Hardware Comparison: CompactLogix, ControlLogix and GuardLogix

CompactLogix, ControlLogix, GuardLogix

With the current trend in machine safety being moving towards integrated control and safety functions, Allen Bradley (like most other major suppliers) offers two versions of its main control platforms, the Logix line of controllers. Based on application size and complexity, facilities will use either the CompactLogix or ControlLogix controller platforms for control. Adding safety features onto these controllers, Allen Bradley offers the Compact GuardLogix and GuardLogix (ControlLogix) functional safety rated controllers. As these controllers are updated and improved, there have been several generations of safety rated controllers. With a future trend towards integrating data, safety, and control into one unit for increased productivity, we will continue to see improvements, both evolutionary and revolutionary.

The ControlLogix (1756 family) and CompactLogix (1768, 1769, and 5069 families) Programmable Automation Controllers are the primary controllers in Allen Bradley’s offering. The differences between the two are seen in the performance specs for the controllers, as the ControlLogix is designed for large, complex applications while the CompactLogix is designed for smaller, less complex ones. As an option to the ControlLogix, GuardLogix controllers add a separate safety controller to the processor unit. The GuardLogix, and specifically the 5580 GuardLogix controllers, are a standard 5580 ControlLogix controller with an additional processor and programming dedicated to safety tasks. While the ControlLogix comes in 3MB-40MB memory sizes, the GuardLogix is limited to 3MB-20MB of standard memory, although with an additional 1.5MB-6MB of memory allocated to safety tasks included. The upgrade to a GuardLogix processor allows for two things, the control of automation functions and the simultaneous control of safety functions, all in one processor unit. Prior to the 5580 series, a safety partner was required for GuardLogix controllers, meaning two separate processor cards were needed if you wanted to do integrated safety. With the 5580 series, a reduced safety certification can be achieved without a safety partner, allowing for all but the highest levels of safety to be achieved with a single processor unit. With a single 5580 GuardLogix processor, SIL2/PLd levels of protection can be achieved. As this safety level covers most risks, the offering of a single processor safety solution was brought about. This lower price point allows more solutions to utilize integrated safety, where the second processor would have driven the cost to an unacceptable level.

The CompactLogix (1769 and 5069 family) and the CompactGuardLogix have a similar relationship as the ControlLogix and GuardLogix controllers. Each Compact GuardLogix controller is a standard CompactLogix controller with an additional safety controller included. Without an available safety partner, the CompactGuardLogix is rated up to SIL2, PLd, Cat3. For smaller systems that don’t require the highest levels of safety, the CompactGuardLogix is an excellent choice of a controller.

Why GuardLogix?

Why GuardLogix, you may ask? Integrated Safety and Control has numerous benefits to automation and manufacturing engineers. The integration of safety functions into the control system, instead of separating them, allows for improved diagnostics, increased coordination between control and safety functions, and improved reaction times and reaction modes for safety incidents. GuardLogix controllers allow you to incorporate safety IO into your control system, reducing wiring required for safety circuits. GuardLogix allows engineers to design control systems that incorporate safety functions into the control directly. The GuardLogix safety program is separated from the control program, but the tags in the safety program can be used in the control program, and the tags in the control program can be imported into the safety program. This programming functionality allows programmers and designers to use the proper IO point for the proper input or output and reduces the need for extra wiring for safety functions. It also allows the operator interface to display more information regarding the safety system, and easier control of the safety system from the operating stations, again with no extra wiring.

One of the greatest benefits of the newest systems is the availability of a non-motion safety controller. Previous versions of the GuardLogix controllers required motion to be included if you wanted safety. Now, there is a safety-only option. The benefit to this is that for a much more manageable cost (10% instead of 30% additional), you can have a controller that is integrated-safety ready. With the cost benefits of the new Logix family memory usage, the addition of future upgrades to safety without having to replace a controller is an excellent option to look at.


The Logix families of controllers – especially the newest ones – are an excellent merging of the future of integrated safety with the present of outstanding controls. With new options that reduce the cost and new techniques that integrate the safety functions more seamlessly into the control system, the difference between a standard and a GuardLogix controller is slowly diminishing. As these differences disappear, the reasoning to not use a GuardLogix controller will disappear as well.

ControlLogix and GUardLogix Comparison
Specification 5580 ControlLogix 5580 GuardLogix
User Memory 3MB – 40MB 3MB – 20MB standard 1.5MB – 6MB Safety
Controller Tasks 32 Tasks, 1000 Programs per task 32 Tasks, 1000 Programs per task
Built In Comms Ports (1) USB, (1) RJ45 Ethernet/IP (1) USB, (1) RJ45 Ethernet/IP
Comms Options Ethernet/IP ControlNet DeviceNet Data Highway Plus Remote I/O SynchLink 3rd Party Process and Device Networks Ethernet/IP ControlNet DeviceNet Data Highway Plus Remote I/O SynchLink 3rd Party Process and Device Networks
Node Capacity 100-300 Ethernet/IP Nodes 100-250 Ethernet/IP Nodes
Redundancy Planned future Not supported
Integrated Motion Ethernet/IP Analog SERCOS Ethernet/IP Analog SERCOS
Standard Task Programming Language Relay ladder Structured text Function block Sequential Function Chart Relay ladder Structured text Function block Sequential Function Chart
Safety Certification   SIL2/PLd (Cat3) standalone SIL3/Ple (Cat4) with Safety Partner
Safety Comms Options   Ethernet/IP ControlNet DeviceNet

CompactLogix Specification Comparison
Specification CompactLogix (1769) Compact GuardLogix (1769) CompactLogix (5069) Compact GuardLogix (5069)
Controller Tasks 32, 1000 programs/task 32, 1000 programs/task 32, 1000 programs/task 32, 1000 programs/task
User Memory 1MB-5MB (L3) 1MB-5MB Control 0.5MB-1.5MB Safety 0.6MB-10MB 0.6MB-10MB Control 0.3MB-5MB Safety
Built In Ports Dual Port Ethernet USB Dual Port Ethernet USB Dual Port Ethernet USB Dual Port Ethernet USB
Communication Options Ethernet/IP DeviceNet USB Client Ethernet/IP DeviceNet USB Client Ethernet/IP DeviceNet USB Client Ethernet/IP DeviceNet USB Client
Max Network Nodes 16-80 16-80 16-180 16-180
Redundancy Backup via DeviceNet Backup via DeviceNet None None
Integrated Motion Ethernet/IP Ethernet/IP Ethernet/IP Ethernet/IP
Conformal Coating Available Available Available Available
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