Bob,

I posted a message requesting this same infor for a friend of mine a
few weeks ago.  The general consensus I received was that, although it
might be trivial for someone with PIC experience (which neither I nor
my friend has), it would probably be better implemented by some other
means.  This is especially true for my friend and me, since we don't
have the programming board and software for doing a PIC project, and
that would be a large, up-front cost, relative to choosing some other
way of accomplishing the task.  Check the archives, and you'll be able
to see the replies (although, the subject for my message was
"chronometer" rather than "chronograph."

One possible solution my friend received in email, that did NOT come
from this group, was as follows:

----- snip ------
Ok the first thing you must do is get the projectile to trip a flip
flop. I would starte by wiring a jk flip flop to toggle.A good
referance to start with would be Forrest Mimm's handbook for engineers
availabe through NV.Next I would wire up a photo diode in series with
the necessary voltage to allow it to trigger the flip flop.The next
part will be tricky.  You will have to position the photo diode with a
light source focused on it so when the projectile crosses the path
between photo diode and light, the flip flop will toggle.Than make
another light diode set and place it a foot away from the first.Now
you will build a counter described in that hand book and a pulse
generator (also there).Now you will have the flip flop enable the
counter which is counting the pulses untill it changes state.A
 little math will do the rest.That handbook should be able to get you
through it all.
----- snip -----

That would certainly be a lot cheaper than using a PIC, especially for
someone who's not already equipped for programming them.
Additionally, my friend is not overly concerned with the actual
speed.  In other words, the feet-per-second reading is not important,
as long as a consistent and accurate reading of some sort is obtained
so he can see the difference between the results of different loads in
the bullets.  Regardless of whether or not the reading is in
feet-per-second or is just a count of pulses, the different readings
would allow him to determine the best load for range and accuracy.
Beyond that, I can't tell you much, since I'm a sword, boomerang, and
archery man rather than a gun person.

Of course, if you DO run across an existing PIC-related plan for a
chronometer, we'd still like to see it for possible future reference.

Thanks!





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---- On    , Bob Blick (bblick@SONIC.NET) wrote:

> A cheapskate friend of mine wants to build a shooter's chronograph.
The
> kind that has two photoelectric gates and reads out the velocity of
the
> projectile passing by it.
>
> He has found such a project on the web, but it uses a mess of CMOS
and you
> read the speed on a voltmeter. I looked at it and gagged. Such a
thing
> would be trivial with a 16F627/8 and an intelligent LCD display.
>
> I'm too busy to code it for him right away (of course he wants to
build it
> right now).
>
> Certainly someone has done this and put together a web page. Even if
it
> uses an expensive 16F84 :)
>
> Thanks,
>
> Bob
>
> P.S. If I ever decide to do such a thing I will post a web page, but
it's
> way down on my list.
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>
>
>

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