Oh, and you still haven't a column to your table identifying the inputs and output(s).

attached is the truth table i can get for alarm to function......anyway, i don`t really understand it to well

 

yea,he said for the engine to running,the key must be in the ignition.
but funny enough,the lecturer didn`t state if the car will be in motion or not not OR that the engine will be off when the key is in the ignition

Very good! You are realizing that you might not have enough information to solve the problem.

 

Very good! You are realizing that you might not have enough information to solve the problem.

telling the lecturer the question is not complete might be disastrous you know.

when i read the question again..i became confused.........any way out?

 

telling the lecturer the question is not complete might be disastrous you know.

Sometimes ambiguous questions are asked to see if the student knows enough to know that's the case.

What I would do is ask clarifying questions. If that isn't possible, or allowed, solve the problem and state your assumptions.

when i read the question again..i became confused.........any way out?

Is what you posted in your first post the exact wording of the problem?

 

telling the lecturer the question is not complete might be disastrous you know.

when i read the question again..i became confused.........any way out?

Understand....just ask the lecturer "is the motor running when the key is on"

eT

 

just ask the lecturer "is the motor running when the key is on"

The lecturer should justifiably question the intelligence of the person asking the question and suggest an alternate career.

 

The lecturer should justifiably question the intelligence of the person asking the question and suggest an alternate career.

Sorry...I disagree...If the lecturer does that...the lecturer should be looking for another career

The lecturer should be expecting questions when intentionally not providing complete information.

 

Sorry...I disagree...If the lecturer does that...the lecturer should be looking for another career

I have been told many times that there are no dumb questions, but, in reality, there are; and that would be one of them.

 

What does it matter whether the engine is running or not when the key is in the ignition?

The relevant question would be whether it is possible for the engine to be running when the key ISN'T in the ignition. If this is not possible (or if it is reasonable to assume that this is the case) then one of the conditions for the alarm is unnecessary.

 

A car ignition system is designed to function such that an alarm comes on whenever any of the following occur;
a)when the engine is running while the door open.
b)the door is open while the headlamp is on.
c) the key is in the ignition while the door is open.
how can i design a combinational logic circuit whose output goes high to trigger the alarm system whenever either of the conditions come up?
state all asumptions.
kindly assist.

First, is there anything that all of these conditions have in common?

Second, is there anything that would say that for one of these conditions to be true that one of the other conditions must also be true?

 

attached is the truth table i can get for alarm to function......anyway, i don`t really understand it to well

First, what is a "headlarm"? Do you mean that the headlight is on?

Ask your self if this makes sense. First, why are the top two rows identical? Do you have a column that you aren't showing us?

Look at the third (and fourth) row. You are showing that the alarm is on if the headlight is on, the key is not in the ignition, and the door is not open. Is that one of the situations in which the alarm is supposed to sound?

Take a moment to be sure that you understand the problem. There is no point trying to find a solution to a problem that you don't understand.

 

I have been told many times that there are no dumb questions, but, in reality, there are; and that would be one of them.

heh...well..does the engine auto start when the key is turned on?

 

heh...well..does the engine auto start when the key is turned on?

For this problem, I'm sure it does. The problem is to teach students about boolean equations, not how to design a car ignition switch functionality.

Forest for the trees man, forest for the trees...

 

For this problem, I'm sure it does. The problem is to teach students about boolean equations, not how to design a car ignition switch functionality.

Forest for the trees man, forest for the trees...

Ok...

Back to problem at hand...

 

heh...well..does the engine auto start when the key is turned on?

What does it matter?

Condition #3: If the key is in the ignition while the door is open, the alarm is supposed to sound. Does it matter whether the engine is running or not?

 

What does it matter?

Condition #3: If the key is in the ignition while the door is open, the alarm is supposed to sound. Does it matter whether the engine is running or not?

Exactly. That was pointed out in the first response.

The OP could choose to include the redundant expression in the solution or simplify it out by stating his/her assumptions.

 

Exactly. That was pointed out in the first response.

The OP could choose to include the redundant expression in the solution or simplify it out by stating his/her assumptions.

Which is exactly what I suspect was the expectation.

 

apparently,does it mean the question is not correct or unsolvable?

I have answered this once. No. The question is correct and solveable.

While kmaps are a good way to solve this problem, since your instructor has not covered them in class means that he expects you not to use them. With all due respect to my colleagues here, their suggestions to use kmaps may be misguided.

Kmaps are NOT necessary for this problem. In fact, not using them will likely increase your knowledge and is why your instructor has given you this problem at this time.

You were VERY close to your answer. Please, re-read our conversations. I believe that you had answered my last question and now should rewrite your description without the unnecessary condition.

 

With all due respect to my colleagues here, their suggestions to use kmaps may be misguided.

For simple problems like this, just reading the conditions solves the problem; but won't necessarily give the simplest expression. A Kmap makes obtaining the simplest expression easy and using one couldn't be considered wrong or misguided unless the instructions prohibited their use.

 

I am about to bow out, since I don't think going back and forth helps the TS. But I think this thread illustrates a common problem. A simple problem to us brings forth discussions of how every possibility might be addressed. Sometimes, alternatives arise, which have no bearing on the original problem.

Granted, there are times when this is appropriate. I am not talking about those. In the cases I have described, we confuse and frustrate the TS.

He has not been taught about kmaps. There is no hint in his description that his instructor expects the simplest solution. In reality, how could he, since he had not taught the subject yet?

Ponder whether the forum has done the TS a disservice.