Hardware Comparison: Micro800 vs. MicroLogix PLCs

We are living in an ever-connected world.  It is expected that by 2025, there will be over 75 billion connected devices worldwide.  And while personal gadgets, smart homes and smart cities account a large part of those devices, there is an equally fervent push to digitize and automate factories as well.  One estimate states that by the end of 2020, 80% of manufacturing companies will adopt some type of IoT technology.  And the same urgency of adoption is taking place in utilities, transportation and logistics.

In the industrial, warehousing and utilities sectors, much of this control is aimed at empowering the automation of equipment to perform tasks at a faster, more accurate and more productive rate.  And this equipment needs control systems and ever improving control technology to adapt to these new requirements.

It is easy to assume that these requirements involve large and complex buildouts connecting an entire factory or enterprise.  And while that is certainly the case for larger companies, there is still the need for small, compact control systems that provide the same level of control as their larger cousins but are built smaller for a variety of reasons.  The need for smaller, or even standalone, control systems include:

• Cost Effectiveness – Companies may wish to implement better control systems incrementally to reduce cost or spread it over time.
• Automation Strategy – Many companies do not have the capital at their disposal for a sweeping control and automation expenditure.  Instead, they may move forward in phases starting with the most necessary equipment that will deliver the biggest ROI.
• End Use – While complex process manufacturing operations are common, a large percentage of manufacturing and warehousing operations are small businesses or those whose product is accomplished on a few machines that are easy to automate.  They may also be used in equipment that requires little or no communication.

MicroLogix and Micro 800 Family Products for Standalone or Small Footprint Control Needs

The MicroLogix controller family has been in service for over 20 years.  Small in design and footprint, they were designed to be used in standalone environments, yet could grow as the enterprise grew providing robust and rugged features such as embedded I/O circuitry in in the controller’s base. 

Their communications channel allows for simple connections to PCs for full-duplex protocols and for tasks such as uploading and downloading. While the MicroLogix 1000 and 1500 are now obsolete, the 1100, 1200 and 1400 are still in service. 

Introduced in 2011, the Micro 800 Allen-Bradley family represented a completely different architecture and platform than the MicroLogix controllers and is designed specifically for standalone equipment.  Envisioned as a product to allow flexibility in purchasing what was needed without unwanted functionality for those types of machines, Micro 800 family products allow users the benefits of a micro PLC at a price comparable to a smart relay.

While the Micro 800 isn’t specifically a replacement for the MicroLogix family, and they are considered two distinct product lines.  However, as two variants of MicroLogix has already been obsoleted, migration to the Micro 800 family is often an option when considering replacements, especially when taking today’s automation requirements into account. 

Comparing MicroLogix and Micro 800 Features

There are several different variants within each family.  However, given the obsolescence of the MicroLogix 1000 and 1500, they are excluded from the following comparison.

Communication

The MicroLogix 1100, 1200 and 1400 all have a single 8-pin Mini DIN.  However, on the 1100, it is in combo with the RS-485 port and the 1400 also has a single 9-pin D shell. The 1100 and 1400 also have single 8-pin mini-DINs for RS -485 ports.  None of the MicroLogix family has USB connectivity. 

Lending itself to modern connectivity application and ease of use, the Micro 800 family 810, 830, 850 and 870 all have USB 2.0.  The 820 has a 10/100 Base T ethernet port and RS232/RS485 non-isolated combo serial.

Both Family groups use Modbus RTU protocols where, except for the 810, the Micro 800 group can use ASCII/Binary and CIP Serial along in addition to Modbus RTU server/client.  This group also allows Modbus TCP. The MicroLogix group, however, is more flexible in its available protocols allowing DF1 half-duplex server/client, as well as ASCII.  All three have 1761-NET-ENI ethernet/IP.

I/O Capabilities

One advantage of MicroLogix over Micro 800 is the number of I/O available.  The MicroLogix 1100 has 16 embedded with up to 144 expanded while the 1200 has up to 40 I/O with up to 136 expanded.  The 1400 has up to 32 but can expand to as many as 256 I/Os.

