Story originally posted August 5,2002

Our initial system provided plenty of computing power to accomplish all of our navigation task.  However, we needed to have the genset running in order to provide 120 VAC to power it.  My goal with this project was to strip the internals from our current computer, build a new aluminum case and incorporate a 12 VDC power supply which would run from the house battery banks.  The computer will be located in the access compartment behind the wheel in the pilot house.  We will have a touch-screen LCD flat panel display in the pilot house and an additional panel in the solon.  The computer will provide entertainment functions as well including DVD, AM/FM, television and games.  Our primary application underway  is the Cap’n Navigation system, or Electronic Charting System (ECS).  This Coast Guard approved application is one of the best and easiest to use ECS around and I highly recommend it.  For those interested, the computer internals consist of a dual-processor 550 MHz CPU, 1 gig (yes 1 gig !) of memory (RAM), and two IDE hard drives for a total of 60 gigs of disk storage, two USB 1.1 ports, a read/write CDROM drive, a DVD drive and other “things” normally found on commercial computers.  You may ask, why not just put an inverter on your boat?  And my answer is, why take 12 VDC from the batteries, convert it to 120 VAC, then in the power supply for the computer take it back down to 12 VDC ??  The loss of efficiency is probably in the 25% range and over a year of operation that could account for several hundred dollars in diesel fuel.

Would I build one of these for you?  Of course I would – just write and I’ll ship one to you within two weeks.  Plan on spending around $1,500 to $2,300 depending on the configuration you request.  I’ll help you make decisions on what you may need.

The case is an all aluminum enclosure with three cooling fans (two intake, one exhaust.  The intake fans are variable speed.  The hard drives are in a removable tray (it can accept four drives).  The power supply is in it’s own tray.  The cabinet can accommodate three 3.5 inch drives and four 5.5 inch drives.

The power supply is from Key Power Inc.

9 VDC TO 18 VDC ( ± 12 VDC )


Output ratings

Total output power : 250W continuous output
Efficiency : 65% typical at full load
Hold up time : 16ms at maximum load and normal input voltage(12 VDC)
Power good : TTL compatible signal out with 100ms to 500ms

Short circuit protection (SCP): All output equipped with short circuit protection
Over Power protection : Peak power protected to between 110% to 125% of continuous rated power
Over voltage protection (OVP): +6V ± 0.5V by +5V

Operating temperature : 0 to 50 degree Celsius ambient
Cooling : By forced air
Storage temperature : -20 to + 85 degree Celsius ambient
Storage humidity : 10~90%

Mean time between failure : 100K hours at 25 degree Celsius ambient

PS/2 Type Dimension : 150(L) x 150(W) x 86(H) /mm

SCHOTTKY DIODE ESAD83-004 (60A 40V) x 4 FOR +3.3V, +5V OUTPUT.
7905 FOR -5V @ 1A

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