Author Topic: Timing Light Reading  (Read 7134 times)

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Offline kponz

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Timing Light Reading
« on: September 08, 2005, 03:52:58 PM »
I've looked through the forums, and haven't found anything on this topic yet...
I was curious if anyone had tried to read the timing light spots on the track?  I want to mark, relative to other data collected during a run, where the timing lights are.  What sort of signal is sent out by the box, and how might I go about reading it?  I'd like to hear if anyone has had any luck with this, or if the SCTA doesn't want people passively watching their lights as the car goes by...

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Offline Glen

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timing lights
« Reply #1 on: September 08, 2005, 04:41:49 PM »
The timing lights(sensors) are infared and battery powered. They are wired to a timer board and the elapse time is converted by the computer. As it is not a wireless system I doubt if this data will be availble for your personal use. the sensors are located at the 2 mile,  2-1/4, 3mile, 4 mile and the 5 mile on the long course. All data is printed out on the time slip. Any other data is up to you to down load from a on board data logger.
Glen
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Offline Dynoroom

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Timing Light Reading
« Reply #2 on: September 08, 2005, 05:08:14 PM »
We just count wheel revs. (undriven) it's worked for us, not exact but relative. The miles are laid out perfect so it's just math, if your off 2 feet entering your still off 2 feet exiting a mile. JMO
Michael LeFevers
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Offline kponz

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Timing Light Reading
« Reply #3 on: September 08, 2005, 05:41:29 PM »
So, if we had an infrared receiver on the side of the vehicle, we might be able to pickup when the vehicle is passing the timing light?  Do you know how high off the ground, what side of the track or any more information about the light itself that might be important?  One thing we would like to look at is tire size change versus speed, and knowing when one precise mile has passed would aid in that.  We wouldn't need the data that is sent back for the timing slip, just when the vehicle has passed the light.

JohnR

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Timing Light Reading
« Reply #4 on: September 08, 2005, 06:50:28 PM »
Count me in on this as well. If I could use a lap beacon receiver to note on my onboard datalogger EXACTLY where I crossed the lights would be great. Right now I press a button on the steering wheel every time I go past a light. Not that accurate.

Offline fastesthonda_jim

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Timing Light Reading
« Reply #5 on: September 08, 2005, 11:35:44 PM »
How about a recording GPS?  I mean they are accurate to hundredths, and are relatively "off" by the same amount all the time, I believe
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Offline kponz

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Timing Light Reading
« Reply #6 on: September 08, 2005, 11:44:56 PM »
I'd like to be able to see both.  I think that the infrared signal would be "instant" whereas the gps signal would have to be interpolated (the best refresh rate from a gps that I've seen is 10Hz).  I think if we have the information about the infrared signal, it would be easy to detect it.

Offline Dynoroom

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Timing Light Reading
« Reply #7 on: September 09, 2005, 03:02:18 AM »
If tire growth is the issue, how about a laser distance mesurement on the tire from the wheel well (worked in NASCAR when they ran bias ply tires). If you know the roll out you have your answer. If you really need it you'll find a way. With the tires we run we've not seen a measureable amount of growth on our data traces @ 300 mph. Of course the guy's who run Goodboots do have a growth issue. Maybe Dave will figure out how to trigger it like you want it. Ain't it fun finding new ways to go fast.
Good Luck!
Michael LeFevers
Kugel and LeFevers Pontiac Firebird

Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...

Offline ddahlgren

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Timing Light Reading
« Reply #8 on: September 09, 2005, 06:59:47 AM »
Ok I will play along what would you learn from this data that would be more informative than an undriven wheel speed sensor? if you are within a couple of feet of the line one way or another there is little benifit for the expense that i can see. The wheel speed sensor has a bunch more info if coupled with a driven wheel speed sensor to measure slip at the same time. Then you know where you are on the track and the traction at that point as well. If you think you might dispute the timing of your car i think you are in for a surprize even if there is a clock failure at the tower i doubt if anyone will take your time in the place of the official time recorded or not.
If you want to learn about the track and its condition I would us ethe following..
wheel speed driven and undriven
gear position
Throttle position
accelerometer 2 or 3 axis
shock pots all 4 corners
steering angle sensor
engine rpm

With these there is little you can not find out about the car and racetrack.
It would take about 4 or 5 k to do this very well and completely with very little left to the imagination of the driver to reconstruct after the run.
Dave

Offline kponz

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Timing Light Reading
« Reply #9 on: September 09, 2005, 10:42:02 AM »
I wouldn't want to measure the time between the timing lights just to avoid the "double referee" problem.  The timing tower is the only source for official speed times, and I would not try to dispute that.  Assume then, that we still want to "watch" the lights go by, could we just use the receiver from an IR lap beacon?  Again, this would be only to be able to line up our other data relative to the track.

Offline ddahlgren

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Timing Light Reading
« Reply #10 on: September 10, 2005, 08:33:19 AM »
why can't you just measure the position on the track with a wheel speed sensor on a driven wheel (as oppsoed to a driving wheel that might have spin)? Simple elegant and less chance for a missed beacon. Less cost as well and will work at any track, plus you get all the info before the first light. Data alignment closer than 10 or 20 feet out of a mile is not very critical as far as I can see as well if your wheel speed reading ever got to that error condition in the first place.
Dave

Tom B

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Timing Light Reading
« Reply #11 on: September 14, 2005, 10:46:59 AM »
I haven't been out in a few years now, but I did some data acquisition when I did go, and we explored this issue.  The officials described what they were using without hesitation.  Unless you transmit, you can't mess their system up.

What works against you is vehicle speed and response time.  Assuming that you are able to receive their signal (which at the time was a constant frequency IR source, I think), your receiver will only be exposed to that signale for a very short time.  Since it is an on/off pulse, you have to see that pulse long enough for your detector to receive it AND filter it AND respond to it (send a trigger into your data acq).  At the time, our vehicle speed was 150-175 MPH.  I believe the conclusion was that it probably wouldn't work, so it wasn't worth the time or effort.

You see, they have the advantage of using your car to break their beam.  The longer your car or the slower your car, the longer the beam is broken.

As for GPS, I've done some playing around reading the serial output from a Lowrance receiver.  The standard output can only be accurate to 2m because of the output number of digits of precision and the update rate on "retail" systems always seems to be 1 Hz (1/second).  Velocity seems to be super accurate, velocity calculated using some earth diameter approximations was not, so I used both the position and velocity signals when I was playing.  Also, very few have a "true" compass, and the units that have them are sometimes not accurate.  If you programmed waypoints when the course was driven, the heading would be accurate without a compass.  Since I didn't have the ability to do GPS when I was assisting, I can't say that this isn't good enough.  My gut feel is that a 1 Hz update combined with wheel speed and accelerometer corrections would work real well at Bonneville.  If not, I found an evaluation board on the internet somewhere (don't know the link right now) for about $800 that had 5 Hz output.  This would provide a nice crossover between car based sensor outputs and GPS sampling frequency as a confirmation of data quality.

Just a few thoughts.

Offline kponz

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Timing Light Reading
« Reply #12 on: September 14, 2005, 11:28:51 AM »
I agree with the GPS, we've had great success with a 1Hz unit, and the speeds it gives are consistent with the timing slips.  I've seen up to 10Hz units, which would be nice.  

As far as the IR beam, what is the pulse frequency?  If we are able to see the beam for even a portion of its pulse period, it could latch, so that the data logger would be able to mark the time, even after the beam has passed.