Rockwell Automation 999 IMC S Class Compact Motion Controller (Cat. No. 4100-999-122) - Manual (Page 70)

4-28 Installation and Hookup
Publication 999-122 - January 1997
Use a clean 5V power supply for 5V registration sensors or a clean 24V
power supply for 24V sensors. Do not use the 24V DC power supply
connected to the IMC-S/23x for the axis-specific discrete I/O.
Using the Registration Inputs
The registration inputs on the IMC S Class are the most sensitive
discrete inputs on the motion controller. Since they are used to latch
axis position within 1 µs, they employ a faster optocoupler and are not
filtered for switch bounce like the home, overtravel, and drive fault
inputs. In applications which use a similarly fast registration sensor,
this is not usually a problem. However, in some applications, the fast
response and lack of filtering mean that extra precautions must be taken.
Since the registration inputs are–and have to be–sensitive because of
their function, it is best to treat them not like discrete inputs but as you
would treat a sensitive analog input. The registration inputs are floating
(not referenced to any common) and are thus similar to a differential
servo amplifier or encoder input. As with a servo amplifier or encoder
input, best results are obtained by using shielded twisted-pair cable for
all registration wiring as shown previously.
The registration input current is 2.5 mA when the input is activated.
While this is a reasonable current for most 5V devices (the marker
channel on an encoder for instance), it is quite low for typical 24V
devices, making them more susceptible to interference. For these
devices, the on current can be raised by a 470
Ω
shunt resistor across
the registration inputs, as shown below.
This resistor increases the current drawn from 24V registration sensors
to over 50 mA. If your registration sensor can handle more on current,
you can use lower resistance values, but be sure to check the power
dissipation of the resistor and size it accordingly. Install the resistor as
close to the end of the 4100-CCAxxF cable assembly as possible.
!
ATTENTION: Use a clean 24V power supply for
24V sensors; do not use the general purpose I/O power
supply.