Moxa white paper---Embedded Computing for Industrial Embedded Computing for Industrial Applications

Moxa White Paper Embedded Computing for Industrial Applications

Released on May 1, 2008 Copyright © 2008 Moxa Inc. All rights reserved. Moxa manufactures one of the world’s leading brands of device networking solutions. Products include industrial embedded computers, industrial Ethernet switches, serial device servers, multiport serial boards, embedded device servers, and remote I/O products. Our products are key components of many networking applications, including industrial automation, manufacturing, POS, and medical treatment facilities. How to contact Moxa Tel: 1-714-528-6777 Fax: 1-714-528-6778 Web: www.moxa.com Email: [email protected]

This document was produced by the Moxa Technical Writing Center (TWC). Please send your comments or suggestions about this or other Moxa documents to [email protected].

Andrew Hsu, Moxa Project Manager

[email protected]

It’s safe to say that everyone knows what a computer is.

However, that said, many people remain blissfully unaware of

the distinction between a general-purpose computer, and a

so-called “embedded computer.” General-purpose computers,

such as the typical office PC, are used to run a variety of

programs and applications. For example, most people have at

one time or another used word processing software,

spreadsheet programs, email utilities, or any of the thousands

of computer games available on the market. In contrast,

embedded computers are designed to handle a specific

application, such as monitoring a security door, reporting the

status of sensors for a control system, or managing traffic

lights at a busy intersection.

There are two main advantages to using embedded computers.

The first is a big reduction in cost. The second is that they are

easy to deploy. In fact, both advantages are related to the size

of the embedded computer. Since embedded computers tend

to be much smaller than general-purpose computers, and do

not require purchasing a monitor, keyboard, and mouse, the

cost is quite a bit less than for a general-purpose computer

system. The reduced size also makes it easier to deploy

embedded computers at a large number of remote locations. The location of your application can have a big effect on the

type of equipment you purchase, and this is also true of

embedded computers. A simple example is an entry gate

application. If the entrance is a door located inside an air


Copyright © 2008 Moxa Inc. Page 2 of 6

conditioned building, then the embedded computer only needs

to function reliably in a narrow temperature band and at a

relatively low humidity. On the other hand, if the entrance is

located outdoors, you may need to use an embedded computer

guaranteed to operate reliably in extremely cold temperatures

(e.g., as low as -35°C), and in extremely hot temperatures

(e.g., as high as +70°C). For embedded applications subject to harsh environmental

conditions, you should look for embedded computers that meet

all of the following specifications: Ready access: A robust design and remote management

capability are a must to reduce maintenance costs and

ensure that the embedded computer operates reliably.

Reliable communication: For applications that require a

distributed system architecture, be sure to use embedded

computers that offer a choice of interfaces and support

secure transmission protocols.

Fit for harsh environments: Many industrial applications

call for a DIN-rail form factor and wide operating

temperature support. For buses and installation on machines

with moving parts, an anti-vibration guarantee must also be

considered.

Versatile expansion options: Embedded computers with a

rich variety of expansion slots, memory options, and

communication ports give system integrators more options

when designing new systems and when reusing existing

equipment for other applications.

Efficient management: Being able to install embedded

computers quickly and easily is essential when dealing with

large systems. In addition, a remote management capability

increases the reliability of your system, and makes it easy to

configure and update firmware and software. The Move towards Greater Versatility Even though embedded computers do not require a monitor,

keyboard, and mouse, they still need some means of



communicating with other devices in the system. At the bare

minimum, the computers should have one or two serial ports

for connecting to external devices. However, for the embedded

computer to be a viable component of a modern control

system, it should also be able to connect to a number of other

interface types: Serial Communication Interfaces (SCI): RS-232,

RS-422, and RS-485 are the standard serial interfaces for

industrial applications.

Universal Serial Bus (USB): Although the

RS-232/422/485 interfaces are still the norm for industrial

applications, USB is starting to make inroads.

Networks: Ethernet is now pervasive in the office and home

environments, and is being used more and more in industrial

settings. In addition, some industrial applications use the

CAN (Control Area Network) protocol.

Discrete IO: Large-scale control systems make liberal use

of General Purpose Input/Output (GPIO) technology.

