Zarcon Dee Grissom's Idea Page
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Updated 15MAY2008
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MCC Thoughts
So what goes in to the design of Mission Control?
I started collecting and assembling computers, from dumpster finds. Some cases got modified to there new tasks, others got gutted. Then as I got more computers on the SETI BOINC task, The issue with power rose in concern. Thing is, power is never as reliable as needed for any Mission Control Center.
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Idea#009

LEGAL NOTE;
This page is in no way, to be the definitive source in designing and/or building Mission Critical anything. It is meant to give an idea of what goes into the design of Mission Control Facilities.


This presents what I am in the process of building. with next to nothing for funding.


I started collecting and assembling computers, from dumpster finds. Some cases got modified to there new tasks, others got gutted. Then as I got more computers on the SETI BOINC task, The issue with power rose in concern.

Thing is, power is never as reliable as needed for any Mission Control Center. FINAO (Failure Is Not An Option), dictates how every piece of equipment is build and used. Nothing critical is ever directly connected to the manes. This is where UPS's come in, however 15minutes simply will NOT do the job.  We don't want shutdown time, we NEED uptime. So an UPS that can deliver hours or even days of uptime is what we need. This leaves us with two choices. Buy a room of gear from APC for thousands of dolors, and leave the fate of MCC on some one else's design and commodity based production. Or assemble the entire system ground up, in-house, to satisfy the needs of the mission it will serve.

bottom line, if there is room in the design and construction of a mission critical system to fail, it will fail at the wost time possible. Learn the lessons and achievements of Apollo 13. Why was there an "A" and "B" buss at all, guess.

Safety must always be obied. don't follow safety precautions on the use of equipment, and FINAO is out the window, witch is NOT an option.


RULE #1

Batteries must always be ventilated to outside air when in use, NO EXCEPTIONS! Batteries produce Hydrogen gas when they are charging and/or discharging, can we say BOOM! A battery connected to the power buses, is always in use. Even fully charged batteries consume a maintenance charge, AKA produce Hydrogen gases.

The best way to accomplish this is to place the batteries outside, however this may not always be possible. Get a big (acid proof) air tight container, put a 12V fan near the bottom of the container blowing in (powered by the batteries), and place a dryer hose (mettle is preferred) near the top of the container to vent the exhaust out side. Do NOT put the fan on the bottom of the container, this will let spilled acid leak out on to the floor. Place it about one inch from the bottom of the container. The exhaust vent should be as short as possibly. Preferably, the container will be placed up against an outside wall, of witch it's vented out threw that wall. The reason for the vents placement, is Hydrogen is light and will rise to the top of the container.



RULE #2

NEVER use substandard wires. Thin wires produce heat, witch is guaranteed to produce Fires. Besides with long runs of 12V power, the wire resistance will reduce the power that is available at the other end. So always use Over-Rated Wire.

The following Table Is for X-gage Wire, ratted for Y-temp, in 30C(86F) conditions.
AWG TW, UF
60C(140F)
ratted
THHW
75C(167F)
ratted
18AWG 14A 14A
16AWG 18A 18A
14AWG 20A 20A
12AWG 25A 25A
10AWG 30A 35A
8AWG 40A 50A
6AWG 55A 65A
4AWG 70A 85A
3AWG 85A 100A
2AWG 95A 115A
1AWG 110A 130A
1/0"aut" 125A 150A
2/0 145A 175A
3/0 165A 200A
4/0 195A 230A
minimum Amp rating of AWG wire at room temp (NEC2004)


RULE #3

Everything must be protected from as much as possible. Consider if something shorts out internally, this could bring down the entire 12V power system. YES even in MCC, fusses are our friends. Place a fuse at each connection of every box, junction, Load, and source of every power line. This will quicken the time it takes to isolate a problem and fix it (For Damage Control).


RULE #4

Ground's must “star” off of key locations, NEVER LOOP. Loops of Wire create antennas, witch can receive deadly spikes from motors and deliver them to equipment. For Negative Ground systems, place one Thick negative wire between junction boxes, instead of one for each buss.



RULE #5

To prevent the BUSS fusses from blowing under normal conditions, Throw out the power companies documents on Mean Power Distribution and Average load. Besides I hate square-roots. This is simple, Add up the MAX current draw from ALL devices that is going to be attached to the buss. This is the MINIMUM amp rating the buss fusses and wire should be ratted at. This will prevent a system-wide-cold-power-up, from blowing buss fusses. Like I said, simple.


Misc Stuff
Simple UPS layout
Well in light of the mess on the original diagram, and several parts that are NOT included due to lack of space on the diagram. I decided to break it down a little.
System Overview
System Overview
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Bus Isolation Unit
Bus Isolation Unit
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Some pics of prototype Bus Isolation Units
Proxy Bus Iso and inverter cutout
Proxy back&assist
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Proxy Bus Iso construction
Construction
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Bus Iso Construction
Construction
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Bus Iso Construction
Construction
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I will take a second to talk about the Power supplies here. First off there not originally 14v power supplies, there actually heavily modified 13.8v power supplies.

Well first off I turned up the voltage a smidgen not to compensate for the loss produced by the diodes in the bus isolation unit, rather to brig the main bus voltage up enough to allow the batteries to fully charge before the forward voltage on there isolation diodes prevented the trickle/maintenance charge from working correctly.

Second off, most consumer electronics are not intended for 24/7 operation. Heavier heat sinks, improved ventilation, and heavier output terminals and wire. Second was the addition of Poly-film capacitors across the power supplies main electrolytic capacitors. This is to reduce the heating up that electrolytic exhibit when there introduced to high frequencies. That and Poly-film capacitors have a lower ESR then Electrolytic capacitors. So given a large enough Poly-film capacitors, employed properly in a switching power supply, they can almost completely snub out any RFI at the source circuitry. Less then 20nV p-p from 20Hz to 10GHz is not imposable to achieve from a switching power supply under any load condition.
PSU Mod
PSU Mod Schematic
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Doubling up the output Schottky diode packs in parallel, will reduce the current each diode is carrying. this will ultimately reduce there combined forward voltage drop, reducing there total heat output, and improve the efficacy of the power supply. It is an absolute must for the replacement Schottky packs to be able to handle the full load (Amps), switching frequency, and the voltage of power supply.

And last but not least, adding copper to the existing power traces, to reduce the voltage drop cross the PCB.


Now a horrifying discovery about one of my inverters I found, when I opened it up to add Poly-film caps to it's circuits. Remember that thing I stated about consumer electronics design. Well Apparently the looks of a car-amp outer heat sink shell is just that and nothing more on some inverters. The internal switching components are attached to a completely separate heat sink, not thermally connected to the heat sink shell of the inverter. That particular inverter relies solely on the air that is dragged threw the internal heat sink by a 40mm fan to cool it's guts, and the outer shell dose nothing to cool the inverter.

T.B.C.


Example 12 Power Grid.

Ideally there would be two power sources at both ends of the buses, verses just the one at the top of the above example.

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