Microship Status 11/10/93

Steven K. Roberts

In this issue:

Audio Network Thoughts
Trailer Width Information
NMEA 0183 AND WEATHER SATELLITE COMMENT
Bay Pressurization System
Updates Various

Audio Network Thoughts

Sometimes it helps to concretize a design with a few specifics. Since one of the early microcontroller projects here is the audio crossbar (AXBAR) system that Isaac Chu will be taking on, I thought I'd add further substance by listing some of the devices we expect to see on the network. Making this list has just demonstrated that we need to go ahead and package TWO of the crosspoint boards, which each handle 32 audio channels, half in and half out, with up to 8 simultaneous links active. (Bear in mind that any input can connect to any one or more outputs, but mixing introduces op amp output noise.)

Inputs (TO THE NETWORK): Speech synthesizer Cellular speaker Mac audio (stereo) TNC audio VHF speaker (marine) VHF/UHF speaker (ham) HF speaker (marine/ham) Radar audio alarm PC audio MCS audio Hydrophones (stereo) DTMF transceiver MIDI synthesizer (stereo) Console microphone Cassette recorder output (stereo) Video recorder output (stereo) (video switched separately) CD/stereo system (stereo) Audio filter/processor system Manpack wireless intercom Cockpit-crew intercom Audio link to tow vehicle

Outputs (FROM THE NETWORK): Speech recognition system Cellular microphone input TNC audio Main speaker drivers (stereo) Headset drivers (stereo) DTMF transceiver VHF mic (marine) VHF/UHF mic (ham) HF mic (marine/ham) Cassette recorder input (stereo) Video recorder input (stereo) Audio filter/processor system Manpack wireless intercom Cockpit-crew intercom Audio link to tow vehicle

Trailer Width Information

Frank Araullo responded to yesterday's help-list with some library research, finding relevant information in the Code of Federal Regulations. It's not clear to me exactly which roads this applies to, but on that subject Frank writes, "The National Network is a set of freeways that the Fed designated as vital in case of emergancy or military need. Now I would figure that most states would make the 8 1/2 foot rule common to all "real roads"; it might be difference for fire trails and such, but I'm not sure if we have to worry about such things. I'm going to check with local DMV on how wide a trailer can be on California roads; checking on other states would require a trip to the County Legal Library downtown."

Here's the relevant bit of legalese:

658.15 Width. (a) No state shall impose a width limitation of more or less than 102 inches, or its approximate metric equivalent, 2.6 meters, on a vehicle operating on the National Network, expept for the State of Hawaii, which is allowed to keep the State's 108-inch width maximum... <stuff deleted> (c) Safety devices... shall not be included in the calculation of width. Safety devices not specifically enumerated... may not extend beyond 3 inches on each side of a vehicle. No device included in this subsection shall have, by its design or use, the capability to carry cargo.

Heck. I was planning to keep spare ICs inside the lenses of my marker lights...

(Uh-oh, a new design constraint just surfaced. Says here that "in no case shall the total gross weight of a vehicle exceed 80,000 pounds.")

This probably means that we can make this as wide as 8.5 feet in road mode if we need to, though whether we WANT to is another question. Thanks, Frank!
NMEA 0183 AND WEATHER SATELLITE COMMENT

Frank Sharp, at Kitt Peak in Arizona, also responded to yesterday's list of help requests. He's sending a copy of the NMEA spec (that's National Marine Electrical Association for those of you who are wondering, and it describes the serial interface protocol common to most marine electronic and navigation devices like compass, GPS, depth sensor, etc.). He also writes,

>We have been using the network wx maps here with qualified success. It seems when a large number of people start accessing a given data base the overload causes the sysop to shut down access....... We're on our 5th source. For me the Coast Guard or direct access to the bird seems more reliable.....

Bay Pressurization System

James Gerken is working on this, and writes:
>Do we have any idea of what the approximate volume of the electronics bay is going to be? Do we have any idea of what the desired pressure range is going to be? Do we have any idea on the expected temperature fluctuations? Once I know some of these numbers, I can start figuring out what sort of air supply we're talking about.

I'll take a few guesses. On the total volume, we're really looking at a number of enclosures -- about a cubic foot for each console, and maybe about a third of the 36 cubic feet available in the engineering section (the rest is for storage). We should also assume that we'll pressurize the video dome, and probably a couple of other things we haven't thought about yet. So let's use 20 cubic feet as a capacity guesstimate.

As to the pressure range, Dave Berkstresser pointed out that high pressures would vastly add to the weight of packaging -- a 1 square foot panel covering an enclosure that's a scant 30 PSI above ambient has to withstand something like 2 tons of force. So the range we really want is maybe 2 PSI above ambient, actively maintained to prevent thermal fluctuations from causing problems (this requires the ability to vent, too, I just realized -- the separate enclosures will each be on the downstream side of a check valve so one catastrophic failure won't expose everything else to contamination).
Finally, temperature fluctuations will cover the full range of ambient temps in which I may be traveling, a bit higher on the console where there will be some greenhouse effects when the sun is astern. Figure somewhere below freezing to just over 100 degrees Fahrenheit...
James continues:

>I came across a product in Flinn >Scientific's catalog, Drierite, that is based on anhydrous calcium sulphate, with an added indicator compound so that it goes from blue to pink when wet. It is reusable after baking, and can dry gases down to a -100F dewpoint, which should be enough for this sort of thing.
Excellent. Is it available in easily handled cartridge form, with some kind of quick release so I can recharge it painlessly with the camp stove?
James also has a friend with commercial fishing experience who is sending some comments on saltwater exposure issues... watch this space for further updates in this critical area!

Updates Various

First, I am very pleased to report that Yendo Hu has offered to assist: "I would be glad to offer help as an advisor to microcontroller and hardware electronic development (at the firmware and transistor,ic,resistor level) for those students working on projects needing the support." This is great news, since he's had quite a bit of hands-on microprocessor experienc and is locally infamous for his balancing machine --

ECE team members working on controllers should get acquainted with him at: yendo@garfield.ucsd.edu.
In the sponsor-relations department, there was some progress today. I spoke with Current Designs and requested minimal decking, high-volume style, to give us hooks upon which to hang our own structure. They'll do it without cockpits or bulkheads, since we'll have to design those, but it will solve the problem of molding a deck to fit the precise hull seam. They will contact Nelson/Marek to confirm details, and then proceed with the layup.

I spoke with our new GPS contact at Motorola, and requested the CORE GPS module -- that's the integrated unit that will live on the bus as opposed to the handheld Traxar that goes in the pack. I also sent them an article from PEN magazine that speaks of my use of their product.
A follow-up call to the east-coast US dealer for the Furuno radar yielded the fact that the Model 1621 does NOT export video, which is too bad. We'll live with it. The proposal for sponsorship is still under consideration.

Finally, does someone who has done installation, wiring, and other hands-on electronics work want to spend a bit of time helping me install the security system in my lab? The rash of recent thefts on campus is making me nervous... not to mention all this publicity about the $1.2 million bicycle! That's such a bogus number... it's an estimate of what it would cost to build if I had to pay everyone including myself. Out of pocket cost? A tiny fraction of that. Current market value? Minimal, since it's valuable only to me. Ransom value? Forget it; I'm into boats these days. Think I'll avoid quoting dollar values on the Microship when the media starts showing up... it's too glib a handle and distracts the viewer from the real issues.

Cheers from the lab! Steve