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reflex tester game?

Discussion in 'Electronic Basics' started by clicker, Oct 5, 2005.

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  1. clicker

    clicker Guest

    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

    Any ideas?

  2. Noway2

    Noway2 Guest

    You could use a signal that indicates that you are counting down, then
    if a button is pressed while this signal is active you can generate an
    error condition that would indicate who the guilty party was. Without
    thinking through the details, it seems to me that you will need similar
    control signals to latch the first button press and lock the others
    out, so you may already have something that will work.

    How were you planning on implementing this circuit? I might suggest
    that you consider a microchip PIC, but it can be done other ways too.
  3. clicker

    clicker Guest

    I'm not up to speed with PICs yet but am comfortable with the more
    traditional 555's and such. I think it could be done this way but I'm
    no expert here.

  4. Noway2

    Noway2 Guest

    Yes, your circuit should be simple enough to implement with timers,
    discrete logic, and some small IC counters and flip flops. If you are
    fairly neat in your workmanship you can probably even get away with
    building the circuit on a breadboard and then fabricate a simple
    circuit board. To me this sounds like a good fun project that would be
    challenging but do-able.

    How familiar are you with truth tables and minimization through
    Karnaugh maps? What about state machine diagrams? If you aren't very
    familiar with this, I would recommend that you get a book on digital
    logic and switching. Probably about the time you get half way through
    the book you will have everything you need to do this project. A book
    on digital electronics geared towards hobby work would likely even have
    projects to build a bread board system. I have a book on my shelf
    "Digital Electronics Guidebook", by Mike Predko, which I believe I
    ordered through Amazon. This type of book may be a good choice for
    you. It covers the digital and analog electronics including
    transistors, counters, flip flops, 555s and up to simple processor
    based stuff.

    With the bread board approach, you can then build up a small section,
    such as one of the truth tables or state machines, counters, etc and
    experiment with each one seperately and then start putting them
    together. If you don't have one, you can probably get a bread board at
    radio shack or an online company. I had one floating around but I
    can't find it to tell you where I got it, but I think it was something
    along the lines of "circuit specialists".

    The way I would recommend starting is to think about the inputs you
    need / have and the outputs you want. Then either draw a set of truth
    tables and or state transition diagrams. This will give you the basic
    logic equations, which you can the minimize to reduce the number of
    gates, wiring., and cost.

    If you are ambitious enough, this would be a good PIC project. I have
    seen books on PICs even in places like Barnes and Nobles and Borders.
    I say that this would be a good PIC project because a lot of the
    functionality you are after would be pretty easy to implement with
    simple software. You could then use the IO pins of the chip to drive
    the LEDs or drive some decoders, etc.
  5. Jasen Betts

    Jasen Betts Guest

    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"

    | ___
    +-|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,

  6. Rich Grise

    Rich Grise Guest

    Yeah - people have been building these things for decades:

  7. Bob Monsen

    Bob Monsen Guest

    How about a random timeout that drops a ruler? The victim puts their
    fingers near the 12" mark, and a solenoid is used to release the thing.
    The score is where they grab it, in inches...

    You can get solenoids here:

    This one is a 12V DC relay, which means you'll need some kind of voltage
    source. This one might work (from the same guys:)

    (check the current rating of the solenoid)

    You can either just have a little normally open button to work it, or a
    timer of some kind.

    Here are some buttons:

    If you think you want a random timer circuit, I can design one that will
    work for you, but the button is probably the easiest, and if you put it at
    the end of two wires, you won't have a problem hiding the activation.

    You'll have to build the stand, get the ruler, and figure out how to
    reset it...
  8. Jasen Betts

    Jasen Betts Guest

    by now you've seen the circuit I desiged yesterday
    there were 4 and gates and two flip-flops per player plus the counter and
    the clock and the or gates etc.

    call it 9 ics for the whole unit including the decage counter, 4 input nor
    gate (or gates) and 555 timer.

    with a microcontroller you could do all of that in a single chip.

    you'd need to know how to program it, and make/buy the hardware to load the
    program into it (there is free software available) ...

  9. You can do this with a dollar bill (or $100, if you're feeling frisky. ;-) ).

    Have the subject stand or sit next to a table, with their forearm resting
    on it and their hand sticking out over the edge. Have them hold their
    thumb and forefinger about 2" (50 cm) apart, and hold the bill in your own
    fingers, where the middle of the bill is in between their thumb and
    finger. Drop the bill.

    No one can catch it.
    "A young Juliet of St. Louis
    On a balcony stood acting screwy.
    Her Romeo climbed,
    But he wasn't well timed,
    And half-way up, off he went -- blooey!"
  10. ehsjr

    ehsjr Guest


    Plus the follow up with pointers to the parts ... great!

  11. JeffM

    JeffM Guest

  12. JeffM

    JeffM Guest

    Have them hold their thumb and forefinger about 2" (50 cm) apart
    Nah. The *count by tens* thing is natural enough.
    It's the converting back & forth that sucks.

    If we'd just bit the bullet in 1917
    when the Industrial Age was hitting its stride
    and the i18n thing was warming up,
    it would all have been so much easier.
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