What PLC to buy?


Thread Starter

rine everett

Requirements: Comm port (RS232) at least 32K RAM Battery BU 20-40 Input lines. any suggestions will be greatly appreciated.

Bob Peterson

This is a very strange set of requirements. With only inputs required, and so few, why would you need so much memory??? There are any number of lower cost PLCs available. Each of the major manufacturers has a low end PLC, however, I don't believe any low end PLC will have 32K of memory in it. Perhaps additional clarification of the intended use is in order before any serious reccomendationsc an be made. Vitually all low end PLCs will have an RS232 comm port and a battery backup. However, some manufacturers do not allow you to use the comm port to communicate with anything other then their proprietary systems. You need to specify exactly why you need an RS232 port as well. Bob Peterson

Robert Dusza

Rine, Try the SCADAPack or SCADAPack Plus by Control Microsystems. We have had exceptional performance from the units and there a variety of batter options available. http://www.cmscada.com Bob Dusza Robert J. Dusza, Jr. Treatment Manager (V) 1-860-647-3219 (F) 1-860-647-3150 E-mail - [email protected] Manchester Water & Sewer Dept. 125 Spring St. P.O. Box 191 Manchester, CT 06045-0191

Luis Carrillo

You could try an OCS from GE Fanuc. The advantage of these are the combination of controller, operator interfase, network and I/O. Good luck

Robert D. Wagner, P.E.

Hi List: Memory usage varies widely between different brands of controllers, even between different series from the same manufacturer. For 20-40 inputs, 32K of memory is typically on the high side, unless you're doing datalogging in the PLC. If you really need 32K (words) of memory, look ar the A-B SLC500 series of modular controllers, they even have a built-in datalogging function. If you really don't need all that memory, I believe you'd be very happy with the Micrologix 1200 or 1500 series. I've found them to be: reliable, easy to use, flexible and expandable. Robert D. Wagner, P.E.


What do you mean for "cost"? A PLC that you do not know how to program or how to maintain or they have no technical support could be a High cost PLC, there are a lot PLC brands that have the caracterisitics that you want, but it is all you need? For me a good one is the A-B Micrologix 1200.
no,no,no Modicon has their momentum. It has up to 64k I believe. I used one with NO I/O, and all the 64k for a data comparison/barcode project. Add the I/O you want, although I don't think they have just 20 inputs alone. Good, fast, cheap, and a REAL modbus port.
You might try Keyence - http://www.keyence.com These are inexpensive, small, and the software is also cheap. Bill Mostia =========================================== William(Bill) L. Mostia, Jr. PE Independent I &E Consultant WLM Engineering Co. P.O. Box 1129 Kemah, TX 77565 [email protected] 281-334-3169 These opinions are my own and are offered on the basis of Caveat Emptor.

Curt Wuollet

Hi All I'm sure this helps the guy out a lot. It does point out that for a wide range of problems there are at least dozens of functionally equivalent solutions. Think of how much further ahead we would be if the effort was spent going forward instead of sideways. 98% of that R&D was wasted on reinventing the same old wheel. Think of how many times the same applications have been reinvented on all of the PLC's that have been reinvented. 98% of that development time was wasted. Any wonder why the industry isn't moving forward? Regards cww www.linuxplc.org