How to avoid a USB meltdown in harsh environments

Brian Foster, B&B Electronics
EETimes (8/27/2012 9:08 AM EDT)

Brian Foster of B&B Electronics points out that like the Hindenburg, USB has potential trouble designed in. This article discusses the problem, and what can be done to remedy it.

On a rainy day in 1937 the German airship Hindenburg arrived in Lakehurst, NJ, after a trans-oceanic flight. The ship dropped its mooring ropes, and a few minutes later it went up in flames. Theories about the fire include exotic tales of sabotage, but most scientists agree that the true culprit was an electrostatic discharge (ESD). And they agree that the potential for disaster was designed into the Hindenburg right from the very beginning.

The problem was a matter of simple physics. Hindenburg’s fabric outer cover was connected to the duralumin frame with non-conductive ramie cords. The cords were coated with a light metal covering that was intended to improve conductivity, but it wasn't very effective. As a result, the outer skin and the duralumin frame were able to develop very large differences in electrical potential. And, on its approach to Lakehurst the Hindenburg passed through a weather front with a high electrical charge.

Upon its arrival, still in the rain, the airship dropped its mooring ropes. Within minutes the ropes were wet enough to ground the airship. When they did, an electrostatic discharge jumped between the Hindenburg's cover and its duralumin frame. Theorists have argued about the ensuing fire, and whether it was initially fueled by a leaking hydrogen cell or flammable paint on the fabric cover. But they don’t disagree about the end result. The Hindenburg was consumed in less than one minute.

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