12-07-2007 12:02 PM
12-07-2007 12:19 PM
12-07-2007 12:37 PM
We are useing the Phoenix contact Socket PLC-BSC-24DC/21 (http://www.alliedelec.com/Images/Products/Datasheets/BM/PHOENIX_CONTACT/Phoenix-Contact_Interconnect...) which has a "Dampening Diode" built in to the base. We use the Phoenix Contact No.2961105 relay.
Additionally the LED turns on and off as expected.
12-07-2007 01:10 PM
Phoenix Contact info is a bit fuzzy as to just what is across the coil of the relay. You might want to install your own flyback diodes. I don't think this is an issue with leakage currents. I really think the some sort of electrical noise is latching up your outputs. Best guess is that noise is either coming in via the output wiring or through your 24VDC supply. A scope might help you find the culprit.
Standard practice for me is to install a flyback diode across a DC coil or a RC snubber across an AC coil of any relay/contactor in a tester/system. The trick is to get the diode/snubber as close to the coil as possible.
12-07-2007 01:19 PM
12-07-2007 01:35 PM
The RC snubbers I use are from Electrocube. Here is link to doc http://www.electrocube.com/pdf/cap13.pdf. You will probably need to experiment to find which RC combination does the best job.
Most of the time I use a simple 1N4007 flyback diode on DC coils. This could be installed directly at the terminal block.
At some point you will still need poke around with a scope. I'm guessing it will take a pretty big disturbance to cause this.
12-13-2007 12:46 PM
Thank you for contacting National Instruments. From what you are describing here, I think there is another aspect that is worth investigating when experiencing these symptoms.
FieldPoint modules can be damaged over time by noisy power supplies. When damaged the [c]FP-DO-401 will have channels that are stuck in the ON position. The LED will turn on and off correctly, but will always output a high voltage. To prevent against this type of failure you will need to attach a properly selected transient voltage surge suppressor between V and C. It is recommend to use a transient voltage surge suppressor (TVSS) to prevent this despite the power supply that is used. However, once the module is damaged, it will need to be repaired by our repair department. Also, it is also wise to use a TVSS with new modules. If a module has previously been exposed to transient voltages, attaching a TVSS will only prevent further the damage from occurring.
If you are using a 24V supply, then one of the following TVSSs could apply:
Littlefuse - LCE24A
ST Micro - P6KE27A
Vishay - P6KE27A
To hook this up to the DO-401, connect the side of the transient voltage suppressor with the line/bar to the V terminal on the terminal block, and then other end to the C terminal on the terminal block.
To return your product for repair, a service request can be made here. You will need to provide software and hardware information, and request repair in the ‘Question Type’.
I hope this helps! Let me know if you have other questions or need additional clarification. Have a great day!
12-13-2007 01:28 PM
Can you elaborate a bit more on what you mean by "noisy power supplies"? Are you refering to an inferior power supply that generates its own electrical noise/transients or to electrical noise/transients from the AC input to the supply that make it through the power supply and to the cFP?
12-13-2007 01:40 PM
What I am referring to here is the second conditions you described, the electrical noise/transients from the AC input to the supply that make it through the power supply and to the cFP. Sometimes power supplies will spike when they are plugged in, and this may cause a noise problem.
12-13-2007 02:20 PM