Red Light Answer

[Bernie Cunningham]

As far as I know, that type of sensor is no longer used, as in where light reflections or flashes would cause them to 'switch'.

These days the units are a sender and receiver across the track and must communicate with each other to 'switch'

[Mike Gray]

Originally Posted by Bernie Cunningham

As far as I know, that type of sensor is no longer used, as in where light reflections or flashes would cause them to 'switch'.

These days the units are a sender and receiver across the track and must communicate with each other to 'switch'

So when the funny cars take out the 1/8 mile and finish line foam blocks there is not just a reflector in the blocks but a receiver or sender?
Did it use to be just a reflector? maybe that's where the idea of wheel reflection got started.
Camera flashes for an instant are very bright, I hate the annoying flashes from overhead strobes at NBA games that are triggered by the photographers camera.
If I watch a replay in slow motion it will white out my tv screen.

[Jeff Stout]

I dont know the equipment at Pomona but what I know the reading device is in the middle on the starting line and when the car is staged it would block the camera flash that is shown in the video. The camera flash may have shined onto wheel but its the wheel facing the outside portion of the lane and would not interfere with the sensing beam. Now the rest of the increments down track have a reflector in the middle and the reading sensors are on the outside of the lanes.Doesnt solve the problem here but I think I would rule out the camera flash. As Don described his problem in WY I would have liked to have seen the tree activate again as the Camaro was still staged when tree was cleared just to see if car was at fault.Just a thought: if the beam is .030 in diameter and the wheel rolls just enough lets say .030 and keeps beam from crossing track and the car would move backwards (somehow?) say .001 then the beam is now uncovered and would register as if nothing was on starting line and go red. Cant be seen with naked eye. Sounds pretty far fetched but maybe.

[Bernie Cunningham]

Originally Posted by Mike Gray

So when the funny cars take out the 1/8 mile and finish line foam blocks there is not just a reflector in the blocks but a receiver or sender?
Did it use to be just a reflector? maybe that's where the idea of wheel reflection got started.
Camera flashes for an instant are very bright, I hate the annoying flashes from overhead strobes at NBA games that are triggered by the photographers camera.
If I watch a replay in slow motion it will white out my tv screen.

Really !!!! yes they are reflectors, all can see that and they continue to pose issues at the top-end. HOWEVER. we're talking about the starting line here ??????????????

Sorry about ya NBA problem !

[Mike Gray]

Originally Posted by Bernie Cunningham

HOWEVER. we're talking about the starting line here ??????????????

I know, just thought I would take a jab at the FC's.
Now if the side that reads the light is on the outside and it reads a light source there could be a problem with a camera flash, not to mention the DISTRACTION to a driver trying to cut a good light.

[Bret Kepner]

Having conducted my own Drag Racing School for fifteen years, it astonishes me how many veteran drag racers still don't understand anything about the starting line electronics array.

Pat's information is absolutely correct. The Stage-Loc system does not rely on a receiver since it has no function in the timing system; it merely keeps the "staged" bulb illuminated even if the front wheel has rocked back out of the actual "staged" beam. I'd venture a guess more than ninety percent of all racers have no idea the Stage-Loc system even exists let alone how it works.

In 2011, all NHRA National Event facilities have Stage-Loc and it's usually a permanent function requiring no activation. This means it is also functioning at regular events at most of these tracks.

Concerning the infamous "stationary red light", Jeff Stout's assumption is not fiction but fact. If the front wheel vacates the beam for a thousandth of a second, a red light will register. It has been proven a "flicker" of the "staged" bulb for less than two hundredths of a second will not even appear in the bulb since the filament will not have cooled before the electricity resumes its current through the filament. A flicker of three hundredths or less will not be apparent to the naked eye so nobody will see it, anyway. The vast majority of all video cameras record at a rate of one frame every 0.040 seconds, (four hundredths), so a flicker of less than that amount will not be visible on video, either.

Sun reflection is still a (rare) problem at some tracks but the effect has been reduced by variable infra-red frequencies used in the system. I still race at a few tracks with the old "headlight and photocell" arrangement and these problems are much more common with forty year-old equipment.

Hang in there, Pat. We'll keep you distracted as long as we can!

[Mike Taylor 3601]

Pat,
I'm sorry to hear about your loss,there is alot of things we never will know the answers to.
You and your family are in my prayers
Mike Taylor 3601

[Racin Mason]

Pat, thanks for all of the info. Can you tell me if it is normal for BOTH the pre stage and stage lights to go out when the red light comes on? I know it is rare that a car is still sitting there to turn on the stage lights when the red light comes on, but i would think that if I did rock out of the stage beam that the pre-stage light would still remain lit since the beam is still being broken.

