Prevent device automatically run when computer restart

[wsl_alan]

I'm using the labview program with severial Daq to control a system with valves and pumps (controled by velay with Daq). I notice when the computer restart with the Daq connected with PC, all the pumps will automatically run just after the computer restart. Or if the PC is on and the Daq is not connected to PC, the pumps will on after I plug the Daq to PC. I can solve this after I run my program in Labview. But I'm afraid that the power shut off will hurt the instrument, as I cannot always look at instrument. Is there any way to left the Daq keep off in the control wire when the PC restart?

[RavensFan]

Without knowing what the devices are or in what manner they are wired to the DAQ device (analog, digital, inverted digital logic?), it is hard to say.

But when you real life equipment that is affected by the whims of the computer, then you need to provide alternative means to protect that equipment.

Your pumps should have an e-stop switched wired in line with them so that you can turn them off without having to rely on the computer.  e-stops are normally closed switches wired in series with your control lines that drive that relay.  When you hit them, they latch to an off condition stopping the pumps no matter what the computer is doing.  When your equipment is not being used, then you should hit the e-stop or turn off the power to those pumps.

Also, what is causing the computer to restart?  Control PC's should be set up in a way that they won't restart due to software updates or the whims of the IT department.  They should be on a battery backup power supply so they can't just turn off and turn on in the event of a power outage.

[wsl_alan]

Thanks. I'm using the USB-6008 Daq and control my device to turn on/off through digital signal. Does the daq automatically provide the digital signal when it plug to an opened PC or when the PC just restart without controled by Labview? Is it a default setting? Can I change this default setting to off when plug in the PC? As it's for remote control, the power condition might be hard to imagine. 

[PalanivelThiruvenkadam]

You can change the Hardware Connection to NO (Normally Open). whenever you are providing Signal via DO, then it should power ON

[wsl_alan]

I'm using a relay connected with daq to control the power on/off. Does the Hardware Connection you mentioned means relay or Daq? Thanks.

[GerdW]

Hi alan,

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@wsl_alan wrote:

Thanks. I'm using the USB-6008 Daq and control my device to turn on/off through digital signal. Does the daq automatically provide the digital signal when it plug to an opened PC or when the PC just restart without controled by Labview? Is it a default setting? Can I change this default setting to off when plug in the PC? As it's for remote control, the power condition might be hard to imagine. 

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Why don't you read the manual for your USB6008? It is very specific on the hardware behind the DIO pins and the power-up states!

When you want more control over your hardware setup, even when PC reboots, then you need to build more (external) safety circuits!

Idea:

1. Use one more DO pin to drive one more relay.
2. Use the NC (Normally Closed) output of the relay to switch the power supply your hardware.
3. When your PC reboots the DO becomes HIGH (due to pullup resistor) and the relay opens: power supply switched off.
4. When your software runs it can set that DO to FALSE to have the relay fall back to NC state…