Rockwell Automation 1771-QA Stepper Positioning Assembly User Manual - Manual (Page 12)

2–2 Assembly and Installation
Publication 1771-UM002A–EN–P – May 2000
Input switch contacts should be compatible with the voltage and
current levels of the input circuits. The pulse output expander
module will accept inputs from open collector logic devices or
grounded switch contacts, and inputs from the Allen-Bradley
Encoder/Counter Module (cat. no. 1771-IJ, -IK). Refer to section
titled “Module Specifications” for additional input specifications.
Each module in the I/O chassis including the processor or adapter
module draws power from the I/O (chassis) power supply. Some
modules require an additional power source.
I/O Power Supply
Power is supplied through the I/O chassis backplane from the 5V DC
I/O power supply. The stepper controller draws all of its power
(1.75A, maximum) from the I/O power supply. Each pulse output
expander module requires a current of 0.80A maximum. These
amounts (4.15A maximum for a 3-axis system) should be totalled
with the current requirements of all other modules in the chassis so
as not to exceed the maximum output current of the I/O chassis
power supply.
Auxiliary Power Supply
Pulse output expander modules require an additional power source
for switch inputs to the module and for pulse outputs to the stepper
translator and motor. The power source can be separate input and
output power supplies for one, two or three axes, a combined power
source for each axis, or a combined power source for up to three
axes. The power supply must be NEC Class 2 listed. Each input
switch draws 11mA maximum when closed. The maximum output
current for the pulse output expander module is 100mA. Refer to
Appendix A, Module Specifications” for additional information
concerning the auxiliary power supply requirements.
The supply voltage can be any value chosen from 5V DC to 30V DC
required by the user-selected stepper translator and/or the switch
input circuits. The variation in the DC voltage level due to ripple
should not exceed the input specification for the stepper translator
because the supply voltage ripple appears at the output terminals of
the pulse output expander module. Power supplies with 15mV
peak-to-peak ripple can be used. However, check the translator input
specification to ensure that the power supply specifications meet
translator input requirements. The supply may require input filtering
to guard against electrical noise.
Power Supply
Considerations