# Elevator Control

Discussion in 'Homework Help' started by Marah, Apr 14, 2012.

1. ### Marah Thread Starter New Member

Apr 14, 2012
4
0
hello , i have a digital home work , its about an elevator control , the home work is ,

we have a first and a second floor and we have 2 inputs up and down , also if we were in the first floor , the door will open for some time and then close , and if we were in the second floor , the door will open for some time and then close , so we have 2 inputs ( up and down ) and we have 3 outputs ( first floor , second floor , door ) , the door is 1 when the door is open .

i have tried solving it , and i get this ,
i make 6 states ; the first , the second , the second is open , the second is close , the first open , the first closed ,
i also make the state table and digram
but there is a problem , i couldnt find a way to make the door open for some time and then closed , we have to use 74LS93 counter , but i dont know how to use it here ,
thank you

2. ### crutschow Expert

Mar 14, 2008
12,501
3,059
You use the counter to count clock pulses. You connect the counter to count the number of clock counts you need for the time the door is to remain open. The number of counts is determined by the clock frequency and the time required. You can use logic gates to detect when the desired count is reached.

3. ### Marah Thread Starter New Member

Apr 14, 2012
4
0
thank you
i make 4 states now ( first floor , first floor open , second floor , second floor open ) and i have up/down inputs and the output door ( which will be one if the door is open )
we learn how to make counters to counts alone , i wondering how can i connect the logic circuit with the counter , and make the counter counts when the door is 1 ?
thanks alot

4. ### crutschow Expert

Mar 14, 2008
12,501
3,059
You use the Master Reset on the counter. What that is a logic high, the counter is reset to all zeros and doesn't count. It will start counting as soon as the signal goes low.

5. ### Marah Thread Starter New Member

Apr 14, 2012
4
0
hello , i start doing it , i make the truth table but i feel that its not correct , or may be i have to use another inputs or outputs , and how can i use the counter with this truth table

present down up next

0 0 0 0 0 1
0 0 0 1 10
0 0 1 0 0 1
0 0 1 1 0 1
0 1 0 0 0 0
0 1 0 1 0 0
0 1 1 0 0 0
0 1 1 1 0 0
1 0 0 0 1 1
1 0 0 1 1 1
1 0 1 0 0 0
1 0 1 1 1 1
1 1 0 0 1 0
1 1 0 1 1 0
1 1 1 0 1 0
1 1 1 1 1 0

where 00 is the first floor closed
10 is the second floor closed
11 the second floor open
01 the first floor open

thaank yooou ,