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4-12 Input / Output
MN1928
4.4.2.2 DOUT8 - DOUT11
Outputs DOUT8 - DOUT11 are driven by a ULN2003 device. The outputs are designed to sink
current from an external supply (typically 24 VDC), but have no overcurrent or short circuit
protection. When an output is activated, it is grounded through the ULN2003.
The ULN2003 has a maximum power dissipation of 900 mW at 25
°
C. The total output
requirements of DOUT8 - DOUT11 must not exceed this limit. The maximum current limit for
an individual output is 400 mA if only one output is in use, reducing to 50 mA if all outputs are
in use. These limits are for a 100% duty cycle.
DOUT8 - DOUT11 are sourced from the same ULN2003 device as the DIR3 and STEP3
outputs (see section 4.5.1), so the current demands of these signals must also be considered.
If an output is driving an inductive load such as a relay, a suitably rated diode must be fitted
across the relay coil, observing the correct polarity. This is to protect the output from the
back-EMF generated by the relay coil when it is de-energized.
Note:
On model NES002-503, DOUT8 - DOUT11 are not available as general purpose
digital outputs. The outputs are used to provide the additional STEP4/5 and
DIR4/5 stepper axes outputs (see section 4.5.1).
DOUT8
NextMove ES
ULN2003
Mint
OUTX(8)
74AHCT244
DGND
GND
Load
supply
24 V
Load
supply
GND
a13
a3
Output Load
(Relay with
diode shown)
Figure 11 - Digital outputs (DOUT8-11) - DOUT8 shown
Servo Systems Co. • 115 Main Road • P.O. Box 97 • Montville, NJ,
07045-0097 • (973) 335-1007 • Toll Free: (800) 922-1103
Fax: (973) 335-1661 • www.servosystems.com
