Quiz Buzzer

Hi all,

I would like to know a simple circuit for QUIZ PROGRAM.

Thanks in advance. sena.

One of the best (simple) designs I came across was published in the Design Ideas section of EDN Magazine June 27, 2002, by Vasiliy Borodai, titled 'Circuit improves further on first-event detector'.

The circuit requires only two wires per button (three if the LEDs are placed at the buttons). The signal at the junction of the LED and the first and second gates could be buffered to drive additional indicator LEDs, or high power lights for an audience.

Disconnecting one of the inputs of the second gates and wiring them all together in a common line to an 1M Ohm pull down (fig a) or pull up (fig b) resistor and a 'Reset' switch to pull this line up or down. This 'Reset' switch can then be used to 'clear' or 're-arm' the circuit quickly if one of the players 'jumped the gun'.

If the capacitors are replaced with wire links, only the 'Reset' button will be able to 'clear' or 're-arm' the circuit. I do however find the 'auto arming' of the circuit (after +-15 secs) to be one of its best features.

Circuit (b) could possibly be implemented using 74HCT00 or 74HCT132 gates running of 5 to 6volts. The 2k5 resistor will probably have to be reduced to

1K or even 680 ohm, to allow enough current through the LEDs. Red LEDs (with their low forward voltage) will be preferred.

Gerhard van den Berg CSIR

What's supposed to happen if a player jumps the gun is to lock that player out for the round. In Jeopardy tryouts, they say, "On the last syllable of the last word" of the clue. If you push your clicker while Alex is giving the clue, you don't get to play that one.

Plus, the ones in the article are monostables. How hard would it be to make them bistable, with a moderator reset button?

Cheers! Rich