EET310 – Programmable Controllers and Robotics

Unit 5

By: Brett Bloomberg

Instructor: William Routt

Online EET DepartmentECPI UniversityDate: 10/21/2016

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:

These final labs that we are to perform have brought the more advanced concepts to light and made us better engineers. We have learned that we can make PLC’s perform circuitry, and Boolean operations with ease. Our programing skills with this lab have increased from the knowledge we learned from the lectures and books. We learned how shift registers, Networking PLC’s, and one of the most important trouble shooting. These labs helped us learn what to look for when something wasn’t working quite right.

Lab 12-9

This lab asks us to implement the shift register spray painting application program shown below. The sequence of operation is as follows.

Each file bit location represents a station on the line, and the status of the bit indicates whether or not a part is present at the station.

The bit address I:1/2 detects whether or not a part has come on the line.

The shift registers function is used to keep track of items to be sprayed. A bit shift left instruction is used to indicate a forward motion of the line. As the parts pass along the production line, the shift register bit patterns represent the items on the conveyor hanger to be painted. LS1 is used to detect the hanger and LS2 to detect the part.

When a part to be painted and a part hanger occur in sequence (indicated by a sequential closing of LS2 follow by LS1 logic 1 is input into the shift register.

The logic 1 will cause the undercoat spray gun to operate, and five steps later, when 1 occurs in the shift register, the topcoat spray gun is operated. Limit switch 3 counts the parts as they exit the oven.

The counts obtained by limit switch 2 and limit switch 3 should be equal at the end of the spray painting run. PL1 is energized and is an indication that the parts commencing the spray painting run equal the parts that have completed it. Logic 0 in the shift register indicates that the conveyor has no parts on it to be sprayed and inhibits the operation of the spray.

Operations:

This program works in interesting ways, but it is a basic shift register. Once you know the basics of how they work, and what it takes to set the bit to a zero or a 1. The requirements that the lab asks you is in order to set a 1 in the 8 bit register you first need limit switch 2 to be set, and then set limit switch 1. The setting of limit switch one locks the bit into the register. When you set limit switch 3 it means that once limit switch 1 does get set that it will lock in a zero into the bit register. The shift register is stored in the internal bit of B3:0. This will let you see the whole register and how the bits are shifting through. When both B3:0 and b3:5 are made each one will display a light indication.

Conclusion:

As you can see if both limits switch one and limit switch three are equal it will light up a light that will show when both the input and the output of the system are equal. This program is fairly simple in design and implicational use of the shift register. Setting a 1 or a 0 in the register isn’t hard. TO get a one limit switch 2 needs to be activated, and to set a 0 limit switch three needs to be activated while limit switch 1 is activated.

Lab 12-10

This lab asks us to implement the shift register program used to keep track of carriers flowing through the 16 stations program shown below.

The program is as follows

Proximity switches #1 sense a carrier, while proximity switch #2 senses a part of the carrier.

Pilot lights connected to output module O:4 turn on as carries with parts move through the machine.

They turn off as empty carries move through.

Station #4 is an inspection station. If the part fails, the inspectors push PB1 as they remove the part from the system. Which turns output O:4/4 Off.

Rework is added back into the system at station #6. When the operator puts a part on an empty carrier he or she pushes pb2 turning output O:4/6 on.

The program is blow.

This is a simple program, but it has a huge function. In order to make this program shift the bits through the register we have to latch or unlatch to move the bit down the O: 4

Conclusion:

This shift register allows the outputs to be used as the register. We used O:4 to monitor the bits that went through the register. Each time it would count to keep track of the parts on the system. The lights will turn off when the spot is empty in the physical world showing that the physical and logical actually match up.

Lab 12-11

This lab asks us to implement the first in first out instruction set of the shift registers. Both the Fifo instructions are output instructions, and they are used as a pair. The fifo laod FFL loads data from a source element and the FIFO unload unloads the instruction data from a file to a destination word. This program permits the stacking of data in a file. Two separate shifts pulses are required: one to shift data into the file (load) and the other one is shift data out of the file (unload).

This is a simple first in first out data shift register, and it works very well. We see with the program below. As you can see from the integer table that I have added numbers into the table to demonstrate how this program works each number that is entered doesn’t matter as much as what the program does with it.

What this program does is takes the random numbers and sets them all to zeros, once that is done it will set them all to 5’s or the first number that is in the shift register. When dealing with registers of this nature it is important to remember that it is first in first out. This means that if the first number in is a 5 the last number will travel all the way down the register until it is unloaded. This will set the entire register as 5’s since it traveled down the line as 5’s. You can reset this by unloading all of the numbers and loading in a zero. This will load in zeros until it is completed.

13-3 Trouble shooting

This lab asks us to look at the PLC program and execute to sequentially turn PL1 off for 5 seconds and on for 10 seconds whenever input a is closed. Troubleshoot the circuit and identify what needs to be changed to have it operate properly. Use the I/o simulator screen and the following. The first picture below is the starting program. This program has errors in it that don’t really allow the program to operate properly, as the application is desired to operate. We see that the system doesn’t turn properly. I noticed that the need for internal bit was unneeded. The first program is the books, and the second is my changed program.

I added the timer latch to the first rung, which makes the pushbutton and user not worry about having to hold down the push button to keep the program going latching in the timer into it allows the user to just have to push the button in order to start the program. My second change was to remove the internal bit used to stop the timers and the latched in first counter. I removed that because it was redundant and didn’t need to be in the program. Once the second timer is done counter it turns off the first timer and turns off the system. When the second timer is counter it turns on PL1.

Having to think about ways to make a program work from someone else’s program certainly makes things interesting. Having to understand their logic of why they programed the things that they programed, and finding out what is necessary and what is not. Being able to understand their logic can be difficult. I think there isn’t a right and wrong way to program. There are easier ways, but there is no right answer in order to make something work or not. You can have a program with 10 rungs do the same thing with a program with 2. It all depends on how you think of the program and the application at hand. Trouble shooting a PLC is different than anything else in the world of automation. It’s the code or the brain of how the system works. It’s not something that comes easy to everyone, but when you have that knowledge and ability to see how the code should flow verses what its actually doing is a skill that is highly valuable.

Lab 13-4

This lab asks us to construct a simulated PLC program for the program editing and control. The program is given and we have to follow instructions on what to do in order to make the program work properly. The PLC program and requirements are listed below.

Once we made all the changes the program looked like this.

As you can see I may not have followed the directions completely. The directions were a little hard to understand in terms of what the start and run rung were and which rung was which since my program started with rung 0 and the drawing started with rung1. This you may think is a simple math problem, but when you are deleting multiple rungs and inserting them as well you lose which rung was supposed to be remove and which one wasn’t. This brings up a whole list of communication errors that can happen when trying to communicate to the program what the program needs to do, and what words and the tone of how to make the corrections.

Conclusions:

Since wrapping up this PLC lab and the main PLC course I have found or renewed my enjoyment for automation and plc programming. I am very interested in learning more about robotics and how to program them as well. I wish we got more into robotics and their applications, but this was a very fun course. I did actually learn a lot and had a very good refresher. We learned about shift registers and other topics that we didn’t learn about in the main course which I thought was very interesting. I enjoyed this course and I am excited that my time here is coming to an end. I am hoping that with all my experience I will find my education a good return on investment, and be fulfilled. This will be a journey.

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.).