Bicycle Mechanics - Wireless computer goes wonky always in the same spot

I have Bell wireless computers (same model) on both of my bikes. I have a route that I ride near my office at least twice a week, and the computer on my road bike always goes crazy at this one spot after I crest a big hill, speedometer reading 40-50+ MPH and going all over the place. One time I stopped, and the computer just kept going crazy and wouldn't quit. I had to keep riding a little farther before it would correct itself. Next time I rode the road bike, same thing at the same spot, but I just kept going and it corrected itself shortly.

When I rode the same route on my other bike with the same model computer, it never blinked once. And I've had that computer longer on the same battery longer than the one on the road bike.

Any ideas? This is the spot where it happens. Nothing crazy around, just houses and trees: http://goo.gl/maps/3E0Po

It is a wireless device which has a receiver which is susceptible to RF interference. There is probably another wireless transmitting device in that area which is interfering with it. Not much you can do about it except avoid the area. Read the "FCC Warning" section of this instruction sheet, which is common to all types of unlicensed wireless devices. http://www.bellbikestuff.com/pdfs/111741WirelessManual.pdf

Call the guys from area 51. You've discovered a hidden source of RF radiation in the operating band of your computer. Maybe it's an alien vessel hidden in one of those innocent looking houses,

I have Bell wireless computers (same model) on both of my bikes. I have a route that I ride near my office at least twice a week, and the computer on my road bike always goes crazy at this one spot after I crest a big hill, speedometer reading 40-50+ MPH and going all over the place.


Simple wireless computers do that in the presence of EM fields from power transformers, overhead power lines, the eddy loss sensors used to trigger traffic lights, industrial equipment, some LED head lights, etc.



Any ideas? This is the spot where it happens. Nothing crazy around, just houses and trees: http://goo.gl/maps/3E0Po

Upgrade to a better wireless computer which has sensors that speak the digital ANT protocol where the worst that will happen is a drop out (very rare at 2.5GHz vs the lower frequencies simple older computers used) instead of ludicrous readings that throw off your totals and averages. A few hundred dollars on a Garmin Edge 200 or 500 should do the trick nicely.

Wired computers cost less, only use a single battery, and don't get jammed by martian mind-control waves.
Ditch the silly wireless, wired wins hands down.

Just seems odd that one computer does it in that same spot and the other one doesn't when they're the same model.

I should be heading out again tomorrow and I'll see what happens there.

Just seems odd that one computer does it in that same spot and the other one doesn't when they're the same model.

I should be heading out again tomorrow and I'll see what happens there.

Wire dress has a big effect on RF pickup (I had problems with one active speaker receiving 94.9FM from a nearby 100KW radio station until I made minor rearrangements to its internal wiring) and there could be running changes in the new computer.

It is common for manufacturers to make running changes on their circuit boards so your two computers may have different "guts" even though they are the same model. Perhaps they left out a component to save a half a penny which makes one work differently, or maybe they are on different RF frequencies. As noted above a wired computer will eliminate the problem.

+1 on wired computers. Cat-eye's Mity 8 and Enduro 8 (same head, Enduro has a heavy duty wire) are wonderful wired ccomputers and now at close-out prices since they've been replaced with newer models. Buy two and never have this problem again.

Wireless devices, particularly ones that aren't properly "coded", are prone to all kinds of odd-ball interference. A friend had heart surgery several years ago and bought a cheap Nashbar heart monitor to assure he didn't exceed his doctor's advice on maximum heart rate while riding during his recovery. We rode together the first time he used it and as we rode past a power company transformer station his monitor jumped to 250 bpm and then to zero! Talk about scared! It took a moment for us to realize what happened and the reading went back to normal a few blocks later. He later bought a Polar ($$) coded monitor and that ended the interference problem.

Another +1 on wired. Additional bonus is, when you get that record cold spell of -22C in Memphis, the less batteries the better. :)

...eddy loss sensors used to trigger traffic lights...

What does that mean? I thought traffic light sensors were all triggered by weight. Chatting with another cyclist here in San Diego, he told me over the last few years, many sensors have been tuned to detect cyclists, not just cars.

