USB 5V output on computer restart

[gohlke]

I have a computer running Labview that controls two solenoid valves, via TTL logic from a USB-6009.  If one of these sends an output of 5V, then the solenoid controller will open the valve.  All works well as long as the computer is logged into windows, but on computer reboots, the usb-6009 sends a signal to the controller, causing the valve to open.  Once the USB-6009 gets an explicit 0V signal, then the valve closes, but until this happens, the solenoid valve remains open.  In the BIOS, we've disabled restart on power outage to prevent rebooting, but ultimately we would like the system to reboot and go back to its scheduled operation.  In the meantime, we'd like the system to not open if we need to restart the computer for any reason.  Is there anyway to set the USB to send a default 0V, or any other solution that people know of?

[ofahed]

Dunno if that helps, i had the same problem with a 24V IO Box. The way I solved the problem was, i replaced the Optokopplers with some that inverted the output Signal.

[mallorim]

Hi gohlke,

Your USB-6009 does not support programmable power up states as can be seen in the Knowledge Base Document: How do I Set Programmable Power Up States and What Boards Support them? However, the Knowledge Base Document: Can I Use a Pull-down Resistor on My USB-6008/6009 Digital Outputs to Obtain a Logic Low Start-up St... discusses the options you have for addressing the problem.

Hope this helps, Mallori M.

[tyrod]

what kind of solenoid valve would i have to hook up to a USB 6009 daq board if I want it to open and close the valve so that fluids can flow through and be cut off, respectively. Are there any solenoid valves powerful enough to use with fluids but also low-voltage enough to be controlled by a 6009 daq? (these are not very high pressure fluids)

[mallorim]

Hi Tyrod,

While National Instruments does not sell actual transducers like solenoids, I can tell you some details that any thrid party solenoid that you are considering will have to meet so that they will work with a the USB-6009. When operating a solenoid, you would need to use the Digital I/O channels of your DAQ device, both to output digital high and low values to open and close the solenoid, as well as if you are doing any type of position readings. The USB-6009 Digital I/O lines are TTL, which means that they can output a 0-5 V signal, where a 0-0.8 V is a low and 2-5 V is a high.  The best thing to do with regards to the voltage and current capabilities of the USB-6009 is to check out the Source/Sink discussion on page 21 of the USB-6009 User Guide and Specifications.

A real discussion point is that the USB-6009 does not have hardware timed digital I/O. This means that you can output high and low values, but these will only update with software timing (when the processor gets to executing that peice of the program). These outputs will therefore be dependent upon the operating system's clock. To really have a deterministic output you will need to look to other pieces of Digital I/O hardware, described below. 

With regards to controlling solenoids, the USB-6009 is not going to be the NI Recommended hardware. Since solenoids are in essence electromagnetic switches, most require a high and low voltage signal as an indication of when to open and close. National Instruments' line of Digital I/O products, like the 6509, 6514,6515, and 6528 and for C Series something like the NI 9475, will be the ideal hardware to use with solenoids. They can used a Hardware-timed output to deterministically generate the high and low values needed to operate a solenoid.

I hope this helps to clarify things,

Mallori