Mark Mischke's Weblog

Cell takes a dipping and keeps on ticking

Scenario: water bottle opens in wife's purse, flooding everything, including her new Motorola e815 cell phone.  We're talking total immersion here.

The phone was flaky that day and wouldn't hold a charge.  I had high hopes, though.  The water bottle was filled from one of those reverse osmosis/deionizer dispensers.  'Deionized' is the key concept here.  Water is an insulator.  When ionic substances, like salt, are dissolved in water, the solution becomes a very good conductor.  I figured that there was a decent chance that everything would be OK once the phone dried out.

Many modern cell phones have a white dot under or near the battery.  The dot turns red if the phone has been in the water.  This feature allows manufacturers to deny warranty coverage to folks who go swimming with thier phones and fib about it.  Supposedly the dot doesn't turn red unless the phone was _really_ immersed.  A little bit of rain shouldn't do it.

After letting the phone dry overnight (it didn't actually 'take on' water - there was no sloshing sound when I shook it), I popped the back cover off and the dot was deep red.  I compared it to mine (same model), whose dot was pure white.  The battery was fully discharged and it wouldn't start up, even under AC power.  I plugged it in and a couple of hours later it was functioning perfectly.  So far it's been two days with no ill effects.

Town forests

It seems to be a lesser-known fact that many communities in the greater Boston area have forested land set aside for public use.  Many folks regularly visit the Blue Hills Reservation and Middlesex Fells, but a lot of people don't seem to know about the smaller hidden gems within their own towns.  When I lived in Arlington, we had Menotomy Rocks, which was just large enough to provide the feeling of being away from it all.  Now, in Natick, we have the Hunnewell Town Forest.  It's a decent tract of land, which can be appreciated from a Google Earth shot.

I suspect that town forests were common knowledge back in the 1970s.  As evidence I offer the broken-down exercise stations along the trails in Menotomy Rocks.  'Stretch Here'.  'Do Pull-ups Here'.  I remember seeing the same things on trails at UCONN when I was there in the '80s, and they were broken-down then.  People have been moving around a lot over the past decade, or so.  As such, they might ot be aware of things like town forests lurking in their midsts.  That being said, there are a healthy number of people in the HTF whenever I'm there, but not relative to the number of people I see out and about, in general.  Natick is a healthy town.  People walk, run, walk their dogs and stroll their babies.  You can't look out your window for five minutes without seeing someone go by.

One thing missing from our town forest is a decent trail map.  I've walked most (all?) of the trails, as well as the unofficial trails, which look like little more than game paths.  A personal goal of mine is to map them all out with my GPS.  Once done, I'll release it into the public domain.  Our forest is well-maintained.  Blowdowns are quickly cleared.  Natick clearly cares about it, so I want to do my part and create a map.

Pimped-out Mac mini

I've liked the Mac mini from the moment it first appeared.  The new Intel-based minis are particularly exciting because they have the potential to provide something I've been looking for since early 2005 - high performance, silence and a small form factor.

The mini seems to be an ideal media center box.  Both the iMac and MacBook Pro offer 2 GHz CPUs, 7200 RPM hard drives and ATI Radeon graphics.  They're designed for performance.  The mini trails with a 1.67 GHz CPU, a 5400 RPM drive and Intel 950 graphics.  This keeps costs down, minimizes heat dissipation issues and is more than adequate for a media center machine.

I see the mini as a viable candidate for replacing my aging 2.6 GHz P4 desktop.  Despite the shortcomings, the mini's CPU and hard drive can be replaced.  I've been working off of my Alienware Pentium M notebook for nearly a year, and I love it - except when I'm doing two processor-intensive tasks at once.  I need the ability to execute two threads simultaneously in hardware.  I don't really care if it's through hyperthreading, dual cores or dual CPUs.  The mini can give me this, as well as all of the other things on my wish list.  I don't play games, so I'm not concerned with 3-D graphics performance.  Having said that, 3-D performance on my Alienware (Intel Extreme Graphics 2) is good enough, and the mini's engine is two generations more advanced.

