Re: Building a Better Buzzer System

cooterchekov <*no_reply_at_yahoogroups.com*> · Thu, 15 May 2003 21:40:25 -0000

--- In quizbowl_at_yahoogroups.com, jp_lien <no_reply_at_y...> wrote:
> I think Edmund has a reasonable idea here, although I'm pretty 
sure he 
> means to run the output of the counter into the select input of 
the 
> mux.

Yeah, that would be a good idea. :)

>  You'd also need some state logic to handle the serialization and 
> flow control, of course, and to freeze the state once someone had 
> buzzed.  Also, you can't run the inputs from the switches directly 
> into digital logic.  You'd need to run them though a comparator of 
> some kind (A Schmitt Trigger, for instance) first (for de-bouncing 
> purposes, amongst other things).
>

My feeling is that that could best be done on the software level. 
The application reading the serial input would see that buzzer n was 
on, would make a note to itself and establish priority of that 
buzzer; then if that buzzer was on for, say, either of the next two 
passes, it would trigger. Granted, this does make a higher frequency 
desirable. Hm...maybe the thing at first just checks if any buzzer 
switch on *either team* is closed, and only then check which 
one...that makes the logic more complicated, though.

> 
> Then again, you could do the whole thing with just a priority 
encoder, 
> although people might get fussy over the fact that certain buzzers 
had 
> a built-in advantadge in ties (although I'm positive the knot-
style 
> quiz wizard buzzers are built this way, whatever they may claim). 

Get the clock frequency high enough and priority shouldn't be a 
problem.

 of all, 8 or 16 
> wireless transmitters and a common reciever are not, to my 
knowledge, 
> going to come cheap.  Also, each of the individual buzzers would 
have 
> to be battery powered, since they couldn't be run off of the main 
> supply anymore (imagine the horror of a battery dying in mid-
tossup).  

There's a trick around that. You give each buzzer two frequencies: 
a "receive" frequency and a "transmit" frequency. You build one 
circuit at the receive frequency and one at the transmit frequency 
and connect them through a transformer. Put a switch on 
the "receive" side. The core element of the buzzer is continually 
putting out power at the receive frequency for each buzzer. You 
close the circuit with the switch and the receive side resonates, 
which means the transmit side resonates too -- transformers are very 
efficient. It puts up a range restriction, but really, when is the 
buzzer going to be more than, say, 30 feet from the master unit? I'd 
worry more about frequency band...too high and, with the amount of 
power you need, you start heating people's fillings.