Limit to # of DAQ's and DIO's in .NET?

[MaxdB]

Hi Fellow .NETTER's

Is there a limit to the number of DAQ's and/or DIO's that you can use in the same .NET system?

We are using 4 USB-6008's and 4 USB-6501's in our system.  

We have been struggling with this issue for over 3 weeks now - it is perplexing - for both the programmer who wrote the .NET program and myself (hw guy).

Basically what we have constructed is a 32 Channel Battery Tester using 64 relays (Qty. 4 ER-16 boxes), 32 load resistors, 4 USB-6008's (DAQ), and 4 USB-6501's (DIO).  We eventually expect to be able to simultaneously test 32 of our battery-powered devices in this tester. 

Here are the things that are good!

16 channels work exactly as they are intended to -

• When the battery reaches a full charge, CHARGE_DONE signal goes high.  This signal is read by a Digital Input on the USB-6008.
• The system then transitions to DISCHARGE where the battery is discharged to let's say a 3.0Volt level through a load resistor.
• When the USB-6008 reads the 3.0Volt level, the system then transitions back to Charging again and the entire cycle just repeats over and over.

The problem is that we can only get 16 channels to work at one time.  It is either the upper 16 or the lower 16 channels that work but never both at the same time.

The interesting part is that when the NI USB device ID's are swapped (effectively causing the Software to recognize channels 1-16 as channels 17-32) the 16 malfunctioning upper channels work fine and the lower channels are now the problem children.

I wish I could say that the issue centers around either the USB-6008's or the USB-6501's but it seems to affect both.

What I have observed in normal operation is that when a test channel is first initialized (test is started) the USB-6501 turns on the Charge Relay right away and indicates "Initializing" in the User Interface(UI).  After about a minute it then reports a "Charging" status in the UI.  The charging status remains until the battery fully charges at which point the system will transition to Discharge thus indicating the same in the UI.  This is expected & normal operation.

On a malfunctioning channel, what I observe is that for whatever reason, the USB-6501 does not turn on right after the test is started/channel initialized.  The UI reports "Initializing" status as it normally would.  Then after a minute, the USB-6501 finally turns on the Charge Relay and about a minute after that goes straight into Discharge for no VALID reason as there is no HIGH CHARGE_DONE signal at the repective Digital Input to the USB-6008.

Here is my system configuration:

The PC is a an HP 8200 CMT Elite Desktop:

Intel Core i5-2500 Processor 3.30 GHz ,Intel Graphics Media Accelerator HD,4GB DDR3 1333 Mhz (2x2GB) memory. System is capable of 16GB, 250 GB 7200 RPM SATA hard drive, 16X DVDRW with Lightscribe, Intel 10/100/1000 Ethernet.

Installed NI Software is:

NI IO Trace 3.0.1
NI LabWindows/CVI Run-Time Engine 2010 SP1
NI Measurement & Automation Explorer 5.1.0
NI Measurement Studio Common .NET Assemblies for .NET 2.0
NI Measurement Studio Common .NET Assemblies for .NET 3.5
NI Measurement Studio Common .NET Assemblies for .NET 4.0
NI Measurement Studio Common .NET Language Assemblies for the .NET Framework 1.1
NI Network Browser 5.0.0
NI PXI Platform Services 2.6.2
NI PXI Platform Services 2.6.2 Configuration Support
NI System Configuration Runtime 5.1.0
NI TDM Excel Add-In 3.3
NI Update Service 2.0
NI-1588 Configuration 1.1.2
NI-488.2 3.0.2
NI-DAQmx 9.5.0
NI-DAQmx ADE Support 9.5.0
NI-DAQmx MAX Configuration Support 9.5.0
NI-VISA 5.1.2
NI-VISA Runtime 5.1.2
NI-VISA Server 5.1.0

I would appreciate any and all comments.

I will certainly forward any SW related questions to our awesome .NET programmer..

Thanks for taking time to read about our issue.

[James-K]

MaxdB,

How do you have the USB devices connected to your machine?  Powered USB hub or individual ports?  

[MaxdB]

Hi James,

Good question & insight,

We tried a 7-port powered D-Link USB hub in the beginning and nothing worked correctly after re-booting the PC (Not even the 16 channels worked).  All the USB devices would just set there and power cycle continuously.  It appeared to be a current-sourcing issue.  Looking back, I suppose that if all 7 devices plugged into the hub hit their maximum rated current (500mA) at the same time (3.5 Amps) then it would overwhelm the 3 Amp +5VDC hub power supply.

Since that experience we installed Qty. 2 of the IO Gear PCI USB 2.0 cards into the host PC and we were using them.  But for fault isolation purposes, I switched to the USB ports on the PC itself.  (It has10 built-in USB ports.)  This seemed to make no difference - still, we could only get 16 channels to work at one time.

Thanks for the question,

Max

[MaxdB]

Oh another thing to mention that is along the same line...

Each of the Qty. 4 NI ER-16 relay boxes are externally powered by 2 separate 5VDC 2.4Amp supplies.  Each supply is wired directly to a pair of the ER-16's.

You could certainly run into trouble on the ER-16's and USB-6501's if you try to power them through the external supply on the USB-6501.  There is not enough current available.  From the way the 6501 manual describes it  -  it sounds like you could damage the 6501.

Max

[MaxdB]

Hello - Checking back...does anyone have any other ideas?

[James-K]

Max,

Can you generate and post a MAX technical report (as described here: http://digital.ni.com/public.nsf/allkb/271F252B4EF0A2E0862570E70056A1E4)?