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fredlf
11-24-2008, 02:43 PM
Anyone else have this problem? My LED headlights interfere with the wireless signal used by my bike computers. I have two brands of lights and two brands of computer, but no matter what, turning on the light makes the computer go haywire.

lynnef
11-24-2008, 03:17 PM
where is the computer sensor located? I've heard of generator hubs messing with wireless computers, but not this.

I'm looking at a wireless computer with the sensor NOT on the front fork, just for that very reason.

OldCog
11-24-2008, 05:23 PM
Well thats pretty strange -- LEDs run off of DC current which should be noiseless from an electrical noise standpoint. One possibility is that there is a DC switcher circuit used in the lights to raise the voltage ----- these circuits use square waves and can be noisy.

To narrow this down get some aluminum foil ---- turn the lights on now and as best you can cover the light with foil (sealing in any electrical noise). Now try the wireless link --- get a strong link working now pull off the foil ? Experiment a bit. If the light is the source you may be able to only cover a portion of the light with foil and get things working

Psyfalcon
11-24-2008, 06:41 PM
Planetbike Blinky and a SI 90 series, but only recently, presumably after the sender battery is a bit worn down.

LED on blinky gives me an intermittent 20+ mph gain, and on solid, I get a (constant) speed of ZERO.

I soaked the LED at one point and it got stuck on solid, I had thought I also fried my computer... until the blinky dried out and turned off.

fredlf
11-25-2008, 08:54 AM
Well thats pretty strange -- LEDs run off of DC current which should be noiseless from an electrical noise standpoint. One possibility is that there is a DC switcher circuit used in the lights to raise the voltage ----- these circuits use square waves and can be noisy.

To narrow this down get some aluminum foil ---- turn the lights on now and as best you can cover the light with foil (sealing in any electrical noise). Now try the wireless link --- get a strong link working now pull off the foil ? Experiment a bit. If the light is the source you may be able to only cover a portion of the light with foil and get things working

Thanks OldCog, I had the same thought that LEDs are DC. But there's no question the lights are the source, blinking or solid beam. I turn them on, the computer goes wonky. Turn them off, normal operation. Everything is on my handlebars in close proximity, so I'll tear some foil from my anti government satellite helmet liner and try it. Sometimes I wonder if wireless computers are worth the trouble...

BTW, the sensor/transmitter is on the front fork, but I think the interference is occurring at the receiver. I wonder where the antenna is in my computer (Shimano flight deck)?

Haven_kd7yct
11-25-2008, 09:05 AM
My boyfriend the electrical engineer has the same problem with his LED blinkie and his wireless computer.

His solution: move them farther apart.

I'll run these other solutions by him, too, to get his educated opinion.... :)

q`Tzal
11-25-2008, 10:16 AM
The white LEDs like to run at 3.65 volts but your batteries will not maintain a consistant voltage over their usage.
A Switched-mode DC to DC converter pumps power to storage releases the energy , at the desired level, on cyclical basis. Circuit conversion efficiency is much higher for Switched DC to DC than other modes thus decreasing power used.
Back about 7 years ago when white LEDs were first hitting the market I saw some surface mount (TINY) chips switching at 100KHz and out putting 3.65V at 4 amps.

more at http://en.wikipedia.org/wiki/DC_to_DC_converter#Switched-mode_conversion

fredlf
11-25-2008, 12:57 PM
My boyfriend the electrical engineer has the same problem with his LED blinkie and his wireless computer.

His solution: move them farther apart.

I'll run these other solutions by him, too, to get his educated opinion.... :)

Thanks Haven. How far apart is far enough? There's only so much room on the un-taped portion of standard road bars. I guess I need to start looking into alternate places to mount the lights.

jr98664
11-25-2008, 08:53 PM
Good timing you guys!

I've been having problems with my Topeak Panoram V12 wireless ever since I got my Planet Bike Blaze LED light. The computer worked perfectly up until that point, but since my previously light was destroyed in a crash, I figured that the computer might have had damage from the impact. Now that explains why it worked fine in the summer up until the point I was riding into the night. I can't believe I didn't think of it earlier.

