I had the microfiche machine at Maker Faire. And I said that I would post some information about it here, so that’s what I’ll do.
The microfiche machine takes light (in this case, from the screen of the microfiche reader) and converts it into MIDI signals that can then be sent to devices that take MIDI input, like synthesizers or computers. We use a phototransistor on the end of an antenna to read the light level from the screen. That information is then processed by a BS2 and converted into a MIDI signal.
In addition to the phototransistor, the microfiche machine has several other inputs.
- two dials and a button to set the highest and lowest note played
- a stop/star button that stops and starts the MIDI signals without actually turning the machine off
- two buttons that are used to calibrate the highest and lowest light signals
- a dial that is used to set the key of the notes that will be played
The BS2 does not have an analog to digital converter, but it does have a function called RCTIME that can be used to detect changes in resistance by determining the time it takes for an RC (resistor-capacitor) circuit to change its voltage. This article talks about how to use the RCTIME fuction and how to construct circuits that can use it. I use the function to measure the light levels from the phototransistor, and to measure the settings of the dials, which are just potentiometers (variable resistors).
Here is the BS2 source code that I use. If you have any questions, feel free to post them.
Update: The IEEE Spectrum website has a little writeup and a video showing the microfiche machine in action.
I just got home from Maker Faire a few hours ago. I’ve been there for the last two days presenting some of my projects, such as:
I talked to a lot of great people, and I got a chance to see a few neat projects, but I spent most of the time at my booth explaining what I was doing. Some of the highlights:
- families playing Unicorn Vs. Dolphin together
- a 14-year-old talking to me about how he had built some things that were similar to the stuff I had on display (I’m pretty sure his stuff was better than mine)
- talking to some high school kids about the projects they were working on in Python
- Darwin Grosse of Cycling ‘74 telling me he though the Microfiche Machine was cool
- looking like an idiot by telling Mr. Grosse that I used Pure Data for a lot of my projects
- giving a short talk about the multitouch instrument
I need to give a few special thanks:
- Heidi, for all her help and support, and not yelling at me for the apartment getting messy, and covering for my complete lack of organization, and worrying about things when I wasn’t worried but should have been, and everything else she always does for me
- to Mike and Tim for including me on the VU Meter project
- to Adam and Amanda for watching my booth while I watched Microfiche play their set
- to Dan Mode for lending me his projector so that I could show Unicorn Vs. Dolphin in it’s full glory
- Noah Thorp for inviting me to give a short talk about the multitouch instrument
- the guys from Tube Time and NYCResistor for being awesome neighbors and for loaning me the stuff that I was too stupid to bring
So, if I talked to you at the Maker Faire and sent you here with promises of source code and diagrams, I will try to get those up tomorrow. Tonight, I need sleep.
