Akom's Tech Ruminations

Various tech outbursts - code and solutions to practical problems

Hardware Hacks Replacing Garmin C330 Li-Ion battery on the cheap (with whatever is onhand)

Posted by Akom • Sunday, December 21. 2008 • Category: Hardware Hacks
I have a hand-me-down Garmin C330, the el-cheapo, no-text-to-speech teletubby-looking GPS unit that every online store was liquidating a few months ago. Mine also has a dead battery, and while it used to run for 1-2 minutes on it, now it barely runs 5 seconds. I can live with that, after all - you generally use it while plugged in, but it is oh-so-handy to be able to hand it to the passenger for co-pilot... co-piloting. So, I had to do something...

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Reviews Vimeo vs Youtube for flight video

Posted by Admin • Wednesday, December 10. 2008 • Category: Reviews
A few months ago I posted my successful flight video recorded with on-board camcorder on my RC plane. I posted in youtube, because, well, that's what everyone does.

The video was an 160MB two-pass Xvid AVI, and once it made it through the youtube hamster wheels, it didn't look so good, especially while flying high over the tree-tops - they all meshed together into a mess of pixels. I complained, but resigned to my low-quality destiny.

Some time passed and it occurred to me to look into Vimeo. Here are the results

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Hardware Hacks Toys Not all that is hackable should be...

Posted by Akom • Tuesday, December 2. 2008 • Category: Hardware Hacks, Toys
Last week I hacked up my RC transmitter and added a Dual Rate switch
Dual Rate switch
See here: (How I hacked it up).

I thought I was so cool for adding two wires, one toggle switch and two drops of solder to an RTF transmitter (oh and a nice hole too). Well, everything worked great on the ground, but once I actually flew the plane, not all was well - the control range dropped to about 60 feet!. I didn't connect the dots at first and thought it was a broken antenna wire or something, or a new flying site (coincidence). Nope.

Apparently, adding two thick wires radomly into a complex circuit and placing them along the perimeter of the case can have some unexpected results. I took the wiring and the switch out, and all is well again, control range is longer than sanity permits me to test (plane is a dot in the distant sky, but still seems to be controllable).

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Hardware Hacks Toys Hacking up RTF RC Transmitter with a Dual Rate switch

Posted by Akom • Monday, November 24. 2008 • Category: Hardware Hacks, Toys
I can't say that I have a good reason for doing this, other than the potential for letting inexperienced family members fly my plane, but I thought this should be easy enough to do:
RTF Radio with DR Switch


The RTF transmitter that came with my Pitts S2A has a bunch of dip switches, which are not so quick to flip on the fly - and I've played with friends' real professional transmitters - and they have what seems to be useful toggle switches to control this stuff. So I figured I'm gonna pretend that I'm cool too.

The transmitter turned out to be very neatly designed, and finding the switch and soldering a pair of wires was surprisingly easy. Moreover, the cute silver pads on the top corners of the transmitter are actually silver stickers, covering up pre-drilled holes intended specifically for what I'm putting in there - a toggle switch.

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Reviews The Mystery B6 balancing LiPo/LiFE/NiCd/NiMh/Pb charger (review, sort of)

Posted by Akom • Tuesday, October 21. 2008 • Category: Reviews
The Mystery B6
I got this charger because the little unit that was included with my R/C plane just did not inspire a lot of confidence. It did charge, just took hours, and gave no hints about why. So I figured I'd go and buy something that gives me a little more information. And I found it. In Hong Kong. But now it's on my desk.

For being able to charge anything, the $50 and two weeks of waiting simply doesn't seem excessive.

As far as I can tell, the Mystery B6 gets a fair amount of negative commentary on the forums. People seem to question its voltage precision and balancing accuracy. So I thought I'd run a very simple test.

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Toys On Wheels, Thrust Vectors, and Gorilla Glue

Posted by Akom • Tuesday, October 21. 2008 • Category: Toys
New Wheels next to old wheels
I upgraded the wheels on the Pitts plane, and what a difference it makes. I never thought it could land (and sometimes even take-off) on grass! (Well, short grass, anyway). I don't nose in every landing now. Just got those 2.50" Sport wheels from the hobby store. The stock wheels are just way too small. I did need to cut the wheel pants slightly to fit them, but I think it is cute the way they stick out. And as you may have noticed, the Fiji bottlenose got a paint job.

Now about those thrust vectors...

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Toys Pitts S2A third video flight, straight and level

Posted by Akom • Wednesday, October 15. 2008 • Category: Toys
I did it! I flew straight and level. Video is available. Since the side of the fuselage seems to be the best place for the 215g that is the camcorder, I needed 200+ grams on the other side... or less all the way at the tip of the wing? Then it hit me... I have two lipo batteries, about 100g each. And that is how the balanced Fiji Bottlenose was born.
Balanced Payload

In addition to balancing the plane correctly, I finally got to cleaning the camcorder lens, which helped a bit with the sunspots and artifacts. I also covered the microphone with a bit of soft grey packing foam to act as a windsock - and the sound is no longer clipping from the airstream.

The details...

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Toys Pitts S2A second on-board video flight

Posted by Akom • Tuesday, October 14. 2008 • Category: Toys
This morning I thought I'd test my luck a little more, and mount the camcorder (Panasonic SDR-S10 at 220 grams) on the side of the fuselage. Visually, it just seems safer there - in a crash I expect the wings to protect it. On the downside, it unbalances the craft a lot - 635g plane with 220g of now unbalanced payload! But I did it anyway.
Camcorder on the side

See the video...

