# Elevator simulation circuit

#### damara

Joined Apr 18, 2019
9
HI Guys
I hope you can help me on an assignment that my daughter is trying to complete by next week. she is trying to do that with the logisim software.she and I have little understanding of the subject. Are you able to help on that assignment here is the requirement:
For this assignment you must implement a simple simulation of an elevator. The elevator has two inputs. Input 1 (C) represents the Current floor (0-7). Input 2 (D) represents the Destination floor to move to (0-7). The elevator is only allowed to stop on Floors 1, 2, 3, 5, and 7. Floors 0, 4 and 6 are private and the elevator will not stop there even if the button for that floor is pressed. The elevator movement is successful if C = 1, 2, 3, 5, or 7, D = 1, 2, 3, 5, or 7, and C ≠ D. Any other values will result in an elevator movement error and the elevator will not move.
Example 1: The current floor (C) is 2 and the floor we want to move to (D) is 5. In this case the move to floor 5 is successful.
Example 2: The current floor (C) is 2 and the floor we want to move to (D) is 4. In this case D is 4 (a private floor) and there is an elevator movement error. The elevator does not move.
Example 3: The current floor (C) is 4 and the floor we want to move to (S) is 2. In this case the starting floor is 4 (a private floor) and there is an elevator movement error. The elevator does not move
The Current floor (C) will be represented by three inputs (3 bits). The three C inputs are named as C1, C2, and C3. The table below shows the assignment of bits to each C value for C1, C2, and C3. The Destination floor (D) that we want to move to will be represented by three inputs (3 bits). The three D inputs are named as D1, D2, and D3. The table below shows the assignment of bits to each D value for D1, D2, and D3.
The implementation for this part must use only the three basic logic gates (AND, OR, NOT) with maximum 2 inputs. You are required to implement a circuit where the user (you) can input a value for the Current floor (C) using value (C1, C2, and C3) and a Destination floor to move to (D) using value (D1, D2, and D3) and the circuit decodes the C1, C2, C3 and D1, D2, D3 values using a decoder (see lecture notes) made up of only the permitted logic gates to determine if the requirement for moving in the requirements section on page 4 is met. The output will be a single LED labelled Successful which is lit if C = 1, 2, 3, 5, or 7, D = 1, 2, 3, 5, or 7, and C ≠ D. The LED is not lit for any other values of C and D

#### Alec_t

Joined Sep 17, 2013
12,318
Welcome to AAC!
In this forum you are expected to post your best efforts at solving the problem and we can give guidance where needed. We don't do your homework for you.

#### damara

Joined Apr 18, 2019
9
my daughter says she has done only the selectors. she is trying to figure out how to get the inputs and selectors to meet but is stuck

#### damara

Joined Apr 18, 2019
9
Welcome to AAC!
In this forum you are expected to post your best efforts at solving the problem and we can give guidance where needed. We don't do your homework for you.
my daughter says she has done only the selectors. she is trying to figure out how to get the inputs and selectors to meet but is stuck

#### MrAl

Joined Jun 17, 2014
8,556
Hi,

Where is the table.

You could write a logic statement and then reduce. Then you can pick out the gates.

#### atferrari

Joined Jan 6, 2004
4,473
Hi,
Where is the table.
You could write a logic statement and then reduce. Then you can pick out the gates.
HI Guys
I hope you can help me on an assignment that my daughter is trying to complete by next week. she is trying to do that with the logisim software.she and I have little understanding of the subject. Are you able to help on that assignment here is the requirement:
For this assignment you must implement a simple simulation of an elevator. The elevator has two inputs. Input 1 (C) represents the Current floor (0-7). Input 2 (D) represents the Destination floor to move to (0-7). The elevator is only allowed to stop on Floors 1, 2, 3, 5, and 7. Floors 0, 4 and 6 are private and the elevator will not stop there even if the button for that floor is pressed. The elevator movement is successful if C = 1, 2, 3, 5, or 7, D = 1, 2, 3, 5, or 7, and C ≠ D. Any other values will result in an elevator movement error and the elevator will not move.
Example 1: The current floor (C) is 2 and the floor we want to move to (D) is 5. In this case the move to floor 5 is successful.
Example 2: The current floor (C) is 2 and the floor we want to move to (D) is 4. In this case D is 4 (a private floor) and there is an elevator movement error. The elevator does not move.
Example 3: The current floor (C) is 4 and the floor we want to move to (S) is 2. In this case the starting floor is 4 (a private floor) and there is an elevator movement error. The elevator does not move
The Current floor (C) will be represented by three inputs (3 bits). The three C inputs are named as C1, C2, and C3. The table below shows the assignment of bits to each C value for C1, C2, and C3. The Destination floor (D) that we want to move to will be represented by three inputs (3 bits). The three D inputs are named as D1, D2, and D3. The table below shows the assignment of bits to each D value for D1, D2, and D3.
The implementation for this part must use only the three basic logic gates (AND, OR, NOT) with maximum 2 inputs. You are required to implement a circuit where the user (you) can input a value for the Current floor (C) using value (C1, C2, and C3) and a Destination floor to move to (D) using value (D1, D2, and D3) and the circuit decodes the C1, C2, C3 and D1, D2, D3 values using a decoder (see lecture notes) made up of only the permitted logic gates to determine if the requirement for moving in the requirements section on page 4 is met. The output will be a single LED labelled Successful which is lit if C = 1, 2, 3, 5, or 7, D = 1, 2, 3, 5, or 7, and C ≠ D. The LED is not lit for any other values of C and D

