Cree & Wireless - Communication Jam

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Cree & Wireless - Communication Jam

Postby clack3rz » Mon Apr 28, 2008 11:12 am

I've just started to use a Cree Flashlight using a CR123A battery, and it seems to jam communication b/w my Polar CS200cad head unit and my cadence sensor. The speed & hr still reads/communicates fine.
It is fine if I select the high or strobe modes on the light, but if I swicth down to low or med the cadence reading stops!
Anyone had this, or knows what the cause/fix is for this?
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by BNA » Mon Apr 28, 2008 11:48 am

BNA
 

Postby Caelum » Mon Apr 28, 2008 11:48 am

The cause is the PWM chip in the cree headlight.

It varies the brightness by using a frequency based method, which seems to be interfering with your computer.


The fix -

don't use low/med modes
use a different light
use a different computer.
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Postby geoffs » Mon Apr 28, 2008 11:48 am

The flashlight you are using must be using a pwm (pulse width mode) circuit to adjust the current to the led. If it's just a torch you are using, is it possible to mount the light further away from the polar head unit such as on your helmet.
The extra distance might be all that's needed.

Fenixstore sells a good mount.

What light are you using??
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Postby clack3rz » Mon Apr 28, 2008 12:47 pm

I used the full-mode on my ride today and it was a 'fix' but I had to carry a spare battery (it lasted 45mins before I needed to change).
The medium mode is enough for me to see and to be seen (and it saves battery life!) However I do want to use high in stretches of road that are poorly lit (or not lit at all).
I'm using Super-Bright Cree Q4 5-Mode LED Flashlight that I purchased from Deal Extreme.
It's what I'm after in a bike light - just the interference is an issue.
I was going to move it and see what the outcome was, but also wanted to understand why.
I'm using a bike mount that I also purchased from DX.
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Postby bigfriendlyvegan » Tue Apr 29, 2008 3:25 pm

I realise this may sound a bit weird and conspiracy theoristy, but we used to use aluminium foil to wrap sensitive components to shield them from interference (I did my PhD in laser physics. If you want real interference, go into an experimental laser lab) . It works against alien mind probes as well.

Wrap the foil around the body of the flashlight and see if it makes a difference. If it does, put some old inner tube over the top for street cred, and you're off.

If it doesn't work, you will need to try some more extreme shielding. Basically you need to create a little Faraday cage to keep the interference from getting out. To do this you need a conductive mesh. You can do this cheaply if you have some co-axial cable lying around. You can either just wrap the cable around the body of the torch, covering the whole thing, or you could strip the copper shielding from the cable and wrap that around the torch.

Try the foil first.

David

NEW THOUGHT: try an anti-static bag, like the ones you get computer components in. They're Faraday cages and might just work.
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Postby Caelum » Tue Apr 29, 2008 4:11 pm

They'd only be faraday cages if they were grounded though, right?


Also - the torch is made FROM aluminium... so i doubt foil will work.
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Postby clack3rz » Tue Apr 29, 2008 4:55 pm

OK - I'll give that a try if relocation doesn't work.
If the foil keeps the aliens away I may wrap my helmet in foil as well - to keep them from using their ESP on me :?
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Postby Pushy » Tue Apr 29, 2008 6:27 pm

clack3rz wrote:OK - I'll give that a try if relocation doesn't work.
If the foil keeps the aliens away I may wrap my helmet in foil as well - to keep them from using their ESP on me :?


Mount the torch on you helmet - not the foil.
If that fails can the cadence sensor be mounted to the down tube, if its currently mounted on the chain stay. This brings it closer to the head unit.
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Postby clack3rz » Wed Apr 30, 2008 10:35 am

OK I moved my Polar unit from the stem to the bars (same side as the speed and cadence sensors) - The cadence sensor was already on the down tube.
I left the flashlight on the right side of the bars.
Works a treat - tested on the indoor trainer - then took it for a spin this morning - no interference, no drop outs - and had the light on medium mode which gave me light on a single battery for 75mins - it was still running fine when I got back home.
No need for alien protective foil.....yet
Thanks for the tips, tricks and the info to understand how/why this is caused.
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Postby bigfriendlyvegan » Wed Apr 30, 2008 10:40 am

Caelum wrote:They'd only be faraday cages if they were grounded though, right?


No. Planes get hit by lightning all the time. They're not grounded (when flying).

David
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