Thursday, April 15, 2010

Protection from electrostatic charge

Various solutions have been developed for protection from electrostatic charge and to combat it effectively. One major problem exists where a plug-in board has been tested immediately prior to insertion into a live system under hot-swap conditions. Rittal now have alternative solutions to combat the discharge under these circumstances.

A new ESD discharge facility effectively removes all built-up charge from the front panel of the plug-in board and rapidly brings the panel to protective earth potential. Achieved via a heavy duty contact embedded in the guide rail, which is in permanent electrical contact with the chassis, the new system has been tested to IEEE1101.11 and UL1950 to 30 Ampere capacity. Initially designed as a rear I/O guide rail for 80mm assemblies, the high current discharge contact and associated guide may also be used for front mounted panels where excessive static build-up is likely.

The new guides include the facility to safely discharge any remaining static or operational charge (such as that stored in capacitors) from boards being inserted into the system directly following a test under power. For this, an additional grounding clip is fastened to the guide rail in the direct path of the PCB which needs to be designed in accordance with IEEE guidelines.

Additionally, the guides have chambers at the front for the insertion of coding keys to prevent incorrect board insertion when used in conjunction with IEEE type lever handles on the plug-in board / front panel. When used at both the top and bottom of a 6U board/front panel combination, these provide almost 4100 different coding variants.

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