UDT's inS7

Could anyone explain what the purpose of a UDT. I see them in an existing program but they do not exist in the same online version and can not be downloaded to. There are some UDT's placed in the DB back-up folder and wondering if they should be backed up or updated and why? Any help with this would be appriciated.

Thank you,

highvoltage8471

As the name Implies they are "User Defined data Types"...

You can create a UDT and can use them as "Data type" in your Data Block and can eventually use them in your program...Hope this helps

That helps. I start siemans class in a few weeks but there is much grey areas as I am used to AB. Thank you for your reply.

The best place to start is always F1...you can also check siemens forum, it will be much helpful to you...

highvoltage8471 said:

That helps. I start siemans class in a few weeks but there is much grey areas as I am used to AB. Thank you for your reply.

Click to expand...

Seen this? http://www.plcdev.com/book/export/html/373

Kalle

UDT's are very helpful when you need to shift around information, automatically, on a bit by bit level. Just one very helpful application.

Hi,
Well UDT are like ice tray. Once you have readied your ice tray by placing some different colored water (structure) in different cells of tray its time to place it in refrigerator (PLC).
Once placed your ice cubes (DB) is ready and you can throw away your tray though it's not advicable.

manmeetvirdi said:

Hi,
Well UDT are like ice tray. Once you have readied your ice tray by placing some different colored water (structure) in different cells of tray its time to place it in refrigerator (PLC).
Once placed your ice cubes (DB) is ready and you can throw away your tray though it's not advicable.

Click to expand...

It really depends though. I would say first check to see if those are even being used. If they aren't then you can get rid of them if you really want to. Make sure nothing is using them though, because if you remove them and functions are using them you can heavily effect the system.

You should definitely document the changes and you can always reimport those UDT's at a future date.

-Josh

the UDTs are not in the PLC, they are in the PC, like comments. UDT is a collection of data in a specified arrangement that makes it easy to drop a bunch of variables in one click.

Example:
UDT "Motor"
Motor Start bool
Motor Stop bool
Motor Run bool
Motor Speed Actual Integer
Motor Speed Setpoint Integer

Now imagine you need to repeat that 10 times in a DB.....

Motor1
Motor Start bool
Motor Stop bool
Motor Run bool
Motor Speed Actual Integer
Motor Speed Setpoint Integer
Motor2
Motor3

The actual variable used in the program will still be an address from the DB but the tag will reflect the motor number or name and the variable. (how it looks will depend on if you use addresses or tags........)

Good luck learning S7 after AB, forget as much AB as you can, it will get confusing.

Get the book Step7 in 7 Steps, it reads like an AB manual and is written by a native English speaker. Don't even try to read Berger until much later.

Thanks all for your very helpfull info. They were good explainations.