Bike odometer/computer mystery
September 15, 2016 6:31 PM   Subscribe

My bike odometer works fine for my morning ride to the office but never works on the way home. Huh?

My bike odometer - a Cateye wireless model like this one -- works most mornings when I ride to work. I then hang the bike up in the bike room for about ~9-10 hours and then ride it home at night. The odometer very often does not work at night. It just stays blank - it does not come on. It seems not to "sense" that the wheel is turning. But in the morning it usually works again! I have tried changing batteries and messing around with the placement of the thing that goes on the spokes but still get the same day/night problem. It's weird. Maybe it has something to do with hanging the bike at work (i.e., vertical position) for most of the day?
posted by Mid to Technology (8 answers total)
From the Amazon Reviews:

"The unit is extremely susceptible to EMI. It completely stops working if I turn on my Night Rider 600 light within 18" of the unit."

Modern technology LED headlights are likely to use a buck/boost converter to control the power to the LEDs, and this is a digital circuit with potential for fierce electromagnetic interference.

Your Cateye is wireless, where the sensor has no wire to the head unit. The headlight you use could be interfering with the signal from the sensor to the head.
posted by the Real Dan at 6:50 PM on September 15, 2016 [8 favorites]

My answer depends a little bit on how many times you've seen it happen. A plausible explanation is "it does't work x% of the time" and by chance the times it hasn't worked have fallen more on the way home than on the way to work. (And that's assuming that you've noticed it every time it's work/hasn't worked, I don't know how much attention you pay to such things.

Hanging it should not have any affect - there's almost surely no sensor in there to detect tilt or anything that would get bothered by being sideways.

Oooh I like the headlight idea, if you're using one on the way home (I'm not this time of year because it doesn't get dark here even now until 7:45pm)
posted by RustyBrooks at 6:52 PM on September 15, 2016

The headlight idea is genius! I use a LED light with a crazy flicker pattern (Bike Planet Blaze). I will try turning off my light tomorrow and see if that does it. Glad if I have the answer but bummed if it means no easy fix!
posted by Mid at 7:24 PM on September 15, 2016 [1 favorite]

Maybe a safer test would be to turn your headlight on, on the way to work. Or test both.
posted by Sunburnt at 7:54 PM on September 15, 2016 [10 favorites]

Also, you could try shielding the headlight's sides and back with aluminum foil to block some of the RFI. You'll have to check the LED for heat, though, because LEDs are very hot little bulbs, and while any product like that with LED bulbs will have build in some kind of heat radiator system in to that, you might be foiling (ahem) that by covering it up with metal. You might find a working compromise of partial shielding.

Can the odometer go on the rear wheel? That could put a substantial shield between it and the headlight: you.
posted by Sunburnt at 7:25 AM on September 16, 2016

The way these work is a reed switch (sort of like a weakly sprung bobby pin) on the fork-mounted sensor is closed by the spoke-mounted magnet, causing a pulse to be sent to the head unit. I can imagine a change in humidity causing the reed switch to stick. Just to throw a different possibility out there.
posted by adamrice at 8:51 AM on September 16, 2016

(Moving the odo to the rear wheel isn't going to work, because the display will still need to be on the handlebars where OP can see it.)
posted by uberchet at 9:19 AM on September 16, 2016

I moved the light a few inches away from the computer and everything works. the Real Dan's answer was 98% genius and 2% head-slapping "Duh!" Thanks!
posted by Mid at 4:04 PM on September 18, 2016

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