Barrel Transcriber With Measuring Roller
By Leonardo Perretti
Hi all, I used a different approach when transcribing tunes from the barrel of the Clay's organ clock; I think it could be useful for someone (and perhaps for Spencer Chase also) to know how I realized transcrip- tion. The system consists of a mechanical part, an electronic part, and software.
The mechanical part is a wooden frame on which the barrel is mounted. The original key frame is mounted on a bar having lateral sweeping capability (the barrel contains ten tunes), arranged in a position (relative to the barrel) similar to the original one. On the same bar, at the edge of the keys, there are sensors, consisting of simple microswitches.
The electronic part is a specially developed card, containing buffers for the sensors, and an up-down counter; it is connected to the serial port of a Macintosh computer through a serial-to-parallel interface. The counter of the card is driven by an optical encoder, fixed on the rim of the barrel.
The software manages the whole, operating as follows. The counter is reset at beginning of the action, manually, by a push-button, then reading begins. The program recursively reads the state of the sensors; if one or more changed their state, then the program records data in the memory, along with the position, and completes recording when the switch goes in an off-state.
The position of data items (the pins, in this case) is determined by the optical shaft encoder; this is a device that is similar to the roller/ encoder of Spencer's scanner; it appears as a potentiometer, and is capable of a certain number of ticks per turn. I used a low cost encoder with 256 ticks per turn, but there are encoders with up to 5000 t.p.t. (at proportionally higher cost).
The use of the encoder offers many advantages; since it is a position sensor, it is independent of the speed, so the barrel can be moved with any variable speed, although it is preferable to maintain a convenient low speed. I move the barrel by hand; the system can be improved by providing a conventional or stepping motor. You can even stop or move backward -- the counter will follow counting backward, and still the position is exactly determined.
The resolution of the encoder is very high: the circumference of the shaft is about 25 mm., comprising a rubber ring for friction improvement, so the resolution is 25/256 = 0.1 mm. (The version with 5000 t.p.t. can achieve 0.005 mm.) When reading finishes, then the data, stored in memory in an internal format, are converted to a standard MIDI file, that is written on the hard disk, and can be utilized by one of the common music programs, such as Cubase or Finale and so on.
I think that this system could be used to scan whatever kind of medium, by just providing adequate sensors and frames. I'm studying a system based on a laser light beam to scan punched supports (it's just an idea for now, I'm going to experiment).
I don't know if this subject has been discussed on MMD before Andy La Torre's optical fiber proposal. (I read MMD since 10 January, and I have not read previous MMD issues yet, because of lacking time). As Spencer, I am interested in knowing new ideas, so that a fast and efficient scanning system can be developed.
Regards
Leonardo Perretti
perretti@mbox.vol.it
[ That's a fine system you describe -- everything is commanded by the
[ pulses from the measuring roller. Our member David Wasson built a
[ perforator in which the driving capstan is also the measuring roller,
[ and which transmits pulses to the Midi Clock port on the computer.
[ His perforator, therefore, has the same command method as your
[ barrel transcriber. -- Robbie |
(Message sent Mon 10 Mar 1997, 23:49:22 GMT, from time zone GMT+0100.) |
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