Fieldpoint write.vi error - 33816 (Unexpected character received from Optomux response)

[beaster]

Hi, I have been running a program for a few months now and yesterday I got an error at the fieldpoint write.vi error - 33816 (Unexpected character received from Optomux response). The program will run fine for approx. 5 minutes and then the error occurs, if I click continue the program will run fine again for another 5-10 minutes before occuring again. The field point module that is being affected is a digital output which is controlling a relay connected to a heating element. When the error occurs it freezes the program and if the relay happens to be on it can cause a potentially dangerous over temperature event. Luckily I happened to be in the room when it first occured but the program is supposed to rund 24-7. I tried taking off automatic error handling but that caused the program to run incorrectly.

What is causing this error ?? Why did it just materialize ? How can prevent it from happening again ?

Any insight would be greatly appreciated !

[Ben]

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beaster wrote:

Hi, I have been running a program for a few months now and yesterday I got an error at the fieldpoint write.vi error - 33816 (Unexpected character received from Optomux response). The program will run fine for approx. 5 minutes and then the error occurs, if I click continue the program will run fine again for another 5-10 minutes before occuring again. The field point module that is being affected is a digital output which is controlling a relay connected to a heating element. When the error occurs it freezes the program and if the relay happens to be on it can cause a potentially dangerous over temperature event. Luckily I happened to be in the room when it first occured but the program is supposed to rund 24-7. I tried taking off automatic error handling but that caused the program to run incorrectly.

What is causing this error ?? Why did it just materialize ? How can prevent it from happening again ?

Any insight would be greatly appreciated !

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I believe Optomux was used for the serial connection scheme (please correct me if I'm wrong) so we are looking for something that could corruprt the serial comm.

Quick Test:

Try disconnecting the relay and run the program without the heater and external circuitry to rule out glitches etc.

Ben

[beaster]

The program runs fine when the relays are not connected (there are 6 being controlled at once). The error only seems to occur when there are multiple relays switching on and off in a short time duration. 

[Ben]

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beaster wrote:
The program runs fine when the relays are not connected (there are 6 being controlled at once). The error only seems to occur when there are multiple relays switching on and off in a short time duration. 

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Please start by confirming that fact well beyond a quick check. If we take the wrong turn now we could be wondering around in "noise-land" for quite a while if we are not sure.

1) "Noise Reduction Techniques in Electronic Systems" by Ott should be consulted for identifying the type of noise and its source.

2) There used to be an old app note about FP and relay modules...too many over-load the suplly for the FP bank ... and they should be at the end of the bank.

3) Check the rating of the FP relay contacts and how much current is passing through the contacts. If they have been pushed too hard they may have worked at first but now aren't able to break the circuit.

4) Try to issolate issue to a single load or confirm it is multiple switch at the same time.

5) Double check all of your groungs, particularly connections that may have come loose.

6) Ferite beads may help if noise is feeding back via the power or ground lines. See Ott for more info.

Just trying to help,

Ben

[ryano]

The problem has been solved ! I isolated the problem to a singal channel and then discovered that a flyback diode was not installed correctly. The flyback voltage must have been the cause of the optomuc response error.

[Ben]

...and yet another game of "Name that Failure" comes to an end. Tune in next time when we try to ID the problem before the question is posted.

Thanks for the feedback. I am glad it helped,

Ben