Using accelerometer to display speed with NeoPixels

I have an old school skateboard with LED sequins right now for nighttime skating/skatejoring (my pit bull pulls me with a Ruffwear Web Master Pro harness). A friend and I were talking about this and suggested I do a brake light-type of lighting to show my speed using relativistic doppler effect (Relativistic Doppler effect - Wikipedia) - would an accelerometer be decent enough to determine my approximate speed? I don't much care for precision in speed, but I don't want errors to add up and have the arduino display incorrect "speed"... Any advice here? I don't want to measure my speed with my wheels, just a heads up. GPS a better option?

Thanks!

would an accelerometer be decent enough to determine my approximate speed?

No, it only measures acceleration not velocity. You could integrate the acceleration to get velocity but it is not very good.

but I don't want errors to add up and have the arduino display incorrect "speed".

That is what will happen.

GPS a better option?

Yes

Many thanks! Am trying to not order parts and just use what I have on hand... damn. Curious - my previous project, I made a GPS tracker for my dog's harness... many people said GPS would provide inaccurate readings when going at a slower speed. What would you recommend to be the best way to measure a dog's speed?

Thanks!!

many people said GPS would provide inaccurate readings when going at a slower speed.

They are wrong. GPS is your best bet.

If you've already got the GPS working I'd try that first. It should just be software to test out the concept The GPS speed on my Garmin seems slow-to-respond, so I don't think it would work as a replacement for my car's speedometer. But, that's not the main function of the Garmin.

Otherwise, I'd recommend doing it the old fashioned way... Measure wheel-rotation speed...

You should be able to do something optically or with a magnet and hall-effect sensor. I think bicycle speedometers use optical or magnetic sensing.

Something like [u]this[/u] might be able to pick-up reflection from a white wheel. If so, you could just paint half of the inside of the wheel white and the other half black. Or, some aluminum or reflective tape might do it.

Or, you can probably bury a magnet for a hall-effect sensor in the wheel near the hub without affecting performance.

I have an old school skateboard with LED sequins right now for nighttime skating/skatejoring (my pit bull pulls me with a Ruffwear Web Master Pro harness).

:smiley: :smiley: When I was a kid, my friend and I used to take turns pulling each other on a skateboard with a bicycle. I liked to go as fast as he could pull me, especially around the corners. When it was my turn on the bike, I'd always hear him yelling, "Pull it!, Pull it!... And I'm pulling him as fast as I can... At least that was what I thought he was saying... Then after he wiped-out he says, "I said cool it!'. :smiley: :smiley: