How can i output a constant dc voltage for a user defined time?

[gth656r@mail.gatech.edu]

Hi,

 I am applying a dc voltage to one of the input pins of  PCI 6221  and want to control and output the same for a userdefined time. I am kinda new to Labview and cant figure out how to output a constant dc voltage for a specified user defined time.

Thanx

Urvi

[tbob]

What is the level of the DC voltage and what is the current drain by the device?  This makes a difference whether you need a power supply or can just use a line off of the serial or parallel port.

[devchander]

Hi Urvi,

You want to generate a DC output from an Analog output channel (present on PCI 6221), the value of which is equal to the DC voltage measured on one of the analog input channels if PCI 6221??

have i understood u right?

Regards

Dev

[gth656r@mail.gatech.edu]

Hey Bob and Dev

Thank you so much for replying to my query.

My main goal is to give a user defined dc voltage(range 0 to 5 volts) to an electroplating bath for a user defined time. One approach that I am trying out is applying 5 volts constant dc voltage as an input to the pci card and then attentuating the voltage using Labview (if possible) to make it equal to the user defined voltage. Then outputting it for the specified time.

Is there a better way of doing this?

I also want to know how to measure the time simultaneously while applying the voltage, so that when the specified time is over I can stop applying the voltage.

I do not know the value of the current drain.

Thanks once again,

Regards

Urvi.

[devchander]

Hey Urvi,

This part of your query dodges me

"One approach that I am trying out is applying 5 volts constant dc voltage as an input to the pci card and then attentuating the voltage using Labview (if possible) to make it equal to the user defined voltage. Then outputting it for the specified time."

You can generate a "user defined" DC voltage on an Analog output channel directly.

why are you first measuring a 5V on an input channel??

Does your application require such a cycle?

regards

Dev

Message Edited by devchander on 01-10-2006 01:27 AM

[tbob]

As Dev said, just use an Analog Out board.  Use Labview to control the voltage output and duration of the the analog out.  You can buy Analog I/O boards that plug into a USB port or PCI slot.  The USB versions are usually cheaper.  Measurement Computing makes a USB version for $109.  PCI versions are over $200.  Decide which analog board you want to use, get the labview drivers, study the examples, and you are in business.

[gth656r@mail.gatech.edu]

Hey

Thanks a lot.. It works but when I stop running the vi, the voltage doesnt go to 0 V but the output retains the last value of the voltage. Is there a way of making the voltage return to 0 volts when I stop running the code?

[devchander]

A simple way is just set the AO value to 0 Volts outside the Loop ( if it is continous generation)

Once you stop the loop, Generate a zero value that analog output channel

Regards

Dev

Message Edited by devchander on 01-11-2006 12:47 AM