What does that mean? I thought traffic light sensors were all triggered by weight. Chatting with another cyclist here in San Diego, he told me over the last few years, many sensors have been tuned to detect cyclists, not just cars.
No, newer sensors detect metal passing over them, not weight.

What does that mean? I thought traffic light sensors were all triggered by weight. Chatting with another cyclist here in San Diego, he told me over the last few years, many sensors have been tuned to detect cyclists, not just cars.

The loops in the pavement are inductors driven by an alternating current. The resulting magnetic field causes current to flow in nearby conductive (usually metal) objects which in turn changes the loop's inductance and resonant frequency which is picked up by the traffic light controller. The circuit can be adjusted to trigger based on how big the change is, where the losses are higher when there's more conductive material nearby and a bicycle needs a much lower setting than a 4000 pound SUV.

The substance only needs to be conductive - it needn't be magnetic too. Aluminum rims trigger the circuit.

I'm somewhat curious about how things work for people with carbon rims on carbon bikes (although the epoxy is an insulator the carbon fiber it surrounds is a conductor).

That is very interesting! So probably me on my bike would trigger it easily (if tuned for bikes not just cars), but a 300lb pedestrian with only about enough metal to trigger an airport security metal detector (belt buckle, shoelace eyelets, Vietnam shrapnel) could stand in the intersection and not trigger a green light?

Sure enough, computer went crazy at the same spot again today. It's just a residential area, with no traffic lights or any kind of overhead power lines or anything. Today it swept up past 70 MPH lol. After a few hundred feet it settled back down.

I have Bell wireless computers

buy something less cheap?

Sure enough, computer went crazy at the same spot again today. It's just a residential area, with no traffic lights or any kind of overhead power lines or anything. Today it swept up past 70 MPH lol. After a few hundred feet it settled back down.
Perhaps one of the homeowners is a ham radio operator or has some other RF source. As recommended, get a wired computer or a better quality wireless.

Crest of a hill, huh? Might be a microwave link that's designed with too little link margin. Look for two towers in opposite directions. One is probably fairly close to affect your bike computer that much.

Be glad you don't live there. Are the local kids kinda weird-looking? Six fingers, that sort of thing?

Most likely (as already stated) you are temporarily near a more powerful source of RF wireless transmissions, and in the same freq. as your bike computer. Lots of homes have wireless now for computing as well as other devices.

Why not both bikes? The wireless bike computers most likely are set to transmit and receive on specific frequencies, and the manufacture probably has a number of frequencies set in their individual devices. If all of them of that brand used only one frequency, and you rode close by the other computer, you might get the data from the wheel on the other bike. I don't know what the reception range might be, so this is speculation.

Never mind- I just looked at the satellite image. Looks like a bunch of 22000 volt power lines overhead nearby- jct of Green Tea and Palmer. That can do it. A slight bit of corona on an insulator will spew all kinds of frequencies out, including the one that the wheel sensor sends to the computer. If you hear a buzzing from the lines, that's a pretty damning indicator of corona. Also, I see a transformer on the street view nearby. A (RF) leaky transformer can put out some pretty horrendous fields as well.

Different computers will have different sensitivity even if they're on the same channel. Also the bike structure acts as an antenna or director of waves, so a different bike will induce different local fields.

Ah I see that now. It usually doesn't go crazy until several hundred yards after I pass those overhead lines, though.

Oh well, may look into different computer I dunno. I actually had planned on going with something different on this road bike, and really only got the Bell computer as more of a temporary solution so I could go ahead and start keeping track of miles straightaway after purchasing the bike. But I never had a problem with it until this came up a couple weeks back.

Do you ever feel "fried"?

I second the recommendations above for older Cateye wired. Various members of my family have a MITY 3, a Velo something, and, um, another one. One of them has only one button, that's for the youngest son. I have the MITY 3, and the wife has another one with two buttons that is not a MITY3, but it does have two buttons, and for the life of me I cannot find any difference between them. Every operation is identical, all three of them share the same mount, etc.

BTW, both of my 2-button ones (MITY 3 included) are two-bike capable, which is sweet, because I can mount harnesses on my road and mountain bikes, and just pop the computer back and forth and I have just one odometer to track everything. Just a few button presses to switch between wheel circumferences.

