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Chapter 4
Signal Connections
Wiring Concerns
For the end of travel limits to function correctly, the forward limit must be located at the forward
or positive end of travel, and the reverse limit at the negative end of travel.
Caution
Failure to follow these guidelines may result in motion that stops at, but
then travels through, a limit, potentially damaging the motion system. Miswired
limits may prevent motion from occurring at all.
Keep limit and home switch signals and their ground connections wired separately from the
motor driver/amplifier signal and encoder signal connections.
Caution
Wiring these signals near each other can cause faulty motion system
operation due to signal noise and crosstalk.
Limit and Home Input Circuit
By default, all limit and home inputs are digitally filtered and must be active for at least 1 ms.
You can use MAX to disable digital filtering for limit and home inputs. Figure 4-3 shows a
simplified schematic diagram of the circuit used by the limit and home switch inputs for input
signal buffering and detection.
Figure 4-3.
Limit and Home Input Circuit
Caution
Excessive input voltages can cause erroneous operation and/or
component failure. Verify that your input voltage is within the specification range.
Encoder Signals
The NI 7330 motion controller offers four channels of single-ended quadrature encoder inputs.
All National Instruments power drives and UMI accessories provide built-in circuitry that
converts differential encoder signals to single-ended encoder signals. Each channel consists of
a Phase A, Phase B, and Index input, as described in the following sections.
74FCT244
1 k
Ω
1/
8
W
From the extern
a
l connector
limit
a
nd home
s
witch pin
s
To the limit
a
nd home
s
witch circ
u
it
s
DGND
Vcc
3
.
3
k
Ω
