EET310 – Programmable Controllers and Robotics

Unit 3

By: Brett Bloomberg

Instructor: William Routt

Online EET DepartmentECPI UniversityDate: 10/11/2016

ECPI’s Honor Pledge: I pledge to support the Honor System of ECPI. I will refrain from any form of academic dishonesty or deception, such as cheating or plagiarism. I am aware that as a member of the academic community it is my responsibility to turn in all suspected violators of the honor code. I understand that any failure on my part to support the Honor System will be turned over to a Judicial

Review Board for determination. I will report to a Judicial Review Board hearing if summoned.Brett Bloomberg

Objective:

This lab helped us reinforce the more advance applications that PLC’s can offer. We learned how to program a cross walk on a busy street, as well as fill a big tank and empty it. These topics and problems that we solved using PLC’s allow us to become better automation engineers, and better problem solvers. This lab took our education and tested our mental ability to figure out how to handle certain tasks and make them automated.

Lab 7-11

This lab asks us to implement the fluid pumping process PLC program shown. The program asks us to make the program complete the following tasks.

When the start button is pushed, the pump starts. The button can then be released, and the pump continues.

When the stop button is pushed the pump stops

Before starting PS1 must be closed

PS2 and PS3 must be closed 5 seconds after the pump starts. IF either ps2 or ps1 opens the pump will shut off and will not be able to start again for another 14s.

The inputs are as follows

Stop I:1/0

Start I:1/1

PS1 I:1/2

PS2 I:1/3

M O:2/0

Tof T4:5

Ton T4:6

As we can see from the picture below that the program is pretty simple. When the start button is pushed the pump will latch on. This only works if PS1 is closed. The pump will pump for 5 seconds once the pump is over the pump time kicks in and takes 14 seconds before it can be run again.

Conclusion:

This program isn’t too bad. It’s a simple pump station program that allows certain sensors to be made and certain safety features like the pump not turning back on for 14 seconds once it’s been turned on. This ladder logic helped us start using timers with both on delay and off delay.

Lab 7-13

This lab asks us to implement the bearing lubrication PLC program shown in this application we are asked to.

To start the machine the operator turns SW On

Before the motor shaft starts to turn, the bearings are supplied with oil by the pump for 10s.

When the operator turns SW “OFF” to stop the machine, the oil pump continues to supply oil for 15s.

A retentive timer is used to track the total running time of the pump. When the total running time is 3 H the motor is shut down and a pilot light is turned “on” to indicate that the filter and oil need to be changed.

A reset button is provided to reset the process after the filter and oil have been changed.

Input/outputs.

Switch I:1/0

Reset I:1/1

Pump O:2/0

Motor O:2/1

Pl O:2/2

Ton T4:0

Tof T4:1

RTO T4:2

The picture above is when the pilot light comes on that indicates it’s time to replace the oil filter in the system. A retentive timer is used to track the total running time of the pump. This will help keep track of time even when the power goes out. When the timer reaches three hours the light will turn on to indicate that the filter needs to be changed. The machine will continue to pump even when the user stops it for 15 seconds after. There is a reset button to reset the counter when the filter has been changed.

Lab 7-37

This lab asks use to implement a traffic flow on a one way street is to be controlled by means of a pedestrian pushbutton so that the green traffic light and don’t walk indicators are to be normally on at all times when the pedestrian pushbutton is not actuated. When the pedestrian pushbutton is actuated, the timing is started and controls the output as follows.

The green traffic light immediately switches “off” and the amber traffic light switches on to begin the stop the traffic flow. The outputs remain in the start for 5 seconds.

The amber traffic light switches off and the red traffic light switches on the outputs remain in this state for 5 seconds, to ensure that traffic has stopped before pedestrians begin to cross.

The walk pedestrians light switches on and the red traffic light remains on. The outputs remain in this state for 15 seconds. Allowing pedestrians safe passage across the street.

The walk pedestrians light switches off and the red traffic light remains on. The outputs remain in this state for 5 seconds to make sure that pedestrians are not still crossing the street when the traffic light changes from red to green.

The green traffic light switches on and the red traffic light switches off. The outputs remain in this state for at least 30 seconds to ensure a minimum amount of automotive traffic flow time even if the walk pushbutton is pressed to start the cycle again.

The inputs and outputs

Walk pushbutton I:1/0

Red light O:2/0

Amber light O:2/1

Green light O:2/2

Pedestrian walk O:2/3

Internal B3:1/0

Internal B3:1/1

Ton T4:1

Ton T4:2

Ton T4:3

Ton T4:4

Ton T4:5

This was one of the harder labs that I have worked on in this course so far. I may have overthink it. To be more complex than it was I learned from this lab that it is difficult to start a timer from a timer. In most of the timers here I was unable to start the timer from an existing timer. Which is why I inserted rung 10. Keeping the green light on while nothing was going on Seemed harder than it should have been. I know I could have gone about it another way that was a smaller code, but I was still able to get it completed. I am sure I have some redundancy within my code that doesn’t need to be there. Really the only hard part about this was keeping the green light going or not going while it turned colors after that it was pretty straight forward.

