Re: Beam interruption / time measurement


"BobW" <nimby_NEEDSPAM@xxxxxxxxxxxxxx> wrote in message
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"Robert Barr" <not@xxxxxxxxxxx> wrote in message
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It's been many a year since I've messed with electronics -- back when a
nice color television used maybe a dozen 6GH8A vacuum tubes. (Good
riddance!)

Anyhow, what I have in mind is a low-cost timing setup, used to measure
the time between two events -- both of which would be the interruption of
a light beam. Extreme accuracy isn't necessary -- 0.01 seconds would be
fine, so no high-speed industrial stuff needed.

I want to measure the amount of time a motorcycle rider uses (without
touching a foot to the ground) to cover a fixed distance, riding as
slowly as possible, for perhaps 20 feet. In other words, a 'slow race'.
You'll see these at various biker events, and it's a whole lot tougher
than it looks. Here's the best I've seen in a long time:

http://www.youtube.com/watch?v=HrJvv_L8WBw

I'm thinking of two pair of tripods, one for the start line and one for
the end, with each pair holding an opto-electric device and a reflector.

The cheapest opto-electric devices I can think of are the safety units
that automatically reverse a garage door opener. I have a pair (from an
old dead opener), and they're pretty cheap on eBay. The problem with
these is, I can't find any source of information about how these operate.
Perhaps it's deliberately arcane knowledge, so that it's difficult to
defeat their purpose.

Does anyone have a link or source of info on how I could use these
critters to my purpose? Or, for that matter, a simpler, cheaper way to
do the job accurately? I've seen timing kits specially made for racing,
but they're asking about $600 and up. I'm thinking of a small fraction
of that.

I also found these, after about an hour of web searching:
http://www.goldmine-elec-products.com/prodinfo.asp?number=B00002&variation=

... but it's hard to tell how much useful information they'd come with.

I haven't decided on what to use for the actual timer & output, but that
might be the simplest part.

(One guy suggested pneumatic switches. Old-timers like me can remember
when gas stations had hoses draped across the pump lanes which, when run
over by a car tire, would ring a bell inside the station. They had these
antiquities called 'attendants' who would come out and put gas in your
car. Honest. Then they'd clean your windows. Nobody believes me, but
it was very common back when 6GH8A's were about $3.50 a copy...)

Robert,

I'll do some thinking about this. I've learned how important slow and
controlled riding is on a motorcycle using the "friction zone" and rear
brake techniques.

If I were building it, I would use a little micro controller, lcd, and
associated switches and/or optical sensors. However, I'll see if I can
come up with something simpler and more off-the-shelf.

Bob


In thinking a little bit more about this, your pneumatic hose sensor (yes,
I'm old enough to remember those, too) sounds like the most reliable and
accurate solution to determining the start and stop points.

That guy in your video is amazing. I can't ride that slowly, yet. There is
no doubt, in my mind, that the motor officers are the best riders on the
planet. I have learned most of my techniques from a guy named Jerry
Palladino and his videos at www.ridelikeapro.com .

Still thinking....

Bob


.

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