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NI USB-6221/6229/6251/6259 OEM User Guide 10 ni.com
Power Switch
The power switch on the USB-6221/6229/6251/6259 OEM device powers
the device on and off. Figure 10 shows the pins on the power switch.
Figure 10. Power Switch (USB-6229/6259 OEM Shown)
Pin 1 is connected to VDC through the fuse (reference designator XF1).
The VDC is the voltage provided by the power supply through the power
connector (reference designator J4) and must be 11–30 V, 20 W.
Pin 2 provides power to the circuitry on the USB-6221/6229/6251/6259
OEM device. When the switch is in the On position, the VDC power supply
from pin 1 is routed to pin 2.
Pin 3 connects pin 2 to ground through a 100 kΩ resistor when the switch
is in the Off position. This allows the internal power supply in the
USB-6221/6229/6251/6259 OEM device to safely discharge to ground
when it is powered off. Figure 11 shows a schematic of the switch.
Figure 11. Schematic of the USB-6221/6229/6251/6259 OEM Switch
J4
Provides
Power to
Device
VDC Comes
from Fuse
XF1
Switch
123
45
100 kΩ
SW1
Outer
Shell
SW1
XF1
FUSE
3
Power to
Device
J4
Power
Connector
1
2
100 kΩ