Lab 8-13

This lab asks us to implement the automatic stacking process show. In this process conveyor M1 is used to stack metal plates onto conveyor M2. The photoelectric sensor provides an input pulse to the PLC counter each time a metal plate drops from conveyor M1 to M2. When 15 plates have been stacked, conveyor M2 is activated for 5 seconds by the PLC timer. The operation can be summarized by.

When the start button is pressed, conveyor M1 begins running.

After 15 plates have been stacked, conveyor M1 stops and conveyor M2 begins running.

After conveyor M2 has been operated for 5 seconds, it stops and the sequence is repeated automatically.

The done bit of the timer resets the timer and counter and provides a momentary pulse to automatically restart conveyor M1.

Use the inputs outputs.

Stop PB I:1/0

Start I:1/1

Conveyor M1 O:2/0

Conveyor M2 O:2/2

Ton T4:1

Ctu C5:1

This lab is pretty easy. We want to make sure that When M1 is running M2 is not running. And that the photo sensor is counting to 15. Once the count is at 15 M2 starts and it starts a timer that runs for 5 seconds. Once this happens the timer resets the counter which also then resets the timer.

This lab was pretty straight forward in terms of counting and timing. I will say that the metal falling onto conveyor two seems like it will causes major errors. We are leaving the metal to fall on its own with no way of guidance which may or may not trip the photo sensor. Which could cause the counter to not count properly by adding another height sensor the conveyor two we could eliminate the count error

with a redundancy checker of height, but with this we are also leaving a lot up to fate in terms of the system running properly?

Lab 8-28

This lab asks us to document a PLC program that will implement the box stacking process. This application requires the control of a conveyor belt that feeds a mechanical stacker. The stacker can stack various numbers of cartons of ceiling tile onto each pallet depending on the pallet size and the preset value of the counter. When the reuired number of cartons has been stacked, the conveyor is stopped until the loaded pallet is removed and an empty pallet is placed onto the loading area. A photoelectric sensor will be used to provide count pulses to the counter after each carton passes by. In addition to a conveyor motor start/stop station, a remote reset switch is provided to allow the operator to reset the system from the forklift after an empty pallet is placed onto the loading area. The operation of this system can be described as follows.

Pressing the start button starts the conveyor.

As each box passes the photoelectric sensor, a count is registers.

When the preset value is reached (20) the conveyor turns off.

The forklift operator removes the load pallet.

After the empty pallet is in position, the forklift operator activates the remote reset switch which then starts the whole cycle over again.

Conveyor start button I:1/0

Stop button I:1/1

Sensor I:1/3

Reset switch I:1/6

Motor O:2/0

Counter C5:1

The ladder logic is as follows.

I may not have put enough thought into this lab as I should have. I may have simplified it too much to not be exactly what is called for. The motor can be reset by the operator, or it can be stopped by the counter. It seems pretty straight forward on how the ladder logic is supposed to work.

Lab 8-36

Using the batch simulator screen, write a program that will implement the following tank filling and mixing sequence.

I wasn’t sure what this was asking for. I just did the program like normal and ran the inputs and outputs. The program asks.

The start button is pressed to start input pump p1.

After 100 gallons one flowmeter pulse per gallon input pump p1 stops automatically and the mixer motor starts.

The mixer motor is automatically stopped after 30 seconds, and the input pump P1 is started.

After an additional 60 gallons are pumped into the tank, the input pump stops and the mixer motor starts.

The mixer motor is operated for 20 seconds and stops.

The discharge pump P3 motor is started automatically and runs until the low level sensor is actuated.

The process stops.

The inputs/ outputs.

Start I:1/0

Stop I:1/1

Flow I:1/5

Low level I:1/3

Mix motor O:2/0

P1 O:2/1

P3 O:2/3

Internal relay B3:0/0

CTU c5:1

Ctu C5:2

RTO T4:1

RTO T4:2

This was an interesting lab to create and took some thought and effort to fully understand and make it somewhat simplistic. I did not use the internal relay I didn’t see the need for it. I may have been able to use it, but I couldn’t find a need to use it. The start button was easy enough lock in the pump flowing and have the first 100 gallons open up the pump once it was done. The counters and flow I thought I did very well. It may not be perfect, but I think it fits for this application. The flow needs to start by pumping 100 gallons into the tank, once that happens it turns on the mixer motor and we turns off after 30 seconds. After the 30 seconds the pump starts back up and it counts for 60 gallons. After that once the pump is full it will start to pump until the low level pump is made.

Conclusion:

I may not have used to correct simulators with these labs, since I wasn’t really sure how to use them and if I was using them correctly. I just stuck with the inputs and outputs that way I knew exactly what was going on. These labs were challenging and a lot of fun too. I feel I may not have understood the traffic lab as well as I should have I had a problem with that one. It was hard keeping the light green and doing everything that was needed while it was off, but turning the light back on again was the challenge. I enjoyed these labs other than that and was able to really gain a good grasp on the advanced topics that PLC’s offer. I believe I am starting to really break down each section of the ladder logic.

References:

Petruzella, F. (2011) Logixpro PLC lab mamual for use with programmable logic controllers ( fourth ed). New York, NY: McGraw-Hill

Petruzella, F. D. (2011). LogixPro PLC lab manual for use with programmable logic controllers. New York, NY: McGraw-Hill.

LogixPro (Version TLP) [Computer software]. (n.d.).