Micrologix Using 1761-NET-DNI and Modbus RTU

[adescoteaux]

Hi ! I would like to know if it is possible to use a MicroLogix 1400 with a 1761-NET-DNI module AND Modbus RTU at the same time ?

Thanks in advance !

 

[Ken Roach]

Welcome to the Forum !

The Net-DNI's serial side only works with DF1 Full Duplex protocol, so you cannot connect it to the same serial port as a Modbus RTU device.

But since the MicroLogix 1400 has two separate serial ports, you can connect the 1761-Net-DNI to one and the Modbus device to the other.

All the communication ports on the MicroLogix 1400 are independent.

 

[adescoteaux]

Thanks for you fast reply ! That is what I Wanted to know.
I have some other questions too, if you can answer to me that'll be great :

How do you setup the different channels to communicate through Modbus and Device-net ? I have some knowledge but this is the first time I use a Micrologix for that application

Thanks !

 

[Firejo]

I don't think the MicroLogix 1400 is compatible with DeviceNet.

 

[Ken Roach]

Let's take a step back and figure out what you expect to do with the 1761-NET-DNI.

That device is mostly made to allow a larger DeviceNet network to exchange a small amount of data with a small MicroLogix or similar controller.

It is NOT a DeviceNet scanner. You should NOT attempt to use it to perform control functions on a DeviceNet network.

 

[adescoteaux]

I want to communicate with an ABB robot for control through deviceNet.

The Micrologix 1400 will act as a master

 

[Ken Roach]

Use a CompactLogix, or even a MicroLogix 1500, both of which support the 1769-SDN DeviceNet Scanner.

The 1761-NET-DNI has very limited DeviceNet messaging capability, and no ability to function as a DeviceNet Scanner. It is principally used as an I/O slave device, not as an I/O scanner.

 

[Geospark]

I want to communicate with an ABB robot for control through deviceNet...

I can only imagine, without looking too deep into this, that the minimum I would be looking at to control a robot over DeviceNet would be a Logix based controller. The MicroLogix 1500 might be capable, but it would not be as deterministic a control method, while only using Class 3 Explicit Messaging. It may or may not matter that much, depending on the application, but I feel it is always important to make this distinction.

Regards,
George

 

[Ken Roach]

I think it was Kathy Mathews in the RA Commercial Engineering department in Cleveland that came up with a vivid analogy whenever people were asking for explicit messaging techniques to substitute for a proper I/O master:

"A crocodile will never fly, no matter how low or how slow."

 

[adescoteaux]

I only need to communicate with a robot for a few I/O. This is the only thing I have to do ? Is it possible ? And how ?

Thanks

 

[adescoteaux]

Up

 

[Ken Roach]

To perform any sort of I/O control on DeviceNet, you should use a controller with a "Scanner" module. The lowest cost ones are the MicroLogix 1500 controller with 1769-SDN, or the CompactLogix controllers with the 1769-SDN.

The 1761-NET-DNI is not an I/O scanner and will not work with your robot if the PLC needs to be the I/O scanning device.

If the robot is the scanner and the PLC is the I/O device, you can use the 1761-NET-DNI.

Please be as explicit and thorough as you can when asking questions about this application.

 

[adescoteaux]

thanks for your reply! I think the robot can act as a master.

Thank you everyone for your answers !

 

[FactoryTalktotheHand]

thanks for your reply! I think the robot can act as a master.

Thank you everyone for your answers !

Why do you think that? Wouldn't the robot need to receive commands from the controller? I don't think the PLC could do that.

I suggest biting the bullet and getting the proper equipment to do this job. You will spend far more time and money trying to get an unworkable solution working than you would have had you just used the proper components to begin with. We're talking about a few hundred bucks worth of components, versus thousands of dollars in labor and parts you will waste trying to get this to work. Look at the bigger picture. Don't spend $2 to save 50 cents.

 

[adescoteaux]

I know and if it was on my hand, I would definitely buy a Compactlogix with a SDN card. But my boss want me to make this work at low cost so....

I had a AB guy on the phone and they just said to me that the 1761-net-dni is backordered. We will probably move towards the compactlogix solution.

Thanks for the info.