Floating issues on NI 9476 DO

[SVR@]

I am using Ni 9476 Digital output module in Crio 9012 with 4 slot chasis, I am facing a wired problem with all the lines are in off state, i can read 8 vdc on each line across the ground terminal and also when i am trying to switch one line to ON State, it drives adjacent line to ON State. Someone Kindly help me to sort this problem.

Note: I have grounded the chasis, but the problem presist.

I have connected an external power supply to the NI 9476, the positive lead of the power supply to the supply pin, Vsup, and the negative lead of the power supply to the common pin, COM.

[GerdW]

Hi SVR,

did you read the datasheet of the NI9476? Did you look at the circuitry image?

 Those outputs are floating, when you switch off.

When you want to enforce low voltages in OFF mode you need to use resistors connected between each DO and GND…

[SVR@]

Hello GerdW

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@GerdW wrote:

Hi SVR,

did you read the datasheet of the NI9476? Did you look at the circuitry image?

 Those outputs are floating, when you switch off.

When you want to enforce low voltages in OFF mode you need to use resistors connected between each DO and GND…

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Hi GerdW,

Thanks for your reply, i am agree with your commands over floating on D0 9476, also i am facing one more problem when i am trying to switch one channel to ON State, it drives adjacent channel to ON State, I was not able to find the root cause for this issue. Waiting for your reply.

[GerdW]

Hi SVR,

what happens when you use a resistor of ~10kOhm between each DO and GND to avoid floating?

How does your schematic look like? What is connected to those floating DO channels?

How do you measure the voltage on those floating DO channels?

[SVR@]

Hi GerdW,

Kindly find the below answer for your question:

what happens when you use a resistor of ~10kOhm between each DO and GND to avoid floating?

   The Floating Voltage pull down to Zero.

How does your schematic look like? What is connected to those floating DO channels?

 I have connected all the channel to a relay of 24 Vdc, which drives solenoids, Contactor..etc

How do you measure the voltage on those floating DO channels?

 Using Fluke DMM

[GerdW]

Hi SVR,

what happens when you use a resistor of ~10kOhm between each DO and GND to avoid floating? The Floating Voltage pull down to Zero.

That's the answer I gave you right from the start: use a pulldown resistor. And it's the standard solution for floating IO: use pulldown (or pullup) resistors…

[dkfire]

How much current does your relay need to operate? 

Is the DO able to supply that level of current? 

Offen a relay needs more current to operate that a normal DO can supply.