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1. 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: info@moxa.com
This document was produced by the Moxa Technical Writing
Center (TWC). Please send your comments or suggestions
about this or other Moxa documents to twc@moxa.com.
Andrew Hsu, Moxa Project Manager
andrew.hsu@moxa.com
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

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Applications
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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

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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
+

4. Moxa White Paper Embedded Computing for Industrial
Applications
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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

5. Moxa White Paper Embedded Computing for Industrial
Applications
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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

6. Moxa White Paper Embedded Computing for Industrial
Applications
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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
support@moxa.com.
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
reproduced or transmitted in any form for any purpose, without our prior written permission.