Weird light/computer interaction

[661-Pete]

Not really a technical query: hence posted in café. Anyone else had this?

Been using a fairly basic VDO C05+ (cordless, analogue) for a few years now. A few days ago I also fitted an ancient filament-bulb lamp next to it on the handlebar, mainly because it's the only lamp I have that takes 'D' size batteries, and I have a surplus of the things I want to use up.

Now I've noticed that when the lamp is on, the computer speed more than doubles at times (it briefly showed 60mph which I certainly can't achieve!) Turn off the lamp and the computer returns to normal. Move the lamp to the other side of the handlebar and the effect seems to go away.

As I said, a simple battery-powered lamp with old fashioned filament bulb. Not as bright as a good LED front, but I don't need that for the commute across town.

Any explanation? As I said, it's bizarre.

 

[Noodley]

Sounds fairly technical to me...but I suppose 'fairly' and 'really' might need to be properly defined - sounds like one for the P&Lers to sort out


Edit - sorry, can't help with your query other than to say my VDO used to do the same when I went under power cables.

2nd edit - actually I might be able to help with a possible explanation. Is there a round sticky-out bit on the back of the computer? Depending on how old the computer is this might be a common complaint with the older VDOs which do not have the sticky-out bit as when I returned mine to LBS and reported the problem with going under electricity cables they did a swap for a newer version (with the sticky-out bit) and it's been fine since. The LBS said it was a common problem, hence the change. I have no idea what the sticky-out bit is....

 

[Slowgrind]

Keep that lamp! Anything that makes you do 60 mph. can only be a good thing!

 

[fossyant]

Electrical interferance - bin the old light, they cost a bomb to run, especially on D Cells...... PS stop pedalling so fast.

 

[661-Pete]

Electrical interferance - bin the old light, they cost a bomb to run, especially on D Cells

going to retire it anyway, once I've used up my 20 or so batteries (bought by mistake).

...... PS stop pedalling so fast.

If only...

 

[Over The Hill]

At a guess, the signal from the sender bit on the wheel is picked up by the unit on the handlebars.
This must be some sort of simple radio signal pulse thing.

My guess is that somehow this signal is bouncing off or being procesed by the light. Is it a metal case perhaps?

Then the computer is reading both the signal and the echo of the signal so will be confused.

 

[661-Pete]

My guess is that somehow this signal is bouncing off or being procesed by the light. Is it a metal case perhaps?

Then the computer is reading both the signal and the echo of the signal so will be confused.

But then, why does this happen only when the light is on? And it's not a metal case, it's plastic (the lamp's old, but not that old!). Of course, the batteries have metal cases.

It's a simple, presumably constant DC current through the filament. All my physics lessons taught me, if you have a constant current flowing through a conductor, it will produce a magnetic field but cannot generate radio emissions. So what then?

 

[Over The Hill]

Errr.. I give up!

I think I was just starting with WHAT is happening before I got to the HOW.

The part of the computer most open to outside influence must be the signal from the wheel to the unit.
From there I am guessing it more likely that an existing signal is being bounced around rather than a new one reproduced.
After that I slightly run out of steam.

 

[Wobbly John]

I've had an LED light interfere with my wireless computer, but I'm surprised a filament bulb light has this effect.

 

[rich p]

I'm with Noodley, here, and at the risk of coming over too techy, it's definitely the sticky out bit...

...or aliens.


p.s. Whenever my computer goes crazy it invariably puts my maximum speed at 55mph.

 

[ACW]

traffic lights do that to my wireless cycle computer, if i stop right next to the lights i am still doing 45 -75 mph according to the computer.