Measuring speed of a passing vehicle

Hi there.
Later this year I have a project for a motorbike championship where I would like to measure the speed of passing bikes. Basically I am running a pyrotechnic effect near the track and would like to synchronise the effect with the passing bikes. I was thinking of infra red beam detectors (such as available from maplins) spaced apart and measuring the time taken for each one to be triggered and calculating the speed from that. Any hints or ideas? I would need to send the result to a PC with some software to run the actual effect. Has anybody done anything like this? Pulsein? timers?
Thanks

>> Any hints or ideas?


Take a hacksaw and walk down to your nearest GATSO...

Sounds like a neat little project...

Breaking a beam of light may work out kind slick...If the beam is low enough to be broke by the tires.

1. Beams would have to be same height.
2. Beams would have to be spaced a certain known distance apart.

When calculating, you will have to use some kind of timer, so that if the beam is broken by accident, it will not measure the speed between two cycles.... Or you can say

if (the second beam is broken) || (Timeout accures) goto reset

I would first see what kind of hardware you have to work with...If you can make a beam work... then PROVE it to yourself. Setup a "test situation" and do a mock test (It doesn't matter if it is accurate to the dots on this i). What matters, is the breaking of a beam, and what signal is given out, when the breaking occures. Then work on writing the software and using your PIC chip to work the data for you.

Dwayne

Quote:

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Originally Posted by Melanie

Take a hacksaw and walk down to your nearest GATSO...

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There is no challenge Mel doesn't have a solution to ;-)

But:
You shouldn't approach too fast, you don't want to be flashed right before utilising the saw!
(Some GATSO's transfer the images directly!)

Quote:

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Originally Posted by kitcat

...for a motorbike championship where I would like to measure the speed of passing bikes. Basically I am running a pyrotechnic effect near the track and would like to synchronise the effect with the passing bikes.

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I think you don't really need to measure the speed.

For each class of starters I would assume the average speed (and acceleration) between two points of the track is something known.
(There wouldn't be a scooter competing with a speedbike would it?)

So all you need is a trigger right at the start, from that you can calculate all the timing for the fireworks along the track.

A simple NTC thermistor could be enough.....

http://www.strangevehicles.com/image...ent/103466.jpg

Luciano

Hi,
Light beams are the accepted method of timing wheeled vehicles (last one I saw personally was used to time a car at over 760MPH).
Use one beam to set a flip-flop (monostable), the other to re-set it and measure the time ths output is high using PULSEIN on the PIC. This should be reasonably accurate.

Robert G8RPI.

Hello Robert,

Robert>>Light beams are the accepted method of timing wheeled vehicles (last one I saw personally was used to time a car at over 760MPH).<<

Humm Robert... this is the speed of sound... It was only broke not too long ago (that I know of ) in the California? desert by a rocket car... But I am not sure about overseas, and their accomplishments... are you sure you are not thinking 760KPH?

Dwayne

All very interesting.
I think I will be having a few problems with many bikes bunched together and multiple triggers. And then there are the front wheels and the back wheels. I could end up having about "triggers happening at once".
I had originally thought of calculating the average speed of the bikes and triggering it by hand or with one beam nit that is a bit of a cop out. I have already started on the PC end. THe system runs from midi and we treat it like a "visual" musical instrument. For anybody who is interested there is a link here to a very bad mpeg of a brief snippett from our show at Alton Towers. We developed moving platforms for the flames which you can see at the front. To get an idea of scale, our flames are about 24' high and the background is Millenium fireworks + lasers etc.
http://elmtreecottages.co.uk/Alton1.AVI
(I'm afraid it is about 24 meg)

GPS Receiver modules are small, lightweight and cheap. They will report back the speed at which they are travelling, and you can have an unlimited number racing around the track reporting the stats back to you. The only drawback is the start aquisition time, but once you've locked, theres no problem.

Hi!

Motorbikes at full throttle position are very loud.

What about a sound detector very close to the race track?

Use a microphone with adjustable gain so it won't be
affected by other noises like your fireworks.
Mount the microphone in a tube, to isolate unwanted noise
and make a directional microphone.

You detect the sound of the passing motorbike and after a fixed delay
you trigger the fireworks. Do that where the motorbikes are
at full throttle so that the covered distance will be always
the same and the noise very loud.

There is no need for speed/time calculation unless you trigger the
firework only for the best speed/ best laps.

Make sure that all the race participants (pilots) are aware of your fireworks
and that the generated light will not temporarily blind them.

Luciano


200 kilometer/hour = 55.5555556 meter/second
200 kilometer/hour = 5,555.5555556 centimeter/second
200 kilometer/hour = 124.2742384 mile/hour (mph)
200 kilometer/hour = 182.2688831 foot/second
200 kilometer/hour = 2,187.2265967 inch/second

Hi,
another method that is used is to have a IR beacon on each bike (different code for each bike) and decode that as it goes by, The typical data rate (38Khz) might give you accuracy problems though.
Hi Dwayne, Yes 760MPH is around the speed of sound, It was broken on 15th October 1997 on the Black Rock desert in Nevada by a British team using a twin Jet powered car - Thrust SSC. I was on the team, see,
http://www.thrustssc.com/thrustssc/Team/team.html
There were a couple of PIC's on board, but no PBP!

Robert G8RPI.

Hello Robert!

Robert

Quote:

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Hi Dwayne, Yes 760MPH is around the speed of sound, It was broken on 15th October 1997 on the Black Rock desert in Nevada by a British team using a twin Jet powered car - Thrust SSC. I was on the team, see,
http://www.thrustssc.com/thrustssc/Team/team.html
There were a couple of PIC's on board, but no PBP!

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Thanks fanastic!...Congradulations...The odds of meeting someone from such a team on a PIC board in UK??? I think I am going to play the lottery now...Thanks for the fabulous link.

I notice you had "Micro Pilots". Ultralights? I thought I saw the wingtip if a flying trike. Alls I can say is...Congradulations, and many more victories for you and your team to come!

I don't know how long you have been a ham, but There may have been a chance, that we have communicated to each other over the years... Been a Extra Class for 30 years.

Dwayne