Drag race Christmas tree

A bike drag race is being formally organised for the first time
in my state by local enthusiasts and a government department. As
they can't afford a full set of pro equipment yet, they asked me
if I could rig up something for them - not for free, but
obviously at a significantly lower cost and, if necessary, with
limited features.

ATM, they are most concerned with the start line rather than with
things like accurate measurement of elapsed time. Everything will
have to be built from scratch. Commercial units are out of the
question for now. This is not just due to cost, but also because
we don't have easy access to the services and facilities you take
for granted in more advanced places.

I can't even ride a bike and what I know about what's needed is
what I've gleaned from the internet over the past 24 hours. None
of the organisers know all the details either. The event is to
take place about 3 weeks from now, so I told them that I'll do
some investigations but can't promise anything at such short
notice.

I may need help with the technical side if I decide to take up
the project, but for the moment, could you please answer the
following general questions first?

1. Do Christmas tree light starting systems normally come
integrated with timers and sensors for elapsed time?

2. How much do they cost? I expect that this varies with the
level of sophistication, but some ballpark figures will help.

3. Are they usually standalone units or software controlled from
a PC?

 

Some do come with everything, but all integrate with the system so
that there is coordination between timing and start.

Check Jegs, or one of the other automotive (custom/racing) supply
houses. There are choices there.

No, standalone. But: you could easily build one using a PC's parallel
port and a bit of software if you are running an early version of
Windows, or running DOS (to allow easy access to the port).

If your PC has a game controller that is another option, but these
have fewer ports for output.

Even a couple of serial ports (the control lines) could be made to
work for your needs if you don't need a big countdown. (say a single
amber then green)

 

I'm thinking of something a bit more complex than simple running
lights, and more accuracy than a 555. I /have/ been considering a
4017, fed from a 4060 14-stage counter with a 32.768 KHz crystal
oscillator to get the 0.5 sec countdown. Then there will be the
detectors for position and foul starts, etc.

 

OK. Thanks for the reply.

I've found out a bit more about that side of the matter.
Portatree seems to offer low-cost solutions. But "low-cost" is
relative and customs hassles make it impracticable to buy from
such sources (I'm in a remote corner of India). In any case, I
asked about prices mainly to get an idea of what's involved with
commercial products.

Again, that question was mainly to get a feel of how it's usualy
done. I'm not so hot with programming and a computer-controlled
option will still involve designing and building the external
hardware like sensors, power supplies, lamps support structure,
lamp drivers, etc. Given the limited amount of time available, I
think I'll stick to a purely hardware approach.

I've been thinking of using a crystal oscillator-counter with a 2
Hz output - probably a 4060 - and good old 4017 decade counter,
latched at the 4th pulse.

There's still an important gap in my understanding of how it all
works. The sources I've read say that the prestaging and staging
points are detected with two beams of light, 7 inches apart, near
the starting line. Fine, I guess I can use laser pointers and
photosensors coupled with the countdown circuit. The gap is that
none of the sources say how a foul start (before the green GO
light comes on) is detected. No mention of a third beam.

Since the staging detector beam is already cut off by the
vehicle's front wheel before the countdown begins, I don't see
how that can be used. Detecting the instant the front wheel
/leaves/ the beam seems unsuitable as variations in the size and
design of the wheel will introduce a factor of uncertainty. Can
you or anyone else provide some enlightenment?

 

Puzzle solved (I think). Although I have not seen a specific
statement to the effect, I've come across some indication that
the time a racer leaves the starting line /is/ taken as the
moment the front wheel leaves the staging marker beam, thereby no
longer blocking it.

I also read that the beam is placed about an inch above ground.
At that height, the wheel of a car or bike would be roughly a
foot wide. From a standing start, the time taken for a part of
that foot-wide section to cross the beam will be an appreciable
fraction of a second. As a point of academic interest, that's
quite significant when reaction and elapsed times are measured to
within a millisecond.

 

You don't need precision timing for the Xmas-tree, just so it's consistent
from light to light, so the driver has a sort of countdown.

As far as staging beams, the vehicls stops at the first beam, with some
kind of "ready" indicator. If the vehicle interrupts the second beam
befor the tree goes green, then it's a foul. Is there some kind of
structure between the two lanes at start? That way you could have two
"foul" beams, so you could tell which one fouled.

So, press the "ready" button, the red light at the top of the tree comes
on, and if the contestants are "staged", you're ready to go Maybe put some
kind of interlock, so you can't start until both vehicles are "staged".
Operator presses "Go" button, the tree counts down, and as soon as the
green comes on, send a "start" signal to the timer at the end of the
track. I don't know how you'd arrange for two "finish line" beams without
something between the lanes, but when somebody wins, who cares what the
loser's time was? ;-)

Good Luck!
Rich

 

According to what I've learned these past few days, even *that*
is still not quite correct. Going past the first beam before the
start (called "deep staging") is usually allowed, but it carries
the risk of also going past the second beam and being
disqualified.

 

If you have a parcel service like UPS, I think Digikey will deliver parts,
but other shops can deliver full systems, too, if there are no export
restrictions to your place.

3 weeks is not much time for building a professional system. The low-cost
solution: Some switches, some lamps and a human operator (someone sitting
beside the start line and switching the switches while watching for false
starts

 

Thanks for your interest, but no way is that possible. In this
remote place - really the most isolated state in India - I can't
even get things shipped quickly from another state.

It's an interesting project but the short time available is
frustrating, especially since I've never anything similar to this
before. But the fully manual option is just not acceptable (I
assume the suggestion was made tongue-in-cheek ). They might
just as well count 1-2-3 with a megaphone.