Allen-Bradley PLC Families Explained: How to Choose & Source the Right Logix Controller

If you have ever stared at a wall of Allen-Bradley catalog numbers trying to work out which controller you actually need, or scrambled to replace a PLC that your distributor no longer stocks, you are not alone. The Allen-Bradley PLC families span five active and legacy ranges and hundreds of catalog numbers, and the part you need may be new, mature, or long out of production. This guide does two jobs. First, it helps you choose the right family for your application. Second, it shows you how to source the exact controller, including discontinued units. At SZCT we quote the full Allen-Bradley range, new, refurbished, and surplus, so once you know what you need, getting it is the easy part.

1. Allen-Bradley PLC families at a glance

Allen-Bradley is the controls brand of Rockwell Automation, and most current controllers run on the Logix architecture. Three software ecosystems matter for your decision: Studio 5000 programs CompactLogix and ControlLogix, RSLogix 500 programs the legacy MicroLogix and SLC 500 lines, and Connected Components Workbench (CCW) programs Micro800. They share EtherNet/IP as a common network. The software is a real constraint, not trivia. Moving from an RSLogix 500 controller to a Logix one means rewriting your program, not just swapping hardware.

Here are the families you will actually meet, arranged from standalone to plant-wide:

• Micro800: the modern entry-level and standalone choice.
• MicroLogix: compact and legacy, still running on thousands of lines.
• CompactLogix: the mid-range workhorse for machines and production lines.
• ControlLogix: high-performance control for whole plants.
• SLC 500 and PLC-5: legacy platforms you meet only on existing installations.

Lifecycle is indicative, so confirm current status at Rockwell before you commit. One note on naming: Micro800 and MicroLogix are different families, not two names for one thing. Micro800 is the current line on CCW, and MicroLogix is the older line on RSLogix 500. Mixing them up is the most common Allen-Bradley mistake.

2. Quick decision: which Allen-Bradley PLC do you need?

Three questions narrow the field fast:

• How big is the application? A standalone machine, a mid-size line, or a whole plant.
• What I/O and communication do you need? Local I/O only, EtherNet/IP, motion, or integrated safety.
• What are your budget and lifecycle constraints? A clean new build, or a like-for-like replacement on an existing line.

Map your answers like this:

• Standalone machine, modest I/O, cost-sensitive, no plant network: Micro800 (Micro850 or Micro870).
• Mid-size machine or line, EtherNet/IP, some motion or safety, tag-based programming: CompactLogix 5380.
• Plant-wide control, high I/O count, redundancy or high availability, large motion: ControlLogix 5580.
• Replacing an SLC 500 or PLC-5: CompactLogix for SLC 500, ControlLogix for PLC-5.
• Any of the above with a safety requirement: the GuardLogix version of CompactLogix or ControlLogix.
• Keeping an existing MicroLogix line running: source the original where you can, or migrate to Micro800 or CompactLogix.

A worked example: a packaging OEM building a standalone case erector with around 20 I/O points and no plant network does not need Logix. A Micro850 covers it at a fraction of the cost and programs in free software. If you are weighing two families, the deep dives below will settle it. If you would rather skip ahead, send us the application and we will spec it.

3. Micro800 family: the modern entry-level and standalone choice

Micro800 is Rockwell's current entry-level and standalone platform. It programs in Connected Components Workbench (CCW), which is a free download, so software cost stays out of the equation. Catalog numbers start with 2080-.

The main models, smallest to largest:

• Micro810: a nano controller and smart-relay replacement.
• Micro820: compact, with embedded Ethernet and a microSD slot, suited to remote and light data-logging duties.
• Micro830: an expandable standalone controller for general machine control.
• Micro850: more I/O and communication options, the workhorse of the line.
• Micro870: the highest capacity and the most expansion, for larger standalone machines.

Choose Micro800 for a standalone machine where cost matters and you do not need to live inside a plant-wide Logix architecture. Do not choose it when the machine must integrate into a Logix plant on Studio 5000 tags, or when it needs heavy motion or integrated safety. In those cases, step up to CompactLogix. The most common mistake here is reaching for MicroLogix out of habit when Micro800 is the current equivalent, or picking Micro800 when the project actually calls for Logix integration.

4. MicroLogix family: compact, legacy, still everywhere

MicroLogix is the previous-generation compact line. It programs in RSLogix 500, not Studio 5000, which matters for any retrofit. It still runs on thousands of machines worldwide, so even though it is winding down, you will keep meeting it.

The lineup:

• 1000 (1761-): a fixed nano controller.
• 1100 (1763-): adds embedded Ethernet and an LCD.
• 1200 (1762-): expandable.
• 1400 (1766-): the most capable, with Ethernet, the flagship of the line.
• 1500 (1764-): an older modular design.