[Jason Oldfield]

I'm not an electro-optic engineer, but I have worked in the field of optics and electronics for 20+ years, and I currently work for a company that makes optical sensors (our sensor works with a VCSEL in the IR-A range at about 800nm). In short, you CANNOT say WITH CERTAINTY that the photographers flash did not effect the receiving sensor. Optical sensors are pretty simple devices really, and as Pat pointed out in his original post the receiving sensor (detector) is a semiconductor device that is "tuned" to a specific wavelength of light. This helps increase the signal to noise ratio, and improve overall signal quality.

However, the match between the detector and wavelength of light that it is trying to detect is not exact, i.e. a sensor that is looking for a wavelength of light predominantly at 800nm doesn't usually reject wavelengths at 799nm and 801nm (it would have to be a REALLY high-dollar sensor). Optical sensors are typically open to a range of wavelengths, with their peak wavelength being the specified wavelength, or the wavelength at the center of a gaussian curve, like so:



As you can see from the above graph, there is a rolloff that would happen with the wavelengths of light seen by the detector. The minimum and maximum wavelengths would be determined by the sensor manufacturer from the type of detector technology used, and the tolerances in manufacturing (which in the end is reflected in the cost).

The same is true for the emitter. Again, the output of wavelengths from the emitter is typically a gaussian curve with the predominant wavelength being the specified wavelength. This is even true for lasers, though with lasers the wavelength range is much smaller than non-collimated light. I don't know the exact type of light source that is used for the stage beams in the timing system, but I highly doubt that they are lasers.

So, how would the photographers flash possibly affect the detector? It all depends upon the wavelengths of light that is emits. What the human eye can see is light in the approximate range of 400nm to 750nm. Light with longer (IR, microwaves, etc.) or shorter (X-rays, UV, etc.) wavelengths than that range is invisible to the human eye. What we see from the flash is white light, which is made up of all of the colors of the spectrum over the visible wavelength range. This is why when you shine a white light into a prism you see the entire spectrum of colors (sunlight through water droplets forming a rainbow is the same thing).

So, from this fact alone you can see that the photographers flash does NOT output a finely tuned wavelength of light. What wavelengths does it output? Well, we can say with a high level of confidence that it outputs an approximately wavelength range of 400nm to 750nm, but wavelengths above or below that are unknown. You would only be able to tell ALL the wavelengths by looking at the output with a spectrometer. In addition, is it possible that the flash outputs the predominant wavelength that the timing system's detectors are looking for? In short, the answer is yes, but at what amplitude is unknown (one would expect that it wouldn't be a predominant wavelength, but again you'd need to analyze the output with a spectrometer to know for sure.)

What is also important to note is that just because the detector is mounted inside a box or tube does NOT mean that outside light sources can't impact their performance. Certain materials are invisible to certain wavelengths of light. The X-Rays are typically defined in the 0.1nm to 10nm range, and can pass through many materials. Most optical sensors use either visible light or IR, and IR can pass through materials as well (this is why the military uses IR sensors to image heat sources of bad guys inside buildings). A nice description of IR light can be found at the link below (take notice of the image of the guys arm inside a garbage bag).

http://coolcosmos.ipac.caltech.edu/c..._ir/index.html

Now, does all this mean for certain that the photographers flash caused this event to occur? Absolutely not, but from a scientific standpoint, it seems awfully coincidental that the photographers flash goes off, and immediately afterwards the red light comes on. I'd have to see the original footage frame by frame (you can't do this on YouTube) to see what the timing difference is because optical sensors are fast acting. If the timing difference is long (i.e. more than a few tenths of a second), it would seem likely to me that something else must have caused this to happen. But, if it is literally the next frame as somebody else posted, stray IR light from the photographers flash is a distinct possibility.

Would that mean that we'd all need to demand instant changes to the timing system detectors? No, because IMHO it would need to be a near perfect storm for this to happen. With ALL the rounds of racing, and ALL the pictures taken, how often have you seen this happen? It is obviously NOT a common occurrence. But, at that point we could at least say that we believe that the system is NOT perfect, and try to work on a better, more fool-proof solution (rather than just burying our heads in the sand and saying, "It's not possible for this to occur.")

Science lesson over...