Problems with Compact I/O adapter and devicenet

Hello all! Our process controls guy took a job with another company and I'm the lucky guy that gets to try and fill his shoes.

We have been having a problem with one of our DeviceNet scanner modules (1769-SDN) where it would lose all of the settings anytime we had a power loss. Since we lost power again last night, I decided I would just swap out the module for a new one. I have fumbled my way thru getting almost everything back to running. The scanner doesn't show any error codes, but I'm having problems with some remote I/O.

The problem I'm having seems very strange. First I'll give the configuration of the RIO rack.

1. 1769-ADN
2. 1769-PA2
3. 1769-SM2
4. 1769-IQ16
5. 1769-IQ16
6. 1769-OW16
7. 1769-OW16
8. 1769-CRL1
9. 1769-SM2
10. 1769-PA2
11. 1769-IQ16
12. 1769-ECR

My issue is that I have power on some of the inputs of cards 4 and 5, but it's not correlating in my program. According to the PLC all of the inputs are off. Additionally, the PLC is trying to turn on outputs for cards 6 and 7, but only outputs 8-15 will turn on, on card 7. Card 6 is completely dead. Everything else seems to be working.

Any help would be appreciated. Been racking my brain and researching for the last 5 hours.

Thanks in advance!!

Well, not sure what was going on, but I redownloaded the settings to the RIO about 8 more times and it finally started working?

Ever since I have got this running, The Node that I couldn't get to take settings to has been randomly dropping communications. It's less than a second that it's out. I have verified the voltage at the adapter, checked all of the cables, checked the resistors.... Is there anything else I can look for?

Big Brunsy said:

Ever since I have got this running, The Node that I couldn't get to take settings to has been randomly dropping communications. It's less than a second that it's out. I have verified the voltage at the adapter, checked all of the cables, checked the resistors.... Is there anything else I can look for?

Click to expand...

Have you verified the voltage at the furthest node ?

No, I have only been concentrating on this one node. Do you always check voltage at the farthest node?

My boss is supposed to be buying me a Molex DeviceNet Netmeter. I will check that first thing in the morning.

Thanks!

Big Brunsy said:

No, I have only been concentrating on this one node. Do you always check voltage at the farthest node?

My boss is supposed to be buying me a Molex DeviceNet Netmeter. I will check that first thing in the morning.

Thanks!

Click to expand...

Yes, it is recommended to.... Each device draws current from the power supply. which causes a volt drop in the cable.

If you were designing the neywork from scratch, you would go through a lot of calculations. The volt drop in each "segment" is calculated (remember that the segment nearest the power supply has the cumulative current for all the devices on the network), then the voltage available for the remotest (most remote?) node can be worked out.

Design spec. calls for a minimum of 19V for devicenet devices.

You are not starting from scratch, so have the physical network to go measure it.

If its not up to spec., you can add additional power supplies at strategic points (i.e. power segments of the network independently), or relocate the existing power supply to mid-network, or shorten your cable runs if possible.

The 0V rail should only be connected to the GND (shield) of the network cable at the power supply, and only grounded at the same place.

This is one of the closest nodes to the scanner. It has 23.96V. the farthest node has 23.17V. this node also comes directly off of the scanner and is the end of that line. The is another cable coming off of the scanner and going out the other way to the rest of the network.

I've been talking with our suppliers tech support and they are starting to think the ADN is going bad. I'll replace that when it comes in and see what happens.

Big Brunsy said:

This is one of the closest nodes to the scanner. It has 23.96V. the farthest node has 23.17V. this node also comes directly off of the scanner and is the end of that line. The is another cable coming off of the scanner and going out the other way to the rest of the network.

I've been talking with our suppliers tech support and they are starting to think the ADN is going bad. I'll replace that when it comes in and see what happens.

Click to expand...

Well within spec.

That is what has me so confused. I've tried most everything that the AB troubleshooting manuals say.

Our supplier recommended a Molex DeviceNet NetMeter to help with troubleshooting. Have you ever used one of these? Trying to decide if it's worth purchasing.

Thanks for the replies!