The Micro 800 family has a smaller number of embedded I/Os with the low end of 12 for the 810 and as high as 48 on the 48 pin 850.  The most flexible member of this group is the 830 with four pin options of 10,156, 24 and 48.  The 820, 830 and 850 have the capability of plug in modules to allow additional digital I/O. 

This nearly doubles the number of I/Os on the 820 and 830 while allowing as many as 132 on the 870.  The base Micro 810 does not have plug in access.  However, the 810 does allow analog I/O channels as does the 820, while in the 830 and 850, analog channels are only available through use of plug ins.

Data and Programming

Almost all Micro 800 family products have higher memory capacity for user program and data space.  The low end is the 810 at 2K/2K for program steps/data bytes.  The rest of the 800 family is almost double the data capacity compared to the MicroLogix family although actual data bytes vary based on number of pins.

In contrast, the MicroLogix family is older and carries less data capacity with program steps/data byte ranging from 4K/4K on the 1100 to 4K/2K (configurable) on the 1200 and 10K/10K (configurable) on the 1400.

Power Supply

All MicroLogix controllers use a 120/240V AC/24V DC power supply embedded into the controller.  By contrast, the Micro 810 has and embedded 120/240V AC/24V DC power supply as well, while the 830, 850 and 870 have an embedded 24V DC power supply with an external 120/240V AC available as an option.

Additional Functionality

In addition to the use of two different platforms, the Micro 800 and MicroLogix families are different in approach.  The Micro 800 was designed to be modular to allow introduction of flexibility based on different needs for an ever-growing list of needs by modern connected equipment. 

In contrast, the MicroLogix family represents an older technological reality where functionality was embedded, and availability depended on how far up the structure in capability and cost the user wanted to go.

As a result, except for PID loop control, floating point math and a real-time clock, which are all available on all models within both family groups, additional functionality is completely modular in the Micro 800 group except for the 810 which only supports an LCD display and a USB adaptor..

MicroLogix Additional Functionality

1. Two digitals on the 1100, 1200 and 1400.
2. High Speed Counter – The 1100 has 1 at 40kHz and the 1200 has 1 at 20kHz while the 1400 has up to 6 at 100 kHz.
3. Data Access – Both the 1100 and 1400 has an embedded LCD while the 1200 has no data access tool.
4. Single Axis Servo Control – All three MicroLogix controllers can handle single axis servo control through an embedded power takeoff (PTO).

Plug-In Functionality Modules for the Micro 800

Additional functionality can be achieved in the Micro 800 group by a wide variety of plug in modules.  Using these modules, either additional processing power or additional functionality can be added. It also allows added communication capability as well.  Except for the Micro 810 base unit, these modules include:

1. Isolated Serial Port – These modules allow more serial communication with both Modbus RTU and ASCII.
2. Digital I/O, Relay and Combo – These can be configured to suit a range of needs such as voltage and current inputs or they can act as a 4-channel relay.
3. High Speed Counter – This module allows user-set min/max values and presets.  It can also improve noise isolation.
4. DeviceNet® Scanner – For use in systems using DeviceNet® connectivity (MicroLogix does not support DeviceNet® scanning).
5. Non-Isolated Thermocouple and RTD Modules – These modules help control and monitor temperature.
6. Backup Memory Module – These modules allow users to automatically backup data and code and includes a highly accurate real-time clock.
7. Trim Potentiometers – On the Micro 800 series, this module offers 6 analog channels to add presets for speed and position as well as temperature.  Contrast this to the embedded 2 channel potentiometer for the MicroLogix family.

While both family groups were designed to be small and flexible, the information above shows that there are drastic differences.  The Micro 800 is built for size, affordability and for modularity to meet today’s complex and expanding connectivity requirements for machine control.

On the other hand, the embedded features of the MicroLogix family, while not as flexible or affordable as the 800 group, allow small controllers that can fit into tight spaces for perhaps more rugged environments. 

When added to the differences in the software, both MicroLogix and Micro 800 family controllers still each have their use.  But while the 800 series group was not intended to be a one to one replacement for the MicroLogix family, as the power of connected factories grows, the use and importance of agile and flexible software platforms will mean that more and more control systems will be built on such platforms, driving a cause for migration from MicroLogix to Micro 800 family products or other Allen Bradley products that can handle the requirements of the modern connected factory.