|
||||||||
|
||||||||
The Dougarydidg is designed to be a big ticket awe and wonder project that forms links between the D&T department and the music and ICT departments. The spark idea for this project came after seeing the launch of the EigenHarp from Eigen Labs. The Eigenharp initially appears as a totally new type of instrument it has a keyboard matrix of 120 keys and further down the instrument what are called the 12 percussion keys. The Eigenharp It really is a thing of beauty and when I first saw it I almost emptied by bank account to get one. Then a number of things struck me. By it's nature it doesn't play like any conventional instrument (No black and white notes), I had just flunked learning the ukulele (due to physical shortcomings - big fingers) and realised that this could easily be my next white elephant. Then I remembered the Native Instruments Maschine and the Novation Launchpad which have a number of keys that can be programmed to be any instrument or drum and is used as a trigger device or MIDI controller. The Native Instrument Maschine ..............................................The Novation Launchpad
Although it is an oversimplification of the EigenHarp in essence this is what it is, a matrix of keys that command sounds. From here I wondered how hard it would be to make a simple version of both units starting with an instrument similar to the EigenHarp. If you are new to electronic music then you will not be aware of a transmission protocol call MIDI. MIDI or Musical Instrument Digital Interface was designed in 1982 in a collaboration between all the big players at the time. Despite the fact that it has aged in many ways MIDI is still the underlying standard that most keyboards or sound modules respond to today. When building a music studio you have a number of choices depending on your skills, some opt for the new VST computer based sounds using a keyboard through a midi interface to activate them on the computer. Alternatively you can go the non computer way :- Midi in its first incarnation was one keyboard controlling another this is how the DougaryDidg works effectively controlling other midi keyboards or devices. The invention of the sequencer or Midi Command Recorder enabled performers to record their keystrokes and then add to them much like multitrack tape recording but with no audio degradation. This was the way many bands created music before the invention of computer based midi recording. In many onstage bands the configuration would be a sequencer connected via MIDI to a number of sound modules or other synthesizers. It would then talk to them all using different channels the sequencer commanding sounds from the rest. This replacing the "out of date" backing track. The Dougarydidg effectively replaces the sequencer becoming that command unit for multiple keyboards. This layout allows combination sounds to be created and is how many top 10 hits were recreated on stage in the 80's and 90's The arrival of VST's had often created a hybrid system with a computer at the end taking over from the sequencer and often making the sounds itself whilst also being the recording device. It also allowed the introduction of a number of other interfaces thus making a mixing desk a thing of the past. This merging of technologies has happened in many other areas and the result is that computer skills can transfer into music skills and vice versa. This generated a myriad of what are now know as midi controllers all replacing what were previously analogue devices that needed wiring to each other. Behringer 2000 Rotary Controller, Mixvibes Pro DJ Controller - The new thing in clubs. The new Mackie controller - a complete virtual music recording and mixing system. So once you stop seeing a musical instrument as a creator of sound but nothing more than a trigger device it follows that it could trigger anything. Sound modules, VST sounds on computers etc. There is a new trend amongst the big club DJ's of taking in devices like that Maschine and making the whole thing they do into a performance where they trigger and mix virtual sounds from the pads or keys instead of loading disks into a player. The result being that techno has moved on to being a live performance that has almost infinite variations. MIDI is effectively an RS232 communication , which may mean little to many people but if I explain that RS232 used to be the main communication protocol for modems, CNC machines and can still be found hidden in many devices even today, you will see how again technologies converge. In one of my past lives when I designed computer systems RS232 was new and growing, most devices ran at 9600 baud, which meant 9600 bits of information per second, that's bits not bytes, thus it was about 1000 characters a second. This was ample speed for a keyboard but it would take a screen 2 seconds to refresh, (A part of me wonders how little we have gained from all the computer power when today it can take much longer to do the same, Ho Hum.) The speeds proceeded to then double 18200,36400,56k and finally 112k. After this the signal degradation meant a new approach was necessary, along came USB. MIDI was strange they opted for a baud rate of 31250 with an error band of +/- 1%. The net result being that computers couldn't talk to MIDI direct. Whether this was an intentional blocking of early computer involvement or for other reasons i don't know, however, it has come back to haunt this project now. When selecting a microcontroller to handle the project it became very obvious that the beloved PICAXE and Genie were not going to be able to develop the require baud rate. They being locked into the old system of 19200 then jumping to 36400. The 1% margin meaning that they would be unheard (out of range) or full of transmission errors. MIDI interfacing a stamp chip is a simple matter of three connections the middle pin needs to be earthed.
