QUIZ MASTER

INSTRUCTION SHEET

Price - Stock No 260

QUIZMASTER is a device which uses electronics to decide who pushes  a button  first,  deciding  who  has  the right to answer the question.  The first button pushed literally grabs the power and uses  it  to  light  its LED.   No  other  button pushed even milliseconds after the first one will light up its LED.  This is achieved by using a  4011  CMOS  I.C  for  each   player  and  connecting  them  through one final output.  The 4011 chip is known as a Quad 2-input NAND.  They are digital chips  and  consist  of  a set-reset  flip-flop at pins 4,5,6 & 8,9,10, with a NAND Gate on the input at pins 1,2.  Pins 11,12,13 of the control chip, together with the  diodes and  flip-flop  outputs, combine to form a multi-input NOR Gate.   As long as the outputs from all the chips remain low, the output  of  the  control chip  is  high.  When a button is pushed the NAND gate goes low triggering the flip-flop high.  This turns on the transistor connected to  pins  4&8, supplying  power  to light the LED for that chip.  As this happens the NOR gate goes low taking all the inputs low, thus preventing  any  other  chip from turning on.  The Quizmaster is reset by a reset button which restores the circuit ready for the next question.        QUIZMASTER  is extremely fast, is foolproof, and cannot be biassed in any way.  It will determine accurately and without any doubt, which button is pushed first.  The circuit is unique in that each player has a module.  Modules  can be  added  for  extra  players  with  virtually  no limit to the number of  players.  The modules are added to the array  and  interconnected  to  the control NOR gate.

To make up the Quizmaster:

Check Your Kit

• Components

Schematic Diagram

PCB Layout

1. Check  the  P.C.Board  for  damage to tracks.  Any breaks can be soldered over.  Check with a multimeter or electronic circuit tester.
2. Identify the Zero Volt links (one black band) and the  resistors, by  their colour bands or with a digital multimeter.  Bend the legs to fit the  respective  locations.   Note  that  R4  will  need  to  be   mounted vertically.  These can all be soldered and the excess legs nipped off.
3. Two diodes can be fitted but make sure that the band on the body  is as the drawing shows.
4. The two I.C.Sockets can be fitted and soldered.
5. The two transistors can be pushed into their places with the flat on the body as per the diagram.
6. There is one short wire link joining pins  3  &  5  on  IC1.   An excess leg trimmed from a resistor can be used for this link.
7. Eight  pins  are in the Kit.  These are pushed into the holes at each of the 3 switches, and at the  9V  and  0V  pads.   These  holes  are oversize to match the pins.  Solder to the board.
8. The  reset  switch is stood up against the two pins and soldered into position.  The player switches can be connected via  leads  to  their pins.
9. The  two  LEDs  are  polarised.   Look for the small flat on the flange at the base of the globe.  This flat is above the K (-ve) leg.  The K leg is also the shorter of the two legs.  Push the LEDs into  place  and solder.
10. The 4011 ICs are the CMOS family of chips and are very sensitive to  static  electricity.  Remove them from their anti-stat cases only when you are about to mount them to their sockets.  When you  offer  them  into position  you  will  find that the legs are spread too wide to fit easily.   Turn each chip in turn on its side on a flat surface and gently push  down to  bend  the set of legs in a bit.  Turn the chip over and repeat for the other set of legs.  Look for the LOCATING DOT, line it up as  the  diagram shows, and push it into the socket.
11. Solder the battery snap to its pins, Red to the 9V and Black to the 0V pin.  Connect a 9 Volt battery and test your quizmaster.  When  you push  a  button  its LED will light up.  Reset by pushing the reset button and try the other player button.  Its LED should light, and no  amount  of  pushing should turn the other LED on.  You are now ready to test your speed against the other player.  If the unit does not work then  you  will  need  to  start  from  the beginning and check everything including:

• correct location of all components
• correct polarity of diodes, LEDs, transistors and ICs.
• is the wire link in place and soldered?
• inspect all soldering and resolder as necessary.
• if all else fails, remove the ICs one at a  time.   Sometimes,  in spite  of all care, a leg of the IC gets bent up under the body instead of  going into its place in the socket.

The Layout Diagram is correct - tried and tested.  If you  follow  it carefully,  giving  attention  to  all  the  detail in the diagram, if you solder making good connections (no dry joints) then  the  Quizmaster  will work first time.

        Quizmaster is a great example of Digital Electronics.  There are only  two  conditions  :  HIGH   and  LOW.  By the use of Gates, Flip-flops, and external components, all sorts of outcomes can be achieved.   eg.  an  AND  gate  requires  two  input pins to be HIGH for the output to go HIGH.

Some common gates are : AND, NAND, OR, NOR.

AND gate

OUTPUT is ON only when ALL INPUTS are ON

OUTPUT is OFF when ANY or ALL INPUTS are OFF

NAND gate

OUTPUT is OFF only when ALL INPUTS are ON

OUTPUT is ON when ANY or ALL INPUTS are OFF

OR gate

OUTPUT is ON when ANY or ALL INPUTS are ON

OUTPUT is OFF only when ALL INPUTS are OFF

NOR gate

OUTPUT is ON only when ALL INPUTS are OFF

OUTPUT is OFF when ANY or ALL INPUTS are ON

   Using  this  sort  of  information  a TRUTH TABLE can be drawn up to check  that the outcome matches the circuit diagram.

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