Allen Bradley (PLC) Question

Hurricane-Dean

Hi guys, i'm trying to figure out this the last 2 weeks and my lecturer just will not help. Here's a quick overview I had to write a program for the sequence A+,B+,A- Delay 2 seconds B- three times. I've done that just I need an instant stop that will stop the cycle instantly and return the Cylinders to their home positions.

Any ideas? anything i put into ladder just stops the cycle dead but doesn't bring the cylinders back? I'm stuck!!

Thanks

steifanc

what kind of valves is the program controlling . ?
and what are the home positions ? is it the reverse of the sequence or all retracted/extended ?

biblio

I have no experience with allen bradley plc's but on the mitsubishi Fx-On programming them in sfc,
I added a normally closed contact to the first or second line of the program, which represents a "reset button". This is used to activate a memory contact which then activates the outputs (y1, y3 or whatever you have used)to drive the solenoids that send A- and B- at any stage in the program. This worked when programming in sequential function chart, so trapped signals were'nt much of an issue but if you are using conventional ladder programming you may need to watch out for trapped signals or outputs remaining on and trying to send A+ and A- at the same time.

steifanc

biblio wrote: »

I have no experience with allen bradley plc's but on the mitsubishi Fx-On programming them in sfc,
I added a normally closed contact to the first or second line of the program, which represents a "reset button". This is used to activate a memory contact which then activates the outputs (y1, y3 or whatever you have used)to drive the solenoids that send A- and B- at any stage in the program. This worked when programming in sequential function chart, so trapped signals were'nt much of an issue but if you are using conventional ladder programming you may need to watch out for trapped signals or outputs remaining on and trying to send A+ and A- at the same time.

i taught the fx series was conventional ladder ? the alpha is the only mitsi plc to use function programming based on a cross between g code and ladder . you cant write a pro gramme with out knowing the function of the valves ie.are they spring or pilot operated , this will denote the structure of the program .

steifanc

biblio wrote: »

I have no experience with allen bradley plc's but on the mitsubishi Fx-On programming them in sfc,
I added a normally closed contact to the first or second line of the program, which represents a "reset button". This is used to activate a memory contact which then activates the outputs (y1, y3 or whatever you have used)to drive the solenoids that send A- and B- at any stage in the program. This worked when programming in sequential function chart, so trapped signals were'nt much of an issue but if you are using conventional ladder programming you may need to watch out for trapped signals or outputs remaining on and trying to send A+ and A- at the same time.

i taught the fx series was conventional ladder ? the alpha is the only mitsi plc to use function programming based on a cross between g code and ladder . you cant write a pro gramme with out knowing the function of the valves ie.are they spring or pilot operated , this will denote the structure of the program .

biblio

Yes the fx-O can be programmed in sequential function chart using GX developer.
It is a little bit different to the function block diagram style language used by the alpha.
Yes i agree more info is needed to write a program, but I see the OP is a student , the sequence shown is a typical training one and the valves used on most training boards I have used are spring return.

dave2pvd

Hurricane-Dean wrote: »

Hi guys, i'm trying to figure out this the last 2 weeks and my lecturer just will not help. Here's a quick overview I had to write a program for the sequence A+,B+,A- Delay 2 seconds B- three times. I've done that just I need an instant stop that will stop the cycle instantly and return the Cylinders to their home positions.

Any ideas? anything i put into ladder just stops the cycle dead but doesn't bring the cylinders back? I'm stuck!!

Thanks

Sounds like non-return solenoid valves.

OP: Include 2 additional lines of code:

"If not A+, then A-" and
"If not B+, then B-".