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VersaMax PLC Component Selection Guide

I. VersaMax Control System Overview
The VersaMax controller system is family of controller that features Nano, Micro and Modular assemblies. Each controller assembly serves a specific application size and may require installation of components to be able to function as a complete and compatible unit for a particular automation requirement.

To design or specify a VersaMax controller, one needs to understand the components and the overall functionality of each. This is the aim of this selection guide. It hopes to provide a user-friendly guide in navigating through VersaMax catalog number of components, enabling any personnel to arrive at the correct and compatible VersaMax hardware.   

II. Common Information

A. VersaMax Minimum Components
Before selecting components for a VersaMax system, it is important to understand that this PLC platform has similar requirements as to any other PLC systems available in the market. To function as a complete unit, a VersaMax PLC as a minimum, must be included with:

– Power Supply;
– Controller or processor or CPU;
– Input and Output (I/O) modules;
– Communication modules
– Carrier modules

Depending on the VersaMax controller selected, specifically VersaMMax modular modular hardware, one may need to specify and select each of the minimum components.

B. Basic Module Functionalities
Power Supply provides power to the internal circuitry of the module as well as backplane power to the attached expansion modules. It is installed to the any component assembly such as local controller chassis, expansion and distributed I/O stations.

Controller or Processor is responsible for processing the user program that is downloaded to the controller.

Input and Output (I/O) modules provide the physical interfacing to field signaling and actuating devices.

Communication modules provide means of connecting the PLC to the programming device or other compatible visualization components such as Human Machine Interface (HMI) or Supervisory Control and Data Acquisition (SCADA).

Carrier modules provide I/O terminal connection, module backplane connectivity and DIN rail attachment.

C. PLC Type and application sizes
There are actually Two (2) types of VersaMax PLCs available based on form: Compact and Modular. Compact PLCs are those units that come with built-in Power supply, I/O channels, communication module and processor while modular PLCs have these parts separated and individually purchased.
Small control systems have I/O count that typically ranges from 0-256 I/O count. Some of these systems are industrial machines such as packaging, sorting, material handling and similar ones. Medium sized control systems are industrial processes with I/O range of 256-1024 I/Os while large control systems have an I/O count beyond the range of Medium sized control systems.

Typically, small control systems are served by Compact controllers while Medium and Large applications utilizes modular controller. This is applicable with VersaMax controllers.

Now that the common knowledge to VersaMax PLCs has been initially discussed, component selection process may be started however, to prevent confusion, a suggested starting point is specified in this article – determine first the application size.

A. Determine the Application Size

To begin with VersaMax component selection, it is important to start by identifying the size of the control system or process. This will immediately determine the type of PLC to use whether Compact or Modular. As previously mentioned, Small application size is typically compatible with Nano and Micro Controllers while Medium to Large application will most likely require a modular controller.

VersaMax controllers have compact and Modular controller versions. For compact controllers, available controller series are the VersaMax Nano, Micro and Micro Plus controllers.

VersaMax Nano controllers covers 10-11 I/Os as seen in the table below:

Table 1: VersaMax Nano Controllers

VersaMax Micro controllers can cover 0-140 I/O count including the supported I/O mdoules. VersaMAx Micro are Micro 14, Micro 23 and Micro 28 controllers.

VersaMax Micro Plus controllers have built-in I/O channels that can reach up to 64 I/O and maximum of 320 total I/Os. I/O points of Expansion module varies however, only the VersaMax Micro Plus support the 64-point expansion module.

Table 2: VersaMax Micro and Micro Plus Controllers

With Compact controller solution, one doesn’t need to worry about any other components aside from the expansion modules.

If the application size falls into the Medium to Large application category, modular controller is the recommended PLC form.

C. Power Supply Selection

Power supply delivers current to the internal circuitry of the controller and provides backplane power to the insertion slots of the add-on modules.

To select a Power supply, simply identify the power source that is existing within the plant. Is it AC or DC? Additionally, size up the output current by adding the individual current draw of the components. The power supply should be sized higher that the total current draw and compatible to the existing supply voltage of the plant.

Image 1: Backplane current consumption as specified in VersaMax slection manual for CPUs.

