Manufacturing AUTOMATION

Thin clients give you more than you bargained for

October 17, 2013
By Jeremy Pollard

In past columns I have covered many HMI/SCADA products that have a web browser interface for various devices. And, with the advent of the cloud, there may be many more reasons to have a browser interface available to you and the plant floor.

A thin client can appear as a definite-purpose appliance that runs Windows CE or Linux operating system, a mobile device running Android, or a re-purposed personal computer that has either Windows installed or a vendor-specific thin client OS.

To be clear, a browser or remote access software such as VNC can run on anything. Remote desktop protocol is for Windows-based systems. Depending on the device, you just need to add a monitor and keyboard/mouse combo.

There are many advantages to selecting an operating platform that allows for user interaction with a browser — cost, ease of maintenance, plant floor security and ease of deployment, along with various benefits for performance. Power requirements are significantly reduced for thin client appliances. For instance, the Esprit thin clients that I use require 0.65 amps compared to six amps for a standard PC.

A thin client runs the screen presentation and the user input handling, and reports back to the server. The computing power of the thin client is not as important as the resources of the server, so older computers can run thin client software quite nicely.


With the introduction of low-cost solid-state drives, a Pentium 4 computer can easily be used as a thin client.

A thin client appliance can cost as little as $25. If you want or need such things as high-resolution video and audio, then the cost can creep up to a couple of hundred dollars. There are many pre-packaged boards — such as the Raspberry PI or the Beagle Board — that can run a Linux browser.

Typically, the embedded software in a higher-end thin client can run a browser, remote access client such as VNC, and remote desktop protocol for Windows-based servers. Your choice will depend on the needs of the user application.

Mobile devices such as a BlackBerry can run just about anything as well. iPads and iPhones can also be used, and thus you have everything you need in a mobile device to interface with any application with a browser interface. For other interfaces, there is probably an app for that!

You can create a profile for these devices so that when the user powers it on, the device is a mobile browser only. This allows for application-specific devices and removes all temptations (such as solitaire) from the user.

Dell Computer Corp. has been reporting reduced sales for a few years, thanks to Steve Jobs and Apple. However, you can take those fully featured computers and turn them into an application-specific device.

Making the assumption that the computer is running a flavour of Windows, you really have three options: Run Windows as normal and run a browser; install a computer-specific thin client operating system; or create an interface of your own, and then tweak the registry to capture the user.

There are many options that turn your computer into a thin client. Google will get you there. However, if you want to run a non-browser interface on a re-purposed Windows machine, you can do so by tweaking the registry. The registry key is below, so that when the computer powers up, the application that shows up is the application name at the end of the string. Simple!

(“HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWinlogon”, “SHELL”, “c:EOA_TCeoa_app_ts.exe”)

Along with the ability to capture the user, your home-grown application can now perform the required tasks with customized software in a secure environment.

The targets for all of these devices could be Citrix, VMware, Hyper-V or any system that resides anywhere and can use any one of the thin client interface protocols.

The real benefits come into play in the current SCADA marketplace. Most major vendors price their systems by screens, users or tags. Some even have their own browser, which has some embedded code to attach to the SCADA server so that they know who is connecting and they can protect their licensing fees.

But, as with last issue’s column on Groov, the move to browser-based interfacing is on. There is a definite move away from Windows, since most corporate users are fed up with paying out of the nose for licensing.

While it may be true that you get what you pay for, in this case you get way more than you bargained for.

Re-think your HMI and SCADA platforms and applications, and use thin clients. You’ll be glad you did!

This column originally appeared in the October 2013 issue of Manufacturing AUTOMATION.

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