Power Flex 70 Drives on Device Net

bmcombs

Member
Join Date
Jun 2003
Posts
1
I am currently working on a project using the Allen-Bradley Power Flex 70 drives and configuring them on Device Net. Also we are using PLC 5/40 E. When you configure a drive on D-Net, D-Net writes 2 words of memory per drive to the scanner module. In our ladder logic, we have to use BTR & BTW logic to configure these words. The max length of words in the BTR & BTW is 64. Well in our job, we are looking at configuring 42 drives! This means a total of 84 words of memory. How do I configure this many words of memory in my PLC. Can I use two sets of BTR & BTW to write the 84 words to the scanner module?
 
Yup.

The 1771-SDN can actually accomodate several BTR/BTW sets to access a total of 357 words of DeviceNet Input and Output data.

If the PLC-5 is sending several block transfers to the same slot, the module can only tell them apart by size.

62 Words - BT #1
61 Words - BT #2
60 Words - BT #3
59 Words - BT #4
58 Words - BT #5
57 Words - BT #6

That's 357 words of Input, and 357 words of Output. That big old piecewise data table can be shared by both channels of the 1771-SDN.

Making a scanlist for both channels is kind of a clunky process; read the RSNetworx notes on that carefully.

The Installation Instructions for the 1771-SDN are the best reading on the matter. They're on www.ab.com/manuals
 
btr

Hi, yes you've gonna make two btr ab btw. First one in word #62 in the scanner and the second in word #61.
 
Let me jump in here an warn you about a MAJOR problem with RSLogix 5 and the DeviceNet scanner.

DO NOT configure the 1771-SDN in the configuration wizard!! This will cause problems with the multiple BTR/BTWs' that you must perform to the module to get access to the total available 357 words that Eddie mentions. I worked with someone who did this in order to get access to the devicenet status data and it caused an automated crane to drop drop a charge bucket for an automated cupola charging system. Of course once the cupola is running you don't want to stop it so you can imagine how tense things (& the mechanics got the crane back in working order) were while he reloaded the old program. It took me a day to figure out that the chassis configuration was causing the issue. Of course Rockwell just says that they never use the configuration wizard anyway.

Just be careful. I can create an example file that will show the problem and it is visible in the offline file.

Darren
 
Last edited:

Similar Topics

Hi All, While Replacing a VFD in breakdown condition which is the right and easy way to replace the drive quickly. We are working with Plant PAX...
Replies
3
Views
1,474
How many power flex 40 drives can you run off one 1756/ENBT card without any significant performance hits? I've searched this site as well as...
Replies
2
Views
3,197
Can I extract parameters froem my power flrx drive with RS5000 or do I need to purchase separate software from Rockwell ? Thanks
Replies
6
Views
2,501
I was wondering if anyone knows a good link/ resource that explains how to program a micrologix 1400 to control a Power Flex 4 drive via RJ45...
Replies
6
Views
3,390
We have several PowerFlex 4 drives around the plant.We had a planned outage that the power company was going switch over to another feed , after...
Replies
7
Views
8,183
Back
Top Bottom