Analog to Digital/Digital to Analog (ADC/DAC): The

capability to convert analog signals to digital signals and vice

versa is a requirement for many industrial applications.

Wireless Communication Interface: Industrial

applications located in hard-to-wire settings can benefit by

using wireless connections to transmit data over a network.

WWAN (Cellular Network)

WLAN (Short Range Transmission)

GSM/GPRS/CDMA

+3G/UMTS/HSDPA

WLAN 802.11 a/b/g

WLAN 802.11 b/g

+



Embedded Computers for Harsh Environments In contrast to secure, temperature-regulated office

environments, harsh environment applications need

equipment with a rugged design. Your embedded computers

should have a robust and compact metal housing, use few (if

any) cables, and use no moving parts such as hard discs and

cooling fans. Hard disks, in particular, crash or fail relatively

often, which makes using flash memory an attractive

alternative. In addition, anti-vibration and anti-shock features

can improve the stability of systems used on buses, trucks,

trains, and other moving objects. Wide Temperature Design A wide operating temperature design is a key factor for

applications that run in critical, outdoor environments, since

temperatures could range from as low as -35°C to as high as

+70°C. For this reason, you should choose embedded

computers made from high quality components that

generate less heat, and have a long MTBF. If you have doubts

about a computer’s ability to work reliably in cold and hot

temperatures, be sure to ask the manufacturer to provide

the proper verification and certification documents. Isolation Protection Electronic equipment can benefit from using optical isolation

technology to protect against ground voltage loops and other

electrical disturbances. The isolator works by converting an

electrical signal into a light signal, which is transmitted across a

short gap in the electronics. When the light signal reaches the

other side of the gap, it is converted back into an electrical

signal. The gap that’s created in the electronic circuit is often

placed between a transmitter and receiver. A common problem for many RS-485 applications is ground

loop currents that flow through the ground line when ground

voltage levels differ between connected devices. To eliminate

this problem, some RS-485 products come with up to 2 KV of



optical isolation protection.

If the RS-485 network covers a fairly long distance, isolation

protection keeps the RS-485 devices’ interface components

from getting fried. You should look for products that offer at

least 2 KV of optical isolation protection. Customer-friendly Features For time-to-market considerations, embedded computers

should be much more than just a hardware box that requires

extensive installations and configurations. Look for the

following important features when deciding what type of

embedded computer to purchase for your industrial

applications: Ready-to-run operating system: Most system integrators

and other embedded computer users now look for computers

with a pre-installed operating system, drivers, file systems,

and common applications such as Open VPN or IPsec VPN.

Protocol conversion: Embedded computers must often

connect to a variety of devices that don’t always use the

same communication protocol. For this reason, you should

look for suppliers that provide convenient protocol

conversion software to ease the task of passing data back

Isolator is installed

here

Higher Voltage Lower Voltage Ground Loop

Computer Room

Serial Device

15 m to 1 km serial connection

Ground is charged



and forth between different devices.

Remote access: Mangers of many existing systems are still

faced with the nightmare of needing to send engineers onsite

to manage their embedded computers. A simple way to turn

this nightmare into a memorable dream is to use embedded

computers that are accessible remotely over an Ethernet or

cellular network. In addition, efficient online device

management tools can save engineers many hours of

frustration. Summary In this paper, we explained the basic difference between a

general-purpose computer and embedded computer, and

highlighted the features that embedded computers should

have when used for industrial applications. The most important

features are:

• Wide temperature design

• Isolation protection

• Customer-friendly features

• Ready-to-run operating system

• Protocol conversion software NOTE: Moxa provides a rich selection of embedded computers for industrial applications.

For details, check our website at www.moxa.com, or contact the author, Andrew Hsu, at

[email protected].

Disclaimer

This document is provided for information purposes only, and the contents hereof are subject to change without

notice. This document is not warranted to be error-free, nor subject to any other warranties or conditions,

whether expressed orally or implied by law, including implied warranties and conditions of merchantability, or

fitness for a particular purpose. We specifically disclaim any liability with respect to this document and no

contractual obligations are formed either directly or indirectly by this document. This document may not be

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Moxa white paper---Embedded Computing for Industrial Embedded Computing for Industrial Applications