Do handheld OIs make sense?

A reader looks for shared experiences regarding cost savings that can be realized with the usage of a wireless or plug-in handheld OI to take care of all their additional in-line networking functions.

QUESTION:

We often sell our machines in multiples and with optional modules for additional in-line functions. Each has its own operator interface, usually networked. We’re thinking that cost savings can be realized with a wireless or plug-in handheld OI to take care of all of them. We need more than a PDA-sized display. Anyone have some experiences to share?

--From October 2006 Control Design

ANSWERS:

A Tablet Might Solve Your Problem
A tablet PC can provide a bigger display than a PDA while still maintaining the portable advantage. It carries the same mobility as a PDA but with a bigger screen so that more graphics information can be displayed for various applications. A bigger screen shows more and therefore meets the need for more complex or more detailed interfaces.

The operator interface of a Tablet PC or PDA is usually networked. The ability to browse the Internet also is demanded. More and more Internet applications such as HTML and CSS require 800x600 or higher resolution, and the Tablet PC’s screen size makes the browsing experience easier and clearer.

The tablet PC is not just for browsing, it also provides a data input mechanism. With a larger screen data input becomes much friendlier. For example, users have more space for handwriting or for a visible soft keypad for text input.

In addition to a bigger screen, the tablet PC allows true functional expandability due to more space for plug-in features such as GSM/GPRS.

GSM is the Global System for Mobile Communications. GPRS stands for General Packet Radio Service, the world's most ubiquitous wireless data service, available now with almost every GSM network.

GPRS is a connectivity solution based on Internet Protocols. With throughput rates up to 40 kbit/s, users have a similar access speed to a dial-up modem, but with the convenience of being able to connect from anywhere. GPRS supports Internet browsing, video streaming, multimedia messages, and other services.

Russell Sung, senior manager for handheld PCs and portable PCs, Advantech, www.advantech.com.tw


PDA Displays Might Be OK
We have seen many ways in which machine builders use PDAs as an operator interface. One is as an actual replacement for the HMI hardware.

For example, our client Micon uses a PDA as the interface for its compressors and other machines. Although this example uses a PDA, a similar system could be configured with any Windows CE devices, such as a Tablet PC. The PDA communicates to the Micon controller via a wireless Ethernet connection.

Micon uses a Casio PDA and our HMI/SCADA software. The HMI gives operators the power of a full-featured operator interface at the distributed unit control level and the ability to monitor and control process activities while walking around the plant, or from home.

The wireless HMI uses a series of screens that Micon designed on a PC with our software development system and then downloaded to the handheld unit. Displays are logically categorized into overviews, graphics, group displays, trends/history and alarms.

We also have seen machine builders using PDAs as an add-on to the HMI built into their machine. For example, we have clients who augment the HMI with wireless devices for alarming and monitoring. 

In this case, the machine builder isn’t replacing the dedicated HMI necessarily, rather augmenting it with mobile or wireless technologies. Note that in both of these examples, the machine builder is actually running native on the Windows CE or Windows Mobile devices.

In the case that machine builders want to replace the HMI altogether because of cost savings, we have seen them use embedded controllers such as Beckhoff Automation’s TwinCat or ICP DAS WinCon--our software resides as a web server on the controller--and they use web access to their machines using either a PDA, laptop, desktop, or any device with web capabilities.

Our software can be installed as a web server on any HMI or controller that has a TCP/IP Ethernet port and is running a Microsoft operating system such as Windows CE, embedded XP, Windows XP, etc.

For controllers such as PLCs that don't run on the Windows platform, our software communicates via Ethernet or Serial using one of our more than 200 drivers written for various PLCs and controllers. These drivers are free and available for download at http://www.indusoft.com.br/download/drivers/.

In addition to the drivers, we have an OPC client to speak to an OPC Server from companies such as KEPware, Software Toolbox, and Matrikon.

Marcia Gadbois, vice president, business development, InduSoft, www.indusoft.com


A Good Example
The Information Ladder (data → information → knowledge → understanding → insight → wisdom) describes the stages in human learning as a progression from data at the lowest level to wisdom at the highest level. It is said: "Data is not information, information is not knowledge, knowledge is not wisdom.”

In our view, data is passed through one or more discriminating filters to generate Information items. When integration rules are applied to information items they result in knowledge nuggets. The distillation of knowledge nuggets leads to wisdom nuggets.

Good decisions require timely and accurate information. Our HMI/SCADA software maintains information items in a tag database, and screen objects display information on HMI Platforms. It provides interfaces to connect screen objects with data sources. It also includes several tools such as data logging and trend viewing that may be used in the process of data analysis to extract useful information.

Our view of the plant recognizes that machines can be outside of the four walls of the factory and distributed, as well as inside the factory. PCs are excellent work horses for collecting huge amounts of data. PDAs and other portable devices bring mobility, flexibility, and agility to the data collection process.

A good example of mobile machine monitoring is a system we deployed for snow-making machines. The machines are controlled by a PLC. A wireless network of PDA and PC nodes is used for supervisory control, data acquisition, system verification, and troubleshooting. It also includes some items for testing and gathering data on the snowmaking nozzle performance.

Snow making begins at about –2 °C. A gun mixes compressed air with water and blasts it into the air where it freezes and falls as snow. The colder the temperature, the more snow can be produced.

The HMI software logs current outside conditions such as temperature, wind speed, and wind direction, along with nozzle gun settings. This information then is used--along with knowledge of the process--to fine tune gun settings and optimize snow making.

Most data logging in the PDA is user-initiated. For example, while making snow it is desired to log the current conditions and gun settings. This happens on demand when a screen button is tapped. The HMI software interface helps finalize baseline flow values and multipliers.

Ramal Murali, president, Software Horizons, www.InstantHMI.com


  March's Problem

I Need a Well-supported Network
I need to find a control network with sufficient vendor and industry support—a control network for which I can find multiple sources of controllers, motors, drives, sensors, power controllers, HMIs, pneumatic components, and hydraulic components. What’s my best option?

Send us your comments, suggestions, or solutions for this problem. We’ll include it in the May 2007 issue and post them on ControlDesign.com. Send visuals, too—a sketch is fine. E-mail us at CDTheAnswer@putman.net. Please include your company, location and title in the response.

Have a problem you’d like to pose to the readers? Send it along, too.

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