Chapter 4
SC-2072 Board
© National Instruments Corporation
4-5
SC-207X Series User Manual
Warning:
If the DAQ device does not use pins 33/34 or pins 49/50 for power connections or
if the external power supply is used, set switch S2 to position B. Failure to set
switch S2 to position B under these conditions could result in damage to your
external power supply, the SC-2072 and its breadboarded circuitry, the expansion
board connected to the SC-2072, and/or your computer. National Instruments is
NOT
liable for damage resulting from such connections.
The base model of the SC-2072, the SC-2072, comes with an additional three-position screw-
terminal block that can be used to supply positive, negative, and common (analog ground)
voltage signals to the board. If you have this version of the board and want to install filter
capacitors for the supplies, you can install them in positions C1 and C2 (next to J4). If you
choose to install capacitors in these holes, the capacitors should be high-quality tantalum
capacitors that are rated at least several volts over your power supply outputs. For example, if
you connect
±
12 V to the board, you need capacitors rated for 16 V (the next rating above 12 V).
Install the positive terminal of the capacitor in the hole adjacent to the plus symbol.
The second model of the SC-2072, the SC-2072D, comes with a DC-to-DC converter and
accompanying filter capacitors. On this version of the board, no screw-terminal block is
installed in position J4. Instead of using an external power source to supply power for your
analog circuitry, the DC-to-DC converter converts the +5 V digital power supply into +15 V and
-15 V, therefore supplying a convenient power source for your analog circuitry.
Warning:
If you accidentally short the terminals at J4 or otherwise connect the outputs
from the DC-to-DC converter together, damage to the converter and your
breadboarded circuitry can occur. Because of the power supply fuses F2 and F3,
damage to your external digital power supply, your expansion board, or your
computer is unlikely. Regardless of how such connections might be incurred,
National Instruments is
NOT
liable for damage resulting from such connections.
Fuses and Power LED
The +5 V line is protected by a 1 A fuse, regardless of the S1 switch setting. If you are using an
external digital supply, the digital ground line is also protected by a 1 A fuse. In addition, a
diode is reverse-biased across the ex5 V and digital ground inputs of J1.
Warning:
If you connect your external digital power supply backwards, the diode D1
conducts, therefore limiting the voltage applied to the inputs to about 0.7 V. In
this case, your power supply can go into thermal shutdown or blow a fuse, but
your breadboarded circuitry, your expansion board, and your computer should
not be harmed. National Instruments is
NOT
liable for damage resulting from
such connections.
If you are using the digital supply and the red power LED does not light when the expansion
board or external power supply is powered on, check both the SC-2072 fuses and the output fuse
(if any) on the expansion board or the power supply. More information on connecting power is
given in Chapter 5, Installation and Connections.
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