Need Help in Digital Electronics

Thread Starter

aniskazi

Joined May 3, 2014
44
Hello This is the question I'm having trouble in... My exams are next week I have solved most of the problems but I can't do this one guys so can anyone help please.
A jet aircraft employs a system for monitoring the rpm, pressure, and temperature values of its engines using sensors that operate as follows:
• RPM sensor output = 0, only when speed < 4800 rpm
• P sensor output = 0, when pressure <220 psi
• T sensor output = 0, only when temperature < 200˚F

Figure 2.1 shows the logic circuit that controls a cockpit warning light for certain combinations of engine conditions. Assume that a HIGH at output W activates the warning light:

(a) Create your truth Table with appropriate input-output combinations
(b) Determine what engine conditions will give warning to the pilot.
(c) Using K-Map technique to obtain your simplified Boolean equation.
(d) Change this circuit to one using all NAND gates and constructs the circuit.
This is the image.

http://postimg.org/image/fydv4resp/
 

Thread Starter

aniskazi

Joined May 3, 2014
44
Show us your work for each step (a) to (d).
Hey I'm confused in the first two parts... about the truth table I know that there are three inputs
RPM ,P and T
so the total input conditions will be 8 but I can't understand that how can
I see wether the speed is < or > 4800rpm and the second part as well about what engine conditions will give the warning the rest two parts I can do by myself and I'm only asking for an idea to solve it :confused:
 

djsfantasi

Joined Apr 11, 2010
5,573
Hey I'm confused in the first two parts... about the truth table I know that there are three inputs
RPM ,P and T
so the total input conditions will be 8 but I can't understand that how can
I see wether the speed is < or > 4800rpm and the second part as well about what engine conditions will give the warning the rest two parts I can do by myself and I'm only asking for an idea to solve it :confused:
That is the purpose of the sensors. The output from the RPM sensor will tell you if the speed is < or > 4800 rpm. Same for the other conditions.

Common sense should get you the second answer. If not, the supplied diagram deserves a look.

This should get you past the first two questions.
 

WBahn

Joined Mar 31, 2012
24,674
Hey I'm confused in the first two parts... about the truth table I know that there are three inputs
RPM ,P and T
so the total input conditions will be 8 but I can't understand that how can
I see wether the speed is < or > 4800rpm and the second part as well about what engine conditions will give the warning the rest two parts I can do by myself and I'm only asking for an idea to solve it :confused:
As Mr. Chips said, show us your work!

If the RPM sensor is 0, what does that tell you?

If the RPM sensor is 1, what does that tell you?
 

Thread Starter

aniskazi

Joined May 3, 2014
44
Hey thanks for the fast reply guys.
Well here is what I've done I have made the truth table and than I used the inputs from the truth table in the circuit and what ever output I was getting in the end I was putting it in the truth table (a) part done and now in the b part If I want to give the pilot a warning I need highs on T P and RPM?
 

WBahn

Joined Mar 31, 2012
24,674
Hey thanks for the fast reply guys.
Well here is what I've done I have made the truth table and than I used the inputs from the truth table in the circuit and what ever output I was getting in the end I was putting it in the truth table (a) part done and now in the b part If I want to give the pilot a warning I need highs on T P and RPM?
Saying that you've made the truth table doesn't tell us anything. SHOW YOUR WORK!
 

Thread Starter

aniskazi

Joined May 3, 2014
44
T P R Output
0 0 0 0
0 0 1 0
0 1 0 0
0 1 1 0
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1

This is the truth table that I've made I used the inputs in the fig and got the oupts.
and I guess now the (b) part will be to take all the 1 outputs form an euqation simplify it and than make a logic circuit? or no?
 

tshuck

Joined Oct 18, 2012
3,527
You should look over your results again, particularly around 100.

Part b seems to be asking just that you identify and list which sensor conditions would result in the warning light being illuminated. It may want you to list the values as minterms, or a Boolean expression. Given the next question, it may want you to derive the Boolean function from the truth table, then simplify it in the following step.

Part c is where you simplify the logic.
 
Last edited:

Thread Starter

aniskazi

Joined May 3, 2014
44
You should look over your results again, particularly around 100.

Part b seems to be asking just that you identify and list which sensor conditions would result in the warning light being illuminated. It may want you to list the values as minterms, or a Boolean expression. Given the next question, it may want you to derive the Boolean function from the truth take, then simplify it in the following step.

Part c is where you simplify the logic.
so the warning light will be on when the output is high so I jsut have to tell when the output will be high as the last three outputs are high so they will make the warning light high so that's my answer right? :D
 

tshuck

Joined Oct 18, 2012
3,527
so the warning light will be on when the output is high so I jsut have to tell when the output will be high as the last three outputs are high so they will make the warning light high so that's my answer right? :D
You should look over your results again, particularly around 100.
[...]
Once you have a correct truth table, you should make a Boolean function that describes when the warning light is on...
 

