Greg,
In real I am spreading the idea. Suppose there are no persons, but
machines, circuits voting, then speed is totaly dependent.  I still
believing a $10 circuit is cheap.  A single key and one lamp would cost
much more than all the electronic gates necessary to make it by the
right way.  If a key spring is stronger then other and it would delay
the contestant answer (even that the rule is "who makes first the switch
click", so key spring doesn't count), initially you don't have a way to
know that, and it makes part of the game, the same way if a contestant
is faster to know the answer but lazy to press the button.  Still
winning who makes first the click at the switch. But you already know
that a priority encoder circuit has a tendency, so it is changing the
situation about who made the first click.

Now, suppose you have 10 PIC units collecting data and you want to know
which one ends up first the calculation or data gattering, would you
still using the 148? for sure not.  Then, by the same price you can have
a "correct" way to do that.

Lets see;  each 74HCT00 can be used to build the necessary flip latches
for two contestants, so you would need 5 units, each one cost around
$0.20, you will spend $1.00 to have the right timming circuit, with less
than 10ns of possible error.  Increasing $1.00 in your Quiz Master to
make it "correct" is too expensive?  I don't think so.  Then use a 10 to
4 encoder and a shift register to send the 4 bits to the pic in just few
wires....

I am not trying to tell you what you should do, just telling you that
there are better ways to do it by the same cost.

:)
Wagner



Greg Brault wrote:
>
> Wagner,
> I disagree.
> Like someone had posted earlier today (sorry, i don't remember!), the
> composition of the switches, spring constants, etc, add more variables
> to the scenerio.  So (as quoted earlier today), the person who may know
> the answer first, and pushes the button in the SAME INSTANT (within
> microseconds) as another player, and even having top priority, still may
> not get it.  Plus, I was in quizbowl for my entire high school career.
> Their systems cost A LOT of money, and i wanted to build one for cheap.
> very rarely did i see two lights on at the same time... indicating two
> people were within that margin of time to do that (this can't even
> happen with the encoder design ... just showing how often that scenerio
> would happen)
> Greg
>
> Wagner Lipnharski wrote:
> >
> > Greg Brault wrote:
> > >
> > > priority chip # is 74148
> > >
> >
> > Tell me which button would be the higher order, I will be there.
> > If everybody presses the button at the same time, I will always win.
> > According to my point of view, this is not the best chip for the job.
> > Simple J-K flip-flops would work better, then feed them to the 148.
> > Wagner