There are Two (2) types of power supply available to the VersaMax modular controllers – standard and expanded power supply. Standard power supply delivers total output current of 1.5 A and 3.3V output current of 0.25 A while expanded power supply has higher 3.3V output current amounting to 1 A which can be used to power larger control systems.

Table 3: VersaMax Power Supply Modules

For VersaMax PLC platform, only modular controllers require specification of Power supply. The built-in power supplies of Nano and Micro PLC are non-replaceable and already sized to accommodate expansion modules.

D. Processor or CPU Selection
To select a controller, focus on the memory capacity and processing speed. A simple rule of thumb can be followed such as the higher the I/O count, the higher the memory consumption; The higher number of analog I/O channels, the higher the memory consumption.

Aside from the memory, consider the processor speed. Most of the time, the default controller processing speed is more than sufficient. Select the next higher processor speed if the control system is used for motion control applications, high-speed sensors and high-speed actuators. If the control system does not have these application requirements, the typical processing speed will most likely be sufficient.

The table below lists the available controllers for VersaMax Modular PLC. Though all these processor support the same number of I/Os, 4096 I/Os, the memory capacity differs as well as communication speed and communication ports.

Table 4: VersaMax Modular controllers

To compute for the memory consumption of I/O signals, assume the following instances: All 4096 I/Os are discrete (instance 1) and all 4096 I/Os are 16-bit resolution analog I/O signals (instance 2).

Table 5: I/O memory sample computation

The computed memory consumption of instance 1 amounts to 512 Bytes only while for instance 2, the memory consumption amounts to 8.192 KB, way far from the 34KB memory of the most basic VersaMax modular controller. This proves that analog I/O consumes more memory however, not enough to occupy a quarter of the controller memory. This leaves sufficient memory areas for internal bits utilization, programming instructions usage such as timers and counters as well as leaves an ample space for system overhead functions.
E. I/O Module Selection
Whether expansion I/O module for compact VersaMax controller or local and distributed I/O module for modular VersaMax controllers, the I/O module selection process is typical. One must identify the I/O type and the signal that must be received (input) and delivered (output).

The I/O module type includes:
– Discrete Input module
– Discrete Output
– Analog Input module
– Analog output module

– Combination I/O modules

Discrete or binary or ON/OFF I/O modules are used for discrete devices. Discrete input modules receive On/OFF signals from devices such as switches, auxiliary contacts and other similarly operating electrical components. Discrete Output modules are used to actuate ON/OFF devices such as Pilot lamps, Solenoid actuated valves, relay coils and similar devices. An example of discrete input is a limit switch while an example of a discrete output is a Solenoid actuated valve.

Analog input modules are used to receive incoming signals from field instruments in the forms of 0-10VDC; 1-5VDC; 0-20 mA; 4-20 mA and other signal types. Typical instruments and devices that provide this type of signals are transmitters, signal splitters, panel meters and the like. Analog output modules on the other hand delivers output signal range of 0-10VDC; 1-5VDC; 0-20 mA; 4-20 mA and are used to actuate modulating devices such as Control Valves, Variable Frequency Drives (VFD), Dampers, Louvers and similar instruments and devices.   

Combination I/O modules are modules comes with both input and output functionality. Combination modules are typically combination of both discrete or both analog function, not the other way around.

When specifying I/O modules, a 20% allowance may be allocated per module. This allowance serves as provision for future enhancements.

For instance, if a control system with 102 discrete input and 86 discrete output devices needs to be specified with the proper I/O modules, it can be determined by having the table below, entered with very simple math functions. It can be observed that the higher no. of I/O density, the lower number of modules are needed.   

Table 6: Sample I/O module computation

The module quantity is always rounded up to the next higher whole number if the computation results to number with fractional value. This is to maintain the provision to at least equal or higher than 20%. This allowance is not a standard but one that is typically used. Depending on the allocated budget, the provision may be lowered or increased to a more acceptable quantity. Finally, the same method applies to Discrete output, Analog input and Analog output modules.

Specific to the VersaMax PLC platform, a wide selection of I/O modules are provided. The selection includes all the field wiring methods such as Current Sourcing and Sinking configuration (For discrete and analog); Single-Ended and differential (for analog); Relay, Triac and opto-coupler (for output). The table below summarizes the considerations for each type of I/O module.

