (not cad/spd option) then when I rotate the cranks I get a reading for cadence and also a speed reading but the bike is stationary. I'm rotating the cranks backwards but I don't think this should be an issue. It would appear that the Edge is using the cadence sensor output to calculate speed readings!!!

For the time being I've removed the speed sensor and am going to use the GPS readings, which will give me cadence and speed which is the end goal but I would prefer not to take this route in the long term.

My Edge 500 firmware is up to date, v3.30 I think, according Garmin Express

Has anybody else had experience of this problem?

0 tigermountrider over 9 years ago

now if I choose to pair as "cadence and speed sensor" (not cad/spd option) then when I rotate the cranks I get a reading for cadence and also a speed reading but the bike is stationary.

Did you mean to say the wheel isn"t rotating? I understand that you are rotating the crank backwards so the wheel doesn't rotate and getting a speed reading. I think it is extremely unlikely that the Edge is using the cadence value. If so it would be corrupt firmware.

The speed sensor detects the earth's magnetic field. Do you still have a magnet on the crank. Maybe it is affecting the speed sensor. I don't know if that could happen but that's about the only thing I can think of.

0 aweatherall over 9 years ago

It could be that some part of the chain is magnetized and that is triggering the speed sensor. If you put the speed sensor on the front hub and spin the cranks backward do you still see the issue?

0 usedtobefast over 9 years ago

Yes the wheel is stationary when I'm rotating the cranks. At first I had a magnet on the rear wheel but even with this removed I still get the same response.

I need to do a couple more tests; 1) With the speed sensor taken off the bike, and 2) as mentioned above with the speed sensor on the front wheel

I'm wondering if there is slight movement happening with the speed sensor which is what I'm picking up, but then the readings I'm getting of between 18 kph and 23 kph seem quite high for slight movement.

0 tigermountrider over 9 years ago

Vibration shouldn't trigger the sensor. It needs to flip over and sense a change of direction in the magnetic field. I think Alan's suggestion of a magnetized chain in most likely the problem. Putting in on the front wheel would solve that in addition to reducing any chance of reception problems.

0 usedtobefast over 9 years ago

Looks like either the chain or the cassette have got magnetised somehow !!

1) Speed sensor on the back wheel and rotating cranks - cadence and speed reading
2) Moved speed sensor to the front wheel - only cadence reading
3) Took speed sensor of the bike - only cadence reading
4) Speed sensor on back wheel and removed chain - cadence only

I don't know if its the chain or the cassette, I suspect the cassette as this is nearer the speed sensor, but the solution is simply to mount the speed sensor on the front wheel. Will be a problem if I ever need to use a turbo trainer.

Thanks for all the help
Paul

0 aweatherall over 9 years ago

I have seen problems with bikes that had been shipped in packing case before. When the bike was placed in the packing case the chain was loose and came close to a magnet that was part of the power meter system that was on that bike. This was enough to magnetize the chain sufficiently that it would affect the speed sensor.

You would need access to a gaussmeter to find out what part of the drive chain has got magnetized.

+1 Dmytro Dikhtiar over 4 years ago

Hi!

I have a similar problem on my Edge830 and Speed&Cadence sensors v.2.

Have you found any solution?