Thursday, March 24, 2011

Promoting the game

Well, arbitur in Germany, you know. Just had my english tests. I am sorry that I have so little time meanwhile, in a few weeks this will change... meanwhile...
Here is a little game I'd like to promote. You may already know it. That's just the demo:
VVVVVV Five times the letter V
 (just to make it clear, the pic isn't by me. found it on
It's a really neat kind of jump-and-run game, in its very own cool style. The full version is much larger and just costs 5$ to download, so you may want to check it out. I spent hours already when I should have learned physics, lol.
Have a nice rest of the day, ladies!

Tuesday, March 22, 2011

tutorial: Coil gun

I decided to put up a tutorial to build a coil gun.
You can read the basics at Wikipedia. Its basically one or more coils accelerating a bullet via a strong magnetic field triggered in the correct timing. There are two different core designs to build a coil gun:
a) multistage coil gun
This means, there are more coils to get the projectile forward. The problem behind this is that you have to time the coils so that the ones behind the projectile are off while the ones in front of it need to be turned on. This requires you to build up some kind of circuit which triggers the coils. However, the potential behind this is that you can accelerate the projectile much better and accurater, resulting in a higher fire power.

b) single stage coil gun
So, the alternative to the multi stage is a coil gun which just uses one coil, turned on with a high current flowing and let it be off before the projectile is through. It results in a much more inaccurate acceleration, giving less potential firepower. However, its a much simpler design requiring nearly no extra circuits.

This tutorial will yet cover only the basics of a single-stage coil gun, and as soon as my multi-stage coil gun is working fine, I will post a tutorial to build it.
So, here is what we need:
a) A capacitor. You need an electrolyte capacitor. They have two important measures: The  voltage and the capacity. You'd like some with a decent high voltage and a middle-high capacity. The formula for the energy contained in a capacitor is E = 1/2 C U ², which means, if you double the voltage, you get a four times higher energy. If you double the capacity, you get the double energy. So guess what, you try to get the highest voltage possible. However, I recommend to not exceed 100 Volt for newbs and for nerds I recommend to not exceed 330V (Why this? It means you can still charge it on a regular plug. Ofc, if you have a 110 Volt plug, you'd not want to exceed 160V. Don't get why 160 Volt for a 110 Volt plug? Its the peak voltage). The more Voltage, the more dangerous it is if you touch it. Then, you do not wan't to have an exceedingly high capacity because that mean's it'll take too long to let the capacitor run empty, resulting in a possible pull back effect for the projectile. Get what I'm saying? The projectile runs through the coil. Now, if the coil is not turned off by the time the projectile is through, it will pull the projectile back. You would not want that. (Moreover, a high capacity may cause a short in the batteries because its basically no resistance at the beginning of the charging process)
For my first coil gun which ofc was just built in 3 hours and was maybe as strong as a decent softair, I had a capacitor with 25000 microF and 100 V (charged to just 90V). You can get capacitors from the internet of course, or you visit some kind of speaker shop. I got mine from that speaker nerd around the corner, I just asked him if he had some capacitors left. Worked fine.

b) a voltage source
You'll need something matching your capacitor's voltage. So, as my first capacitor had 100V, I had 10 9-Volt blocks which means it did charge with 90V (yeah it was just for aestethic reasons not 11 blocks with 99V). Well, you can calculate how long the batteries will last.  Let's say you got 600 mAh, this means 600 mA one hour long at 9V. So, this is 0.6*9*3600 ~ 19 kJ of energy. My capacitor with 25000 micF and 90V (charged) contains 1/2CU²=101 J of energy per shot, so it will last around 190 shots. It's enough.
Now, I better don't tell you how I charged my second coil gun, because it's too dangerous. It involves a glass of water, some salt, some wires and a plug with 230V (and a bridge rectifier).

c) A coil
 Well, this basically means a lot of wire with a thin isolating layer to prevent shorts. I did the coils myself, so I went to the speaker nerd guy and asked him about old coils. He gave me alot with 1-3mm thick wire. Basically you just spin it around the barrel as long as you want the coil to be, and then you add the next layer right away. You have to watch out to keep the same direction all the time, otherwise your coil will be useless. Don't worry, the coil will look a bit shitty, but it's alright though. However, try to keep the first 1-2 layers as clean as possible. The coil shouldn't be too long, this will make the magnetic field too low. However, having the coil too short is worse because it may pull the projectile back in and moreover, its harder to spin a shorter coil.

d) a barrel
you should use some massive plastic or aluminum here. Really no iron or steel, because it's magnetic and will make the magnetic field veeerrry, very slow, unable to shoot a projectile. I used some thin plastic barrel.
You have to spin the coil around it.

So, what you actually do is (I will not explain how exactly you do this very well, because that depends on your favors):
You take the capacitor and attach it to the voltage source for a few seconds (batteries should do the trick under 15 seconds normally). You then put a projectile 1-4 cm before the coil and in a single clean strike attach the capacitor to the coil. Beware, you need to seperate it from the batteries before to not cause a short.
The result is a strong magnetic field. Why? Well, if your wire has a resistance of 0.05-2 Ohm, which is realistic (since its just a wire, probably even pretty thick), and you attach a voltage of (for example) 90 Volt to it, you have a current of 1800-45 Ampere. Well, I had like 300 probably at the peak. This is really high.

 PS: Watch out to not make the coil wire too long, a high inductivity will lead to slow magnetic buildup times.

