If you believe the hype (and after my wife explained that I was going to be the Easter bunny and
Santa soon what else have I got to believe in) then this would be a good application for Zigbee.

Looks like Chipcon has the physical level covered now:
http://www.chipcon.com/index.cfm?kat_id=6&dok_id=104


-----Original Message-----
From: "M. Adam Davis" <adampic@UBASICS.COM>
Sent: Nov 14, 2003 10:56 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE:] Remote Quiz Buzzers

Well, the cost of a receiver in each box is about $8, but then you have
to add additional code, etc.

Digikey apparently carries some citizen oscillators, CSX-532T SMT TXCO
which have +/-1.5ppm at 25+/-2C and 2.5ppm over the entire temp range
(-30c to +75C).

2.5ppm means they could be off by +-9mS after one hour.

They cost $9 each, though.

But for small teams (10 on each team) and relatively fast transmitters
with small data packets you could easily get an update from each
transmitter more than once a second.

However, I figure that a two-way system is probably better overall
anyway.  It does make the code a bit harder (synchronizing slaves to the
master is non-trivial - doing so over radio is harder), but the benefits
can outweigh the cost
* Have a light on the player's control telling them who has control.
* No need to hand synchronize them.
* Overcome issues such as spurious reset of the control without
retrieving the box.
* Put flash in them, and remotely update for a new game type
* They can contact each other (interesting uses)
* for simple games, no master needed - one 'slave' can assume
mastership, and the lights can tell who pressed first.
* Add an LCD so players can see 'secret' information

For one off cost would be:
Radio (RX and TX) $10 (cheap laipac modules)
Flash PIC, crystal, LED, PCB $10
Project box with membrane keypad $8

So for under $30 per box you can build a full system with all the
flexibility one could want.  Add some simple encryption routines so it's
not trivial to fake a fastest press...

If I only had the time.  Wired quiz show boxes are sold for over $300
for 8 players in two teams.  Just have to make them really durable...

-Adam

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