I have a cateye wireless on one bike and a trek wireless 8 on my other. Never had a bit of trouble unless battery needed changing. I have 15000 miles all over the place never any interference. They are dead accurate by wheel rollout method. Typically my garmin fourunner is off by less than 1/2 of 1%. I did 30 the other day on the bike garmin showed 29.96.
I will keep my wireless.

I have a cateye wireless on one bike and a trek wireless 8 on my other. Never had a bit of trouble unless battery needed changing. I have 15000 miles all over the place never any interference. They are dead accurate by wheel rollout method. Typically my garmin fourunner is off by less than 1/2 of 1%. I did 30 the other day on the bike garmin showed 29.96.
I will keep my wireless.
There is nothing inherently more or less accurate between a wired and wireless bike computer. They both have pulse generators and a time base clock that use a user set wheel circumference to calculate distance and speed. Typically you get one pulse per wheel revolution and if the pulse it received by the reading head, they read identically. The only problem with wireless is stray RF can interrupt the pulse count or add to it. If there is no interference or the computer is made to ignore it, it reads properly.

I installed a Cateye Mity on my road bike in 1993 or '94, and except for two battery changes since then it has been very reliable up to this year. This year the few rides I took on my road bike I noticed I had to wiggle the head of the computer to get it to read - I suspect there might be a problem with the connections or wires, and I prolly can't get parts for the 20 year old computers, though. :(

I did win a new Sigma Sport wireless in a draw at a mtb race this fall and I have that on my commuter bike. I ride my commuter bike through a nuclear waste dump twice a day and get no interference. I suspect the *ahem* affordable Bell computers aren't the same quality.

I installed a Cateye Mity on my road bike in 1993 or '94, and except for two battery changes since then it has been very reliable up to this year. This year the few rides I took on my road bike I noticed I had to wiggle the head of the computer to get it to read - I suspect there might be a problem with the connections or wires, and I prolly can't get parts for the 20 year old computers, though. :(
Not to worry, the current wired handlebar mounts will work with your old cyclometer head.:) Also, I find that cleaning the contacts with a pencil eraser to scrub off the crud followed by a dab of silicone grease restores the reliability.

BTW, both of my 2-button ones (MITY 3 included) are two-bike capable, which is sweet, because I can mount harnesses on my road and mountain bikes, and just pop the computer back and forth and I have just one odometer to track everything. Just a few button presses to switch between wheel circumferences.

That sounds cool. Does it also have separate odo functions in addition to the total? I like to keep track of mileage on each bike, like car odometers, but having a total number is nice, too.

The ticker in my sig is total miles ridden on both bikes since I started back riding the 1st of May.

That sounds cool. Does it also have separate odo functions in addition to the total? I like to keep track of mileage on each bike, like car odometers, but having a total number is nice, too.
No, there is just one cumulative odometer function on these Cat-Eyes. They do have a two separately resetable trip distance functions that could each be dedicated to one bike (and wheel diameter) but the trip distances have a 1,000 mile maximum and go back to 0 after that. The cumulative odometer will read up to 99,999 miles.

Well looks like a wired computer is going to be mandatory now. I discovered that my new Cygolite Expilion 700 renders my wireless computer completely inoperative. Light off, works fine. Light on, speedometer just stays on 0 mph while riding.

Darn, I liked not having the wire. Oh well.

Well looks like a wired computer is going to be mandatory now. I discovered that my new Cygolite Expilion 700 renders my wireless computer completely inoperative. Light off, works fine. Light on, speedometer just stays on 0 mph while riding.

Darn, I liked not having the wire. Oh well.


ANT+ is virtually immune to interference. You might consider an ANT+ wireless computer: Bontrager Node, some Cateye and Mavics, and of course Garmin.. There are others as well. A Garmin and Node that I have specifically work fine alongside the Exp 700.

I just discovered yesterday that my Cygolite on daytime flash/strobe mode is what makes my wireless computer (still using wireless on the KHS) go wonky. When the light is on steady, the computer works just fine. Seems a little weird that the flash mode of the light causes all that interference but the light on steady does not.

