I found some basic flaws in my design already. I made the mistake of not taking sideway pressure from the drill itself into account. The telescope slides have a sideway tolerance of about 1mm. I will continue anyway, maybe I find a way to correct this by adding guides or the machine will at least give me the means of drilling exact holes and help me build the next one ;)

the drilling guide

a long hole. a crater, rather

21st of december: all parts drilled

• cheap (why, of course!)
• USB solution
• ready PCBs
• open source if possible

Most CNC configurations still rely on a computers LPT port. This is due to the fact that a program can access this port in realtime as opposed to the USB port, which is buffered. There are several solutions on the web using microcontrollers to execute the code given through the USB port. I went for the one done by [planet cnc] in combination with classic l297/298 motor drivers by [PMinMO]. Both provide ready to use parts, kits and schematics to do your own board designs. I went for the kit solution instead of designing my own boards because I wanted to spend more time on mechanical design. PMinMO provides a truly great documentation with his boards, by the way! I got a PCB and a preconfigured chip from planet cnc. He provides a software with drivers for windows (costs though) that should also work under Parallels and such.

I soldered one driver and the controller board together but haven’t gotten around to do any tests yet…

soldering the smd parts to the driver board

the controller (w/o chip) and one driver, waiting to be tested

After spending most of the summer doing technical coordination for the [Festival Über Lebenskunst] I went directly to helping the team of Tomas Saraceno set up his exhibition at [Hamburger Bahnhof], Berlin. I really enjoyed that, Tomas having a nice team and his works keep impressing and inspiring me.

Right now, badly in need of a job to earn as much as I can before going to Thailand in January, I started a soldering job at [Koma Elektronik], helping them to assemble their circuit boards .

Of course, I kept working on the [Diskokugel], trying to improve the circuit. Read more about that [here]. I also contemplated some on my actual intentions with this object. I will share that with you soon.

And, to make things worse, I got inspired by an [instructable] to build my own CNC-mill. That is just another example of how I constantly underestimate the time and effort (and money) of the tasks I keep imposing on me. I’ve already invested 3 weeks into it without any visible result and I keep going… Il post some pictures soon, however.

On other news: Halloween came and after laughing my ass off watching this [cookie monster video] repeatedly, I had to refer to it with my costume for the annual party in Frankfurt.

God's away on bizniz...

...

The TDA7053 has a DC volume control input, which made us hope that we would simply connect it directly to the 4094 register to switch it on and off, making the 4066 switch obsolete. Unfortunately that didn’t work. The 7053′s offset voltage rises with the applied control voltage, thus producing a crack at the output when raised rapidly. Ultimately we got the thing working by keeping the control voltage at ~0.7V and switching the audio signal on and off with the 4066. However, since in this version all amps are constantly active, I am afraid the whole system would be prone to interferences and the power consumption would be very high. I had a very hard time testing the whole setup. I don’t know if it was my breadboard or whatever, but something started oscillating regularly and there was never a setup tat was save from that or other interferences. Christian told me however that he got something working.

I am not sure how to proceed yet. I think I will stay with the old circuit for now and see how far it takes me. After all, one result of the experiments with the TDA was that a higher volume makes it harder to locate the source of the signal. That would be sort of counter productive. It also shows that there are possibly limits to the use of this whole technique…

I used the five prototype circuits to build a walk-in sphere of 40 speakers. The speakers were attached to nylon strings stretched from the ceiling to the ground, so you could bend them aside to step in. In an effort I provided a crude interface in PD that provided a joypad for people inside the sphere to select different programs, such a random, sound going in circles, etc.

Contentwise, we had placed a call for content, which resulted in one piece that was handed to me and which worked quite well. I have yet to get the adress of the composer to thank him again ;)

The result was quite to my liking and so was the feedback (apart from nobody understanding the interface, but in the end that didn’t matter much). The sphere was fun to use. I personally found it pretty dizzying standing inside the speakers while the sound came from a different direction every 25 milliseconds. Unfortunately, as of now there are no pictures to show. The  installation stood at LEAP only for two days, in which I had forgotten to bring my camera. Hopefully I will find someone of the PDCON who made good ones.

[UPDATE: pictures of the building process and a picture from a mobile phone (thanks ckp and astring!)]

a picture by astring

in action. the nylon-strings could be bent apart to step inside. (pic by ckp)

arrangement of the circuits

some notes

more notes

0.2beta

I started the project “Diskokugel” in autumn 2009. The vision was to build a ball made of speakers that can be turned on and off individually. This ball would turn while sound would be “reflected” in one constant direction, just like light from a mirrorball. So I went to the [sublab], a hacker space I am co-founder of, and asked for help. I got it galore from Christian, who volunteered to design a circuit that would both be cheap and easy to build.

