I've been wanting to build a fun reflex tester for my kids. I've got
the basic idea of using a decade counter to light a series of leds. The
lights would start the countdown and when it got to the last one it
would signal the kids to see who could hit a button the quickest. I was
thinking of something that would have 4 or so buttons so they could
play as a group.
There would have to be some way to make sure anybody who jumped the gun
didn't win the game and also some way to make sure somebody can't just
hold the button down continuously from the start and fool the game that
way.
Any ideas?
hmm you need to disqualify anyone who presses early
so there's 3 states for each input
unpressed, pressed early, and pressed on time
to store 3 states takes 2 flip-flops
make 4 of these... "input units"
(reset)___________________
| ___
+-|R Q|--- cheat
(early)------------|~~\ | | _|
| & )--|-|S Q|O-----|~~\ out
__ +--|__/ | ~~~ | & )---
(press)--| \ | | +---|__/
| & )--+ | ___ |
(enable)-|__/ | +-|R Q|--+
+--|~~\ | |
_____ | & )----|S Q|
(early)------------|__/ ~~~
now, how to hook the 4 input units together.
_____
the (early) , (early) (reset) and (enable) inputs are common
among all the input units, (press) is wired to go high when
the button is pressed.
reset goes high momentarily to clear the output and start a new game
(attach it to the decade counter output 0 pin) ...
_____
(early) is inverted (early) or vice-versa (attach (early) to out 9 (or
whechever out on the decade counter means _____
press now) and use an inverter (or out 8) to get (early)
wire the 4 outs to a 4 input nor gate (or equivalent) and the output of
that to enable.
how it works,
after reset (early), and (enable) are both high and so any signal on
(press) will set the upper flip-flop.
_____
once it's time to press early goes low (and (early) goes high) now any
high signal on (press) will pass through the lower and gate and set
the lower flip-flop
if the lower flip flop is set and the upper is not set that's two high
outputs to the last and gate which makes out go high,
that makes a high input to the 4 input NOR gate (discussed above) which
makes enable go low blocking all the buttons from effecting any further
flip-flops until the game is reset.
the winner is the one with a high "out"
(attach the indicator this output)
Any cheats will have a high "cheat" output.
if you want the game to restart autommatically after a winner has been
found attach reset further down the decade counter and use a 4
input and gate to detect the case when all four players cheat.
the "christmas tree" traffic lights used for starting drag races have a
random delay between the yellow and the green light you may want to
consider implementing this feature in your game so that players must
react to the "go" light instead of just judging when it will light,
Bye.
Jasen