Mar 272012

Built a small quadcopter. Receiver from ehirobo, transmitter from Helipal. All quadcopter parts from Hobbyking. It’s fun to build and fun to test. Firmware worked nearly out of the box. Awesome small little wind machine.

The only problem: Instead of using 2900 kV motors I got 2000 kV which results in 32% less rpm, which affects obviously the amount of lift it can produce with the same propellers. Fix: different propellers, more Volt, or more thrust. Right now I need about 85% thrust to lift. Good enough to learn I guess. But new propellers are already on my shopping list (3 blades instead of 2).

Some observations:

  1. The yaw gyro axis needs to be reversed.
  2. Set P to 50%, I to 0% and P(yaw) to 20% for starter. If you see oscillations, tune those parameters.
  3. If I is set too high, there’s a lazy motor syndrome showing: one motor will start very late. But not an issue in flight.
  4. A simple 4 channel transmitter is sufficient. More are not used anyway.
  5. The transmitter should be in “airo(plane)” mode, not “heli” mode.
  6. The cheap and simple KKmulticopter board with only 3 gyros is sufficient and it already beats any helicopter hands down in terms of stability.  At the same time, it does not take away anything else from the pilot as it’s missing all the other sensors some other quad’s have (e.g. barometer, GPS, accelerometer).
  7. There are quite a lot of versions of the software for the HK  Multi-Rotor Control Board as it’s KK board compatible. A solid one is the one from Rolf Bakke AKA kapteinkuk itself. I use version 4.7 and it seems to work fine.
  8. All those small little screws like the M2 screws for the motor mount, something non-metric and tiny for the prop saver (looks like hex sub-1mm), the 2mm diameter motor axis…I already wish for a larger quad with M3 screws as the minimum size. And it turns out that it would be only minimally more expensive, as small motors are like shoes for children: small does not mean cheap.

BTW, I used yaw by hanging the quad on a long rubber band. Since yaw relatively weak, it did not work well in my hand. I could feel it reacted on me turning it left or right, but I could not really say whether it’s amplifying or counteracting yaw. Turned out it’s amplifying it, and it was very obvious once I lifted the quad into the air on those rubber bands.

 Posted by at 09:34  Tagged with:
Mar 232012
Synology DS212j

Finally got a small NAS. Although it was tempting to get a bigger/faster one with 5 or  4 disk slots and a fast CPU, it’s way overkill for my purpose, so in the end, I went for a small DS212j plus a (for now) 3TB disk.

It’s plenty fast (75MB/s read via NFS), the GUI is awesome, the capabilities more than sufficient. It has some kinks though:

  • The OS is on the disk and not in flash memory.
  • If you have 2 different size disks, then if you create a mirrored volume, the rest of the space goes unused instead of being able to use it as a non-mirrored volume.
  • Volumes always take full disks (or what is left after the OS is copied on them)
  • To enable NFS, you need to first enable it, and then create shares (which are usually for Samba shares), and there enable NFS sharing too.
  • To enable home directories, click on the user modules and click there on “User Home” and enable it and say which volume to use.
  • Disk groups names are hardcoded: Disk group 1, Disk group 2 etc.
  • Volume names are hardcoded: Volume 1, Volume 2 etc. They map to mount points called /volume1, /volume2 etc.
  • The media server does not ask for the location of files. It defines it to be on a volume you pick.

If you have only 2 disks, do yourself a favor and get 2 of identical size and use a RAID-1 (or their hybrid volumes). Alternatively expect no mirroring whatsoever. If you have more disks (4 would be a good start), then this is much less of a problem.

Mar 052012
nVidia Power Management

My Dell Vostro 3700 is all good and nice, but too hot. All the performance I usually don’t care. CPU performance is nice to have, but thr GPU is overkill unless I play games, which I have not done for years.

nVidia’s Linux driver has some hidden power management settings, which until today I could never enable. The nvidia-settings tool always showed high performance (Graphics clock 575MHz, Memory clock 790MHz, Processor Clock 1265MHz). The lowest performance is 135/135/270MHz. Obviously much slower, yet fast enough for pushing windows around the desktop.

Finally this did it (and here some more explanations):

PowerMizerEnable=0x1; PerfLevelSrc=0x2222; PowerMizerLevel=0x3; PowerMizerDefault=0x3; PowerMizerDefaultAC=0x3

This sets the performance to lowest possible (0x03=lowest) for all possible power-situations.

Screen is still snappy, and even Google Earth, which is probably the most taxing program I run in terms of graphics, is still perfectly ok to use. The result is about 6° less temperature (idle machine runs at 67 instead of 73°C. That allows the CPU to run a bit faster, or alternatively more cores to run in parallel without either the fan spinning faster, or the system forcing a shutdown due to overheating.


 Posted by at 22:28  Tagged with:
Mar 052012
Kubuntu 12.04 LTS Beta 1

Kubuntu 12.04 LTS Beta 1 is out and curious as I was, I gave it a try. I had some good reasons:

  • The company’s remote access RDP client behaved funny with my dual monitor setup after messing with the Java runtime environment
  • My Dell Vostro 3700 gets really hot really quick and there’s a known regression in the Linux kernel

The first one caused me to boot into Windows 7 again, which is at least annoying, the latter causes my CPU to run not at 1.6GHz which would be its nominal frequency, but 1.2GHz max, without Turbo-Boost. Luckily the CPU is still very fast for my purposes and 4 cores plus hyperthreading, 6GB RAM and a GeForce GT 330M help.

So I tried the update to Kubuntu 12.04 LTS Beta 1 which is well described here and which worked equally well, with one minor problem which was Dropbox: while it tried to reinstall or re-download the Dropbox Debian package, it was just sitting there…after 2h I killed it and then the install process continued. The fix is as simple as a

aptitude reinstall nautilus-dropbox

and that fixed everything.


Most things look just as before with minor changes, some things are much nicer (Dolphin’s icons now move around nicely animated when resizing its window), and both issues I had with the previous install are either gone (no issues with the VPN RDP client anymore) or much better (temperature definitely decreased during normal operations)


 Posted by at 22:05  Tagged with: