Controlling a power supply with LabVIEW 8.2.

[archangel_hp]

I don't know why but it still doesn't work. Maybe I have the configuration wrong? Or maybe I have the wrong values in the PID. I don't know, I just know that when I run the program the voltage output is very small and doesn't seem to change with anything I do. Here I will attach my program (I guess it won't work because the instrument drivers may be missing), please tell me if there is something that can be fixed. Thank you.

[BillMe]

I can't address your PID issue, but I would still question the design here. Constant voltage mode will hold the programmed supply voltage while letting the current vary (as the load varies). Is this not sufficient for your needs? I'm only asking as I usually try to find a simpler method of doing something unless circumstances dictate otherwise. Why not let the supply do most of the work for you .

[Erik_1]

I'm controlling two Lambda Zup36-12's with Labview - I know it has already been said but the remote sensing pins are there to accomplish exactly what you are trying to do with a external PID controller (in this case labview). Why are you trying to circumvent the built in controller (which is tuned for that power supply)? Unless you are specifically trying to force the power supply to perform off-nominal (i.e. respond more slowly, overshoot, etc.) I would use the remote sensing pins. The manual contains straightforward instructions on how to configure the supply to use the remote sensing pins.

[archangel_hp]

Hello Erik, thanks for your reply. I know about the remote sensing feature of the power supply, but I think the manual says something about the max voltage drop for a 60 V model is 0.5  V and I'm not sure if I may get more than that in my system. Thanks again.

[Pablo Bernal]

I opened your VI, as you said I am missing the ZUP and ag34405a VI's. I am also missing the PID block that you are using (derivative with one pole). I can see the terminals anyways. What I see is that you are only giving input to the Setup Terminal. The setpoint you are giving seems to be the difference between the desired voltage output and the actual voltage reading. 

Using the  PID.vi  block that comes with the PID toolkit, in your case, the setpoint input would be directly the desired voltage. The process variable would be the voltage reading. Then you have to give the tunning parameters or Gains. There is an auto-tunning PID VI but it might not work, it depends on your system. There is an output range. This depends on the interface with your powersupply, the variable that you want to manipulate in order to increase or decrease voltaje, it could be the current limit.

I hope that helps.

Have a nice day!

Pablo Bernal

AE Mexico

[archangel_hp]

All right, I made a simple program just to see how the PID box works. However, I don't know if I made the program wrong or if the error here is the same as with the power supply program. In this program, I just have a substract function to simulate a voltage drop. Thanks again for your time.

[Erik_1]

The manual does indeed specify that the max voltage drop per lead be less than 0.5V. If your voltage drop is greater than 0.5V then the system is most likely designed improperly...trying to force the power supply to operate in a condition not supported by the manufacturer (and not adhering to sound electrical system design) is most likely not the best idea.

[archangel_hp]

Hello Erik. As I've stated before, there is nothing wrong with the system setup. Actually, I'm not forcing the power supply to do something that's beyond its operation. That's why I want to make the controller with LabVIEW and not use the remote sensing option that the power supply has.

[BillMe]

I can tell you that from my experience working with many, many different kinds of power supplies that have provided power to some VERY expensive UUT's.....we ALWAYS use the remote sensing feature where available. When it's NOT available we measure the drop and offset the voltage setting and let the CV mode of the supply handle the load variations.

[Brian_Beal]

This got off subject at some point.  He was asking about a Labview programming issue, not a hardware issue.  The majority of the posts are responding to his setup, and not the programming.  He never asked for advice on his setup, stated that he is aware of how the power supply works, and only wants programming help.