🚀 go-pugleaf

In article <1990Mar19.154615.22362@tree.uucp> mirandor@.PacBell.COM (W. Le Roy Davis (1-23-90)) writes:
>I am looking for the circut for a very inexpensive three event detector.
>I work with the Boy Scouts, and they have this "pine box derby" involving small
>(8" long) cars on tracks.  They run three at a time.  I need an easy to main-
>tain circut that detects the cars crossing the finish line and determines 1st,
>2nd, and 3rd place.  I would like to keep the circutry down to 74xx type chips.
>I have had several friends suggest timed circuts, but that is getting too
>complex.

Well, Just thinking for a few minutes, I have a circuit that you can use
to drive light bulbs (120 VAC) which make it nice and easy or everyone
around to see what order they crossed in.  The numbers below represent
counts of gates, flip-flops, etc - not necessarily #s of chips required.
(i.e. I think OR, AND, etc gates come 4 or 6 to a chip, but I don't 
remember off-hand (are they 14 pins?  That would make them quad-2-inputs
which I think are quite comman 74xx chips).  Anyway, for a triple
event detector, my simple sketch requires, approximately the following
numbers (to give you an idea of complexity - keep in mind this is a 
rough concept that I'd clean up and run through Logimac (TM) before
submitting to you.)


A 5V power source.  I could probably come up with a power supply if
needed, but 5V ps's are pretty common if you're dealing with 'lectronics
anyway, so I've not included that.

9 LED's (preferably the super-brights, so you can use the 5V rather than
having to cut it back to 2V (though diodes would make that easy, anyway)

9 switching transistors (one for each of the LEDs)

9 Flip-Flops (A Clocked S-R (if such a beast is available) would be
	optimal, but I could work something in if I can't find a part
	number for one)

The reason for 9 of the above is obvious:  1st, 2nd, & 3d place lights, for
	3 tracks...

3 2-input OR gates.
6 2-input AND gates
3 inverters

3 NC momentary contact paddle switches (to be used to detect passage of
	cars)

1 NO momentary contact pushbutton switch - to clear the lights.

*******

If you think this sounds simple enough, let me know and I'll come up
with a schematic for it - at least one that can be breadboarded - I hate
trying to come up with PCboard schematics, so that's up to you if you
want to do it!




-- 

Thomas J. Kopp - Carroll College, Waukesha, WI
	tkopp@carroll1.cc.edu 	 uunet!marque!carroll1!tkopp
"Some people aim to live the longest.  My goal is to live the most." - Me