Auto/ Manual switch

jeddog

Member
J
Join Date
Nov 2011
Location
mornington peninsula
Posts
8
I am writing this ladder for a competence test. The outputs seem to over ride each other and not work.

eg when on manual, the auto stops the outputs from working and visa versa

Can someone please have a look and let me know where Im going wrong?


regards James

PS. Written with Mitsubishi GX Developer

Auto Manual switch.jpg
 
You have 2 rungs which are setting Y001, Y002, and Y003.

You can only have one rung which is setting your outputs, otherwise the program goes with whichever rung executes last.

For Example, Lets say X000 is 0 and X003 is 1:
Rung 0 executes and Y002 is set.
However Rung 2 executes, and because X000 is 0, any outputs on that rung are evaluated as 0 because that entire rung is "false."

You must have your logic for setting all your outputs on one rung each.

A useful phrase to remember: Last One Wins.

Example for Y001:

Code: 
   X000   X005    M0
--|   |--|   |--| \ |----------- |
                                 |
   X000   X003                   |
--| \ |--|   |---------------------------------(Y001  )

Notice how your conditions for turning on output Y001 exist as one rung.

Some programming platforms (Allen Bradley) have special output instructions called Latch / Unlatch (Set / Unset) which can act as a toggle for a bit. This enables someone to turn on an output in one rung (or multiple rungs) and turn it off in another.
 
Last edited:
As the 'M' is your auxillary relays use these to your advantage.
sometimes it is better to put your outputs at either the beginning or My preference at the end of your program.
It is a good Idea to setup a common format.
This type of PLC Program, where possible,
Similar to Inputs, Program control,Other, timers / counters,Outputs.
It is not important - But - makes it easier to fault trace and adjust.
The Mits software won't let you break the program into sections yet.

----] [--------------(m10) First Y000

----] [------------(m11) second Y000


And so on
 
If you have any problems Attach Zipped version of your program.
the program stores on your disk as
- File Name
- File Directory

we need both zipped in that order
 
no problems James - We will be seeing more posts.
There are plenty Mits posts on this site.
 
thanks for that Okie it will be a good link for JEDDOG.
by the way Jeddog - i am work for myself and sub-contract as a programmer.
i live in Narre - so if you need help PM me
 
I was just remembering the old Relay wiring method.
it is funny realy. in a 'star/delta' starteer
as you can't use the same coils for both star and delta.
Why would you consider doing it in a PLC
 
Hi
This is a bit simplistic but i usually use something like this



Code: 
// Auto and manual selection from inputs
// top section of code
   Auto     Manual                        Auto Mode
----| |-----|/|----------------------------( )----
                     
                     
 
   Auto Mode                              Manual Mode
----|/|------------------------------------( )-----                     
                     
// End section of code, outputs to system
 
  Auto Mode         Auto Conditions       Do Whatever
----| |--------------| |-------------------( )------
                                       |
                                       | 
   Manual Mode      Manual             |                
                   Conditions          |
----| |--------------| |---------------[
 
 
/CODE]
 
Thanks everybody,

For some reason, This ladder logic stuff has hit me right between the eyes. I love it.. its like a puzzle that has many different solutions

Just this little help from you all, has helped so much...

Cheers James
 
Last edited:
Easily Done James,
R u an A Grade?
As far as ladder Logic I've been doingit for 35 years now.
Bugger the house wiring- only done my house.
 
Would you believe I'm a 43 year old, third year apprentice electrician, doing my certificate 4 in PLC two nights a week at Chisholm, Frankston as well as a day of trade school a week.
I was a Viticulturist for over a decade and got very over it. So i headed to the mines in the Pilbara, WA and worked as a A.T (trades assistant). When i got back I started with a company called UGL, and was offered a apprenticeship when we were doing the sewage upgrade at Boneo (down here on the Peninsula). Now I'm working at the sewage upgrade at Thompson Rd Bangholm with a company call Nilsen. I find all this electrical stuff so interesting, and do injoy the PLC side.

love to know where the programming could lead me.

cheers James
 
Good on Ya Jeddog.
I drove past there this morning had to go to Carrum,
I C u r not used to the area - Nilsen has been out in the industry since my apprenticeship - I started in 1976
 

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