Hi

 

What do you have so far?
What particular PLC are you working with?
Although the basic Boolean instructions are identical across makes, the way mathematical, data registers, timers, counters can differ between makes.
Max.

 

From wiki:

Logical AND with NOT
------[ ]------------------[\]----------------( )----
Close Door Obstruction Door Motor

The above realizes the function: Door Motor = Close door AND NOT(Obstruction).

This circuit shows a pushbutton that closes a door, and an obstruction detector that senses if something is in the way of the closing door. When the normally open pushbutton contact closes and the normally closed obstruction detector is closed (no obstruction detected), electricity is able to flow to the motor which closes the door.
http://en.wikipedia.org/wiki/Ladder_logic

 

I predominantly use the FX (Mitsubishi) series.
What do you have for reference material? The manual should be available from the MEAU site if you don't have.
Hint: with E-stops input, there is a MCR master control relay that you can disable a whole section of code with rather than using the instruction on every rung.
If you can post what you have we can look it over.
Max.

 

I predominantly use the FX (Mitsubishi) series.
What do you have for reference material? The manual should be available from the MEAU site if you don't have.
Hint: with E-stops input, there is a MCR master control relay that you can disable a whole section of code with rather than using the instruction on every rung.
If you can post what you have we can look it over.
Max.

Since they are just doing ladder diagram... and this is homework... I don't think they need to know PLC specific language/commands.

 

I whipped up one scenario with 5 rungs, (not debugged) If this is a practical project, you probably also need to know how the conveyor motor is controlled, is it a two speed Induction motor for e.g.?
Max.

 

ok thanks that great. I'm sure its an AC Induction motor single phase that is being used.

 

Something like this will be a starting point.
Max.

 

Thanks a lot for your help Max

 

Do you mean to set up a simulation or to run /test the actual conveyor?
You can probably do it just by hooking up the inputs only and the output LED's will tell you the status of the outputs without actually hooking the motor etc up.
Max.

 

To test the actual conveyor. Different connection leads for each, unsure what type of unit I need to use to connect them to run tests. Do you know what I would need ? Thanks

 

If you are talking about the actual conveyor you need a suitable interface between the outputs and controlled devices, either the SS or relay out would feed an external contactor coil or aux relay controlling the motors .
So far there has been no actual pic or dwg for the electrics and conveyor itself, so without these it is just guess work as to what you actually need.
You also need to draw up an electrical schematic of the whole system.
Max.

 

Thanks nandu. The only reason I decided to go with the PLC as it was something I have done before, but was several years ago. Do you think using an auxiliary relay would be a better way to go? If so what type of software/hardware would be required to get the conveyors physically moving ? The setup looks similar to simulink? Thanks

 

The secondary of the control transformer should either be set up as a neutral on the 0v terminal, or if not grounded then a fuse should be used in both conductors.
Probably no need for the transformer if 120v equipment is used.
Max.

 

X1 is the switch board button that moves the conveyor, x2 being the sensor that stops it. Y1 is the motor. What sequence would I add to allow the conveyor to start moving again without having to push x1? Would it be possible to have the conveyor move say 5 seconds after the object is clear of the sensor ? tried a number of ways but cant get it to work. Thanks

 

It should be easy to get the motor to continue for 5 sec after tripping the LS, but what is the decision maker to re-start the conveyor?
Max.

 

So did you plug the prog in I wrote and debug that rather than starting again, if you run the program and use the Monitor feature you should be able to tell where any error may be if present.
If you post the results we can help further maybe.
If I get a chance today I could hook my simulator up a see the result of the ladder I posted.
What is the exact Mits PLC number you are using?
Max.

 

I think I have something close, I assume you only have one motor speed now?
Max.

 

Yes just one motor speed is needed.

 

Thanks Nandu