PLCs or PACs: —It'’s all in the application

We focus on programmable controls for discrete machine applications. Although they still come with different names, what they do is becoming more and more the same.

By Patti Pool, Contributing Editor

Patti Pool

Statistical research isn’t needed to know there are far more installed PLCs in industrial applications worldwide than programmable automation controllers (PACs). PLCs, the workhorses of machine automation, are the most understood technology by engineers worldwide.

According to various market sources, about 80% of industrial applications are solved by simple PLCs, such as microPLCs with digital I/O that use ladder logic. As users pushed the envelope of these PLCs, they weren’t always successful. Engineers said they needed more capabilities for complex applications. Enter the PAC, so named it seems by ARC. These new controllers include multi-domain functionality, a single multi-discipline development platform, software tools, open, modular architectures, and use of de facto standards for network interfaces, languages, etc.

Many vendors now offer PACs, but PLC vendors responded by adding multiple protocol support to connect with other devices in the process. “Another primary development that has literally revolutionized the way PLCs are programmed, communicate with each other, and interface with PCs for HMI, SCADA or DCS applications came from the [commercial] computing world,” says Jeff Payne, AutomationDirect’s product manager. “Ethernet communications on the plant floor have doubled in the past five years. While serial communications remain popular and reliable, Ethernet is becoming the media of choice with advantages that can’t be ignored, such as network speed, ease of use in setup and wiring, availability of off-the-shelf components, and built-in communications setups.”

The PLC now has been tasked with motion control, too. From simple open-loop to multi-axis applications, the trend has been to integrate this feature into PLC hardware and software.

A tutorial from National Instruments points out that “although PACs represent the latest in programmable controllers, the future of PACs hinges on incorporation of embedded technology. One example is to use software to define hardware. Field programmable gate arrays (FPGAs) are electronic components commonly used to create custom chips, allowing intelligence to be placed in the new device. FPGAs let engineers quickly create applications that incorporate custom control protocols or high-speed control loops.”

So is it PLCs or PACs for you? Vendor support is critical if you use PACs. One observer who has several PC-based control systems in his factory remarked that, “Computers are changing so quickly that most of what I just bought today might not be available in six months to a year. On the other hand, I know that if a SLC500 dies, I can get one just like the one I put on the machine eight years ago. This is a major hurdle in my eyes for the PACs.”


Product Roundup:

Programmable Controllers

Scalable Embedded Controllers
S-Max 50xx VLC and ILC 350 VLC embedded controller platforms using Steeplechase VLC flowchart programming combine secure PLC control functions with PC-based performance, capacity and connectivity options. Version 7.0 software offers sub-millisecond logic scans and flowchart programming. Phoenix Contact; 717/944-1300;

Fast and Furious
MicroSmart Pentra micro controller’s logic engine processes basic instructions in 0.056 µsec. It has more memory, field-upgradeable firmware to keep the controller updated, and seven communication ports for a barcode reader, Ethernet connection, modem or RS232C-compatible devices. IDEC; 800/262-4332;

Combo Touch Panel and PLC
EZTouchPLC combines the original EZTouch panel with the functionality of a micro-modular PLC. It integrates users control and visualization needs into one total device for a small to medium machine that requires a touch-type graphical display. EZAutomation; 563/359-7501;
On the I/O Rack Controllers

On the I/O Rack Controllers
Snap PAC R-series programmable automation controllers are designed for cell control, data acquisition and remote monitoring where the I/O needs are geographically contained. The Snap-PAC-R2 version supports 512 points of analog, digital, and serial I/O modules. It offers PID loop control, floating-point math and string handling and dual-Ethernet. Opto 22; 800/321-6786;
All Bundled Up

All Bundled Up
Box PC system is a fanless, dust-protected computer that operates with most commercial display units, and can be used for remotely operated applications. The system comes bundled with InTouch HMI and pre-installed ActiveFactory trending and analysis software. Wonderware; 949/727-3200;

A Strong Pulse
PCM-3240  four-axis stepping/pulse-type servo motor control card simplifies stepping and pulse-type servo motor control, providing added motor performance, and fits into a standard PC/104 board, eliminating  mechanical interference in the embedded controller. The card’s MCX341-motion ASIC provides  2/3-axis linear interpolation, two-axis circular interpolation, and T/S-curve acceleration/deceleration rate. Advantech, eAutomation Group; 800/205-7940;

16 MB More Memory
ControlLogix family features 16 MB of memory for data-intensive applications requiring higher memory capacity. It allows centralization of alarming, and for information-intensive applications that require recipe data, and it provides larger storage capacity to locally store more data, enabling users to switch recipes. Rockwell Automation; 800/223-5354 x1970;

Plug-in PLC
Solves-It programmable logic controller (PLC) is packaged in a standard relay-style housing with an 11-pin plug-in base. It programs in ladder logic with function blocks using PC-based EZ Ladder Lite software which is included free. The basic unit has four inputs, four outputs and four programmable LED indicator lights. Divelbiss; 800/245-2327;

