SD, SM, MS, etc. sockets

The card is read once at power-up. The data is written during calibration, which happens at build time and once a year after that. The idea of removable storage for the cal data was that the calibration is for off-board optical components rather than those on the PCB itself. So a dead board can be swapped out in the field and the uSD card transferred to the new one.

Typically once per day, sometimes more. I don't know the details of the bootloader, we bought the OS off-the-shelf. From testing I know it only takes one O/C contact to hang the CPU during boot, and we have never had a problem here with fielded units.

Fairly benign, commercial-office-type environment, no extreme temperature, no severe shock&vibe. For a more demanding environment I'd be wary of using sockets at all. Buried in the spec for the embedded PC connectors is the gem "Max allowable disconnect time under shock : 1 us" I can't imagine some of the faster interfaces e.g. PCI, USB reacting well to this.

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Hi Mark,

[attributi>> Mark Borgers>>> A lot of digital cameras use SD memory and have the

I'd be happier if you'd said 9 *years*! :>

(I plan on burying these in the ceiling, walls, etc. so having to dig them out every 9+ months would not be fun)

How do you ensure the atmosphere inside the vessel is (and remains) dry?

Ah, OK.

Yup. I recall designing kit for maritime use and having to conformal coat everything. Made repairs a real PITA.

The relief is only activated for *service*? I.e., the vessel doesn't vent while submerged?

Almost as much fun as *sodium*! :> (actually, I wonder which would be more aggressive?)

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D Yuniskis

Battery lifetime was the controlling issue. It may be that the CF cards would have been good for many years. I have CF based loggers in the shop (Persistor CF-2) which haven't had the card pulled in about 5 years of intermittent operation.

I've generally avoided conformal coatings for oceanographic stuff. It just doesn't seem worthwhile as any salt water will get at the wires and connectors anyway. Some of the controllers for GPS-guided parachute systems will probably end up with conformal coatings as the specs say they have to work from 0 to 25,000 feet and in sand, rain, and salt spray. We can't afford the weight of a hermetically sealed container, so some movement of air (and water) into the case is likely when the thing descends through a rainstorm. At that point, it only has to work for another 10 minutes, though.

It was a screw-down vent. When the system came back you opened the vent. If it started hissing, you went away for a few hours.

This was much better than releasing the screws that held the end of the pressure case in place and watching it push out against the screws! (a little of that always happened anyway--as pushing in the end cap compressed the gas inside a bit.)

Good questions. A lithium battery isn't all lithium and I think the metal gets oxidized as the battery discharges.

Mark Borgerson

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Mark Borgerson
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Understandable. In my case, I have power available to the devices *and* they are inaccessible. :< I want to make sure I don't shoot myself in the foot.

Understood. But they are in a reasonably comfortable environment (25C, controlled RH, etc.). In the ceiling (here), temps will easily hit 60C. They will be exposed to periods of very high humidity (rain storms). Plus, all the "cruft" that gets in there (how can you get

*dust* inside the ceiling?? :< )

Yup. But, a fisherman (or repair shop on the shore) can replace a wire; damage to a board means a trip back to the factory. :-(

Hopefully not *11*! :>

Ah, OK. Like rotating the cap on car radiator 1/4 turn

*before* removing.

I think I will leave that for others to play with! :>

I've watched sodium, phosphorus, magnesium, etc. things burn and the idea of putting the fire out by removing the skin from my body is not a pleasant thought! :<

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D Yuniskis

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