Archive for February 2008

more laser cut acrylic

I’ve been on a rampage with the laser at Techshop over the last 3.5 weeks. Here are three new pieces I’m working on:




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3d geometry exporters for second life

And so it begins.. what was once a neat trick now becomes a real feature. Build 3d stuff in a “real” 3d drawing program, and export it to a set of data that Second Life can translate into OpenGL primitives. Good. Now, Google, command-c, command-v, command-option-s… Oh, wait, does that conflict with google earth interests? I’ll have to ask Nate about that.

(click here if the movie doesn’t play)

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better photo of the laser cut acrylic

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Bright shiny edges. Excellent light transmission… the idea mill is churning.

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new stuff for feb. 2008

I did this painting at this month’s First Friday live painting event at Works/San Jose. I’d be happy to sell it to you. )
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And then I’m into all kinds of new new new new stuff thanks to my training at Techshop. Here’s some acrylic test pieces. I’m over the moon on the cut quality on these. I have some fairly big ideas that I’m going to try out on this front.
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Here are some larger hardboard abstracts that I’ll be sealing and painting. I’m so excited to be able to get this level of precision into my build quality. Once I paint them, I think that will be a nice combination of machine precision and human imprecision :

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And then we’re working on a mobile for our coming addition to our family. Here’s the first pass at the cast of characters. I output these at 100% of the design spec, but we both agree that I can redo these and bump up the size. A lot. Although, I’m totally shocked at the fidelity to the design that the combination of the laser cutter working on the 1/4″ hardboard can reproduce. I probably just got lucky with where I put the holes and how much space I added around them.

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check out the detail:
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Note the circles at the white arrows. No problem at all. Every one of the holes I put into the pieces produced a clean 1/4″ thick hardboard peg. I love this machine. It’s freakin’ awesome.

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Guitar Rising


DIY drum triggers… reading the sensor scientifically

I’ve learned so much about piezos, microcontrollers, serial data capture, graphing. All from people I’ve never even met in person. Tod E. Kurt’s work on the Arduino MIDI drum kit lead me to want to replicate the project for myself, and I’ve been running into some very tricky problems with the sensors triggering samples two or three times. I got a boost of confidence that I was detecting a real problem thanks to the fine work done by mschaff’s Ardrumo project. Now, thanks very much to Tom Igoe’s article on Sensor Graphing using a tiny arduino sketch, the terminal, and, I can actually scientifically diagnose the reason why this is happening.

Using the DIY kick pedal that I’ve been working on…
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I was able to capture and graph the data that the sensor is outputting. Here are a few screenshots of the highlights:


This first screenshot shows a good peak, right at the beginning of the strike. Then the ringing begins. If, for instance, I had the threshold set to 500, this would trigger not just one, but *three* midi notes. Ok, but what if I had set the threshold to closer to 750? a big problem with that is that I’m losing a lot of the dynamic quality of the kick pedal. I’d have to hammer on it just to register above the minimum value, and then there’s no way to play it quietly. Every kick would end up being 750 or higher.

But wait, there’s more! Here’s another reading:

Wow, so even if I had set the threshold to 750, I’d *STILL* get three notes off this one kick pedal strike! And then just to mix it up even more:

Here is yet another pattern of the data. a short hop at the beginning well under a reasonable threshold of 250, and then a reading over 500, and then an even higher reading on the “second wave”…

So, the question still remains… how to get a clean sensor reading? Here’s my current idea:

Drum Trigger Sensor Reading
Charting it out helps. Now I just need to try to write the code so it follows this to test it out. Comments and suggestions are welcome. )

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Classes at techshop

I’ve been taking classes at Techshop this past week. Here are a couple of photos of the CNC Plasma cutter class, and the sign I made with it. )
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I also took two laser cutting/etching classes, TIG welding, and CNC Milling. Basically all heavy duty cutting and pasting operations.
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I would highly recommend taking some classes there. The instructors are nice, and the environment is really conducive to exchanging ideas and helping each other learn. I’ll be starting up my month long membership next week! I’m very excited to get in there and get some stuff done!

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