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DATA-LINC GROUP
5
DDAA1000/SRM User Guide
PN 161-09981-002C
rev 8/04
Discrete Operation
Requirements
1. The outputs of the units cannot directly drive a relay. The digital outputs are open collector current sinking to the
common ground. An external power supply must be used to provide DC power to any relays.
2. The maximum voltage on the relay driver outputs is 24 VDC.
3. Ensure that the pull up voltage is sufficient for your relay. i.e. a 12 VDC relay needs 12 VDC, a 24 VDC relay needs 24
VDC.
4. Each digital output can sink up to 100 mA for the purpose of controlling the relay coil.
5. If driving inductive loads, place a voltage suppression diode across the relay coil.
6. There is one common ground for all input and output connections.
Connections
The discrete connection to the device is made via the terminals labeled “Contact Closure Input” and
“Contact Closure Output.” The digital input expects a dry contact, such as a switch or even just a jumper wire.
The output is open collector. The following diagram illustrates the output drive circuit connection for a discrete unit.
Figure 3: Simplified Open Collector
DDAA1000
Output
Output
1,2,3...,8
Common
DC Supply
+ -
Customer
Supplied
Relay