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| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I can see November from my house :-)
Late at night, by candle light, Marco Trapanese penned this immortal opus:
The 1N4148 will likely survive a good bit of pressure due to its small size making for small surface area in relation to volume. Fuses, even hermetically sealed, will crush under less pressure. There are some with thick walled ceramic bodies but I don't know their ratings off-hand.
The hermetic seal makes a big difference. If the part is sealed, the body must be able to withstand the pressure difference, since the pressure inside will remain constant. This is exactly the same as a submarine. It is designed to withstand a certain amount of pressure difference. If the pressure difference goes too high, the hull will be crushed.
If the part is not sealed, the dielectric oil will enter the part and possibly (or probably) affect its electrical properties.
If the fuse was sealed, it would collapse at a certain pressure. How much pressure it would take, nobody knows. A fuse like that is, however, not sealed. You can, in fact, pull the end caps off with your bare fingers. If such a fuse was submerged in oil, the oil would enter the fuse and change the fuse's properties. Since oil has much higher thermal capacity than air, I'm guessing the fuse would withstand much more than its rated current before it blows.
Could you make your ROV a two-chamber solution? One pressure proof chamber for the electronics and one oil-filled pressured chamber for motors, shafts and stuff that can withstand the pressure. Electrical connections between the high-pressure and low-pressure chambers should be fairly simple, and you probably already have experience with those.
Do you have a vague idea of the number and thickness of wires (yes, at that pressure oil may migrate through the interstices among the strands) that will go to the electronics? And what about heath dissipation?
I don't think that 1.1 A will be sufficient for even a fin servo motor.
Do you think it's possible to find some that are not hugely expensive?
I would start with having a miniature pressure vessel turned from a bar of solid bronze, something big as half a beer can, and test the individual components, starting from the ones that are better left out of the pressure proof chamber, like power transistors and temperature sensors.
Marco's uncle should be able to do it.
The main problem are probably going to be the batteries.
Well, actually they don't need to, as the extra wire is used for either the base of the phototransistor or the output enable, so both are in fact optional.
Or maybe they do, since they need at least three wires on the output side, which is powered, while the simpler optos only need two.
Like I said before, the question is not related to ROVs. I just have a oil-filled tank with some electronics that should withstand to that pressure. It's a test equipment so no problem about temperature or whatever else.
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While "heat capacity" is the measurable physical quantity that
characterizes the amount of heat required to change a body's
temperature by a given amount, "thermal conductivity" is the property
of a material that indicates its ability to conduct heat.
http://en.wikipedia.org/wiki/Heat_capacity
http://en.wikipedia.org/wiki/Thermal_conductivity
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