Temperature Seeded Audio Project, Day One

Today is a good day for my Temperature Seeded Audio Project. The main reason for this: I discovered the power of using the Arduino platform along side the Processing platform. My concept demonstrating prototype took only one afternoon to build using this combo. I thought the construction/coding would take a week! Using the Arduino and Processing together allowed me step back and see the design aspects of the project without getting bogged down with gritty code details. Pretty stoked on the progress.

More about the overall project in my next post, but briefly, I've been interested in using real time data about the environment to make music for a while. My intention was further propelled by this interview with Brian Eno: Eno Interview

My preliminary idea is to create a temperature sensor that samples current ambient temperature every second. This data is then simultaneously saved to an SD-Card in log file format, and served to my wireless network available to any device or code that points to it's URL.

First the Hardware: For the microprocessor I chose an Arduino Mega with attached Ethernet Shield. For the sensor I chose a simple thermistor based voltage divider circuit connected to an analog input of the Arduino.

Then the firmware: Here is the Arduino Sketch code.

And finally the software: Here is the Processing Sketch code.

Here is a screen shot of both sketches running simultaneously. You can't hear the piano, but it plays a different note every time the temperature changes.

Pressed buttons

To solidify then dismantle the lies and half truths I tell myself on each project. To break into manageable blobs the ideas. To let other people know about it because I'll need their help. To laugh at myself. To watch myself grow from amateur to mediocre dog and pony photographer. To get hired baby. To blur the lines between crappy photo blog, introspective high school live-journalish road musings, and application notes and schematics for audio concepts.

Meet Newman, my new rear bike light.

Compliments of Colin Pringle, I adapted this circuit to make a dual LED rear bike light out of a mint tin:












I did have to improvise a bit on Colin's circuit as I only had certain things available in my junk drawer(s). R1 and R2 are both 1k ohm resistors and I switched R3 and R4 to be 680 ohm resistors. The lights blink 180 degrees out of phase from one another.

Here is the finished Newman:

















And the inside:


















It's good to be posting again. This little guy took about an hour. This is just the beginning, time to start doing more.

Listening

I listen to Noam Chomsky and he tells me I'm a blind consumer nestled well within the walls of the most powerful empire that man has ever seen. He tells truth to me that seems false because I'm not used to hearing it.

I listen to Lao Tzu who tells me to do nothing unless it maintains the balance of world. The world no longer seems in balance to me.

I listen to Frederick Nietzche who tells me my soul must strive towards being a supersoul, that I must reach the highest path or if I am incapable, help those capable of reaching their highest path.

I listen to Richard Feynman and he tells me follow through with analysis of a small fraction of the world I am presented with. At least there is wonder in that.

I listen to Socrates and he tells me to question everything I am presented with and thus accomplish nothing.

I listen to myself and take a walk in the rain listening to Rachmaninov's Prelude in C sharp Minor. Myself tells
myself to stop listening so much to other people.

Light Sensing Tone Generator

A while back I came across a circuit (from Forest Mim's scrapbook) that claimed to be a tone generator that had an output frequency which was dependent on the amount of light incident on two Cadmium Sulfide photo resistors. I had gathered the parts before my latest tour and was reinspired when I saw Dana from The Akron Family using what seemed to be the same circuit on stage.

So tonight I sat down and built the thing and it didn't work at first so I did something really exciting. I entered the oscillator part of the circuit into some simulation software to see what the virtual scope thought SHOULD be going on. I wasn't able to find a 741 op amp so I went with an ideal op amp. Next I measured the resistance of both CdS photo resistors, 1st with my thumb covering the sensor and next with a desk lamp shining directly on it, fixed ~ 5cm above the surface of the CdS. This was to give me a rough range of the change in resistance. This ended up being between 2.5k and 13k. It didn't have to be exact, I just wanted to get an idea of how the relaxation oscillator was going to behave.

It turns out the original circuit didn't vary in frequency that much, no matter how much light was incident. This was due to the range of my CdS photoresistors. I took off the 'balance' potentiometer from the original Mims circuit, which nominally added 25k in series to each photo resistor and re ran the simulation. It showed a ~300Hz difference after the tweak. The cool thing about this isn't the accuracy of the numbers but the fact that I could play around with a circuit in Multisim and get an idea of what needed to be changed without having to physically build the circuit each time. This was a huge time saver.


Here is a shot of the Multisim circuit I simulated:


And here are some shots of the virtual scope output and frequency counters:





The final circuit is crude but it works! With the lights off and the use of a flash light this thing sounds pretty interesting. I recorded some audio output and ran it through some frequency analysis software which had much higher frequencies than listed in the simulation. This is due to non ideal opamp (741) and the LM386 stage, the frequency response of the output speaker (a cheap 8 ohm radio shack speaker) as well as noise from the room that was picked up from the laptop mic. Needless to say it would be nice to have an audio analyzer, a scope and while I'm at it the full version of Multisim.

Here is the finished circuit I wired up on a breadboard tonight:



Here is the original schematic:



The circuit I created omits R3, R5, C5 and C2 is 100pF.


Things to do would be add a MAX1044 charge pump so it can run off of just one 9 volt battery and of course build it into an aluminum stomp box. Also I need to take out the LM386 based audio amp stage and build something that brings it to line level output range.

Pale Blue Dot

http://www.youtube.com/watch?v=wupToqz1e2g

I love this Carl Sagan reading:

"Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there--on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves." -carl sagan