Help with 1770-KFD and DNet

[JoseM]

I'm trying to use a 1770-KFD to connect to a devicenet network. When the driver is installing, it tries to initialize the adapter but the driver doesn't show up on the list of running drivers under RSLinx.

It also took out the DeviceNet network on that machine where I had to power the machine down in order to recover.

I've notice that if you are trying to upload a Dnet network, it bugs down the system so much and it faults out the equipments that are part of that network.

Can anyone help understand why I can not communicate with this network using the 1770-KFD adapter?

 

[Ken Roach]

I suspect that you have a badly installed DeviceNet network.

The 1770-KFD absolutely should not "shut down" a DeviceNet network. When installed on a dropline, it remains passive until you get RSLinx Classic configured, at which point it can attempt to communicate on the network at the baud rate you specify.

I'm not familiar with circumstances that would allow the KFD to start using the wrong baud rate; I supposed that could cause a Bus Off error. Be sure you know the baud rate of the system before connecting to it.

And the messaging that the 1770-KFD does, called Explicit Messaging, is the lowest priority type of message on DeviceNet. It is specifically designed to have minimal impact on the I/O traffic of the network.

The first thing to do is power down the DeviceNet and check the resistance between the blue and white wires. If it's anything other than about 57 to 61 ohms, you have a termination problem.

 

[JoseM]

I did not participated on the development of this network Ken, because it was done years before I join this company.

Now any idea how can I determine the "Baud Rate" at which this network is communicating?

There is a connector for DeviceNet on the door of the control panel where all the drives are located. I connected the 1770-KFD there and then use the RS232 cable I use to connect to processors to connect to the box.

Do you recommend to check the resistance at the connector I just mention, Ken.

 

[Ken Roach]

It's surprisingly difficult to determine the baud rate of a running network, except when you have a truly passive device like a Woodhead NetMeter.

The Scanner modules generally display their configured baud rate when you first start them up.

If you have an AC drive like a PowerFlex, that has a HIM module as well as a 20-COMM-D, you can use the HIM to access the 20-COMM-D (use the Device Select function) and look at Adapter Parameter 06 (DN Act) to read the Actual DeviceNet Data Rate.

You can check the signal line termination resistance anywhere on the network. Be sure that the network power is off, though, because the transmission of any signal on the network will throw off your ohmmeter.

 

[JoseM]

This panel has a bunch of 160SSC drives but I believe that there is at least one Power Flex 40 in there.

Can I go to this PowerFlex now without fear of interrupting the Devicenet network?

Can I find information about the "Device Select Function" on the PowerFlex manual to learn how to use it.

*****NOT*****
Parameter A103 tells me the "Baud Rate" and its set to 9600 which is what the 1770-KFD driver has as a default.

 

[Ken Roach]

On the PowerFlex 40, with the 22-COMM-D module, you want to read the value of Parameter 5, "DN Rate Actual".

Parameter 103 is the "Baud Rate" for the RS485 "DSI" protocol port on the drive. It's not related to the serial data rate of the 1770-KFD.

 

[JoseM]

You are right Ken. But that parameter that you mention is a parameter for the 22-COMM-D module correct, and how can you see those by using the Power Flex VFD interface.