Allen Bradley Micrologix 1000 versus PLC 500


Thread Starter

Orc General

Which one is more modern? Micrologix 1000 or PLC 500? Which is better bang for the bucks?

Steve Myres, PE

If by PLC 500 you mean the SLC-500 series, the SLC's have been around longer than the Micros. I think the Micros were introduced in the mid 90's. But the difference is more one of application than which controller is more "modern". The SLC's in common use today are much more powerful, expandable, and expensive controllers than a Micrologix.

The only place where a SLC would be considered for the same application as a Micrologix 1000 would be one of the original SLC's with built in I/O, which are barely used anymore, AFAIK.

Alan Hartwell

The MicroLogix 1000 was developed after the SLC 500, so in that sense the MicroLogix is more modern.

As for bang, it depends on what you're blowing up. If the limited I/O of the MicroLogix suits your application, it will be a less expensive solution by far. With the SLC-500 you can mix and match various I/O as well as a wide range of third party modules.
The Micrologix works fine for alot of low IO machinery and process control. If you own the RSLogix 500 programming software it can be used with all of the micrologix lines.

There are option modules and network communications like DeviceNet available for the Micrologix products as well.

Jeremy Pollard

Be careful of the limitation of data memory vs program memory - for data storage go for the SLC 500

Cheers from: Jeremy Pollard, CET The Crazy Canuckian!
Integration and Automation Training, Consulting, and Software

Juan De los Santos

You should look at the Micrologix 1500 or 1200, you can not program on line but if you have the Micrologix 1000 as an alternative, that is not a problem.

William Sturm

If you value your time (like most people do), then you
should consider the on line programming feature of the
SLC 5/03 or higher. If you have a complex program,
the time it takes to upload-edit-download many times
during debugging can add up quickly.

marc sinclair

Both of these PLCs are dated and very expensive, the software is expensive and tied to one pc with the dodgy token disc. Look at the offerings from Telemecanique - Twido and Siemens - S7-200

Steve Myres, PE

Bill makes a good point about online edits. I recently had to troubleshoot a machine with a MicroLogix 1500. The cycles of upload/test/go offline/tweak can get to be time consuming, expecially since you will have to take the PLC out of run mode, shutting down the process. Five to ten minutes of programmer time and machine downtime to make and test a program change that could be done in 30 seconds and is not critical enough to merit shutting down the process (scaling values for a new HMI display point, for instance).

Also, math is much more awkward in the Micro. No CPT instruction for complex assignment statements, for example, so what could be done in a single CPT box in a SLC requires five or six boxes plus some scratch variable memory to hold intermediate results.

That having been said, I've happily used the Micros on machines that were digital control only, and the logic was pretty simple. The design of the machine was pretty stable too. We shipped the first unit, and on field installation, I thought of a feature that would be nice to have, added it, and after that the code didn't change for all the units we built over the following three years. If you have an application like that, the Micro may be just what you need.

Juan De los Santos

If you appreciate your time, and if you want reliability and a long term support for you and your customer stick with Rockwell. Spite of the cost of the software, your development will be useful also on the new development like Micrologix 1500, 1200, etc.

I am talking far away from the States, at the south of South America, here we know what is the reliability of this "new development" you can not communicate the old PLC families like the tsx with the new ones, no software
compatibility, etc etc.

Also, if you think the software should be paid by the PLC user, you should no have problems with the price, because the decision about high price or low price is subjective and market related.

marc sinclair

Sadly here in the UK - although AB support is good from Rockwell, the PLC hardware is only available from one supplier - many people,source AB hardware from the US where one can save 30 - 50% on the inflated UK prices, even after taxes and duties.

Let's also put this communication fear to bed. With a little ingenuity it is possible for _any_ piece of equipment talk to _anything_ else. a couple of years ago I connected a new PLC control system to a steam engine. The two systems in the workshop right now are a mixture of Siemens, AB, and Hitachi all talking to each other using Profibus - all ROCK SOLID. - Not down to me, but a victory for international standards.

I am always wary of being tied to a single supplier, The great thing about standards like IEC1131 is that there is no excuse now that "Our guys don't understand manufacturer X Y Z" I like to shop around and use the most appropriate equipment available, reliability is not really an issue anymore, anything I can build will outlast the mechanisms they control :)

Long term? in my business - food - machinery is usually amortised over 5 - 10 years by then major work is needed and/or new processes are in vogue - and the plant is usually upgraded - and now thanks to the recycling directives - I'll see it all again soon :)

Marc Sinclair