Number Guessing circuit -- I in creating this circuit

Click For Summary

Discussion Overview

The discussion revolves around the challenges faced in creating a number guessing circuit as part of a final year project in electrical and electronic engineering. Participants explore issues related to circuit simulation, component interactions, and potential design flaws, focusing on both theoretical and practical aspects of the circuit's functionality.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant describes the circuit's components and their successful operation in subcircuits but notes issues when simulating the complete circuit, specifically with the LEDs not functioning as expected.
  • Another participant suggests that the problem may stem from stability issues or spurious oscillation due to factors like grounding, lack of a ground plane, and the absence of decoupling capacitors.
  • A third participant points out the importance of ensuring that the voltage on pin 18 of the LED driver 74154 is low and questions the current sinking capability of the 74STD family compared to the older 74154.
  • One participant highlights a potential oversight in the circuit design, noting that the wipers of certain switches are not connected, which could affect the operation of the counting mechanism.

Areas of Agreement / Disagreement

Participants express various concerns and hypotheses regarding the circuit's issues, but there is no consensus on the exact cause of the problems. Multiple competing views on potential design flaws and solutions remain unresolved.

Contextual Notes

Limitations include missing assumptions about the schematic's left side, which could clarify the intended operation of certain components, and the dependence on the quality of the separate power supply used.

Vincci
Messages
1
Reaction score
0
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 separately. But when I try to simulate the full circuit the LEDs will not light up as they are supposed to.
VBw2K.jpg

F
0oEh2.jpg
upload_2016-10-31_23-8-44.png
 
Engineering news on Phys.org
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.
 
Last edited by a moderator:
  • Like
Likes   Reactions: berkeman
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?
 
Last edited:
  • Like
Likes   Reactions: berkeman
The wipers of S2 and S13 are not connected to anything!

Edit:[/color]
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.
 
Last edited:

Similar threads

Determining inductive reactance from a 3-phase AC circuit
  • · Replies 17 ·
Replies
17
Views
4K
Heavy Amplifier Circuit Oscillation Happened
  • · Replies 3 ·
Replies
3
Views
3K
What is the correct way to wire a piezoelectric circuit on a breadboard?
  • · Replies 5 ·
Replies
5
Views
2K
Can't tell if I made a chaotic circuit or if I broke the sim
  • · Replies 1 ·
Replies
1
Views
2K
Actuator-solenoid valve circuit
  • · Replies 5 ·
Replies
5
Views
6K
High power switching circuit problem.
  • · Replies 7 ·
Replies
7
Views
3K
Master Power Switch for 3 Circuits?
  • · Replies 5 ·
Replies
5
Views
2K
How can I create a circuit to control LED lighting with a switch in reverse?
  • · Replies 10 ·
Replies
10
Views
2K
Can a MOSFET be used to replace a mechanical potentiometer in a PWM circuit?
  • · Replies 10 ·
Replies
10
Views
3K
Optimizing Circuit Design: Voltage Range, Internal Resistance, and Wire Sizing
  • · Replies 15 ·
Replies
15
Views
2K