Table 4. Power Switch Pin Descriptions
Pin
Signal
Description
1
VDC In
Connects to VDC through a non-user replaceable fuse (reference
designator F1). The VDC is the voltage provided by the power supply
through pin 2 of the power connector (reference designator J8) and
must be 9 V to 30 V, 20 W.
2
VDC Out
Provides power to the circuitry on the NI USB-7856R OEM device.
When the switch is in the on position, the VDC power supply from pin
1 is routed to pin 2.
3
100 kΩ to
Ground
Connects pin 2 to ground through a 100 kΩ resistor when the switch is
in the off position.
+5 V Power Source
Use the +5 V terminals on the I/O connector 5 V referenced to DGND to power
external circuitry.
Caution
Never connect the +5 V power terminals to analog or digital ground or
any other voltage source on the NI USB-7856R OEM device or any other device.
Doing so can damage the device and the computer. National Instruments is not liable
for damage resulting from such a connection.
The power rating is 4.75 to 5.1 VDC at 0.5 A.
Autonomous Mode
You can run the NI USB-7856R OEM device without a USB connection to a host computer
using Autonomous Mode. To collect data the NI USB-7856R OEM device acquires in
Autonomous Mode, you must reconnect the NI USB-7856R OEM device to a host computer.
Caution
Data is lost and is not recoverable upon reconnection if a DMA FIFO
overflows while the NI USB-7856R OEM device is disconnected from the host
computer or if the NI USB-7856R OEM device loses power at any point.
Autonomous Mode includes the following capabilities.
NI USB-7856R OEM User Manual | © National Instruments | 13
