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PostPosted: Fri May 19, 2017 2:02 pm 
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Dear Velleman support,

We have recently bought the VM140 card to use it to control a climate chamber. The card has everything on-board, we need for this. I have installed the card (new drivers on 64 bit windows 10 PC with touch screen), the demo app works fine.

Then I have written a user interface in WPF + c# so the user can control the settings of the temperature chamber from a PC with touch screen.

Everything works like it should, but now and then we have a problem with the connection to the card. I have written a procedure in my program, if the program loses the connection to the card it will try to reconnect every 5 seconds. I have tested this by unplugging the USB connector and reconnecting it again, and this works.

But now and then something happens so the PC loses the connection to the card and is unable to reconnect. The big problem is that the card thinks it is still connected (LED, LD 12 continues on)! If the card does not realize that the connection is gone, it will keep the last received output status instead of pulling all the outputs to default value (off). This is a big problem because if at that moment the heating or cooling is on. Then the chamber keeps heating or cooling. This has also the consequence that the PC is not able to reconnect.

I think this is because the card is not aware that the connection is lost and thus is not accepting new connections. When I disconnect the USB cable and reconnect it, the PC is able to reconnect and to continue the program.
What the reason is of the lost connection, I don't know. Maybe electrical interference on the data wires of the USB wire?

I was not able to simulate this by disconnecting the USB wire, because the card sees a disconnection and reacts to it (LED LD12 starts to blink)

I found that I can get the card in this status by cutting the white Data - wire of the USB cable. Then the card is keeping its last received status and the program (also the demo program) is not able to reconnect after reconnecting the data - wire until I unplug / reconnect the USB cable.

I have tried to find a solution by trying to cut the power to the USB port with my c# program, but until now I did not find a way to do this.

So at this point I am stuck, and the complete project is unreliable until I find a solution to this problem.

Is it possible to provide me a solution to my problem?

Thanks!

Best regards,

SDM


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PostPosted: Fri May 19, 2017 3:00 pm 
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One possible cause to this problem may also be some sort of electromagnetic interference.
You may try to isolate the possible source of the problem.
First disconnect all the wires connected to the card except the USB cable and power supply.
If possible, move the card and PC to a place where is as low as possible electromagnetic noise from relays, motors etc.
Run your program to test if the problem occurs.
If problem still occurs, the cause may be something else than electromagnetic noise.


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PostPosted: Sat May 20, 2017 7:02 am 
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Thanks for the advice.

I already have let my temperature control program run in rest (no temperature control actions, just my program open reading sensor values) for several days and I never had any problems. When I have started the testing with heating and cooling, then only sometimes, the problem occured. So electromagnetic interference or electrical interference is possible, because of the heater elements and the wind propellers.

I dont think I can avoid this, because the pc + VM140 have to be near the chamber. The thing is that I need to able to handle this type of problem if it occures.

Thanks!


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PostPosted: Mon May 22, 2017 3:09 pm 
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Joined: Mon Dec 11, 2006 12:03 pm
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OK.
One possibility may be to reset the microcontroller IC3 when the card stops responding.
IC3 can be reset by short circuiting capacitor C5.
I tested with the C# demo software:
After IC3 reset the software can reconnect the card without any problems.

There is still a problem: You need some means to perform the reset e.g. other interface card...


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