Hello , i am currently in the process of trying to self learn myself basic PLC and have recieved some notes from various people to aid this. However i am stuck on this particular problem. Any help would be appreciated.

The problem is a conveyor belt system that comprises of 3 conveyor belts, each driven by a separate motor : M1, M2, M3 and must meet the following specifications
Starting:
· One pushbutton must start the motors in the sequence M3, M2, M1. This ensures that material from the previous belt is carried off before more is added
· M3 must start immediately when the start button is pushed
· After a 30 second delay M2 must start
· After another 30 second delay M3 must start

Stopping:
· One push button must stop all motors in reverse order : M3, M2, M1 to allow material to be cleared from the belts
· M1 must stop immediately when the stop button is pressed
· After a 40 second delay, M2 must stop
· After another 40 second delay M3 must stop
X0 - start button, X1 stop button
Y0 - M1, Y1 - M2, Y3 - M3

 

Can you elaborate on what you do not understand? Can you show us what you've worked out? Is this on an actual PLC?

You need to look into Timers and Latching Outputs.

This may help:
http://www.plcs.net/contents.shtml

Also, be sure to check out their online simulator.
http://www.plcsimulator.net/

Another Simulator
http://www.thelearningpit.com/plc/psim/psim.html


More Info:
http://engineeronadisk.com/V2/book_PLC/engineeronadisk.html
http://www.educypedia.be/electronics/control-systems-plc.htm

 

Im having trouble coming up with a ladder logic diagram. I dont have a scanner to show you my rough attempts at a ladder logic diagram.

Thank you for the links though. The more i read online, the more im making sense of it.

 

Do you understand the basics at this point?
N.O. Contacts, N.C. Contacts, Output Coils?

I recommend looking at some examples and trying to follow them through. The ebook on this site has a Ladder Logic section that touches on the basics.
http://www.allaboutcircuits.com/vol_4/chpt_6/1.html
http://www.allaboutcircuits.com/vol_4/chpt_6/6.html

I don't mind writing the ladder logic for you, but I would rather you fully understand the subject and be able to work it out yourself. It will benefit you more in the future, when you start writing your own ladder logic. Also, I would have to find some spare time. I'm only on here for about 15 minutes at a time and that's usually on my phone. I am also a terrible teacher, but I'm working on getting better.

 

i have completed it now. A teacher i used to have at college helped me understand it a bit better . Helped me understand what is happening through the rungs of the ladder. i do understand NO and NC contacts and latching etc. Thanks for those links though. any help is appreciated

 

No problem. That's what we are here for. To help each other out and learn from one another. Glad to hear you worked it out.