Movi, Movi
Movi-PLC slimline controller integrates PLC control and motion control. IEC 61131-3 and PLCopen motion standard-compliant, the configuration software includes a library of tested standard control and motion function blocks to help set up applications. The basic class manages up to 12 axes synchronously over the system bus. Advanced class handles 64 axes. SEW Eurodrive; 964/439-8792;

All Together Now
Ensemble Epaq standalone controller for applications from laboratory experimentation and general-purpose positioning to advanced OEM systems controls up to six axes of motion control, and if users need higher current or voltage levels than the integrated amplifiers provide, standard Ensemble drives can be interfaced to operate motors up to 30 A peak power. It can mix and match drive types in the same positioning system using a common programming and control platform. Aerotech; 412/967-6854;

Update With Ethernet
SLiCk Convert is an online utility that instantly converts a SLC500 program (ladder logic and documentation) to a SoftPLC-formatted application file that can be downloaded into a Tealware or other SoftPLC-based system. Users that have invested engineering, testing and training on systems based on SLC500 have an alternative path toward upgrading to an Ethernet-enabled system without major investment. SoftPLC; 512/264-8390;

Loop Controller Extends I/O
Model 353 loop controller has add-on Ethernet I/O modules for Modbus TCP/IP protocol. Modules transfer data using standard Ethernet networking techniques and can be mounted to the controller locally or remotely. A range of analog and discrete modules are available. Ethernet functionality allows web browser configuration and simple setup and calibration without special software. Siemens E&A; 215/646-7400;

Firmware Brings on Motion
VersaMax Micro 64 controller’s 3.6 firmware release creates motion control commands for jogging, find home, go home, blended move, and stop motion. The controller supports up to four axis (65 kHz pulse out and 100 kHz in) of motion control and stepper or motor control. GE Fanuc Automation; 800/433-2682;

Make the Next Move
NextMove e100 motion controller provides real-time control, onboard analog and digital I/O, and a USB port for simple connection to PC hosts with ActiveX support tools. It includes support for three traditional analog-controlled servos and four steppers, and a CANopen interface for adding local or remote I/O or other components. It links seamlessly into local and wide-area networks, and provides simpler system building and commissioning. Baldor; 800/828-4920;

Logical Deployment
Programmable MVI56-ADM and MVI56-ADMNet modules available in both serial and Ethernet feature a debug port for setup, configuration and diagnostics. Independent control of the two application ports allows for flexibility and expandability. Memory usage is user-configurable, supporting the storage and transfer of up to 5,000 registers to/from the control processor. ProSoft Technology; 661/716-5100;

Machine Controller Plus
MP2200 machine controller combines with MotionWorks v.6 to provide a larger, more-configurable rack system with nine slots. Other extended features include 233 MHz CPU, removable Compact Flash memory, USB serial interface and the ability to control up to 256 axes. Yaskawa Electric America; 800/yaskawa;

Better Communication
X20 CPU features a 100 Mbps Ethernet interface for use as an online interface or networking. A CAN and RS232 interface is integrated into the system, which can be rack-mounted. An extended CPU can be used if separate Ethernet, CAN, or RS232 interfaces are necessary. It’s equipped with a 25 mm slot for Profibus-DP, CANopen, and DeviceNet interface modules to be used. B&R Industrial Automation; 770/772-0400;

Real-Time Motion Control
ACR9000 controller processes floating-point calculations onboard in the 100-500 ms range, allowing the controller to serve as a preemptive multi-tasker with up to 24 programs simultaneously. It can handle four communication channels concurrently, allowing communication with the controller for troubleshooting, while leaving the HMI on a production machine fully online and active. Parker Compumotor; 707/584-2541;

Future-Proof Control Platform
PSSuniversal enables communication via all common standard fieldbus systems in combination with SafetyBus p. Head modules connect to all common fieldbus systems, enabling a structure of decentralized inputs and outputs with pure standard control functions or, in conjunction with Safety­BUS p, with pure safety functions. The system meets Cat. 4 in accordance with EN 954-1 or SIL 3 in accordance with IEC 61508, as well as other international standards. Pilz Automation Safety; 734/354-0272;

Small CNC Solution
IndraMotion MTX compact rack-mounted CNC solution for small machines, networked multi-station transfer machines and flexible cells controls up to eight axes in two NC channels with an IndraLogic PLC. It can process up to 200 NC blocks per second, and has a 300 block look-ahead rate to achieve shorter machine cycle times. Bosch Rexroth; 800/rexroth;

PC-Based PLC Has PID and Web Server
Type IPC FEC Standard PLC based on PC architecture has a built-in Ethernet interface, a web server, and an integrated PID controller module for closed-loop control functions. A front-panel plug-in sensor/actuator wire connector handles inputs, outputs and the power supply. FST PLC programming language has a STEP operation for programming sequences and basic arithmetic functions, and works via Ethernet or a web server. Festo; 631/435-0800;

Eliminate Motion Controller
The Wago-I/O-System has a motion control capability that provides stepper motor and servo drive control in a 12-mm wide package. By integrating stepper motor and servo drive control into the fieldbus node (PLC or PC-based), users eliminate the need for a separate motion controller. Wago; 800/din-rail;