Lifecycle reality and what it means for buying

Rockwell has retired this family model by model. Based on current public lifecycle information, the 1000, 1200, and 1500 are discontinued, the 1100 has been pushed out of standard distribution, and the 1400 is the last MicroLogix still in production, now in its mature phase with a migration flyer in the box pointing toward Micro800. Channel status and stock keep shifting, so confirm the current lifecycle stage before you commit. The procurement takeaway is simple: as new stock thins out, new-old-stock, refurbished, and surplus become the realistic way to keep a MicroLogix line running.

Need a discontinued MicroLogix?

A 1100, 1200, or 1500 is rarely available new through standard channels anymore. We source these as new-old-stock, refurbished, or surplus, tested and warranty-backed. Send the catalog number for current stock and lead time.

Request a Quote

Picture a maintenance engineer replacing a failed 1400 on a ten-year-old line. They want the same part, not a redesign. Sourcing the original controller avoids reprogramming and re-validation.

5. CompactLogix family: the mid-range workhorse

CompactLogix is the mid-range Logix family for machines and production lines, programmed in Studio 5000. Two generations matter:

• 5370 (1769-L1/L2/L3): the earlier generation, sized small, medium, and large, using 1769 Compact I/O. Still in service, but superseded.
• 5380 (5069-L3): the current platform, built around Compact 5000 I/O and EtherNet/IP, with higher performance. This is the one to specify for new designs.
• 5480: a 5380 variant with an integrated Windows environment for combined control and edge computing. A niche choice for specific workloads.
• GuardLogix 5380: integrated safety to SIL 2 and SIL 3 in the same family.
• Compact 5000 I/O (5069-): the modern I/O platform that pairs with the 5380.

Choose CompactLogix for mid-size machines or lines that need tag-based programming, EtherNet/IP, and some motion or safety, but not plant-wide scale. For a new build, specify the 5380, not the older 5370, so you are not designing onto a maturing platform. CompactLogix is also Rockwell's migration target for SLC 500, which we cover in the lifecycle section.

6. ControlLogix family: plant-wide, high-performance control

ControlLogix is the high-performance family for plant-wide control. It lives on the modular 1756 chassis and programs in Studio 5000.

• 5570 (1756-L7): the earlier generation, now maturing.
• 5580 (1756-L8): the current high-performance controller, with large I/O capacity, integrated motion, and a 1 Gb EtherNet/IP port.
• GuardLogix 5580: integrated safety in the same chassis.
• ControlLogix Redundancy: a genuine differentiator at plant scale, for processes that cannot tolerate downtime.
• 1756 chassis: modular, with a wide range of communication and I/O modules for backbone duty.

Choose ControlLogix for plant-wide control, high I/O counts, redundancy or high availability, large motion systems, or a controller acting as the integration backbone. ControlLogix versus CompactLogix in one line: pick CompactLogix for a machine or line, and pick ControlLogix when one controller has to run the whole plant, needs redundancy, or carries a very high I/O count. The cost step up is real, so size it to the job rather than over-spec by reflex.

7. Side-by-side comparison: full spec table

Use this table to verify specifics across the families in one place.

That covers how to choose. The rest of this guide covers how to lock down and buy the exact controller, starting with the catalog number printed on the label.

8. How to read Allen-Bradley catalog numbers

The bulletin number, the digits before the dash, tells you the family at a glance:

Now a worked example. Take 1756-L83E. The 1756 puts it in the chassis-based ControlLogix family. The L8 marks it as a 5580-series controller. The 3 indicates the memory tier. The E indicates the EtherNet/IP-capable variant. So a single string tells you family, series, memory size, and built-in communication.

One honest caveat: the bulletin prefix is the reliable signal. Suffix meaning varies from family to family, so the only way to be certain you are ordering the exact controller and firmware is to match the full catalog number, not just the series name. If you are not sure what you are holding, look it up in our Allen-Bradley Model Library or send it to us and we will identify it.

This is not academic. The full catalog number is what gets you the right part, the right firmware, and an accurate quote. Asking for "a ControlLogix 5580" leaves room for the wrong memory or comms option. Asking for 1756-L83E does not. The classic mistake is ordering by series name and receiving a controller with the wrong firmware or I/O variant.

9. Lifecycle status and migration paths

Rockwell uses four lifecycle stages: Active (current, fine for new installs), Active Mature (still produced and supported, but a newer family exists), End of Life (production ending, with a defined support window), and Discontinued (no longer produced). Status changes over time, so confirm at Rockwell's lifecycle pages before you decide.

The main migration paths:

• SLC 500 migrates to CompactLogix (5380). Rockwell offers conversion systems that reuse existing wiring to cut the changeover effort.
• PLC-5 migrates to ControlLogix.
• MicroLogix migrates to Micro800 or CompactLogix, depending on whether you need standalone simplicity or full Logix integration.

