Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 23)

Chapter 1
Installing Your Controller
1–7
Inductive load devices such as motor starters and solenoids require the use of
some type of surge suppression to protect the controller output contacts.
Switching inductive loads without surge suppression can significantly reduce
the lifetime of relay contacts. By adding a suppression device directly across
the coil of an inductive device, you will prolong the life of the switch
contacts. You also reduce the effects of voltage transients caused by
interrupting the current to that inductive device, and prevent electrical noise
from radiating into system wiring.
The following diagram shows an output with a suppression device. We
recommend that you locate the suppression device as close as possible to the
load device.
OUT 1
OUT 5
OUT 6
OUT 7
OUT 2
VAC/VDC
OUT 0
OUT 3
COM
+ dc or L1
OUT 4
Snubber
ac or dc
Outputs
dc COM or L2
If you connect a micro controller FET output to an inductive load, we
recommend that you use a 1N4004 diode for surge suppression, as shown in
the following illustration.
OUT 1
OUT 5
OUT 6
OUT 7
OUT 2
VAC/VDC
OUT 0
OUT 3
COM
+24V dc
OUT 4
Relay or Solid State
dc Outputs
24V dc common
1N4004 Diode
Using Surge Suppressors