Analog signal to easyport not working

[espeno]

Hi,

I have an Festo Easyport D8A connect to labVIEW via RS232 and serial to usb cable. With the program attached I am able to connect just fine and turn on every digital output and read digital and anlog input.

The problem accures when I try to use the analog output signals, I have 2 analog signals (pump voltage and proportional valve), with boolean signal I want to choose the control signal to be analog or digital signal for the pump, the proportional valve is just analog.

What I cant figure out is when I run the VI I am able to first run the pump with digital signal, I am also able to change so I can controll the pump with the analog signal, when i increase the signal the pump runs faster, but when I turn down the analog signal to 0V the VI starts to run very slow. When i try to increas the voltage again nothing happens, and when I turn over to digital control again, this suddenly wont work either. The same thing happens with the prop. valve.

I think the problem is my poor job with the invoked nodes, I do not think i fully understands how they work. Something else I think might be wrong is the activeX control for my easyport, the picture shown as reference on the front panel is not the same box I use, I have not been able to find the correct one. But I still think it`s strange the my VI is able to use the analog output for some time but suddenly shuts down.

Can anyone pls have a look at my VI and see if there is anything wrong with the invoked nodes I use to send signals? Or if you have any toughts on the activeX it would be much appreciated, or anything else that may get me on my way.

Thank you.

With kind regards

Espen Olsen

[JarmoLE]

Hello espeno,

What driver are you using for your Festo Easyport?

I am just wondering where the information is received for the ActiveX server, as the Easyport Module control would more logically be a LabVIEW constant unless the driver is common for multiple devices.

Have you tested with individual invoke node so that they work separately? I would suggest to test the analog input and output individually and check if the error comes from turning the output voltage to 0. This could be worked around by setting a small +0,00001 to your code to make sure that the analog output would never go to 0. But first check where the actual issue is located.

Also if you control the pump with the digital signal and set that to OFF state (0 state) does the problem affect the analog output?

Let's try to work forward if you could find the answer to those questions.

Best regards,

Jarmo Levo

Applications Engineer

National Instruments

[espeno]

Hi,

thanks for your reply. Im using Festo USB driver 2.12, downloaded from;

http://www.festo-didactic.com/int-en/services/software/software-licences-trial-version/activex-contr...

AS for the activX server I right clicked the refnummer and choose from a list, only had one option for the easyport.

Anyway, I think i found a solution to my problem. I changed the Seriall to USB cable and went into advanced setup, where I changed the Latency Timer from 16 to 4 ms, now it seems to work 🙂

Thanks anyway for taking the time to responed.

With kind regards

Espen Olsen

[JarmoLE]

Great to hear that you found a solution!

Regards,

Jarmo

[tonystart2003@gmail.com]

Hello Espen Olsen,
I think your idea about the water bottle is very good, but there are some places I don't understand the values like 3276.8, 0.0088, 11.138. How did you calculate it? .I am researching Festo's tank but it has an additional PID so the system can automatically balance.
Glad you could help. Thanks a lot. Good healthy
Your
Tony

[tonystart2003@gmail.com]

hello. I can help me!!!

[GerdW]

Hi Tony,

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tonystart2003@gmail.com wrote:

I don't understand the values like 3276.8, 0.0088, 11.138. How did you calculate it?

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"3276.8" is a typical value when handling I16 registers: the (absolute) max value for an I16 register is 32768 (= 2^15), and the register seems to hold values with a resolution of 0.1 (=1/10), so you need to scale the I16 value by 3276.8 to get the "real" scaled value…

Those other values should be explained in the manual, especially for the level value (maybe based on tank size?)…