Re: Investigating possible effects of EMI on FireWire cameras
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From: Stefan R. <st...@s5...> - 2014-06-09 14:25:42
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On Jun 09 Alex John wrote: >>>> On Sat, 2014-06-07 at 13:50 +0800, Alex John wrote: >>>>> The cable is spliced >>>>> and joined again using molex connectors and shielded with aluminum >>>>> foil for extra protection. We are thinking that it shuts down because >>>>> of EMI. [...] > The cameras that die are always the external cameras. The difference is > that we have cut the cables and used our own underwater cables including > connectors. The camera that is in the hull connected straight using the > original FireWire cable never has any issues. Both cameras are running > on the same power system. Did you use stock 1394 cable material, or other material? Here are some points from the IEEE 1394 reference cable constructions concerning the shields and their connections to the plugs, for comparison: - Each of the two data pairs has got its own shield. In addition, there is an outer shield around everything, including the power pair. - In 4-4, 4-6, 4-9, 6-9 pin cables, the two inner shields around the data pairs shall be in contact with each other and shall be isolated from the outer shield. - In 9-9 pin cables, the two inner shields should be isolated from each other and shall be isolated from the outer shield. - The inner shields shall be connected with the 4-pin connector's plug shield, or with the 6-pin connector's VG pin, or with the 9-pin connector's dedicated Twisted Pair A Ground Reference and Twisted Pair B Ground Reference pins, respectively. - The outer shield shall be connected with the 6- or 9-pin connector's plug shield. [These and the other parameters of the reference cable constructions, such as permissible length and wire gage, are just examples which work, not strict requirements. Actual requirements of the standard are specified in terms of performance criteria, as far as I understand, not being an electrical engineer.] Did you als modify anything at the device side, i.e. boards or chassis? If so, the question is whether termination and isolation of the signal pairs, power pair, and shields are affected by those modifications. -- Stefan Richter -=====-====- -==- -=--= http://arcgraph.de/sr/ |