Re: Investigating possible effects of EMI on FireWire cameras
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From: Damien D. <dd...@do...> - 2014-06-07 07:27:49
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Hi Alex, On Sat, 2014-06-07 at 13:50 +0800, Alex John wrote: > Good morning, > > I am using a pair of FireWire cameras (Guppy/Guppy Pro) connected via > an AVT pci controller card (TI-TSB43AB22A). I'm using them as vision > cameras for an underwater autonomous vehicle. I'm facing a very weird > issue where the cameras shut down when certain thrusters are fired. > The device disappears from the device list and has to be physically > replugged to raise it again. That looks like a power supply issue to me... At least I would start investigating there with a multimeter to see if/how the voltage drops on the supply rails when the motors run. If you use batteries or an umbilical (any other option anyway? :) you may get voltage drops due to batteries limitations or wire resistance. Next step is using a scope to check the noise on the supply voltage, if the motors run on the same supply as the cameras. > Is anyone here familiar with this kind if issue? 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. > > Reducing the data rate does not seem to help. All thrusters firing as > fast as possible on land does not seem to cause any issues but as soon > as the vehicle is in water we lose the FireWire devices. I imagine that motors won't draw maximum current above water as the medium is much less dense. The motors' current will be higher underwater (higher torque required) and the supply rails may then drop significantly. OTOH 1394 cameras have DC-DC converters to deal with the varying supply voltage found on 1394 busses, so they should be able to cope with transients. Of course the cams may fail if you supply them at a nominally low voltage (e.g. 5V) and the voltage drops further down. What kind of supply are you using? If you supply 12V to the cameras they should be able to cope with supply variation pretty well. Damien -- Damien 高原 Douxchamps http://damien.douxchamps.net/ |