Allen-Bradley 1747-OC Series, User Manual

Page: 91 / 126

1747-UM001A-US-P - March 2000
Using the Open Controller 7-5
Using the External Watchdog
Contact The watchdog contact output is a solid state switch that can switch a voltage
range of 4.5V dc to 26.4V dc.
You need an external power supply to use the external watchdog. Adjust the
external load switched by the watchdog output to 20 mA or less. The
watchdog output is normally off and turns on as a result of a watchdog
timeout condition. You must adhere to the watchdog output polarization to
guarantee proper operation.
Figure 7.6
External watchdog contact output wiring diagram
A
0
1
2
3
4
5
6
7
B
contact
(side view)
dc or TTL
input module
user
power supply
terminal
identification
common
watchdog contact
Use 22-26 AWG shielded
twisted-pair wire
+ dc
input 0
input 1
input 2
input 3
input 4
input 5
input 6
input 7
- dc (common)
50 cable ft (maximum)
Ground the shields at one end only.
Chassis mounting bolt preferred.
Select resistor for 20mA
maximum current
STATUS
BATT
COM 1
LED 1 LED 2
LED 3 LED 4
COM 2
OC 586 CPU
STATUS BATT
COM 1
LED 1 LED 2
LED 3 LED 4
COM 2
OC 266 PENTIUM CPU
1747-OCF
1747-OCE
Allen-Bradley HMIs