Looking for help on an assignment.

[Jalic]

I'm in a course at college for PLCs as part of my electrical degree.

So, If I were to ask for some help, or a point in the right direction here, would that be frowned upon?

Here's the assignment, and after that I'll post a picture of the simulator and what I have so far.

"Process System Requirements

Selecting ?A? on the selection switch and pressing the START PB will begin the box filling operation which is indicated with the RUN PL. Each box is to move under the silo and stop which turns off the RUN PL. Upon sensing the presents of the box, the system will activate the solenoid and begin to fill the box which illuminates the FILL PL. The fill process will continue until the level sensor detects a FULL condition noted by the FILL PL deactivating and the FULL PL illuminating. The conveyor will move the filled product down the line and bring in the next box noted by the illumination of the RUN PL. The process continues until the STOP PB is pressed at which time the fill process will be allowed to finish.

Selecting ?B? on the selector switch will allow the START PB to act as a ?jog? PB to move product down the line.


To review:

Selecting ?A? along with pressing the Start PB initiates an automated fill process.

Selecting ?B? and pressing the Start PB only runs the conveyor motor to move product out of the way or performs a jog operation.



Restrictions

Ensure the box does not overfill or spill. You may use the sensors that are provided to help meet this requirement.

You may not use selector switch: position ?C?."

 Here's what I have so far.

http://img78.imageshack.us/img78/7972/plchomeworkhh0.png

I can get it to the point where it will fill the box full, then stop. But I can't seem to get it to continue moving. Everything I try ends up making the box move a little then stop, and makes the solenoid open and pour all over the floor.

Any help or ideas would be greatly appreciated.

[Dogface]

sounds like the conveyor won't run as long as the pack sensor detects a box.  Using relays, allow the pack sensor to stop the conveyor only one time per box.  (clear the relay when the sensor is false again)  I prefer latching relays for this.

Switch selector position B with  Start button pressed should open a N.C. relay that keeps the pack sensor from stopping the belt.

In a real world situation you would want to implement a timer in such fashion that clearing the above mentioned relay would only occur if the sensor was false for a specified amount of time.  This would keep the sensor from cycling due to irregularities in the box, conveyor, etc...

If this dosen't help.... http://users.adelphia.net/~s1ick/jpeg001.jpg
Don't look if you don't need to.  It's just a logic puzzle.

[Jalic]

Sorry it took me so long to respond, I've been busy with work and school. Thank you for your help.