And while we are here, please do not write such an amorphous mass of text in consideration to those you expect to read it. As it is, I would not take the pain.

#### damara

Joined Apr 18, 2019
9
Hi,

Where is the table.

You could write a logic statement and then reduce. Then you can pick out the gates.
I'll see if I can get a table for you

#### damara

Joined Apr 18, 2019
9
And while we are here, please do not write such an amorphous mass of text in consideration to those you expect to read it. As it is, I would not take the pain.
Sorry about the long text I wanted to give as much info

#### MrAl

Joined Jun 17, 2014
8,556
I'll see if I can get a table for you
Hi,

Ok and since you mentioned that i thought you would want to show the table.
I could show you a simpler example too.

#### damara

Joined Apr 18, 2019
9
Hi,

Ok and since you mentioned that i thought you would want to show the table.
I could show you a simpler example too.
Thanks Mate. I'll take any help that i can get. I should get that table later on

#### damara

Joined Apr 18, 2019
9
Thanks Mate. I'll take any help that i can get. I should get that table later on

I have attached the table

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#### damara

Joined Apr 18, 2019
9
Welcome to AAC!
In this forum you are expected to post your best efforts at solving the problem and we can give guidance where needed. We don't do your homework for you.
Hi . I have upload what she has done so far. she hasn't finished but she thinks she got it but would like some comment. for a strange reason i couldn't upload as a CIRC file so i renamed as a PDF file. rename the file to CIRC after you download.

Cheers

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#### RBR1317

Joined Nov 13, 2010
674
I'm not too sure just where this design process is going, but the circuit should have six bit-inputs and only one output. Doing a logic table is always a good start; however, the next logical step would be to construct and minimize a 6-variable Karnaugh map (doable but not for beginners). A different approach might be called seat-of-your-pants logic design (I started out using this until I learned more formal techniques). For instance, one may notice that the output is true whenever the LSB of both inputs is TRUE (except when both inputs are equal, i.e. the other two bits of each input are equal). As you notice things that enable or disable the output, mark them off the table then see what else you can notice. So, design the logic to implement the things you notice, then combine them all to drive the output.

FYI, this site only accepts a limited number of file types for upload. Is .zip among them?

Last edited:

#### RBR1317

Joined Nov 13, 2010
674
FYI - Here is an example of a truth table I put together trying to answer the question whether it would be easier to detect the valid states to drive the output, or to detect the invalid states and invert that to drive the output. I did not arrive at a satisfactory answer. Maybe you will see something I missed. Note that the grey shading indicates floors 0,4,6 and red indicates equality of current and destination floors.

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#### damara

Joined Apr 18, 2019
9
FYI - Here is an example of a truth table I put together trying to answer the question whether it would be easier to detect the valid states to drive the output, or to detect the invalid states and invert that to drive the output. I did not arrive at a satisfactory answer. Maybe you will see something I missed. Note that the grey shading indicates floors 0,4,6 and red indicates equality of current and destination floors.

Thanks for that . I'll have a look

#### RBR1317

Joined Nov 13, 2010
674
Here is an example of an elevator solution; however, it probably won't satisfy the assignment because Example 3 has the current floor set to "4" whereas this solution sets the current floor being 0,4, or 6 as a "don't care" condition (we don't care how the logic handle this situation because the system will never be in the state where the current floor is 0,4, or 6. If the destination can never be 0,4, or 6 then how could the elevator be on one of those floors?) This solution only checks for equality of current & destination and whether the destination is 0,4, or 6.

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