Project # 22 – Random Number Generator



Project # 21 – Random Number Generator

In this project you will convert the basic 0 to 9 counter into a random number generator. The circuit is not really producing random numbers, but because of its speed it will seem as if it is. The functional diagram for the circuit is shown below:

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Procedure:

1. Start with the 0 to 9 counter you built in projects 16 through 19. Undo any changes you made since then, if you have made any. Do not go further until you have a working 0 to 9 counter.

2. Remove the switch from wherever it is in your circuit. The counter should still work without it (except that you can’t use it to reset it to 0 anymore.

3. Convert the 555 into a high frequency clock (100 Hz, or higher).

4. Connect the output of the 555 clock to the switch and the 2.2 K resistor as shown. Connect the switch and the 2.2 K to the clock input of the 4520 binary counter (pin # 1) as shown above.

5. Once the circuit works, obtain teacher’s initials. Please note: the circuit should only produce the random numbers 0 through 9, no blanks!

Conclusion:

Explain fully the logic behind the circuit’s operation. What is the purpose of putting the switch in the position shown? What is the purpose of the 2.2 K?

Optional:

1. Convert the random number generator into an “Electronic Die (pl. for dice) Game”. The game should produce random numbers between 0 and 6 (OK, so a real die has no 0, what do want from me?).

2. NOTE: you may have to change the order in which the 4520’s outputs go into the NAND gates. Theoretically this should not be necessary, but in practice it sometimes is. The problem has to do with the speed at which the gates respond to changes at their inputs.

3. Slow the circuit down greatly so that you can see if it is actually counting from 0 to 6 and then resetting. At this point obtain teacher’s initials.

Optional Conclusion:

1. Draw a schematic diagram of just the logic gates you used to convert the circuit into a 0 to 6 counter. Show in your diagram where the 4520 outputs (Q3, Q2, Q1, Q0) go and where the output of your logic circuit goes.

2. Try to figure out why the order in which you place the 4520 outputs into the NAND gates might have an effect (it may not reset after the number 6 is reached). The NOTE given in step 2 should give you a hint, but you need to give a full explanation.

Do not take the circuit apart. Keep this sheet and your report handy!

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