Control Logix versus Micro Logix PLCs

[eeprom]

Hello,
I have been programming for many years, and I have been using AB MicroLogix PLCs for several. On several occasions in the recent past I have had salesmen try to get me to switch to ControlLogix. The price difference between these two families is tremendous. A ControlLogix CPU would cost many times what a Micrologix CPU would. And that does not take into account the software.

A Micrologix1400 would cost me around $700 plus programming time. With that PLC I could handle any digital I/O, any type of analog I/O, data logging, messaging to other PLCs and VFDs, and a decent range of math functions. In fact, the only shortcoming I find with the 1400 is that doing any complicated math is tedious.

If I were to purchase a ControlLogix processor for the same project, it would cost more than $5000.

Can someone tell me what I would gain by switching to a ControlLogix CPU?

 

[djs]

Thye ControlLogix is capable of controlling much more I/O then the MicroLogix. The MicroLogix is usually limited to a ma of four I/O modules. In contrast the ControlLogix can handle hundreds of I/O modules. It is the difference between controlling a single machine and controlling an entire plant.

 

[catserveng]

I recently upgraded the controls on a small engine driven cogen system using a MicroLogix 1500 and a PanelView Plus. The system went in fine, works well, and is based on similar control systems I have used for years.

About 2 months after completing the project the AB Sales rep was in plant and the Plant Manager showed him his "new" system. The AB Sales rep imediately proceeded to tell him the MicroLogix for a poor choice for his system and that a ControlLogix or CompactLogix based system would have been more suitable. So even though I had been using this platform successfully for a number of years, it is not longer "suitable".

If you are happy with the performance of you MicroLogix, it handles the I/O you need for you system, and you can meet you programming needs with it, I see no benefit to change platforms, unless you have lots of spare dollars.

Sure, there are some pretty neat things you can do in RSLogix 5k you can't do on other platforms, but do you need a racehorse to pull a milkwagon?

My 2.5 cents worth,

Mike L.

 

[msherb]

There are quite a lot of things you can do in with ControLogix that can't be done with MircoLogix. Examples would be function block programming (especially handy for PID loops), user created functions, additional math functions, additional protocol support using backplane mountable modules, and the additional I/O that was mentioned earlier. ControLogix is the only one that has been certified for SIL applications as well (unless you count the Uber-expensive Guard-Logix).

That being said, it's all about what you are using it for. I have used both successfully in differently scaled projects.

 

[automatic2]

Tagged data, structured data, structured text, love it.

 

[eeprom]

I am granting that it is a more developed processor, but how do you justify the cost? I could purchase an industrial computer with an operating system (such as a Honeywell Tritium) with I/O for $2500. This is a full fledged computer with operating system, built in web development, automated text messaging notification for alarms, auto email of data....the list goes on. This is half the cost. It can support digital I/O, analog I/O, RTDs, thermocouples, etc.

When you get down to it, it seems that all you are saving is the programming time, which is significant. But on a project of less than 50 I/O, it seems like using a semi-truck to go grocery shopping.

 

[catserveng]

Another possible option is to use the Compactlogix with the 1769IO, I haven't used many of them, but I think it has many of the same functions available as the ControlLogix platform.

I'm still a fairly big user of the MicroLogix, they still serve my uses well, and I can setup a customer with the RSLogix500 Starter software for about $600 if they need to do anything with it.

Mike L.

 

[controlsdude]

RSLogix5000 can be used on multiple hardware platforms

Compactlogix plc
Contrologix PLC or PAC High dollar (mac truck at grocery store as someone pointed out)
flexlogic plc
softlogix pc
drivelogix vfd
guardlogix plc or safety

maybe flexlogix would be the low ball plc might fit your needs.

 

[automatic2]

any 'immediate' application can be dealt with on it's own terms, and that may be adequate. However, many 'immediate' applications are a 'cog in the wheel' where integration is critical. Ad hoc solutions can be a liability when adding up the sum for plant wide control.

Many Technicians, Engineers, Designers, etc., are complacant in thier careers, and may not serve the 'larger' effort. In many cases, sales people have exposure to what is possible along with industry trending.

If your mandate is to mitigate expense, so be it, but if a salesperson can assist in elevating one's career while providing for a company's needs, I'm on board.

 

[eeprom]

I use Allen Bradley products all the time. I like their products, but they are really no better than Siemens or IDEC, or any other PLC. They are the most expensive PLC out there, almost twice the cost of Siemens. With Allen Bradley I always have the feeling that I am getting ripped off. They are the microsoft of the PLC world. Everyone else makes products which interact well with other brands. Not AB. They do have good tech support, and of course they charge for that too.