OK, it's clear that I like the mini for its form factor, silence and performance potential.  I'd have to raise the bar a bit in order to make it a viable desktop replacement.  I'd want a faster CPU and a faster hard drive.  That's really about it.  I'm not worried about thermal problems, since I've read about people swapping thier mini's 1.5 GHz Core Solo for a 2.0 GHz Core Duo with no negative fallout.  I've also read that the thermal characteristics of 2.5" 7200 RPM drives and 5400 RPM drives are nearly identical (check out the specs on Hitachi's site).  Realistically, I'd probably go with the 1.83 GHz Core Duo because it has the best price point.  The 2.0s seem a bit overpriced.  Apple also charges too much for RAM.  I need 2 GB, and $300 feels a bit high for the upgrade.  I figure that if I'd have to open the case to install everything else, snapping in two memory sticks won't be a problem.

Here's my proposed shopping list for a pimped mini (prices from apple.com and newegg.com):

We're looking at just over $1200 for a tiny, fast and silent development machine.  Sadly, here's where my fantasy ends.  I've found my Holy Grail, but I really can't justify the cost right now.  My notebook and my P4 desktop still serve me quite well, despite their shortcomings.  Plus, Spring has arrived and the cash is better spent on house-related stuff.  I figure that I'll be ready to upgrade later this year, and Intel is promising the next revision of the Core Duo, so everything just may come together very nicely.  I've waited for over a year, so a few more months won't kill me.

• 1.5 GHz Core Solo Mac mini          600
• SuperDrive upgrade                   50
• 1GB DDR2-667 (5300) SO-DIMM (x2)    180
• 100GB 7200 RPM SATA drive           195
• 1.83 GHz Core Duo CPU               190

It's 2006. Where's my laser gun??

Laser weapons have been a cornerstone of science fiction ever since the laser was invented in the early 1960s.  The very first laser could punch holes in razor blades.  Lasers are (usually) pretty simple devices, and I believe that lethal human-portable and/or vehicle-mounted lasers have been around since the '70s.  I recall reading about high-powered airplane-based lasers, presumably for the purpose of shooting down aircraft and/or missiles, during the same era.  I've been interested in lasers since I was very young.

Progress in the fields of electronics, optics, materials science, (etc.) has resulted in smaller, more efficient high-power lasers.  I suspect that it's now possible to build a reasonably efficient human-portable laser weapon that would mimic conventional firearms in terms of size, weight and lethality.  A laser gun.

But we'll probably never see such a weapon.

Lasers emit light.  Light reflects off of things.  Laser light is particularly intense - especially laser light with enough intensity to cause physical harm.  Even subtle stray reflections of such light could cause immediate and irreversible blindness to anyone unlucky enough to be in the way.

I do believe that the archaic firearm will eventually be replaced, but it will probably be replaced by a railgun or a particle beam weapon.  Not a laser.

High-brightness white LED array - the next step

Looking back in the archives, I first mentioned doing this back in January.  I bought a pack of 100 27000mcd 5mm (standard size) white light LEDs on eBay for about twenty bucks.  My initial plan was to just breadboard 'em up, but that began to feel too ugly.  Far too many bulky solder connections in too little space.  Plus, I'd be embarrassed to show it to anyone.  :-)

I looked into designing and etching my own PC boards.  I've done that in the past, but it involves corrosive chemicals and sometimes you don't get a good etching.

I found a free CAD program (ExpressPCB) that assists in PC board design from both component and connection perspectives.  It's pretty easy to use and offers one-click ordering of small-to-large quantities of your design.  I designed a board to mount 20 LEDs along with thier dropping resistors.  Quantities are in multiples of two, so I ordered six, figuring I'll probably mess one up.  Total cost was around $100.  I could have easily burned that much getting myself set up for etching again.  Plus, the manufactured boards will save me a ton of time that would have been spent drilling tiny holes.

When I get the array up and running I'll post pictures if it's worthy of them.  I expect to have one hell of a bright, compact light source when I'm done, running off of only 24V at around 0.5A.