I just repaired such a beast.  My wife is doing seminars teaching kids about
money, so we picked up a unit that has 8 paddles going to a box with lights
on it and a reset button. Whoever presses the button first gets his light
lit,
and blocks everyone else out.  FYI.. the game is Jeoprody and it is played
with
Mojos!

It uses SCRs, and when the SCR is latched, it pulls down the triggering
voltage
supplied to the switches so that none of the other SCRs can trigger.  To
reset,
the supply is simply removed, and the SCR resets.  Each gate has a small
capacitor to ground to debounce the switch.

Pretty simple, but it took me an hour to figure out how the darn things
worked,
and find suitable replacement SCRs(one was fried).

I've also the same thing with home-made RS latches using NAND gates. You
need 3
quad nand packages to get 4 channels.  Using 4 gates as inverters. I have a
schematic kicking around if anyone is interested.  It is in Protel, but I
could
convert it do PDF.


Craig

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Bob Ammerman
> Sent: Friday, September 22, 2000 5:29 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: circuit for 1 of 4 select/latch function..?
>
>
> No, this is not a 'first to press' or 'lockout' box but rather a 'last to
> press' box.
>
> Bob Ammerman
> RAm Systems
> (contract development of high performance, high function, low-level
> software)
>
> ----- Original Message -----
> From: Gennette, Bruce <bruce.gennette@TAFE.NSW.EDU.AU>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Friday, September 22, 2000 12:16 AM
> Subject: Re: [EE]: circuit for 1 of 4 select/latch function..?
>
>
> > What you have described is a quiz show first-to-press indicator.
> >
> > If you do a search for this type of circuit I'm sure you'll find lots of
> > solutions (except for master reset, which you'll have to work out
> yourself).
> >
> > Bye.
> >
> >         -----Original Message-----
> >         From:   Chris Eddy [SMTP:ceddy@NB.NET]
> >         Sent:   Thursday, 21 September 2000 10:21
> >         To:     PICLIST@MITVMA.MIT.EDU
> >         Subject:        [EE]: circuit for 1 of 4 select/latch
> function..?
> >
> >         I am trying to sketch a circuit that has four select
> push buttons
> > for
> >         inputs, and four seperate digital outputs.
> >         I want to push a button and latch that output, and unlatch any
> other
> >         selected output which was previously selected.
> >
> >         I have invested a few hours and all I have to show is some burnt
> > brain
> >         cells.  I am drawing a big blank.
> >
> >         The solution can be logic gates, comparators, transistors, but
> > yikes, no
> >         processor.  Customer wants no EMI analog answer.
> >
> >         Any of you folks remember this stuff?
> >
> >         Thanks
> >         Chris Eddy~
> >
> >         --
> >         http://www.piclist.com hint: The PICList is archived three
> different
> >         ways.  See http://www.piclist.com/#archives for details.
> >
> >
> > --
> > http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> > use mailto:listserv@mitvma.mit.edu?body=SET%20PICList%20DIGEST
> >
> >
>
> --
> http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> use mailto:listserv@mitvma.mit.edu?body=SET%20PICList%20DIGEST
>
>
>

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
use mailto:listserv@mitvma.mit.edu?body=SET%20PICList%20DIGEST