I've heard ancient burial grounds (http://www.youtube.com/watch?v=QGQr5hCpzr8) can mess with electronics something fierce.

Seems a little weird that the flash mode of the light causes all that interference but the light on steady does not.

Well, a flashing light involves a current that keeps changing, whereas one that's constantly on is powered by a steady current. You need a variation in the primary current to induce a secondary current in another conductor that's not connected electrically to the first one. The primary conductor is in the light in this case, and the secondary one is in the computer.

...noticed I had to wiggle the head of the computer to get it to read - I suspect there might be a problem with the connections or wires...
+1 On lightly 'sanding' the contact points in the cradle - they often develop a layer of crud/oxidisation which can be easily removed by a 'rough' (sometimes grey-coloured) pencil eraser or a very light grit sandpaper. :thumb:

Also, the Bell computers, although cheap, often are *exactly* the same as more expensive models, just branded differently. ;)

Well looks like a wired computer is going to be mandatory now. I discovered that my new Cygolite Expilion 700 renders my wireless computer completely inoperative. Light off, works fine. Light on, speedometer just stays on 0 mph while riding.

Darn, I liked not having the wire. Oh well.

You can often fix this problem by moving the light away from the computer.

You might try wrapping the light in aluminum foil. This makes a Faraday Cage and might be enough to keep the RF energy contained within.

It would work better to wrap the computer, but that isn't an option, since you need to let a signal in.

If the foil works,you can experiment to find out how little and where to place it to make a shield without wrapping the entire light.

You can often fix this problem by moving the light away from the computer.

Not really possible the way the handlebars, tape, controls, etc are set up on both of my bikes. On both bikes the computer mount must sit directly adjacent to the stem. On my MTB I have the light mount rigged up to the stem itself, and on the road bike it's on the other side of the stem.

re: cleaning electrical contacts... DO NOT SAND THEM. use a pink soft pencil eraser. sanding will strip off any remaining anti-oxidation coating (gold, chrome, etc), and while it might work short term, it will corrode up even faster. pencil erasers do a fantastic job of removing just the oxide.

...cleaning electrical contacts... DO NOT SAND THEM...sanding will strip off any remaining anti-oxidation coating (gold, chrome, etc)...
Ooh - good catch. :thumb:

I'm pretty sure the contacts on my £4 Aldi bike computer are just steel, so at least no harm done there. ;)

I seriously doubt ANY electrical contacts are steel, it makes a lousy conductor. more likely, they are chrome or nickle plated brass

Yes, outside RF interference, most likely the cause...
I've heard also that supposedly, Some Mavic Mektonic group users in the 90's supposedly had problems with their remote controlled RDs shifting themselves when riding near or under signal towers and high tension wires..... It all comes down to how well the equipment is shielded from stray signals or how the signals are designed to be proprietary to the equipment.

Chombi

I'm somewhat curious about how things work for people with carbon rims on carbon bikes (although the epoxy is an insulator the carbon fiber it surrounds is a conductor).

I built a couple of V/T amplifiers with carbon fibre casework and as part of the development measured the conductivity and RF shielding of the casework, both of which were surprisingly high. I assume this is down to having enough fibre to fibre contact to ensure a conductive path. This was wet layup CF but I'd expect the same effect to be present with prepreg.

I seriously doubt ANY electrical contacts are steel, it makes a lousy conductor. more likely, they are chrome or nickle plated brass

No it's surprisingly common to make electrical parts of steel, often with copper plate and solder finish. Many power resistors are made this way, you have to go out of your way to find ones with copper leads. The reason is that steel is a worse conductor of heat than it is of electricity, so for a small reductuion in circuit efficiency you gain some reliability- the leads won't be as prone to conducting enough heat to melt the solder that attaches them to the PCB. Of course it's also much cheaper than copper.

The intersection of "good conductor" and "good spring" is quite small and mostly expensive (eg beryllium copper).

Try wrapping your bike fork, frame and helmet in aluminum foil. Won't solve your computer problem but will look cool.

put a metal colander over it, and wear one, too.
no weird rf signals, and no voices, either.