control logix vs compact logix

I have a job where i was going to use a control logix processor. Its overkill but it was a standard. The machine is a packaging machine, fairly simple around 32 inputs, 4 thermocouple inputs, 4 or 5 analog inputs, 32 outputs,2 analog outputs 1 or 2 PID loops.

Cost has become an issue!!! they have asked me to look at the compact logix line as a cost saving, Other that the cost savings is there anything i should look for?. The machine will be communicating with a PV+ over Ethernet. I was looking at the parts and have come up with the 1769 series. however there was a a 1769-boolean that basically said it would turn on an output if an input came on...Isnt that the whole purpose of the PLC??? i must be missing something!!

Any input?

Thanks

D

CompactLogix is as capable as the full 1756 platform, it just can't deal with a huge amount of I/O, or integral bridging between communications platforms.

I use CompactLogix (and even the FlexLogix CPU's) in areas that are basically self-contained units of machines or processes.

If cost is an issue, and you don't need the huge communications resources of the full 1756 platform, then there is no reason to ignore it's little cousin and brother.

whats the deal with the 1796-boolean??

darrenj said:

whats the deal with the 1796-boolean??

Click to expand...

I have no idea. CompactLogix programs up exactly the same way as ControlLogix. Same instruction set, a bit lower processing speed than an L55 ControlLogix platform, and fewer communications connections.

Aside from that, in many cases, you can easily switch programs between the three platforms with little change.

thanks..What i figured but nice to hear it from someone who knows..

Darren

Sorry didnt mean to hijack this thread, but how different if flexlogic as compared to control logix? Are you limited to 1 rack or can you go more then that. I was thinking of replacing Control Logix with Flex Logic for smaller budget projects. Just havent had a chance to research on both platforms.

My suggestion is to consider CompactLogix, not FlexLogix. There are four new CompactLogix-family controllers coming out in the next two years, while the FlexLogix will not be enhanced to support v17.

The principal problem people get into is when they look to the CompactLogix to do everything the ControlLogix does, only cheaper. If I had a nickel for every time I heard "but I need DH+ on the CompactLogix"....

CompactLogix has less memory, processes slower, runs fewer tasks, supports fewer connections... it's a smaller controller than ControlLogix. Which is exactly what many single-machine control systems need.

The 1769 Boolean module is a specialty module built for high-speed assembly machines; it runs onboard boolean logic on its onboard I/O that doesn't require the CPU to solve the program, which takes execution speed down into the submillisecond range.

I have installed several FlexLogix PLC's.

They can have two local racks. One of the racks extends right onto the "FlexBus" of the controller. The other requires an expansion module and cable. Both racks can be 8 slots long.

I usually use only the "Local 1 FlexBus" rack. If I need more than 8 slots I add the 1788-CNC(r) and put all the IO on ControlNet using 1794-ACN adapters.

The processor has 2 communication adapter slots. You can have a DeviceNet, ControlNet, or EthernetIP adapter in any combination. I have usually used a ControlNet and an EthernetIP card for my systems.

The only real short coming of the systems are the communication limitations. They do not have as many connections available as a 1756 system. I can't remember off the top of my head what the limits are though. As long as the system only needs HMI and Networked IO I have never ran out of connections. If you have a lot of Comunications to do then it might be a bad choice.

One of the things I like best is the ability to grow a system. I have had 2 different systems that ended up being added onto until they out grew the abilities of the FlexLogix CPU. I just added a 4 Slot 1756 rack with the correct Communication modules and made all the IO remote via the network of your choice. As stated above, the program will convert over with minimal problems

They are a great little system for the money.

RSL

Ken,

That's too bad about them not supporting Flexlogix after version 16. I really think they are a handy little system. I much prefer 1794-IO to CompactLogix IO.

RSL

I have a job where i was going to use a control logix processor. Its overkill but it was a standard.

One of my customers specs the ControlLogix platform. Upon checking with them this includes the CompactLogix also. I think their spec should instead say the RS5000 platform.

The only real disadvantage to the CompactLogix for small systems is that the analog modules do not do the scaling and alarming for your - you end up doing those functions in your program instead (like you used to do on the SLC). If thats not a big deal then the CompactLogix is a good alternative.

Darren,

I am curious...just how much of a difference in cost is there between Contrologix and Compactlogix? And therefore, how big of an issue is cost?

Are we talking saving 10% or 50%.

The reason I ask is if you can do the same thing with each platform, then there is no barrier to going with the least expensive control platform.

However, if the controller is only 5% or 10% of the overall cost of the machine, then you will need to look elsewhere for cost savings.

If the controller cost $10,000 on an overall cost of $100,000 and you save $2,000 by switching platforms, you in essence save 2%. But if your goal is to strip 20% off the cost of the machine...you will obviously need to look elsewhere for cost savings. Then you have to determine if these cost savings are beneficial for the overall production of the machine or are you cutting corners and sacrificing quality?

I just compared a L61 system versus a L35E system. To have the same functions (DeviceNet and EtherNet) the cost for a ControlLogix system is 7181 and 4460 for the CompactLogix. Almost all IO is on DeviceNet which is not included in the above price comparison

Stephen Luft said:

Darren,

I am curious...just how much of a difference in cost is there between Contrologix and Compactlogix? And therefore, how big of an issue is cost?

Are we talking saving 10% or 50%.

The reason I ask is if you can do the same thing with each platform, then there is no barrier to going with the least expensive control platform.

However, if the controller is only 5% or 10% of the overall cost of the machine, then you will need to look elsewhere for cost savings.

If the controller cost $10,000 on an overall cost of $100,000 and you save $2,000 by switching platforms, you in essence save 2%. But if your goal is to strip 20% off the cost of the machine...you will obviously need to look elsewhere for cost savings. Then you have to determine if these cost savings are beneficial for the overall production of the machine or are you cutting corners and sacrificing quality?

Click to expand...

Stephen, I will give approx numbers here, don't want to get specific
1756 processor (Control logix) $4,350.00
1769 processor (Compact logix) $2,470.00

of course you sacrifice function's and speed but its a good savings. not only that but you also save about $800.00 on a back plane and 1500 on a Ethernet module (The compact logix processor i quoted has one built in)...\
BUT!!! i have to buy 2 of everything if i change product lines (for spare parts) so the savings are not that much,

the speed isn't that big of a deal on this machine but it was a good heads up from Alaric about the scaling, that will suck but again is livable, on the order i am looking at its just over 40,000 for control logix or around 36,000 for compact logix (and thats with the spares) so i am looking at around a 4,000 savings.

Connections, Connections, Connections!

Ken already stated it but I just wanted to highlight the need to look at this when considering the Compactlogix vs Controllogix. It is the most overlooked difference between the two platforms.