Control analog solid state potentiometer with Labview

[pfrymier]

I want to use an NI 6221 USB to control a 100 ohm potentiometer.  I am trying to replace a manual potentiometer that controls a power controller for a high watt light source.  The potentiometer is rated at 2 watts but may not actually be drawing that much power.  I have 2 analog output channels on the 6221 and 24 DIO channels.   I know only basic electronics.  I prefer something turnkey that would take a analog signal from the 6221 and control a resistance.  Can anyone give me any tips about how to accomplish this?

Thanks in advance.

[KateB]

Hi pfymier,

Since you need something turn key, replacing potentiometer with digital potentiometer would be an option.

However, if you don't need any third party stuff, I cannot think of a turn key solution so far.

Regards, Kate

[pfrymier]

I have looked into this further upon KateB's suggestion.  I have found the device I probably need is a digital potentiometer as KateB suggested, but I have been unable to find one that would be controlled via LabView.  I have determined that controlling it via an analog output channel on the 6221 is probably not the way to do it.  All the digital potentometers I've seen use some sort of serial communication.  I will probably therefore use either the serial or USB interface on a computer and a program to send commands to the digital potentiometer.  One product that looks promising is:

http://www.controlanything.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=UPOT8ProXR&Category_C...

I am not sure if I will be able to use LabView to control it although I am sure it can be done. 

If anyone knows of a similar product that comes with a LabView driver, that would be the perfect solution.  It would save a lot of time figuring out how to get Labview to write some simple commands to a communications port .  I'm sure this is very doable, maybe even simple, but I have reached the point that I prefer to throw money rather than time at the problem.  I advise several graduate students but none seem adept and really getting under the hood of LabView.  I had to do this as a graduate student and I am sure I could figure it out, but time is more precious now.  So if a company sells a product with LabView driver VIs so that I can plug it in and just start writing instructions in LabView, that would be ideal.

Thanks in advance.

[dansch]

Hi pfrymier.

I think you are on the right track with the digital potentiometer, unfortunately I have not seen one that can be directly controlled with LabVIEW. I have seen some companies which have communications chips that can be controlled through a serial port using LabVIEW, and this comm chip then interfaces to the potentiometer chip using SPI or I2C. However, it seems like the solution you linked in your last post is probably the simplest solution. While there is not a driver already made for this device (that I can find), a quick browse through the manual shows the ASCII commands used to control the potentiometer on page 43. It appears that there are only a few possible commands, and that it should be pretty straight-forward since the device appears to the computer as a COM port. Thus, once the device is connected to the computer and shows up in Measurement & Automation Explorer (as a COM port), you should be able to run a basic VISA example program and write the corresponding ASCII characters to the device. While this is not an out-of-the-box solution and may be beyond what you are willing to develop, using VISA functions in this way should make it quite simple to communicate to the device. Please let us know if you come across a more ideal solution or if you go this route and get everything working. Thanks,