Case: 15" x 10" x 4.5"!!!
Mini "Kinda Portable" Desktop PC
Case: 15" x 10" x 4.5"!!!
This computer was designed to be as portable and inexpensive as possible while supporting a real glass CRT and
being powered by +12 volts only. Jeez, why didn't I just get a laptop? Reasons:
1. LCD displays, even good ones, have problems displaying shades of grey with real linear accuracy and without
artifacts. They also have problems in cold weather. Both of these characteristics can make CCD work difficult.
Plasma displays may work well in cold weather but generally do not support grayscale at all.
2. Although you can get used laptops capable of running a CCD camera for $400, these generally are equipped with
older with poor quality LCD displays (some capable of actually showing only 16 or 32 distinct levels of gray although
the electronics might support 256 shades). A new low-end laptop with a "good" screen is still around
$1300, which is pretty expensive to use in the field.
4. Older laptops are generally not supported well by their manufacturers (if indeed they still exist) and repairs/parts,
if available at all, are extremely expensive and proprietary. Parts for newer laptops are also expensive and generally
require factory installation. I recently tossed out a laptop I had invested $300 in for this reason.
5. Older laptops generally use NiCd batteries, which have notoriously bad performance in cold weather.
5. Laptops, old and new, generally don't have more that one parallel and two serial ports. Port expanders, expensive
and proprietary, add considerable bulk and might require AC. They also sometimes have peculiar incompatibilities
with software.
6. Laptops are generally not expandable or upgradeable internally.
7. Laptops are not very rugged, unless industrialized or militarized, and those are ungodly expensive.
8. Most importantly, I had most of this stuff lying around or could get it cheap!
This computer was built into a nice old fashioned steel equipment box about 15x10x4" and has a "mini
AT" style P166MMX/32M "all in 1" processor board from PCCHIPS installed. It is powered by a National
Semiconductor DC-DC evaluation board. The CPU board has on-board video and sound, but the sound has been disabled.
A very small network board was installed in a PCI slot for data transfer to my home network. This machine runs
DOS and Windows software for my Quickcam and CB245 CCD cameras. I had originally intended this machine for use
with Mel Bartels' stepper control board, but instead at the last minute I installed it in this instead, hence,
the holes.
The unit has an 810 meg IBM 2.5" hard disk with a tiny adapter to 50 pin connector IDE. 2.5" drives generally
require only 5 volts, and very little current, even upon spin-up. The power supply is on the margins for powering
this computer, so it has to start in two steps, so, two on/off switches - one turns on the power supply, and the
other outputs that power to the computer/hard disk. The motherboard would not otherwise boot, probably because
of the high inrush as the caps on the motherboard are charged. However, the entire computer is very efficient,
drawing only 2.15A at 12 volts. Plumber's epoxy is used as the strain relief for the 12V cigarette lighter input.
Yes, I know I should have used a connector, but this WAS supposed to be a low-budget project...
There are three red LED's angled down mounted on the front, and there is a brightness control for them. This illuminates
the keyboard area. Because there aren't any LED mounts capable of this, I used my trusty plumbers' epoxy, which
I swear has saved me dozens of hours in "one-of" electronics projects.
The video monitor is a 9" B/W VGA, which is powered with a very small 120VAC inverter. A wired keyboard (a
mini point-of-sale full-travel keyboard ) is used with a small mouse, but an infrared keyboard/pointer has also
been used.