1769 SDN device net scanner does not supply voltage to the network

[Tebi]

Hello forum!

I'm using AB Compactlogix 1769 L35E CPU energized by 1769-PA2 power supply which is also supplying to 1769-SDN DeviceNet scanner, both via backplane. Trying to build a simply DN network connecting the scanner to a Balluff BNI DNT-104-000-Z004, which is a 16 PNP digital input block, since is only input module I rely that no extra power supply will be required.

The problem is that when connecting both scanner and input block via my DN thick cable (Balluff BCC07YY), the input module does not energize. In fact I got no voltage reading when measuring voltage between scanner V+ and V- terminals. I measured voltage at 1769-PA2 power supply DC output (which is not in use) and its providing 24VDC, also scanner is powered on so I do not think the problem could be power supply nor backplane.

Scanner display shows 92 number, scanner manual says that 92 error is "no devicenet power" and has the following description:

No network power detected on DeviceNet port. Provide network power. Make sure the module drop cable is providing the proper power to the DeviceNet port.

Which I do not get, is not the power supply from 1769-PA2 via backplane enough? 

Is not the scanner supposed to provide voltage to the network?

I've no grounding connection connected to PE yet (just between devices GND terminals)... is that a problem for testing this small network? It will be done soon but now I'm waiting for cable material.

Actually I'm online using Studio5000 and have 1769-SDN DeviceNet scanner device declared at the project, there is no warning nor major fault displayed from the software.

Thanks for reading.

[alan_505]

DeviceNet needs its on dedicated 24v supply, and to perform properly it needs to have particular rise time characteristics.

Alan.

 

[Ken Roach]

Quote

 

Which I do not get, is not the power supply from 1769-PA2 via backplane enough? 

Is not the scanner supposed to provide voltage to the network?

 

DeviceNet devices are isolated from the PLCs, drives, and I/O block main power.     For this reason, you must provide a separate DeviceNet power supply to power the network.

This can seem counter-intuitive when you are accustomed to networks like Profibus or AS-i, or when you're connecting only one Input block.   But many DeviceNet products like photoeyes or proximity sensors don't have  separate power supply, so they must receive their network power and signal from the bus cable.     And PLCs aren't always part of a DeviceNet, so we can't rely on them to be the power supplies or load up their internal power supplies (a big DeviceNet can consume several amperes).

[pcmccartney1]

Ken is right.  You must supply power to the V+ and V- terminals on the DeviceNet Terminal block.  Generally, to be compliant, you need to supply an ODVA certified +24VDC Power Supply.  Almost everyone has something to offer.  I've used Phoenix Contact QUINT Power Supply for hundreds of control panels with DeviceNet.  Be aware that there are limitation to the available amperage that can or should be supplied to the DeviceNet network.  It needs to be less than 8 Amps.  If you exceeding this limit, you need to consider supplying an additional DNet Scanner and ODVA Power Supply.

[Tebi]

Thanks everyone!

Now my small DN network is perfectly working, actually I'm using a power supply that do not have DeviceNet specs. But since my PLC is just communicating with a DI block and a valve bank, issues has not been presented. I will check for a power supply that has DN supply specs :)! 

[BobLfoot]

Check out this "DeviceNet Tech Resource" or as we used to call it "DeviceNet Bible"

https://rockwellautomation.custhelp.com/app/answers/detail/a_id/44883/page/1