Streamline Embedded Design
cRIO-9014 controller based on Freescale MPC5200 processor on Power Architecture technology and Wind River VxWorks RTOS provides processing speed, memory and storage required for embedded industrial applications such as high-speed machine control, machine monitoring/protection, data logging and embedded device prototyping. National Instruments; 800/258-7022;

Reduces Scrap
CPC400 multi-loop temperature controller uses Tru-Tune+ adaptive control algorithm to improve tuning by automatically optimizing control parameters whenever necessary to keep the system at the target temperature. This improves yield and reduces wasteful scrap and the need for reworking mis-processed material. Watlow; 800/watlow2;

CX9000 DIN-rail-mount embedded PC is scalable for a variety of control applications, has a 266 MHz Intel CPU, and runs on Windows CE for TwinCat software. No external storage is needed; the device boots from internal flash memory, and features a 47x100x91 mm design. Beckhoff Automation; 952/890-0000;

Simple Software for Complex Machines
Combination PiCPro software and MMC-D64 controller supports up to 64 axes of high-performance motion control. PiCPro is used to program MMC-D64 controller, and provide connectivity to MMC smart drives and AKM servo motors. It combines IEC61131 ladder logic or structured text programming with 100 MHz Ethernet motion control. Danaher Motion; 866/993-2624;

Powerful Functionality, Expandability
CP1H high-speed micro PLC delivers motion and position control and communications capability. It has four axes of servo motion control, integrates process data with sequential control, and uses high-speed multi-axis counter inputs and pulse outputs to calculate inverter positioning and drive chain control. Omron Electronics; 886/88-omron;

Fixed I/O PLCs
DL05 and DL06 fixed I/O PLCs can perform motion control applications. For simple counting, positioning with steppers, PLC models with DC I/O support high-speed input or pulse outputs directly from their built-in I/O points. Expansion slots accept analog I/O or an independent high-speed counter module for servo applications. AutomationDirect; 800/633-0405;

A Leap Forward
RMC100 multi-axis motion controller has a CPU option that works with the RMC100 Series I/O modules and is programmed using new RMCTools software. The combination can handle eight synchronized axes. The RMC 150E CPU can handle eight dual-loop position-pressure/force axes and reference axis, twice the previous maximum for fluid power and electric servo motion control applications. Delta Computer Systems; 360/254-8688;

Ultra-Compact PLC
FPS V3 compact PLC is equipped with a RISC processor operating at 0.32 µsec/basic instruction. It has floating-point calculation, two built-in axes of motion with linear/circular interpolation, PID instruction that supports up to 24 loops, and four channels of built-in high-speed counters. It supports up to three serial ports, has a programming capacity of 32 K steps, and supports up to 384 I/O. Panasonic Electric Works; 908/464-3550;

Don’t Bug Me
S2E/S2T programmable controllers have on-line debug functions for input force, coil force, data set, status latch and sample trace. A program for a T-Series CPU can be downloaded to the PLC without modification. Device/register tags and comments can be stored in the CPU and viewed in the on-line mode without access to the original program. Toshiba; 800/316-0920;

Multi-Level PAC
Telemecanique Modicon Premium programmable automation controller (PAC) has multiple CPU levels, plug-and-play rack support and communication protocols, plus memory upgrades. It has integrated multi-axis interpolated motion control, integrated safety relays and reflex functionality. Diagnostic and maintenance capabilities include diagnostic function blocks, run-time screens, and field-exchangeable memory. Schneider Electric; 847/397 2600;

Program in IEC 61131-3
NET Concentrator System (NCS) offers sequential control language programmability based on IEC 61131-3 including ladder, function block diagram and structural text. It can act as a single PID loop controller with simple cascade, split-action and inverse capabilities. Moore Industries-Int’l; 818/894-7111;

Stay Discrete
Micro-VersaTrak µIPm RTU/controller has a built-in mix of 14 discrete and analog I/O, four serial ports and a 10/100 Ethernet interface. It is pre-loaded with open-source Linux and industrial IPm firmware. Programming is done using any mix of languages, high-level C/C++ and more. It has 16 MB of flash disk and 16 MB of fast dynamic memory, along with an industrial PowerPC CPU. Sixnet; 518/877-5173;

Integrated Solution in a Small Size
Mini8 controller performs PID loops in a programmable logic controller. It offers up to 16 PID loops and has 14 plug-in I/O slots. The controller handles signals such as thermocouple and RTD inputs and relay, logic and analog outputs. It has setpoint programmer along with math, logic and timing functions for simple multi-loop PID control or custom solutions. Eurotherm; 703/669-1330;

Embedded Machine Designs
EMC 40 Series controllers offer the capabilities of a multi-zone PLC with analog functions on a 4.5x7-in. board for flexibility in embedded applications. There is a range of communications options, and the basic control board features 24 Vdc isolated digital inputs and six 24 Vdc isolated digital sourcing outputs that share 750 mA of current. Athena Controls; 800/782-6776;