Table 7: I/O module selection considerations

F. Carriers Selection
Now that the basic module has been selected and the type of controller is identified, the next question is how to mount these modules. Are these components DIN rail mounted, or do they need specialty modules for mounting and interconnection?
For VersaMax Nano and Micro PLCs, DIN rail mounting is the supported mounting method. Expansion modules of Micro PLCs are DIN rail mounted as well and connects to the backplane via the pre-installed expansion port of the host device. No need for specialty mounting accessories.

The VersaMax modular controllers on the other hand user carrier modules. These modules provide I/O connectivity, Backplane connection and mounting. There are Three (3) carrier types available for selection:

– Terminal-style I/O carriers that enable modules to be mounted parallel to the DIN rail;
– Compact Terminal-style I/O Carriers for mounting of module perpendicular to the DIN rail and
– Connector-style I/O Carriers that enable modules to be mounted perpendicular to the DIN rail with built-in interposing relays.

This mounting and connectivity solution is one distinct advantage of VersaMax Modular controllers. With the capability of being mounted perpendicular or parallel to the DIN rail, panel space can be maximized. Additionally, with carriers constantly connected to the backplane, removal of the I/O module will not disrupt the operation of the system.  

G. Communication Modules Selection
Communicationmodules handle controller communication to partner devices such as Programming workstations, Human Machine Interface (HMI), Supervisory Control and Data Acquisition (SCADA) systems and other compatible partners devices. Both the compact and modular VersaMax controllers are provided with RS232 ports as minimum. Other controller versions are equipped with a secondary RS485 port for multi-drop, daisy-chain topology and Ethernet port for modern networking capabilities. Below table summarizes the communication support of each VersaMax CPU.

Table 8: Built-in ports and supported communication modules

Optional communication modules may be added to meet the connectivity requirements of the plant.

H. Specialty Modules Selection
Specialty modules are optional modules as well. These modules are installed to the PLC assembly to enable a specific function. The rule of thumb with specialty modules is to simply install if needed. These modules include:

Table 9: Specialty Modules

Notice how versatile the I/O module of VersaMax modular controller. A single module serves Specialty discrete, motion and counter functionalities. These modules may be installed locally or as part of Remote I/O solution.

I. Distributed I/O component selection
In terms of scalability, the VersaMax modular controllers offer the maximum scalability features. Compared to Nano PLC that has fixed hardware and Micro PLCs with limit of Four (4) expansion modules, the modular controllers can be expanded up to 4096 I/O Points of any combination. In addition, scalability comes in different architecture – local, Expansion and Distributed I/O architecture.

Local I/O expansion refers to an expansion where additional modules are installed to the same rack where the CPU resides. In the case of Micro PLCs, this is the only expansion available. With modular controllers, this is just one of the options.

Table 10: I/O Scaling options

Another option for scaling up a VersaMax modular controller installation is with the use of Expansion racks. This rack, which is basically a remote module, can be mounted up to 2460 Feet away from the main processor and permits installation of additional Seven (7) groups of Eight (8) modules per group. This allows I/O components of a VersaMax controller assembly to be strategically placed in different areas of the plant to significantly reduce wiring homeruns and simplify wiring and termination of signals.

Another way of VersaMax I/O scaling is with the use of Remote I/O units. This method is similar to the previous method however, it uses Remote I/O units instead of Expansion modules. Each remote I/O unit can be installed with a maximum of 1024 I/O points. Transmission speed is significantly faster as data transmission depends on the communication protocol supported by the I/O unit. Supported protocol by the remote I/O station are PROFINET Slave, Version 2.2 Class A IO-Device, DeviceNet Slave and EGD and Modbus TCP Server using 10/100BASE-T; Fiber 100BASE-FX; Shielded, dual twisted pair cable, terminated at both ends and Ethernet twisted pair physical media and ProfiBus. Remote I/O can cover up to 2 Km m bus length which can be further extended easily with the use of repeaters and converters.   

Table 11: I/O Scaling Distances

J. High-Availability and Redundancy
High-availability and redundancy features are Two (2) of the most important considerations when selecting a PLC. Only the VersaMax Modular PLC are capable of complying with this requirement as this PLC type support Hot-swappable I/O modules and capable of being configured with Redundant I/O using application code, Network Media redundancy and controller redundancy. These redundancy feature significantly increases the availability feature of any VersaMax PLC assembly.  

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