Wireless "Who's First" Game-Show Buzzer

[pc88]

I'm brainstorming ideas on how to implement a wireless game-show button system. There are a lot of inexpensive RF modules available, but the trick seems to be how to account for potential simultaneous transmission from multiple remote units. Any ideas?

 

[Pommie]

The simplest way is to time multiplex the transmitters. The Master transmits a sync signal and then the slaves take turns to answer. If you want it accurate (fair) then the buttons need to send the number of milliseconds after the sync pulse that the button was pressed so that the master can work out which was first. The disadvantage of this method is that the buttons have to be transceivers.

Mike.

 

[KMoffett]

I built a "wired" system that's been used for several years, and have also considered making a wireless version. What is "simultaneous" in the game show world? In a Jeopardy buzzer system you're dealing with peoples' response time and mechanical switches, before it even hits the electronics. Seems that independent frequencey (not encoding) pairs of transmitters and receivers should reduce the possibility of interference, and be well within the contestants' concept of "fair" timing. I would need 6, but have not looked into yet.

Ken

 

[Hero999]

What about modulating the trnasmitters with slightly different frequency signals or tones?

The receiver could use some PLL tone detection system that possiblt locks onto the the first tone it receives.

You could use an array of tone decoders for the different frequencies and look at which one locks on first.

Human reaction times are around 120ms at best so anything that can respond in less than say a tenth of this time is probably fair enough.

 

[KMoffett]

What would be the reaction of the receiver (1?) when it receives modulated RF signals "simultainously" from two transmitters on the same carrier frequency?

Ken

 

[pc88]

The tone detection system seems to be the easiest. I'd probably even do the decoding in software using a fast enough uC+ADC. For instance, DTMF decoding can be done in software with a modern microcontroller.

As for receiving simultaneous signals, I am content with just flipping a coin if the signals arrive within a certain amount of time (like 1/100 sec.) Besides, aren't the idiosyncrasies of the buzz-in system part of any game show?

Just wondering if there is any other ideas that I've overlooked. I wouldn't mind doing some form of time-division multiplexing if there was a simple way to synchronize the buzzers with the base station.

 

[Hero999]

What would be the reaction of the receiver (1?) when it receives modulated RF signals "simultainously" from two transmitters on the same carrier frequency?

Ken

If it's flooded with all the signals simultaniously then is could possibly output some kine of error message, otherwise is can respond whichever signal it receives first.

Another option is to use very slightly different frequencies and just transmit a plain carrier, like a morse code system.

 

[KMoffett]

Another option is to use very slightly different frequencies and just transmit a plain carrier, like a morse code system.

That's what I was thinking about. I think some R/C transmitters are set up like that, with different "channels", so flyer's at the same field don't winding up controlling someone else's model airplane. I wonder if there are cheap versions of these in tx/rx pairs?

Ken