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KPCI-3160 User’s Manual
Installation
3-17
Wiring I/O to your external circuits
CAUTION
Ensure that both the computer and the external circuits are turned
OFF before making any connections. Making connections while the
computer and external circuits are powered can damage the com-
puter, the board, and the external circuits.
External circuits must properly match the input and output requirements of the board. For exam-
ple, input signals often require pull-up resistors and elimination of contact bounce. The follow-
ing subsection presents pull-up and de-bounce circuits and discusses using +5VDC power from
the board for these and other applications.
Monitoring contact closure at an input
To ensure that the KPCI-3160 reliably monitors an open contact as an input-high condition, con-
nect a 10kW pull-up resistor between the input line and a +5VDC source. See
Figure 3-5
.
Figure 3-5
Contact-closure monitoring at a KPCI-3160 board input
Eliminating contact bounce at an input
The effects of contact bounce may be eliminated by programming in your application software.
However, it is often desirable to eliminate contact bounce from the signal, using a de-bounce cir-
cuit between the contacts and the KPCI-3160 input.
Figure 3-6
shows a typical de-bounce circuit
that can be used with Form C contacts.
Figure 3-6
De-bounce circuit for an input of a KPCI-3160 board
Digital
Ground
+5V
10k
Ω
Digital
Input
#n
External Pull-up Resistor
Switch
KPCI-3160
Board
Digital
Common
GND
+5V
10k
Ω
10k
Ω
TTL
Compatible
AND Gate
To Digital Input of a
KPCI-3160 Board
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