How can I set the duration of 10 independent TTL outputs using PCI 6503?

[Albe_Ok]

Hi,

I need to control 10 actuators with TTL pulses. The driver for them produces the load for the duration of the input TTL pulse. The needed duration is about 2000 ms. I am wondering if it is possible to use PCI 6503 to produce 10 independent TTL pulses with the controlled duration.

Thanks

[jaced]

Hi,

If I understand what you are trying to do correctly there is a way to perform this execution with your card. As I understand it, you wish to send 10 completely independent control signals from the you 6503. These signals will be changed programmatically at different times during execution. If this is the case, then you should be able to complete this by creating a channel for each line you wish to change and writing to said line at the desired time in your program. This is not the most elegant solution to your issue but it will ensure that each line is controlled independently of the other; another consideration is because you will be using system timing your timing will be controlled by your operating system which may or may not allow the program to execute immediately when it is called. I have attached an Image of how I invision the program flow, you may need to alter this to fit your application exactly.

I hope this helps.

Message Edited by jaced on 10-10-2007 05:45 PM

Message Edited by jaced on 10-10-2007 05:46 PM

[Albe_Ok]

Thanks, JaceD. The timing is not that important since its not ultrafast application. As long as I can software control the TTL output duration to each of 10 output channels independently, it works for me.

[Albe_Ok]

Hi JaceD,

I faced a problem with my PCI-6503 DAQ board. When I write to a digital channel on a particular port, the suggested vi works fine, but the rest 7 channels on the same port are reset. Originally all channels are pulled up to +5 V, I want to keep them like that and selectively write low to a specific channel. I suspect that reset takes place whe DAQmx creates virtual channel to write to and configures the port for digital output. Is there any way to configure all ports for output and set them all to high state and then just write to a particular channel instead of configuring a port every time when writing to it?

I would really appreciate your input.

PS Could it be that another PCI board works better?

Sincerely,

Al

[jaced]

Hi Al,

This appears to be a limitation of the PCI-6503 board which is explained in this document, boards which do not share this issue are listed in the linked article.  You may be able to work around this by writing your data in an array and using one channel for all lines much like the Write Dig Chan.vi example program found in the NI Example Finder>>Hardware Input and Output>>DAQmx>>Digital Generation. My thought is to modify this example to operate much like my previous post in that you will write your data and then reset the lines to a default state. I hope this helps!!