Here is the nuance most guides skip: migration is not the only option. Two strategies are both valid, and the right one depends on your situation.

• Migrate when you are starting a new project or running a major upgrade and can absorb the reprogramming and re-validation.
• Extend the existing platform when you need a like-for-like replacement, the process is already validated, or downtime and budget rule out a redesign. In that case, sourcing the original controller as new-old-stock, refurbished, or surplus is the right call, and usually the faster and cheaper one.

If you are on the extend path, the next section is for you.

10. New, refurbished, or surplus? Sourcing Allen-Bradley PLCs the right way

There are three ways to buy an Allen-Bradley controller, and each fits a different situation.

• New: factory-sealed, current production, bought through standard channels. Right for active families and new builds.
• Refurbished: tested and reconditioned units, backed by warranty. Right for discontinued or hard-to-find parts, or to control cost on active ones.
• Surplus and new-old-stock: unused units from excess or cleared inventory, often the only route to a long-discontinued controller.

Counterfeit and mislabeled Allen-Bradley parts are a real risk on the secondary market, so vet any refurbished or surplus supplier against a short checklist:

• Is each unit tested before shipment, and can they show you the result?
• Is it backed by a warranty, and for how long?
• Can they trace the part and show actual photos, not stock images?
• Will they confirm the exact catalog number and firmware before you pay?
• What are the return terms if it does not fit?

Picture a line down on a Friday, the failed controller discontinued, and a genuine replacement needed before the next shift. That is exactly where a specialist with tested surplus and refurbished stock beats waiting on a back-ordered new unit. SZCT supplies new, refurbished, and surplus Allen-Bradley controllers, tests them before shipment, backs them with warranty, and ships worldwide, including the parts that are no longer easy to find.

11. How to get an accurate Allen-Bradley PLC quote

To get a fast, accurate quote, send us a few details:

• Catalog number(s), the full string, for example 1756-L83E
• Quantity
• Condition preference: new, refurbished, or surplus
• Firmware or revision, if your application requires a specific one
• Destination country, since it affects lead time and any compliance requirements
• Timeline or urgency

Each item earns its place. The catalog number removes ambiguity, the firmware affects compatibility, and the destination country affects lead time and shipping. With these in hand, we return pricing, stock, and lead time within 24 hours.

You can copy this straight into a message: "Please quote: [catalog number] x [quantity], [new / refurbished / surplus], to [country], needed by [date]."

Reach us by WhatsApp, email, or Request a Quote. No obligation, and no pressure.

FAQ

 

 

What is the difference between MicroLogix and CompactLogix?

MicroLogix is the legacy compact line on RSLogix 500, mostly retired. CompactLogix is the current mid-range Logix family on Studio 5000, with more performance, EtherNet/IP, and tag-based programming. For new mid-size machines, CompactLogix is the choice.

Is the MicroLogix family discontinued? Can I still buy the 1100 or 1400?

Most of the family is retired. The 1400 is the last model still in production, in a mature phase, while the 1100, 1200, 1000, and 1500 have largely left standard distribution. You can still buy them through new-old-stock, refurbished, and surplus channels. Send us the catalog number for current availability.

What software does each Allen-Bradley PLC family use?

Micro800 uses Connected Components Workbench (CCW), which is free. MicroLogix and SLC 500 use RSLogix 500. CompactLogix and ControlLogix use Studio 5000.

What replaced the Allen-Bradley SLC 500?

CompactLogix, and the 5380 in particular, is Rockwell's migration target for SLC 500. Conversion systems reuse existing field wiring to reduce the changeover. If a full migration is not practical yet, you can keep SLC 500 lines running with sourced original parts.

ControlLogix versus CompactLogix, which one for my plant?

Choose CompactLogix for a single machine or line. Choose ControlLogix when one controller has to run the whole plant, needs redundancy or high availability, or carries a very high I/O count. ControlLogix costs more, so match it to the scale of the job.

Where can I buy discontinued or hard-to-find Allen-Bradley PLCs?

From a specialist that carries new-old-stock, refurbished, and surplus inventory and tests before shipment. SZCT sources discontinued Allen-Bradley controllers worldwide. Request a Quote with the catalog number and we will check stock and lead time.

Choose with confidence, then source the exact part

You now have both halves of the decision. You can match an Allen-Bradley family to your application, from a Micro850 on a standalone machine to a ControlLogix 5580 running a plant, and you can read a catalog number well enough to order the exact controller, including the discontinued ones.

If you are still choosing, browse our Allen-Bradley PLCs category and Model Library. If you already know what you need, send the catalog number and we will return pricing, stock, and lead time within 24 hours, by WhatsApp, email, or Request a Quote.