Number Guessing circuit -- I in creating this circuit

In summary, the conversation discusses a problem encountered while simulating a circuit for a final year project in electrical and electronic engineering. The circuit comprises of three subcircuits, each tested separately and working fine, but not functioning properly when simulated together. Possible reasons for this issue are identified, including grounding, power supply, decoupling capacitors, and incorrect connections. It is suggested to check the voltage on pin 18 of the LED driver 74154 and ensure proper connection of the wipers of S2 and S13. It is also noted that for the circuit to function, U1 must be free-running and driving U4 B-inputs.
  • #1
Vincci
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I need help in creating this circuit. It was given as my final year project for my foundation in electrical and electronic engineering by my lecturer. Every component seems to work perfectly fine especially when it is tested in sub circuits. The problem arises when I try to simulate the whole circuit the LEDs which each represent a number from one to sixteen just continuously switch on and off. I have attached the circuit diagram from which I am to recreate the circuit from. The transformer, 230 A.C power source, IC6 , C3, C4, D17 and D18 are not going to be used as a powered bread board will be used as the power source.
Ps: I have separated the circuit into three subcircuits which the first one comprises of the 555 and power supply, the second comprises of the 74161 and 7400 and the third comprises of the 74157 and 75154. And all of these circuits work perfectly fine when tested seperately. But when I try to simulate the full circuit the LEDs will not light up as they are supposed to.
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  • #2
I am thinking you may have a problem with stability/spurious oscillation because of five factors:-
1. You are splitting it into three sub assemblies. Grounding then becomes an issue.
2) The board does not have a ground plane
3) You have your own separate PSU which might not be good enough
4) No decoupling capacitors used. When the LEDs turn on there is a big current splash on the +ve rail.
5) The 555 also applies big splash to the +ve rail.
 
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  • #3
Welcome to PF.
The voltage on pin 18 = nG1 of the LED driver 74154 needs to be low. Check that.
The old 74154 could sink 16mA to turn on a LED. How much current can the 74STD family sink?
 
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  • #4
The wipers of S2 and S13 are not connected to anything!

Edit:
This causes U4 pin 1 to remain High, always selecting the B-input (pins 3,4,10,11).

U2 must be always counting and driving the U4 B-inputs.

For U2 to be counting, U1 must be free-running. Since the left side of your schematic is missing, I can't tell if U2 is intended to free-run.
 
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FAQ: Number Guessing circuit -- I in creating this circuit

1. How does the number guessing circuit work?

The number guessing circuit works by using a series of logic gates and binary inputs to systematically narrow down the possible numbers until the correct number is reached.

2. What components are needed to create a number guessing circuit?

To create a number guessing circuit, you will need logic gates such as AND, OR, and NOT gates, binary inputs (such as switches or buttons), a binary-to-decimal converter, and a display to show the guessed number.

3. How accurate is the number guessing circuit?

The accuracy of the number guessing circuit depends on the complexity of the circuit and the number of possible numbers it is programmed to guess. With a well-designed circuit, the accuracy can be very high.

4. Can the number guessing circuit be used for any range of numbers?

Yes, the number guessing circuit can be programmed to guess numbers within any range. However, the complexity of the circuit may increase as the range of numbers increases.

5. Are there any limitations to the number guessing circuit?

One limitation of the number guessing circuit is that it can only guess whole numbers. It also requires a certain amount of time to go through each logic step, so it may not be suitable for fast-paced applications.

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