So I then returned to my first love the Parallax Stamp. I fell out with the Stamp's on price when i discovered the PICAXE but I must say that in many terms the Stamp is a far superior microcontroller. It has many functions that the PICAXE and Genie yet aspire to but they are 10 times the price, a major factor when designing school projects. But as i said the Stamp has much more power in some areas (Not enough for it to be the chip of choice) the stamp allows you to create a baud rate mathematically which for the MIDI project was ideal. Furthermore using the BS2P version of the chip means that toe 24 pin and the 40 pin version can be used in the same circuit board as they are pin for pin compatible. This if you wish to make the smaller version of the Dougarydidg you can use a BS2P24 instead of the BS2P40 which is half the price just by slotting it in down the power end of the chip socket. This is one of the unique features of the stamps and it means that you can make circuits that have upwards compatibility. So the next step was to make a prototype to prove the electronics. (Picture of Prototype). The Eigenharp uses very clever switches that have five basic functions and much more. The nearest I was able to find was a joystick switch from farnell part no 1435775.
ALPS - SKQUCAA010 - NAVIGATION SWITCH, 5WAY - Data Sheet This is a very interesting little switch that I predict will appear in many future projects. Prototype Circuit 1 This circuit was designed in Circuit Wizard as it was due to become very complex.
This is the basic circuit for the first eight keys. In the first incarnation the idea was that each key produced a binary number on the bus when pressed and then one of four lines as it is rocked back and forward. Each switch has six legs with a pinout :-
The power rail sends power to each switch which is then waiting for it to be pressed.
The initial prototype only had one unique function per switch taking the connectors in clockwise rotation from the power connector, the first contact at 4pm is the same on each switch the diode that connects to the return rail A is the same on each switch. The same is true of the contact at 6pm and 7pm each having their own return rail B & C that is the same on each switch. The contact at 11pm is the one unique connector on each switch starting right to left switch one has a single connector to line 2 which becomes binary 1. Switch 2 has a single connector to line 3 which is binary 2. Switch three has two diodes connecting to line 2 and 3 which when added together make binary 3. On to switch 4 which has a single connection to line 4 which equates to binary 4. Thus switch five has two connections to line 2 and 4 adding up to binary 5 and on we go. The switch at 12pm uses line 1 and is the same on each switch. I then connected this into a standard project board i had in stock that utilized a Basic stamp BS2P24 unfortunately this board is no longer made so although can recommend its use they are no longer available. I then designed the next three boards to ensure it was technically possible to make a 32 key unit. Board B Keys 9 to 16
Board C Keys 17 to 24
Board D Keys 25 to 32
The Prototype Itself.
Having established that the prototype was on to something but we needed to expand the power making each contact a unique connection. The whole circuit needed to be redesigned. Bus board One. Keys 1 to 8. The blue lines represent diodes.
Each of the switches now makes five unique numbers the contacts at 11pm and 12pm got to the top bus and the bottom three got to bus two. Thus when the unit is played three movements make chords and two the single keys. On the chord the number is taken from the bus then two notes added to the instruction by the software.
Board Two. Keys 9 to 16 The blue lines represent diodes.
The red areas are where diodes are that close that it will be necessary to shield the legs from touching and shorting out. Board Three. Keys 17 to 24. The blue lines represent diodes.
