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Old 03-18-06, 04:27 PM   #1
TheRCF
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Conflict with electronics!

I have a Vetta V100HR computer (includes cadence and heartrate - only the heartrate part is wireless).

For a long time, I wasn't using the heartrate part, though periodically the computer would show HR numbers - which I chalked up to periodic interference from electrical sources on my route. Usually these numbers were pretty low (like 40).

Then, at some point, I started getting really high numbers most of the time, usually over 200. Then when I decided to use strap on the HR monitor, the numbers almost never made sense - again, being often over 200 (that's way past my max!). I tried replacing the batteries in the strap but it didn't help. So I stopped using it (I had replaced the battery in the computer not all that long ago).

But a couple weeks ago I had a bike tuneup and when I got it back, the HR stayed at zero almost all the time, as it should. I couldn't figure out any reason for that correction, but eventually I put the HR strap on again. Seemed to work while sitting in my apartment, but when I attached the computer to the bike again and started riding, it just stayed at zero!

Well, today I tried again. I started to wonder if maybe my headlight was causing a problem with blocking the signal (a Viewpoint Gen3 Digital model which does sit right next to it and slightly above). So I slid the light off the mount and, sure enough, the HR worked again. So I held the light near the mount, but a little off to the side so it wouldn't physically block a signal. But the HR went back to zero anyway. Eventually I tried turning off the light, but holding it in the same position and the HR worked again. Even when the light was on the mount it worked, but as soon as I turned on the light, it would go to zero!

Now, while I say it worked with the light off, I should point out that there was some inconsistency - it would work and then not work for awhile, back and forth. Also, the numbers often didn't make sense, almost as if it was only picking up half the heatbeats or 2 out of 3, etc. Basically it seemed that even having the light near the computer unit MIGHT affect it, but not always. Turning the light on always killed it.

Riding home, I put the light in my backpack, but the results were still intermittent, which baffled me.

Then I remembered that there was a period of time when the computer usually didn't do the automatic shutoff (where it only shows the time). So I thought maybe that was because of the light causing interference even when off and so perhaps part of the problem was that the battery had drained much faster than normal, even though speed, etc, all seemed to be fine. I replaced the computer battery and the HR started working well IF the light was not near it. If the light was there, it might give results that were too high. If the light was on, the numbers tended to go even higher, though there was not absolute consistency on that, but almost.

Anybody else ever experience anything like this? Besides using a different light (really can't afford that, especially if another might do the same thing!), anybody have any solution? I've tried moving the computer and light as far apart as possible, but the change was only an inch or so which isn't going to do it. All my rides typically involve riding 36 miles or more while it is still dark, then I do 14 or so in daylight after breakfast.

Bob
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Old 03-18-06, 05:12 PM   #2
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I've heard of people creating shielding around lights with Al foil...cheap and worth a shot. If the light has a ballast of any kind that may also be generating interference.
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Old 03-18-06, 05:41 PM   #3
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Don't know if it has a ballast - it's an LED light and the digital part apparently means it maintains the light level consistently until it is drained so much that it can't (as opposed to gradually getting dimmer). Don't know if that could be a factor.

I did get a litle aluminum foil from the breakfast restaurant, but couldn't solve the problem. I haven't tried it since putting in a new computer battery though.
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Old 03-18-06, 05:55 PM   #4
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Look for any loose metal parts that may rattle when you are riding. A vibration between two metal parts emits a radio signal. Possibly there is something causing this in your headlight.

When shielding with aluminum foil. place the shiny side toward the headlight. This is the side that reflects the signals.
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Old 03-18-06, 06:19 PM   #5
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Quote:
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Look for any loose metal parts that may rattle when you are riding. A vibration between two metal parts emits a radio signal. Possibly there is something causing this in your headlight.

When shielding with aluminum foil. place the shiny side toward the headlight. This is the side that reflects the signals.
It wouldn't be metal parts because a lot of my tests have been with the bike just standing still in my apartment or elsewhere.

I did try moving the light further away - it has kinda a funny design. The mount sits to one side of the stem and then a section curves over to put the light itself right about the stem so it is centered. So I tried setting it up so it actually curved AWAY from the stem. Didn't work, though maybe it will mean it will work occasionally.

Then I tried the aluminum foil again in that position - putting the shiny side inside (I'd bet I did it the other way before), and my quick test seemed to work. The battery compartment sits under the light and I covered both parts. Then I tried just covering the batter compartment, but it didn't work. Too bad since that would have been much easier to secure. Covering just the light did work. Now I have to figure out a way to do this so it doesn't come apart. Aluminum foil is not exactly the sturdiest stuff!

Thanks for the suggestions.
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Old 03-18-06, 06:23 PM   #6
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Wireless computers and HRMs are particularly sensitive to washout... especialy if they don't use digitally coded descrimination. Things like headlamps, powerlines and traffic sensors can cause them to read erroneously or not at all. I have to use a wired version on my MTB because my shocks use a piezo-electric valve to govern the damping rates and the resulting EMI causes the computer to cut out. Also HID lights tend to produce more EMI than halogens. I don't have a problem with my halogen lights with my RB's wireless computer. I do occasionally have issues with traffic loop sensors.

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Old 03-18-06, 06:33 PM   #7
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> especialy if they don't use digitally coded descrimination. <

Ah, this is something I've wondered about. So, I gather there are such units? If so, any recommendations?

> Also HID lights tend to produce more EMI than halogens. <

Okay, I know what halogens are, but HID? I know what the initials stand for, but don't know if my LED light fits (but I doubt it).
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Old 03-18-06, 06:39 PM   #8
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Originally Posted by TheRCF
> especialy if they don't use digitally coded descrimination. <

Ah, this is something I've wondered about. So, I gather there are such units? If so, any recommendations?
Actually I think your Vetta uses digitally coded signals. While this helps the unit descriminate and thus pull a signal from a lot of noise, it still doesn't make it imune to complete washout conditions where the signal is so obscured by broad spectrum interference noise.


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> Also HID lights tend to produce more EMI than halogens. <

Okay, I know what halogens are, but HID? I know what the initials stand for, but don't know if my LED light fits (but I doubt it).
You're correct. LEDs are not HIDs. HIDs work on an arc-lamp principle which is one reason they tend to emit a substantial amount of EMI. It is however likely that your LED units have some sort of internal logics (for power management probably) that may rely on oscillators that can also produce a fair amount of EMI.
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Old 03-18-06, 07:41 PM   #9
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Your "digital" headlight most likely varies the light intensity by sending voltage pulses to the LED. These pulses generate a bit of electromagnetic interference that is probably interfering with your HRM signal.

Aside from replacing the light with a simpler model, your best bet is to try to separate the two units as best you can. sometimes a few inches is all it takes. You could try a Minoura Space Bar to raise or lower one of the units or even try to mount the light head on your fork.
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