Dry-Ice Canon fun

Use frozen carbon dioxide (dry ice), mix it with water and pipe the steam into a PET bottle. When the bottle at roughly 22bar explodes you can shoot for example a toy chicken over more than 80 meters (We had serious problems to build a projectile that is not destroyed by the power of the launch). We built the device for a creativity competition at our university.
And well, we could not place an object accurate on 20m but for shure we did it with the biggest impact.


Music on Amazon and iTunes

If you are curious, here some detail about the construction:

For us secure handling was not only an option. We have seen some people that put water and dry-ice together into an bottle close it and put it into a pipe. But you have good chances that it will explode in your hands. So we put an PET bottle into our pipe and connect it with an CNC made adapter to the presure reservoir outside. Beside that, all parts are made from steel and welded. We experienced that a 1.5l coke bottle (actually we used Deit bottles that explode in a better way) can withstand up to 22bar of pressure (what is more than most sources on the internet report)

The next design decision we had to make was a system to quickly inject all the water while not blocking the exhaust of the considerable amout of CO2 gas that is generated as the water mixes with the dry-ice. We first tried it with an single valve but had a problem to get more water it at some point when to much CO2 was exhausted. Howerver two, one for water injection and the other valve for the gas exhaust were ways better.

Finally, the manometer is not necessary but nice to have as it makes the firing a bit less surprising. All in all we spent about 90 Euros.

This blog makes money... erm gifts!

I lately discovered CuriousInventor as they sell some quite interesting diy kits like the touch strip LED display that looks perfect for synthesizer controlling to me (Hope to get one for christmas). But the really interesting thing to me is that you get a PanaVise Junior Clamp for free if you link them from a page with Google PageRank of 2 or higher (this page had 3, when I checked). So lucky me, I get a gift worth 18$ at their shop for free. Who said making profit from the web would be hard? ;)

It's done

Finally Summer of Code 2008 is over for me and it has been good. Although I had a lot to do this summer, I can say that I really enjoyed working on my project. So thanks to Google, Musicbrainz and Philipp for his mentoring.

Screencast

I made a little screen cast showing my project in action:

Implementing an finite state machine

I have to confess that informatics has to offer some really useful concepts. One of them is the finite state machine. Basically it works like this: The system is in a certain state. Then you have transition matrix that contains the condition for a transition from one state to another. If the update() function is called matrix conditions are checked. If a conditions is fulfilled for the current state a transition is done and the system enters the new state. Here is the current transition matrix:


The states used are:

• Init: asks the user to drag in some files
• add_files: at least one file dragged in
• to_many_files: over fifty files dragged in. Tells the user that less would be better but doesn't force him to do so
• select_ungrouped: asks to select the "ungrouped cluster"
• choose_method: ask to put mouse over scan or lookup to get an detailed description of the two methods
• explain_lookup: As it says, explains the lookup process, advantages and disadvantages
• explain_scan: same here
• process_scan: displayed while scan is in progress
• process_lookup: same
• successful_finished: explains the color thing and so on..
• unmatched_files_scan: if scan produced unmatched files the user could try should try lookup.
• unmatched_files_lookup: if lookup produced unmatched files the user could try scan
• please_submit: if both methods failed, the user is asked to help MB by submitting the files if possible
  

Overall the implementation is quite flexible and hopefully easy to maintain.

Second part started

I'm glad the wiki thing worked and I'm already working on the in application support part of my project.

The goal is to guide a first time user through the process of tagging. This will be accomplished by a little box above the two main panels that provides information on what to do next automatically and based on the users action.

Although I realized that there a many ways users are working with Picard, I decided to go a simple way that should work for most users. As the user advances in using Picard, he'll find his own favorite way of tagging.

Help me to improve support texts

Hi,
under the hood the wizard now is quite finished. But as I'm not a native English speaker I need your help at improving the support texts given inside the wizard.

They are, as Robert stated a bit to formal and stiff.

I really would be glad if some of you could have a look at the wiki page, where you can edit the texts.