Board Three. Keys 15 to 32 The blue lines represent diodes.
The microcontroller Board The red wires are wire connections.
The programming socket connects as below.
these are the first four connectors on the top of the chip as seen above in the microcontroller board. When connecting the keyboards to the microprocessor board the top set of lines need to be crossed over. if you are soldering from the back then it will be the bottom set.
The finished Prototype
So having designed the circuit boards The body / microcontroller housing was designed in pro desktop.
Body File In Pro- Desktop - Download The optional centre section was also designed in pro D.
Body Middle File In Pro- Desktop - Download The Head Section was also produced in pro desktop.
Head File In Pro- Desktop - Download The Backing Pieces were also made on Pro Desktop.
BodyBack File In Pro- Desktop - Download The middle backing pieces were also made on Pro Desktop.
Middle Back File In Pro- Desktop - Download The head backing pieces were also made on Pro Desktop.
Head Back File In Pro- Desktop - Download STL Files - Downloads How to make the parts. Each part is made in two operations the first being the manufacture of the inside cavity which is then followed by the manufacture of the outer profile. To manufacture the back of the body section we must use a modified pro desktop file. You may use a larger cutter to rough out but a 6mm flat router cutter should be the finishing tool. When using 3D geocam use a 15% step over for best accuracy. Making the Body Section Pro Desktop Modified File . The file has been modified to remove the holes.
Body Back Trenching Drawing - Download Body Back Trenching Drawing STL - Download Once the first machining has been completed the next side is best done on a a jig. Industry used to use jigs on most jobs. It is only the introduction of new machines that will perform all their processes at once that has altered this. A simple jig made from 3mm acrylic screwed to 9mm MDF using acrylic cams cut on a laser cutter. Body Jig.
The cams are used to grip the work then held in place with a screw. Calculating the Offsets The acrylic centre piece is 100mm from the back and 32.5mm from the side. to calculate the offsets we must know the distance from the edge of the block to the edge of machining.
Thus the rear offset or (Y) is 100mm - 7.5mm = 92.5 Then the side offset or (X) is 32.5mm - 9.01mm = 23.49 Finally we need to account for the distance between the inner surface and the edge.
from the drawing we can see this is 28.00 we must now subtract this from the (Y) total. = 64.50 To represent it pictorially.
Making the Middle Section Pro Desktop Modified File . Again the file has been modified to remove the holes.
Middle Back Trenching Drawing - Download Middle Back Trenching Drawing STL - Download Once the first machining has been completed the next side is best done on a second jig. Middle Section Jig.
The cams are used to grip the work then held in place with a screw. Making the Head Section Pro Desktop Modified File . Again the file has been modified to remove through the holes.
Head Back Trenching Drawing - Download Head Back Trenching Drawing STL - Download Once the first machining has been completed the next side is best done on a second jig. Head Section Jig.
The cams are used to grip the work then held in place with a screw. Making the Body Section Back Pro Desktop Modified File . Again the file has been modified to remove through the holes.
Body Section Back Trenching Drawing - Download Body Section Back Trenching Drawing STL - Download Once the first machining has been completed the next side is best done on a second jig. Body Section Back Section Jig.
The cams are used to grip the work then held in place with a screw. Making the Middle Section Back Pro Desktop Modified File .
Middle Section Back Trenching Drawing - Download Middle Section Back Trenching Drawing STL - Download Once the first machining has been completed the next side is best done on a second jig. Middle Section Back Section Jig.
The cams are used to grip the work then held in place with a screw. Making the Head Section Back Pro Desktop Modified File .
Head Section Back Trenching Drawing - Download Head Section Back Trenching Drawing STL - Download Once the first machining has been completed the next side is best done on a second jig. Head Section Back Section Jig.
The cams are used to grip the work then held in place with a screw.
Program for the Microcontroller
Basic Program as a Download
|
