Electronics (Please scroll down)
Please note that this site is entirely voluntary. I am sharing my experiences and thoughts with others who may be interested. I CANNOT be responsible for any errors or omissions, nor any problems you may encounter when using these ideas. I WILL however be pleased to answer any questions you may have and consider any suggestions. Pete.
This is NOT a stand alone system, it requires a computer to drive the interface.
I use an old 486 lap top in DOS mode.
Update as of June 2003
I have now designed and made a custom single sided printed circuit board. This has reduced the number of straps required on the component side from 112 to 41. The electronic tracker bar has also been modified and now operates on a 12V gel battery. I have continued with my efforts to produce plans but this is proving to be very difficult. The biggest problem is whether the software would run correctly on other computers. Without a range of machines to test it on, it is impossible to tell. However, the most inovative part of the project is the new tracker bar. It is VERY simple and has the minimum of moving parts. It's possible that plans may be available for just the tracker bar, then it will be up to the user to choose a system to operate the solenoids. None of the above is "set in stone" and I will post updates when things change.
Regards Pete
This project is to design and build a system for the organ that will play the notes by electronic means, rather than using a paper roll.
The project is now working well (7th April 2002).
I am changing this page to reflect the actualities rather than the theory.
I am aware that this has been done already. However I don't have the resources to purchase a ready made system.
This information is intended to assist anyone who may be thinking along similar lines.
At present the software and documentation are not suitable for general use. I estimate the cost of materials to be about £30, given that you already have a suitable computer and 12v-14v power supply.
The electronics make the organ sound "snappier" and it's great not having to punch all those holes !
What you need to have:
1) A 486 or better computer with a printer port.
2) A power supply (12v - 14v), a car or gel battery seems to work but NOT a switched mode computer supply ?
3) A printer extension cable (25 way). A parallel scanner cable will do.
What you need to make:
1) A new lid, with a step in it to accomodate the new tracker assembly.
2) 20 coils, one for each note on the organ.
3) An electronic interface card, constructed on "strip" (vero) board.
Software:
1) Piet Paardekam's "midibook" program.
2) Program to convert the output of "midibook" to a file suitable for the interface.
3) Program to drive the interface using the file mentioned above.
Please note that the software WILL NOT run from a DOS "window". You have to boot the machine to a DOS prompt. I have tried running from windows but the timing is all over the place. This is because windows takes time out every so often to do "housekeeping tasks"
The air supply will continue to be manually provided (by cranking).
This is an overview of how it works.
I have decided to use the .PRT file produced by Piet Paardekam's program "midiboek". If you want to know about "midiboek" you will find a link to Piet's web site on my links page.
The .PRT file is a transient file which changes each time you run the "midiboek" program on a new midi file. This means that a copy of the file needs to be made. Suppose the original midi file is called "dingdong.mid", after you have used "midiboek" on the file, you should exit the program and rename the file ##midi.prt to dingdong.prt. By this method you will end up with a .prt file for each midi file you want to use.
The .prt file contains details of every note in the music. It consists of Note Number, Note Start and Note Stop. The start and stop values are in tenths of a millimetre from the begining of the music. The information is stored in the file as ASCII text.
The next stage is to produce an intermediate file which extracts the required information and stores it as numbers rather than text. I have decided that a resolution of 1 millimetre is sufficient for operating the organ, so all start and stop numbers are divided by 10 before writing to the intermediate file. Note numbers will be in the range 1-20 for the organ.
At this stage, a file has been produced containing one line of data for each note in the music. Each line of data contains 3 numbers, Note number, Note Start and Note Stop.
As the printer port is to be used for this project, the note number values have to be sperated and put into one of 3 groups. This is because the printer port handles information in groups of 8 bits (binary digits). To send details about the 20 notes, the inforamtion has to be sent to the printer port in 3 groups of 8. The mathematicians amongst you will note 3 times 8 = 24, therefore we have 4 spares which could be used for operating something other than the basic 20 notes.
This is a schematic of the interface.
Here are some pictures which you can enlarge by clicking on them.
