©
National Instruments Corp.
11
FP-DIO-550 and cFP-DIO-550
In this example, the binary mask 10100110 converts to 166.
The following table shows the bits in the pattern value.
The binary value 10000100 converts to 132. To configure this
example, set output channel 2 mode to Set High During Match. Set
the Pattern Match Mask to 166. Set the Pattern Match Value to 132.
Protection for Inductive Loads
When an inductive load, such as a motor or relay, is connected
to an output, a large counter-electromotive force may occur at
switching time because of the energy stored in the inductive load.
This
flyback voltage
can damage the output and the power supply.
It is best to limit flyback voltages by installing a flyback diode
across an inductive load. Typically, you should mount the flyback
diode within 18 in. of the load. Figure 8 shows one channel
connected to an inductive load with a flyback diode.
Figure 8.
Digital Output Circuit (External Power Supply Not Shown)
The [c]FP-DIO-550 contains flyback diodes to prevent excessively
high voltage from damaging the module. National Instruments still
recommends using an external protection circuit across any
inductive load.
Channel
7
6
5
4
3
2
1
0
Bit
1
0
0
0
0
1
0
0
Conversion
×
128
×
64
×
32
×
16
×
8
×
4
×
2
×
1
V
OUT
COM
C
[c]FP-DIO-550
Optocoupler
Output
Protection
V
Flyback Diode
for Inductive Load
Load
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