Speedometer missing spoke part
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Speedometer missing spoke part
I have an old speedometer with the sensor on the fork but the part (magnet? piece or steel?) that goes on the spoke is missing.
I also have a part for the spoke from a different bike.
What are the chances that I'll get correct speedometer readings if I install the spoke part?
I'm calling it "spoke part" because I don't know whatcha call it .. maybe sensor target.
And I don't know if it needs to be a certain size/strength of target, or conversely if the sensor simply detects a binary "the sensor target is passing" signal, and counts those to get RPM. Probably that...
I also have a part for the spoke from a different bike.
What are the chances that I'll get correct speedometer readings if I install the spoke part?
I'm calling it "spoke part" because I don't know whatcha call it .. maybe sensor target.
And I don't know if it needs to be a certain size/strength of target, or conversely if the sensor simply detects a binary "the sensor target is passing" signal, and counts those to get RPM. Probably that...
Last edited by rseeker; 06-15-19 at 11:16 AM.
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It's just a magnet that induces a current in the coil of wire that is the sesnor. The pulse of Alternating Current is what the computer is counting. So any magnet of sufficient strength to induce a detectable current would work.
What the computer is doing is a frequency=speed calculation. It has some version frequency counter, probably in conjunction with the clock crystal.
((pulse/time)*wheel circumference=rate) There's nothing fancy going on in there to screw up.
2 wheel magnets makes you twice a fast!
What the computer is doing is a frequency=speed calculation. It has some version frequency counter, probably in conjunction with the clock crystal.
((pulse/time)*wheel circumference=rate) There's nothing fancy going on in there to screw up.
2 wheel magnets makes you twice a fast!
Last edited by base2; 06-15-19 at 12:00 PM.
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That's just a nagnet; any magnet will do. if you can't get it close enough to the sensor, get a stronger magnet. Search for 'neodymium magnet.'
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But pretty much anything that securely attaches a small magnet to a spoke should work, and N/S magnetic polarity doesn't matter. I'll often test mine with a fridge magnet.
Alas mine worked right up to the mile 49 rest stop at the county line on a century, then wouldn't register anything more. Multiply removing and reinstalling it in the base didn't work, replacing the battery didn't work... Probably messed up the wiring leaning against a trail sign for a picture. I've bought and broken enough of these that if I ever get my act together and fix them I should just bring an entire spare sensor/wire/mount along.