Meanwhile, I was looking for ways to find cheap speakers.

0.1 alpha

I thought, I could take advantage of the German recycling system, checking the places where people deposit electronic trash, which are administrated locally by the cities. There I was told that it is forbidden for the personnel to let people take some trash, so I wrote a letter to the city to ask if they could grant me access. They told me, that they only administer those places and that the actual trash is owned by some kind of foundation, so they are not allowed to touch it. When I wrote a letter to that foundation, they wrote back that they, too, are not in fact owner of that waste and cannot allow me to take parts of it away to use them, nor could they tell me who to ask. In fact, it would be easier to ask electronics shops, because they are obliged to take in electronic trash and could maybe grant me access to it.

Five boards to run tests

I decided to end my investigations at that point, being afraid to end up in the sicilian sea with concrete shoes. Better not mess with waste management… That made me look for commercial alternatives and led me to the purchase of 1500 chrome speakers from Hangzhou, China. This transaction was preceded by a tiring process of bargaining, exchanging samples, managing shipping costs and import regulations. By the end of that time I had moved to Berlin and the first circuit board from Christian had long been tested.

Now, that the actual size of the speakers (diameter: 50mm) was clear, I started constructing the actual object. I had to find out that my goal to distribute as many circles (speakers) on a sphere as possible is a still unsolved mathematical problem (see [Tammes Problem]. So I ordered a styrofoam ball with the targeted size (40cm in diameter) and started to experiment. I found a solution and later on a mathematical proof that shows that my solution is the most I could make of what I had. It’s 200 speakers on a ball that size. My solution, in the end, was to work with the pattern of a [truncated icosahedron], also known as: soccer ball. This was during the World Championship, of course :)  I started soldering.

soldering 0.1 Alpha

I took regular wire you use in the garden and electronic solder and soldered everything on top of the styrofoam ball I had purchased. It took about 3 days to get the first version done, which rolled of my bed and burst into pieces one day later. This wasn’t as unfortunate as one might think, because it was a different pattern than the one I’m using now. Another day of work and the current version was done. I glued speakers to it to have an idea of what it would look like in the end. The result was quite satisfying.

Not pretty. But robust.

The crash of the first model had shown that the ball constructed from wire rings wouldn’t support itself (at least not if it was built the way I did it). There was also still the need to find a place for the required circuit boards. I was looking for some kind of connection from the center to the outside. So I used an icosahedron, connecting each of its 12 corners to the pentagons on the surface. I found a way to solder a more or less exact icosahedron. Actually, I wanted the thing welded for more stability, but a series of unfortunate events (I have a magic talent to break things. It is contagious) led to the return to the good old electronic solder. It’s done.

From the inside you can see the chrome bodies

To increase the sound quality I needed bodies for the speakers. I kept looking for something cheap and convenient such as yoghurt cups until, suddenly, christmas arrived and the solution hung in front of my nose: Christmas balls. The chrome look of these will make it even better.

Speakers, switchboard and Arduino connected.

With the basic construction issues solved, I turned back to the electronics. I programmed an interface in [PD] to interface with the [Arduino] that takes care of the serial communication and controls the switching process. The control circuit has a part built in that synchronizes the switching of speakers with the zero phase of the audio signal. This is supposed to prevent the Speakers from cracking when being switched on or off. Technically, this works perfect, but cracking still occurs. It’s mostly audible when playing pure sine waves or when switching really fast. We are still looking for the source of this and hopefully will resolve the problem soon (or choose to ignore it). Then, a series of circuit boards can be produced and we are close to finishing the whole thing. About time, if you ask me.

Behold! I finally upgraded my [bike sound system], adding extra power, a subwoofer and a battery charger for everlasting supply. It doesn’t look as decent as the last one did but it totally rocks. The first test run was a trip to the [Fusion Festival], around 120 kilometers. The dynamo provides enough power to reload the batteries while the system is playing.

I started of with the [TDA7052] 1W amplifier I had already used with the old sound system, only this time I used two, one for bass and one for mid/high frequencies. But the TDA is made for 8Ohm speakers and my bass speaker had 4Ohms and so had the two high/mids in parallel. So I decided to get something bigger. Now I have an [AN7148] delivering 2×2,5W at 12V 4Ohm which is totally sufficient to predominate the occurring head wind and most traffic noise :)

The battery charger was built according to the circuit provided by [forumslader.de] . Documentation is in German only but it’s extraordinary! It’s housing has still to be completed. To be done in time for the Fusion Festival I was a bit in a hurry.

The AN7148 in its housing. Batteries (9xNiMH) sit at the right.

The battery charger