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Protecting the Relay Control Digital Outputs from Flyback Voltages
If the NI 9683 is switching an inductive or energy-storing device such as a solenoid, motor, or
relay and the device does not have flyback protection, install a flyback diode.
Figure 17. Connecting a Flyback Diode to a Relay Control DO Channel
NI 9683
Selecting a Wire Gauge for Relay Control Digital Outputs
The relay control digital output is capable of sinking 8 A of inrush current for a period of 300 ms
on a 60 second cycle and 500 mA of continuous current. Each channel is functionally isolated
from the other channels and the rest of the board, meaning that each relay control digital output
has a dedicated current return pin.
When using cables, make sure the current rating of the cable is able to handle the expected
current for your application. For example, a typical 28 AWG flat ribbon cable is rated at 225 mA
of continuous current per wire. In order to use the relay control digital outputs at their maximum
current capability, cables within category 24 AWG or lower should be used.
Sourcing Digital Input
The NI 9683 provides connections for 28 simultaneously sampled digital input channels
separated in ports P0 and P1. Ports P0 and P1 are independently powered using separate power
supply pins, VI P0 and VI P1. This allows you to connect the DI to multivoltage systems.
The NI 9683 has sourcing inputs, meaning the DI sources current from the VI P0 or VI P1 to the
sinking output device.The NI 9683 internally limits current signals connected to DI.
Each channel has a DI pin to which you can connect a digital input signal. The supply pins, VI P0
and VI P1, are referenced to the ground of the board. The DI operates in the low range or high
range based on the VI P0 or VI P1 voltage. Refer to the
information about the low range and high range.
You can only connect 3-wire sinking-output devices to the NI 9683. Connect the sinking-output
device to the DI pin and the external power supply lead to the VI P0 or VI P1.
Relay Control DO+
Relay Control DO–
NI 9683 User Guide and Specifications | © National Instruments | 13
Flyback
Inductive
Diode
Device
Specifications
section for more
External
+
Power
–
Supply
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