Jeopardy Circuit Question

Apr 01, 2005 5 Replies

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NodakBarnes 21 years ago

I have a question about a Jeopardy Circuit I found on the internet and decided to build. To start, here is the link to the circuit so you understand what I am talking about:

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I have constructed the six button circuit and after exhaustive testing and reconstructing on the breadboard numerous times finally got fed up with it and modelled it in Multisim 7. Come to find out, it didn't simulate properly in Multisim either. Looking at it more carefully with a logic probe I came to discover that the two NAND outputs (pins 6 and

9) of the 4023 being "ganged" together does not work. I "isolated" both outputs by feeding them through an OR gate via a 4071 and it then worked as advertised. First, is this the proper approach to fix this problem? And also, I was wondering if the resistors (R1 - R6) supposedly used to clamp down the inputs in case of noise are really needed? Any help appreciated...Thanks!

Wallace Barnes

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OBones 21 years ago

I think you could have used two diodes instead of a OR gate. It takes less space and less power, and should work just as well.

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JeffM 21 years ago

Then again, he could have renamed them.

My guess would be some variant of Visio. It is clueless about **wires** and **components**.

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Tom Del Rosso 21 years ago

I'd like to know what CAD program was used to draw those diagrams, so I could avoid it like the plague.

Here's a circuit, for 2-8 inputs, that was posted in abse a few years ago.

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Reply in group, but if emailing add 2 more zeros and remove the obvious.

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John Woodgate 21 years ago

I read in sci.electronics.design that Tom Del Rosso wrote (in ) about 'Jeopardy Circuit Question', on Sat, 2 Apr 2005:

The six-button graphic includes a filename 'jeopardy2.sch'. That may give a clue!

The diagram are both schematics and PC board layouts, and serve neither purpose very well.

Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

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peg 21 years ago

You could wire 4023 pin 6 to 11, pin 9 to 12 separately, no parts required. R1-6 are pulldowns, without them the inputs float.

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