Digital output giving a high signal when off (NI6323 / SCB-68A)

[CE-EM]

Hello,

I'm using a NI-6323 card connected to a SCB-68A board to control a motor using a digital output.

I'm facing an issue when turning off my computer : I actually get a high level (5V) in the Dout and the motor starts running by itself. It looks like the pin is set as a pull-up.

Is there a way to set it as a pull-down?

Did anybody face the same problem?

Thank you for your help.

[CE-EM]

Hello,

I'm using a NI-6323 card connected to a SCB-68A board to control a motor using a digital output.

I'm facing an issue when turning off my computer : I actually get a high level (5V) in the Dout and the motor starts running by itself. It looks like the pin is set as a pull-up.

Is there a way to set it as a pull-down?

Did anybody face the same problem?

Thank you for your help.

[GerdW]

Hi CE,

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@CE-EM wrote:

I'm facing an issue when turning off my computer : I actually get a high level (5V) in the Dout and the motor starts running by itself. It looks like the pin is set as a pull-up. Is there a way to set it as a pull-down?

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According to the specsheet: no.

Why is the motor still powered when you switch off the computer?

Is there no safety circuit in your testbench? This would be the proper way to handle such situations!

[CE-EM]

Thank you for your answer, I understand that I should have safety circuit to avoid any moving parts.
However my questions was more about how to configure the digital output as a pull down to avoid getting a high level on the output when turning off my computer.

Best regards,

[GerdW]

Hi CE,

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@CE-EM wrote:

However my questions was more about how to configure the digital output as a pull down to avoid getting a high level on the output when turning off my computer.

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Options I can imagine:

• Add a safety circuit to enable the testbench only when your computer/executable is actively switching a DO to FALSE
• Wire an additional resistor from DO to GND as a pull-down.
• Switch off the computer as last part of your testbench…

[crossrulz]

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@CE-EM wrote:

However my questions was more about how to configure the digital output as a pull down to avoid getting a high level on the output when turning off my computer.

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This is something that has to be fixed in hardware.  Add a buffer circuit.  There are many buffer chips out there that include an enable line (commonly active low).  You can then add a pull-down resistor on the buffer output going to your motor controller.