With my light off, it would read perfectly, and with the blinking mode, it would end up reading exactly half of the distance over the course of a ride. I rarely use the light in steady mode when it's light enough to see the display, so I might as well experiment with that.

Now, I could just move them farther apart, but there's only so much space in which I can place either part and have it face squarely ahead (quite important if you want cars not to hit you). In which manner and direction is the interference propagated? What other solutions would work well?

Haven_kd7yct
11-26-2008, 11:02 AM
jr, one question my boyfriend said to ask was: does your light screw up your computer in flashing mode, or steady? He's betting it messes it up while flashing, but not as a steady beam.

Then he started to get all technical: essentially, a flashing LED uses "pulse width modulation": PWM circuit, which sends out a weak pulse, which can interfere with other communications. It's more powerful and at a higher frequency, and your computer is intercepting that signal.

Distance apart will depend on battery strength in your light. Or, have a weaker signal by your light.

Oh, and then he starts rattling of rf formulas, something about irradiating antennas, etc. Confusing.

His solution: if you can't move it farther away (for instance, mount the light on your fork instead of your bars, or as far away on your bars as possible), use your light in solid beam mode, not blinkie.

Now, if it makes it wonky in steady mode: dunno. Try the foil, let us know so I can tell Scott about it. :)

jr98664
11-26-2008, 07:51 PM
Well, I think I've solved the problem. I went for a test ride and found that it worked perfectly with the light off. With the light blinking, the overall distance would be halved, as the light was on half of the time. With the light on steady, it would read a top speed of zero.

To solve the problem, all I did was get the front wheel spinning, then I found exactly where the light had to be in relation to my cyclocomputer's receiver to break it, and then moved the cyclocomputer far enough away so it wasn't a problem.

I was beginning to get worried that my cyclocomputer was a piece of junk. Thanks everyone!

OldCog
11-28-2008, 09:31 AM
My boyfriend the electrical engineer has the same problem with his LED blinkie and his wireless computer.

His solution: move them farther apart.

I'll run these other solutions by him, too, to get his educated opinion.... :)

Excellent point (guess I'm getting rusty) as electrical noise will be reduced by distance. But --- if the electrical design in question is really crappy its EMI interference can radiate a fair distance.

The other thing you can do is pop the LED light open and see if there is enough space to press some aluminum on the inside of the inside of the lights plastic housing. Pick up a small tube of superglue gel to glue the foil. Of course you don't want any of the foil to touch any electrical parts or connections - that would be a short circuit. Use some black plastic electricians tape to cover any possible contact points.

Think this sounds silly? Try this --- take a 3 inch square of foil and carefully poke your car key thru the center of the foil. Now wrap the foil up over the top the key sealing it up --- now try to start your car. (this is assuming you have one of the common factory anti-theft options where the key is scanned by the cars ignition system) The foil is blocking the wireless scanning of a RFID chip in the key.

fredlf
12-01-2008, 10:50 AM
Moving my light just an extra inch from the computer solved the problem. I seem to recall that EM radiation falls away geometrically with distance, so even a small change makes a big difference. I'm going to try shielding my light as well, just for hoots.

fredlf
12-01-2008, 10:52 AM
jr, one question my boyfriend said to ask was: does your light screw up your computer in flashing mode, or steady? He's betting it messes it up while flashing, but not as a steady beam.

Then he started to get all technical: essentially, a flashing LED uses "pulse width modulation": PWM circuit, which sends out a weak pulse, which can interfere with other communications. It's more powerful and at a higher frequency, and your computer is intercepting that signal.

Distance apart will depend on battery strength in your light. Or, have a weaker signal by your light.

Oh, and then he starts rattling of rf formulas, something about irradiating antennas, etc. Confusing.

His solution: if you can't move it farther away (for instance, mount the light on your fork instead of your bars, or as far away on your bars as possible), use your light in solid beam mode, not blinkie.

Now, if it makes it wonky in steady mode: dunno. Try the foil, let us know so I can tell Scott about it. :)

In my case, using the light in steady mode interfered withe computer as well. I think this is explained by the DC switching/voltage regulation detailed in the other posts. What a cool forum this is...