Defcon:Blog Keklkakl blog blag


CoreXY experimentation update: pen plotting with motor moves

The prototype for my CoreXY experiment now moves by motor control. Using Marlin software on an Arduino Mega with RAMPS1.4 to drive the motors, I go through several speeds from 800mm/min to 24000mm/min, (that's 400mm/sec) moves. I have made no care to precision in the belt, and adding that to unevenly tightened belts, flex in components, and finally a pen that's not really fastened well, there is noticeable flaws in the resulting drawing. However, this also means the prototype highlights what areas of a final build will need extra attention.

Relevant links:


CoreXY experimentation

Based on the CoreXY concept and ideas from FABtotum to avoid crossing belts, I'm experimenting to see if I can get away with as few mounting-points for belts/pulleys as possible. This video shows that my prototype moves, as well as showing the CoreXY movements. Moving resistance feels very low, even if this is very simply built (no linear rollers/brass bearings, no attention made to precicion...). Next step: moving the parts using the motors 🙂

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Arducopter AC 3.1.2 Loiter test on PX4

Finally I've gotten stable Loiter, by getting GPS and Compass away from pesky annoying interference. I wasn't able to show long-duration position hold as I had planned, because my battery went flat a bit early 🙂

The AC version I am using is quite old, so it is not representative of current AC Loiter state. I have also done minimal tuning of nav/loiter when doing the test.

The frame I am using is a HobbyKing Q450 (really a Whirlwind FY450), equipped with generic 20A ESC's and NTM 28-30S 900 motors spinning unbalanced 1045SF plastic props, so the PX4 is seeing quite a lot of vibration. The GPS is a uBlox Neo-7M + HMC5883l compass from HobbyKing:


Pathfinder Mk.0 Tricopter maiden flight

Maiden flight of my first bujild of a tricopter. The build is based on the common / David Windestål trike-design, but using aluminium 10x10mm profiles, FR4 as material for center-plate. Flight controller on this one is a KK2.1.5, ESC's are HK SS-series 18-20, tail servo is a TGY-9018MG.


FPV November – Biri Bruk

Evening flight in November at Biri Bruk.
Aircraft is my HCopter APM2.0

Soundtrack: "Son of a Rocket" Kevin MacLeod (
Licensed under Creative Commons: By Attribution 3.0


FPV forest flight in October

FPV-flight in the forest.

Music by MiuGlitch/Miu


Xen on Debian Wheezy (with VLAN networking and LVM storage).

TODO: Add an introduction paragraph, or ingress (so having READ MORE makes sense...)

Preparing the operating system

The absolutely first step in getting a Xen capable Debian Wheezy server, is to install Debian Wheezy. Really, there are no special tricks to this “step”, simply install a base system to your liking. I would reccomend NOT installing any X/Desktop environment at all; keep your Xen server a text-based system. Remember to install SSH server, as you'll probably be remote-managing the system. I'll also suggest you install NTP, VIM and Screen as part of the base install. After completing debian-installer:

apt-get install ntp vim screen

The rest of this prep-section is specific to my setup, you may skip down to “Installing Xen” if you like. In my setup, I'm using two RAID sets, one hardware-array with RAID1 for my root filestystem, and one software-array with RAID5, used as a physical volume for LVM. To set up these, the following packages are needed:

apt-get install mdadm lvm2

Next, to create my sfotware-RAID, I used (after a lot of testing to get acceptable IOPS from the disks):

mdadm --create /dev/md0 \
      --verbose \
      --level=5 \
      --chunk=256 \
      --raid-devices=4 /dev/sd{a,b,c,d}

That creates my /dev/md0, as I said, I'm using that as a PV for LVM:

pvcreate /dev/md0
vgcreate sraid5 /dev/md0

Installing Xen

With the basic operating system installed and (lightly) prepared, it is time take a plunge, and install Xen itself.

Continue reading ...


Networking with VLANs on Debian Wheezy

This is a short note on using tagged VLANs on Debian Wheezy. Setting up and using VLANs on Wheezy is slightly changed from previous versions. The most notable difference is that vconfig is finally deprecated also for Debian, and that the “vlan-raw-device” stanza is gone from configuration.

In this short document, I assume that you know how to set up VLAN trunking and -tagging on the network-equipment that your Debian-box is connected to.

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Et svevende blikk på Gjøvik Gård – Mikrokopter + GoPro

Et overblikk på Gjøvik Gård / An overview of Gjøvik Gård. - - -


Bacula backup server on Debian Lenny, with remote SQL server

This node is a REALLY REALLY incomplete scratch-space for my bacula-related node…

What is Bacula?

First of all, if you are reading this, I hope you have at least a minimal knowledge of what Bacula is. As in, at leas you know that is is a system for backup, recovery and verification of computer data. Hopefully, you also know that it is a scalable, enterprise-ready solution, and you are prepared for that.

As with everything else that gets labeled 'enterprise', and even 'scalable', Bacula is a system that is split into several parts, and is highly configurable. This gives great flexibility, at the cost of being rather complex to set up compared to smaller, simpler systems.

If you are looking to back up your workstation, and only that, bacula is probably not for you. The same is probably true if you are looking at doing backups for a small set of computers; say two-to-four. On the other hand, if you are planning on doing backups for a greater number of systems, across operating systems, and/or require dependable backup volume control, bacula is probably very well suited.

If you are coming from a commercial Enterprise backup solution, you may be surprised (hopefully pleasantly) to see that setup of Schedules, Clients, Jobs and the like are done in text-based configuration files, rather than a point-and-click GUI (or cryptic command line console).

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