Thread Starter

aniskazi

Joined May 3, 2014
44
Once you have a correct truth table, you should make a Boolean function that describes when the warning light is on...
yes corrected the truth table

t P R OUTPUt
1 0 0 1
1 1 0 1
1 1 1 1

so i got the eq: T P' R' + T P R' + TPR
correct?
I tried to simplify it:

taking TR' as common I got TR'(P' + P) + TPR
since(P' + P)=1
TR' +TPR ?
 

WBahn

Joined Mar 31, 2012
24,674
so the warning light will be on when the output is high so I jsut have to tell when the output will be high as the last three outputs are high so they will make the warning light high so that's my answer right? :D
It's already been pointed out that your truth table in Post #8 has a problem. So fix that (and don't edit Post #8 since people have referred to what is already there -- instead post an updated truth table in a new post) and then let's continue.

It might help if you start converting your logic diagrams (the simple ones) into word phrases. For this circuit, it would be something like: The warning light is on if the temperature is high AND either the oil pressure is high OR the rpms are low. Compare that sentence to your truth table.
 

tshuck

Joined Oct 18, 2012
3,527
yes corrected the truth table

t P R OUTPUt
1 0 0 1
1 1 0 1
1 1 1 1

so i got the eq: T P' R' + T P R' + TPR
correct?
I tried to simplify it:

taking TR' as common I got TR'(P' + P) + TPR
since(P' + P)=1
TR' +TPR ?
Part c asks you to use a K-map, specifically, to do the simplification...
 

Thread Starter

aniskazi

Joined May 3, 2014
44
It's already been pointed out that your truth table in Post #8 has a problem. So fix that (and don't edit Post #8 since people have referred to what is already there -- instead post an updated truth table in a new post) and then let's continue.

It might help if you start converting your logic diagrams (the simple ones) into word phrases. For this circuit, it would be something like: The warning light is on if the temperature is high AND either the oil pressure is high OR the rpms are low. Compare that sentence to your truth table.
okay and so my b part wants to know just that when the warning light will be on so it will be on when I got highs in my output in my truthtable :D so the answer is:
When Temp will be high and press or RPM will be high the warning light will get a high at the output giving a warning to the pilot.
 

tshuck

Joined Oct 18, 2012
3,527
okay and so my b part wants to know just that when the warning light will be on so it will be on when I got highs in my output in my truthtable :D so the answer is:
When Temp will be high and press or RPM will be high the warning light will get a high at the output giving a warning to the pilot.
I think it might want you to describe it in terms of the pressure/rpm/temperature values given, e.g. "if the RPM is less than 4800 while the pressure is less than 220 psi and temperature is above 200°F, then the warning light will be..."

Your last statement is wrong - what happens if temperature is high, pressure is low and RPM is high?
 

Thread Starter

aniskazi

Joined May 3, 2014
44
I think it might want you to describe it in terms of the pressure/rpm/temperature values given, e.g. "if the RPM is less than 4800 while the pressure is less than 220 psi and temperature is above 200°F, then the warning light will be..."

Your last statement is wrong - what happens if temperature is high, pressure is low and RPM is high?
okay I guess I will just give a separate statement for each high output just like you mentioned above
if temperature is high, pressure is low and RPM is high than my output will be a low and there will be no warning like that ?
 

tshuck

Joined Oct 18, 2012
3,527
okay I guess I will just give a separate statement for each high output just like you mentioned above
You needn't do a separate statement for each row in your truth table, i'm just pointing out that since the information is presented, you may want to respond with the numerical values that the signal states correspond to.

if temperature is high, pressure is low and RPM is high than my output will be a low and there will be no warning like that ?
... What does your truth table say?

Look at the bolded words:
When Temp will be high and press or RPM will be high
What happens when RPM is high? Your statement implies that if temperature and RPM is high, the output is high - is this true? Is this always true?
 

Thread Starter

aniskazi

Joined May 3, 2014
44
You needn't do a separate statement for each row in your truth table, i'm just pointing out that since the information is presented, you may want to respond with the numerical values that the signal states correspond to.


... What does your truth table say?
It's a low the previous truth table I made had mistakes...
but it's a low if T is HIGH, P is low and RPM is HIGH
 

tshuck

Joined Oct 18, 2012
3,527
It's a low the previous truth table I made had mistakes...
but it's a low if T is HIGH, P is low and RPM is HIGH
... So
When Temp will be high and press or RPM will be high the warning light will get a high at the output giving a warning to the pilot.
Can't be true then because if temperature and RPM is high, the warning light is not necessarily on.
 
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