National Instruments NI 6509 - Manual (Page 16)

NI 6509 User Guide and Specifications 16 ni.com
Figure 5. NI 6509 Signal Connections
Protecting Inductive Loads
When inductive loads are connected to outputs, a large
counter-electromotive force may occur at switching time because of the
energy stored in the inductive load. These flyback voltages can damage
the outputs and/or the power supply.
To limit these flyback voltages at the inductive load, install a flyback diode
across the inductive load. For best results, mount the flyback diode within
18 inches of the load. Figure 6 shows an example of using an external
flyback diode to protect inductive loads.
41
43
45
47
67
69
71
73
50, 100
NI 6509
+5 V
+5 V
LED
Port 7
P7<7..4>
Port 0
P0<3..0>
GND
TTL Signal