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Toys Pitts S2A Bottlenose motor mount rebuild

Posted by Akom • Monday, October 13. 2008 • Category: Toys
I didn't see this coming - hesitated in my landing approach, caught a gust of wind, clipped a cute little pine tree - and dove straight down 15 feet, carefully missing the soft lawn and hitting the packed dirt road. Front end demolished - engine cowl and engine mount are in pieces, fuselage cracked. The prop saver may have helped the motor survive this adventure.
New Engine Mount (mount cross is inside bottle)

I tried to find suppliers for these parts (again), but nothing turned up. Other than buying a whole new plane, I don't see a way of getting a new motor mount (that seems a little silly, no?). The fuselage is easy, Gorilla glue got that back together in an hour or two. (In fact, I've already glued the fuse with it once, and that weld did not break).

But the mount?

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Toys First Video Flight!

Posted by Akom • Sunday, October 12. 2008 • Category: Toys
I've been thinking about aerial photography for some time, and I've worked out exactly what equipment I'd get too, but for now I'm not allowing any funds for this expenditure. I figured that AP is way in my future, but this morning I just decided - what the heck. FPV (First Person Video) may not happen right now, but at least I can record the flight and watch it later. So I went and weighed my SD camcorder... Panasonic SDR-S10. 220g or so - not too bad (My ultra-compact Optio S550 is 270g, and that's only a still camera!!!). The plane is 635g with battery. Hmmm...

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Code and Hacks Blackberry Pearl Causes Windows XP to freak out with USB Device Not Recognized

Posted by Akom • Tuesday, October 7. 2008 • Category: Code and Hacks
This was annoying. Whenever the blackberry was plugged in (USB), windows would ding and show a baloon saying "USB Device not recognized", and this would continue forever, repeating about every 10 seconds! Clicking the baloon would show you the USB device tree, with a very helpful "Unknown Device" shown in bold. It took some time to figure out that it's happening only when the BB is connected. It sort of seemed as if someone is rapidly connecting/disconnecting the USB cable.

Well? Turns out that this is sort of what was happening. It was a bad cable. OK, perhaps not a bad cable, but one that the blackberry didn't like. And, unlike what some people suggested, having it plugged in through a hub is not the culprit. Interestingly, the cable that was malfunctioning was heavy duty, with ferrites. The cable that works is thin and flimsy.

Code and Hacks Firefox 3 Uber SSL Security madness for Self-Signed Certificates

Posted by Akom • Tuesday, October 7. 2008 • Category: Code and Hacks
Or the infamous "Or you can add an exception" thing.

Apparently since Firefox 3, if you stumble on a site with an invalid SSL certificate, be it expired, self-signed, or bad in any other way, you are greeted (as before) with a warning. Only this warning requires 8 steps to bypass, not all of which are intuitive to the normal power user. Moreover, in my experience, Firefox will prompt you again and again once your restart it, despite the fact that you checked "Permanently store this exception". And why do I need to "download" the certificate anyway? The browser must have already retrieved it by now since it's warning me about it.

I actually considered downgrading to Firefox 2... but I found a solution.
Here is what you do:

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Toys Sapac Pitts S2A electricals and motor replacement

Posted by Akom • Monday, October 6. 2008 • Category: Toys
I killed the motor. Apparently ramming into pavement at full throttle (don't ask. From now on, when something goes wrong on takeoff, I abort) is not such a good thing for a long thin shaft and a firmly bolted prop. A few flights later, the motor died and started singing instead of spinning. One of the windings seemed to be busted (based on measuring voltage with a drill).
Measuring Current

Anyhow, I did some measurements when it was all good, and here are some specs: With the stock Sapac 2830 motor and the 3-blade 9x8 prop, the battery put out as much as 12.5A at full load (my measurement, massive analog meter). The battery is 10C, 1200mAh, meaning that 12.5A is about as much as you could ever expect it to put out, in other words - running dangerously high. I also got a 10C 1800mAh battery and the plane had noticeably better thrust (haven't measured the current), so it actually did want more than 12A!

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Code and Hacks Old Hard Drive, New Motherboard and the Windows Stop 0x0000007B error

Posted by Akom • Saturday, September 27. 2008 • Category: Code and Hacks
My old motherboard finally died, so I managed to free up another one and threw it in. This is one of my very few windows machines, dual boot Win2K/XP. Neither one worked with the new motherboard - 2K gave me a very nice bluescreen with the infamouse Stop 0x0000007B error, while XP simply quietly rebooted.

The old board was the wonderful (back in 2001) Gigabyte 7VRXP (1.1) sporting an Athlon XP-1800+. The "new" board is a NVidia based A7N8X-VM, complete with an Athlon XP-2000+. I managed to downgrade my server to an Intel Atom low power setup (see separate post), so this one was available, moreover - it has n AGP 8X slot and the old board - only 4x. Yes I know this is ancient hardware, but I have no interest in spending hundreds on all new hardware when all I want is something to run Nero and Realflight. (And occasionally, Blackberry JDE).

Anyway,

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Reviews Gentoo Linux on D945GCLF with Atom 230

Posted by Akom • Friday, September 26. 2008 • Category: Reviews
I decided to downscale my asterisk server (currently Athlon XP2000) to something that's not quite as power hungry. The server barely does anything most of the time, but consumes just over 100 watts.
The Atom 230 on the D945GCLF

$70 later I was staring at this very cute little green square, complete with a chipset fat/heatsink and a very naked CPU (needs no cooling at 5 watts). It looks hilarious in my small tower case, hides entirely behind the vertical ATX power supply (I realize I can run this off a Pico PSU)
Power improvement? (Same case, power supply, hard drive) A7N8X-VM with Athlon XP 2000+ : about 100-110watts at idle. D945GCLF with Atom 230: About 45 watts at idle. (At this rate, the power savings will pay for my expenses in 10 months, roughly - including the $30 for the 2GB DDR2 RAM)

The following is a small list of issues and solutions I've come across while migrating my Gentoo server over to this thing.

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