Help a Newbie....

[Tom Jenkins]

FCC, take a look at the rung where you have the two jogs and a rung in parallel. What will happen if you press the jog button? What if you don't? What if both contacts aren't even there?

 

[Vetteboy]

Outputs

Also, FCC, what if you got rid of the motor coil, and changed the memory coil to motor, remembering to also change your memory XIC to motor XIC. Same thing, right? Cleans it up a little.

 

[Tim]

FCC,
What helps me out sometimes is looking at it as a schematic. Though not all plc code can be seen as this due to scanning issues, it does serve a purpose. Your memory internal relay is nothing but a software relay. The ladder code is set up similar to a schematic. To get the memory relay on, you must provide a current path. Look at the diagram and follow the current path from left to right. The relay has its + voltage and is waiting on the - voltage, so it can turn on. Will the -voltage make it to the "CR" relay when you press the jog button?
I hope this helps you.
Good luck!
Tim

 

[jpd24]

PLC stop/start

Not to confuse the newbie but I don't know how familiar he/she is with motor control to realize that you only need one PLC controlled stop and one PLC controlled start. The other means of stop/start can be actual PBs. The motor contactor will interlock itself and usually you will have an auxillary contact on the starter to give you an input to the PLC. This means that you only need two outputs and one input for each motor.
I realize that it's a PLC class and that's good practice but not always necessary in the real world.
The practice I need is getting schematics into replies.