Larry Cotton’s MIDI Robot Marimba: Update

Over 4 years since Larry Cotton’s “player marimba” was featured in Make and subsequently retrofitted for MIDI using MD24 MIDI decoders, the instrument is still going strong. Larry recently updated the drive circuitry, replacing the original relays with NPN Darlington transistors to drive the mallet solenoids. Video of the marimba in action can be found here and here.

MIDIMarimbaLarry writes:

My MIDI Marimba (which uses 2 of your MD-24′s) is 90% refurbed.

The MD24′s work perfectly, and are more than capable of triggering the TIP-120′s, a vast improvement over relays, etc.

I also added RCA plugs and jacks to the mallets, for easy servicing and assembly/disassembly.

The first pic shows early stages of the new wiring. The power supply’s pretty beefy for the solenoids, with adjustable output around 12V, and 5V for the MD24′s.

The second pic was taken just before all the wires were stuffed in and the plexiglass cover installed.

The third pic shows it all buttoned up. That’s an iRig Keys keyboard on the floor, and an ancient Gateway laptop running Cakewalk software. I’m also using an M-Audio Uno to deliver MIDI to the MD24′s.

The wonderful little iRig Keys allows the marimba to be recorded and played manually. Kids love it.

MD24Wiring

InteriorWiring

MIDIMarimbaSystemThe picture below shows an initial test of the MD24 and TIP120 driving one of the marimba’s solenoids. Video here.

TIP120Test

 

 

Dubi’s MIDI Accordion

MIDI CPU user Dubi from Israel has completed an extensive MIDI conversion of an Iorio Accorgan. He writes:

I have been using Iorio Syntara as the model for you. The Syntara used to be an Accorgan -

Iorio-Accorgan

I removed the electronics:

SAM_0610

but I used the switches:

SAM_0611

There are 41 notes on the right side of the accordion , so my choice was for 6 inputs (0 to 5) and 7 outputs (6 to 12). There is a need to modify the existing switch circuit to have the configuration of 6 by 7:

SAM_0612

SAM_0613

I installed the midi controller , and midi connector and of course power connector of 12 Volt.

SAM_0614

SAM_0615

In order to have a good looking accordion , I designed a new panel .. And installed it.

SAM_0617

The right switches are connected 6 x 7 , first 0 to 5 are the inputs and 6 to 12 are the outputs of the right side.

The sysex table for the right side:

// Fixed Header, Configuration Layer 0
F0 00 01 5D 04 01 00

// Control Terminal 0-5: Data Only
00 00 7F 00 00 00
00 01 7F 00 00 00
01 00 7F 00 00 00
01 01 7F 00 00 00
02 00 7F 00 00 00
02 01 7F 00 00 00
03 00 7F 00 00 00
03 01 7F 00 00 00
04 00 7F 00 00 00
04 01 7F 00 00 00
05 00 7F 00 00 00
05 01 7F 00 00 00

// TREBELE Section
// CT 6 Matrix Select Output: Data Register 00h, note number 53-58
06 00 2C 01 35 00
// CT 7 Matrix Select Output: Data Register 00h, note numbers 59-64
07 00 2C 01 3B 00

// CT 8 Matrix Select Output: Data Register 00h, note numbers 65-70
08 00 2C 01 41 00
// CT 9 Matrix Select Output: Data Register 00h, note numbers 71-76
09 00 2C 01 47 00
// CT 10 Matrix Select Output: Data Register 00h, note numbers 77-82
0A 00 2C 01 4D 00
// CT 11 Matrix Select Output: Data Register 00h, note numbers 83-88
0B 00 2C 01 53 00
// CT 12 Matrix Select Output: Data Register 00h, note numbers 89-94
0C 00 2C 01 59 0A

// BASS Section
// CT 13 Matrix Select Output: Data Register 00h, note number 36-41
0D 00 2C 03 24 00
// CT 14 Matrix Select Output: Data Register 00h, note number 42-47
0E 00 2C 03 2A 00

// CHORD Section
0F 00 2C 02 3C 00
// CT 15 Matrix Select Output: Data Register 00h, note number 60-65
10 00 2C 02 42 00
// CT 16 Matrix Select Output: Data Register 00h, note number 66-71

// Fixed Footer
F7

// Global Volume
F0 00 01 5D 04 02
48
F7

The left switch circuit has to be modified as well to 6 input and 4 outputs:

SAM_0605

SAM_0608

SAM_0609

In the left side there are 12 notes of the Bass section and 12 notes of the Chords section. Each 12 notes has to have it’s own Matrix. so I used the same 6 inputs and 2 outputs for the Bass side and 2 for the Chord section:

bass

Once again In1 to In6 are connected to 0 to 5 and Out 1 & Out 2 to 13 and 14 of the midi controller. The same applied to the Chord section , i.e. inputs are the same conneted to 0 to 5 and the output of the Chords to 15 and 16.

The Bass section is straight forward as in the table above. However , in many instruments as well as in the accordion Chords can be played inversed. and in order to get the correct Chord range as well as match the Acoustic part of the accordion, it is advised to change the above

Chord table, use deferent location in the Note space and use a conversion map to correct for the “Chord range”. I used location 18 to 23 and changed the Note map to produce the “Nice Chord Range”:

F0 00 01 5D 04 05
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
10 11 12 13 14 15 16 17 30 31 3E 3F 40 41 42 37
38 39 3A 3B 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F
30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F
40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F
50 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F
60 61 62 63 64 65 66 67 68 69 6A 6B 6C 6D 6E 6F
70 71 72 73 74 75 76 77 78 79 7A 7B 7C 7D 6E 7F
F7

There have been few “glitches” had to go through Factory defaults after upgrading to version 1.4 and also had to change the “Global Velocity” Parameter (seems to be deferent in the beta version. Frankly, I have not done yet a complete research . I was satisfied with the results. Works like charm.

Regards,
Dubi

 

MIDI CPU Configuration Parser-Debugger and Builder

Highly Liquid Forum user joacofz6 has created a MIDI CPU control terminal “config parser-debugger and builder” for the latest MIDI CPU firmware (v1.4beta). It is a spreadsheet document (tested in Excel and Open Office so far) that builds MIDI CPU configuration code based on drop-down menus. It can also be used to analyze the contents of a MIDI CPU configuration dump.

Thanks, joacofz6!

builder-screen

 

parser-screen

MPA open-sourced, on sale

The complete design (PCB, bill of materials, firmware source code) for the MPA MIDI decoder has been posted under the Creative Commons Attribution-ShareAlike license. The source files can be found at the MPA support forum.

The MPA has been placed on sale at the Highly Liquid Store and will be discontinued after remaining inventory has been depleted.

The MPA (MIDI potentiometer array) is a general-purpose MIDI decoder with 8 independent 5V logic outputs and 4 independent digital potentiometer outputs.

MPA-480