Toshiba said it couldn’t be done

Jim McNiven of Diagnostic Instruments in Livingston, Scotland reports on the design of a rugged portable computer.

In industrial applications, engineers often take laptops with wireless PC cards into situations they were never designed to cope with. The problem? Such systems were simply not designed to meet the needs for such rugged environments.

Siemens recognised this market gap and decided to develop a high performance, ‘extreme rugged’ portable device. The new device had to be capable of creating a user experience equal or better to anything that could be achieved by a laptop PC.

Diagnostic Instruments (DI) of Livingston, Scotland, already had its own draft specification for a similar device that matched Siemens’ design criteria very closely. DI’s current products also demonstrated its capability in meeting the demanding 2 metre drop test. In addition, the Di-225-IS (intrinsically safe) product was under development, and was designed to use the NEC 4121 processor, which Siemens wanted for the new device – so DI had prior experience of using this processor. As a result, DI landed a contract to design the new system for Siemens.

The new Windows CE based device – called MOBIC T8 (Mobile Internet Communicator), would have to combine the ability to survive severe rough handling, with leading edge performance. In both respects, it needed to outperform anything currently on the market.

The perceived market requirement was for a device which offers battery life lasting a full 8 hour shift on a single charge, a high degree of data security and robustness, a colour TFT display and recreation of a PC experience, full wireless capability for mobile applications, and the ability to withstand a 2 metre drop and high pressure water jets. A demanding specification, and one that Siemens refused to compromise on.

DI was told by several professional organisations that meeting the stringent drop test criteria with a full VGA display was impossible. Even Toshiba, the suppliers of the display, said it couldn’t be done. The test involves dropping 5 units a total of 26 times. This covers every corner, edge and face of the unit! Each drop is from 2m onto plywood backed by concrete.

To meet this requirement, DI designed an innovative ‘cradle’ to house the delicate display and backlight assembly. Once in place, the cradle allows the assembly to travel up to 5mm in three dimensions during an impact, absorbing the energy and protecting the display.

The MOBIC also had to be sealed to IP65 against water and dust ingress. This means it had to be placed on a rotating table, where it was subjected to high pressure water jets, 3 minutes on every face. For the dust test, no dust is allowed to enter the casing while placed in a vacuum chamber for 8 hours, with an agitator stirring up the dust in the chamber.

MOBIC has an internal backup battery, so even if the main battery fails or is removed, data is still held within the device. Flash is used to store operating system (32Mb) and program data. Solid state memory (64Mb RAM) instead of disc based technology ensures that drops don’t destroy data.

MOBIC is also designed to offer wireless connectivity, via a number of formats. More and more off the shelf cards with CE drivers are being launched by the major card manufacturers, opening up the possibility of using the MOBIC along with GSM, WLAN, and GPS.