And since you all don't care and I wouldn't either, here are some Videos of such guns to satisfy your real needs ;)

 Nice made coil gun, not too strong though.

Decent one as well, especially it's pretty strong for the energy I feel.

 Very strong, but for the energy and the SCR triggering (it's a multistage) not that high.

Really weird rail gun, makes a huge EMP as well. Neat!

The navy researches as well:

So far, thanks for ignoring the upper part of that posting. I'll provide some images of my 680J Coil gun the next days as well, at least it pierces 1.5 mm steel. That's tough isn't it? ;)

Monday, March 21, 2011

Two little videos I liked, you know, modern animation arts and stuff...
this evening I'll post a little tutorial about how to build a coil gun, so if you're a nerd, stay prepared! If not, just ignore that since it's pretty technical ;)

Sunday, March 20, 2011

Flash game

Just a little post today, since I don't have much time. Abiture test in germany, you know.
I guess you know this little game, if not, play it. Share your time/score here (classic mode), I'd be interested. AND! Please share your gender as well, because I'd like to see if there's some tendency in image recognition ;) Maybe you can see a bias here.
Well, here's the link:
I guess I like the game because I am fascinated by the way how we can recognize patterns and images very fast without really being able to tell why. This is one of the reason there aren't really much physical useful robots yet: They can't recognize their surroundings by imagery because its a very calculation-intensive process for them to even tell a door from a window. Well, as I said, time runs by and I got to learn some physics as well. See you soon and play the game, share your highscore ;)
I'll add my highscore ASAP.

Saturday, March 19, 2011

OPTE project

So, this is only for people who didn't yet know this. Its a piece of internet art and interesting from the technical point of view as well.
I am talking about the opte project. For a brief introduction, visist
What this is: A map of the internet. No, really, it draws a node point for every host it detects and there from makes a web to near nodes. They even figured something to filter out local networks (since they have the same IPs over and over again). Now, you can see some major nodes which are the carriers that route the network traffic all over the world, most of them by some big providers such as Verizon and Telekom and stuff. Looking at this is pretty beatiful imo, especially since it features a 4000x4000 pixel map.
Moreover, it gives you a neat idea of how the internet is built and what it truly is. A masterwork of the humanity, one of the greatest things we ever accomplished.

Minecraft cannons

So now seriously, how to build a minecraft cannon? I saw a lot of videosshowing how to build such a cannon and stuff. However, I don't get to get it working. I mean, I can build it with 1-2 rows TNT and it works fine. But sometimes, just if I take too much TNT (3 rows รก 4 TNT for example), it blasts the cannon and I can start to build it again.
If any of you folks know exactly how to build a decent cannon, tell me please. I don't know why it doesn't work.
Greets and out.

Thursday, March 17, 2011

Getting rid of the spam

I just set up my root again. In fact, it got hacked. I realldy didn't expect to be the internet such a war zone and now I get why everyone says "son don't get a root unless you really know what you're doing!".
It was the second time it had some kind of rootkit and/or spambot. I had 130 GB traffic in february, nearly all of it due to unwanted mail traffic.
Seriously, how does this even pay out for the dudes that write the worms? I mean, did ever anyone clicked that viagra ads they spam out to random email addys?
However, I changed my ssh port, disabled root login and installed chRootKit and am fine since 9 days know. Guess thats the whole deal huh?
Seriously what the ****, as the everyday internet user you really never see what's behind the scene. 10 different russians and chinese attacking your server via bruteforce 24/7 is not exactly what I expected when I heard of "hacking attempts".

Minecraft server setup

Well, today I decided to put up some small minecraft server. It was very easy to set it up on my debian root at first, but soon you get into a lot of mess when setting up additional features. In fact, after a few hours I switched to BukkitCraft, which is a new mod for minecraft. It was developed to provide an easy way for plugin and mod developers. Well, my server now has some cronjob rendering a map via mcmap, has iconomy, townsy, permissions etc. This means you can have your own town there and be a resident in a town, be part of a nation, trade with others, teleport sometimes, and something very awesome are the features MinecartMania supports. Users on my server started to set up some automatic farms with it for sugar canes and sell them every day. This whole stuff is a lot of fun on a multiplayer survival server, it generates a very realistic feeling ;)
You can ask me for support setting up a similar server, I'd love to help someone out. If you want to play on the server, feel free to message me to get the adress to try it out.
Peace out ;)

Okay, I decided to get a bit more detailed. So if you're running *nix or best, Debian, you can do this:
First, get java if you dont have it. You can try this out by typing "java-version" You'll need 6 or later afaik.
Well, if you don't have it:
aptitude install openjdk-6-jre-headless
I got the jar file from Place it into your minecraft root directory, mine is /home/***/minecraft_test
Then you can make a new shell file, named It should contain the following:
java -Xmx1024M -Xms1024M -jar craftbukkit-0.1.1-snapshot.jar nogui
You can add options there as well ofc.
 Well, now get the plugins you want from
Meanwhile you can run, or, if you don't want to have the window open all the time, screen and execute it over there.
Stop the server again and take a look what he created. There is some file which should be updated according to your needs. Then you can put your plugins in the /plugins/ folder. Run the server again. It should have created some additional folders now again. Take a look into them, update the .yml files according to your needs. Be careful to not break the syntax.

Well, test your server now.
If you need help, feel free to contact me!
I do not have a lot of time currently because I have a load of tests the next days, but I'll make a lot of updates here soon.