Building Ruggedized Embedded Computers

Today, computers are ubiquitous devices used in all kinds of different applications. Many of those applications require that the computer can withstand adverse environmental conditions. These demanding conditions include heavy shock and vibration, extreme temperatures and quite a lot of similarly tough conditions that are not usually handled very well by electronic devices. There are several ways to tackle these requirements.

The first measurement to create a truly ruggedized computer is to build the electronic device in such a way that it can handle mechanical abuse. This can be achieved by using light-weight components, which are firmly soldered to the printed circuit board. This alleviates the risk that a component is pried loose under continuous vibration.
Furthermore, the printed circuit board itself must be kept at a small size. Together with strategically placed mounting holes and their corresponding screws, this keeps the amplitude of mechanical oscillations down to a minimum.

The mechanical hardness can be further increased using a suitable material for the printed circuit board. Polyimide material lends itself to that task. Although it is expensive, it is a very sturdy material, which is not easy to bend or to break. As an additional advantage Polyimide is specified for a wider temperature range than standard materials.

There are more things to consider for PC/104 modules. Especially the connectors need the designer’s attention – they should be lockable to assure that they won’t fall off. Because of the size of PC/104 boards, it is often advisable to make the mechanical construction of the enclosure in such a way that the board is tightly held by it.

One of the main concerns in today’s electronic appliances is the allowed temperature range in which the device can be operated. Most contemporary components are only specified for commercial temperatures ranging from 0°C up to 60°C. The well-known PC components, such as processors, chip sets and memories are not offered in a wider temperature range. Truly ruggedized computers for mobile applications, however, need to operate in temperatures ranging from –40°C up to 85°C. If such conditions must be guaranteed, the only valid option is to extensively test the complete electronic modules over the required range. This can be done by putting each and every device in a climate chamber that runs a temperature profile, which is usually custom-defined. Functional tests are done at critical temperature and power supply conditions. Of course, these tests are expensive. However, experience shows that devices surviving such an extensive run-in test can safely operate for an extended time in real-world conditions.

LiPPERT delivers PC/104-Plus modules that are build according these practices. The Cool SpaceRunner was especially designed to survive under aerospace conditions. It is a complete PC system especially build to operate in very harsh environments. It comprises a Pentium class processor together with the necessary chipset, all the standard peripherals of your desktop PC as well as DiskOnChip memory and a PanelLink interface for EMC-free connection of LC-displays.

(Original appeared in Extension Media's PC/104 & PC/104-Plus Embedded Resource Catalog 2003)

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