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 Forum index » DIY Hardware and Software
CV Keyboard
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Dragon's Lair



Joined: Dec 29, 2006
Posts: 185
Location: Nakusp BC, Canada
Audio files: 1

PostPosted: Mon Dec 10, 2012 11:37 am    Post subject: CV Keyboard Reply with quote  Mark this post and the followings unread

I started off to build a simple cv keyboard, but "feature creep" crept in (pun intended) and it turned into this.
I made up some pcb's to retrofit the Fatar keybed to be a resistor network.

The keyboard has 4 buffered outputs each for CV, Gate, Trigger, Bender and Modulation (sine and square outputs),
it will also have a ribbon controller built in, but the ribbon will be on a separate pcb (for now anyway)
For controls it has an Octave switch, fine tune, portamento, LFO rate and amplitude, a scale control for the ribbon
and pitch and mod wheels with a switch to route the lfo sine to the keyboard cv
The keyboard can be scaled for any size keybed, I designed the keybed pcb's to be "modular" there is one pcb
for the left side and one for the right side, the pcb's in between are all the same (1 octave each)
So far everything is working as it should, I missed a couple of holes on the right keyboard pcb, and integrated the
octave switch and output board on to the keyboard pcb, so right now I am waiting for them to be made.
The biggest problem is trying to find keybeds and pitch/mod wheel assemblies, I have emailed Fatar numerous times,
but have never heard back from them, so for now the only option is to use salvaged keybeds, so if anyone has any
non functional gear with the fatar keybeds in them, let me know.

Now I have to build a case to put it all in, problem is, my table saw and other tools are in an unheated workshop, and it's -6c today!!


Keybed-1.jpg
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Here is a pic of the original Fatar keybed (salvaged from a M-Audio keyboard)
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Keybed-2.jpg
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...and here is a pic of the retrofit boards, two are installed, the resitors are mounted on the bottom but
they could also be on the top if you want
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Keybed-3.jpg
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Here is a pic of the bottom, with the boards installed
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Keybed-4.jpg
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and one of everything hooked up to my modular for testing.
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moogasm



Joined: Dec 29, 2009
Posts: 13
Location: San Diego

PostPosted: Mon Dec 10, 2012 5:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

Can you post some details on the pcbs (schematic, parts list, etc.)? Does it use a constant current source and resistor ladder type approach? Are you planning to sell these?
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AndyR1960



Joined: Feb 16, 2007
Posts: 285
Location: Manchester UK
Audio files: 5

PostPosted: Tue Dec 11, 2012 1:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Unfortunately Fatar are well known for not responding to such requests Sad but Doepfer have wheel assemblies (single or dual assembly) and Fatar keybeds for sale.

http://www.doepfer.de/zubeh_e.htm#Keybeds

I thought about using a similar solution, but I was always concerned if the rubber contacts introduced any resistance - Can I presume that the contacts act as a clean switch and pass through the CV voltage cleanly?

Thanks
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richardc64



Joined: Jun 01, 2006
Posts: 614
Location: NYC
Audio files: 25

PostPosted: Tue Dec 11, 2012 3:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, take a perfectly good matrix keyboard, suitable for digital scanning, and convert it to single buss for a finicky, resistor string voltage divider and droopy sample & hold analog design.

That makes sense.

_________________
"I am endeavoring, ma'am, to create a mnemonic memory circuit... using stone
knives and bearskins." -- Spock to Edith Keeler
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Dragon's Lair



Joined: Dec 29, 2006
Posts: 185
Location: Nakusp BC, Canada
Audio files: 1

PostPosted: Tue Dec 11, 2012 11:02 am    Post subject: Reply with quote  Mark this post and the followings unread

richardc64:
Who pissed in your corn flakes this morning?
..... and people ask me why I don't post more of my designs here.
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AndyR1960



Joined: Feb 16, 2007
Posts: 285
Location: Manchester UK
Audio files: 5

PostPosted: Wed Dec 12, 2012 2:44 am    Post subject: Reply with quote  Mark this post and the followings unread

@Dragon's Lair - Please don't be put off.

I built my CV controller using a standard MIDI keyboard connected to a Doepfer MCV4 MIDI/CV converter (the CV out then gets mixed with the remainder of the controller circuitry).

I would love to be able to take the MCV4 out of the equation as the extra drain on my PSU is noticeable... a simple classic current source CV controller would be a far better option to reduce the extra load.

Yes, please keep the project going... as I'm definitely interested Smile

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Cynosure
Site Admin


Joined: Dec 11, 2010
Posts: 682
Location: Toronto, Ontario - Canada
Audio files: 35

PostPosted: Wed Dec 12, 2012 6:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Bill has a PCB for converting Fatar keyboards to both CV and MIDI keyboards.

http://electro-music.com/forum/topic-29746.html

I have the PCB but haven't had a chance to build it yet. I plan on building it in the new year.
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Dragon's Lair



Joined: Dec 29, 2006
Posts: 185
Location: Nakusp BC, Canada
Audio files: 1

PostPosted: Sun Dec 16, 2012 1:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Bill's pcb still scans a diode matrix keyboard, which is the best way if you want CV and Midi.
My keyboard is strictly CV, the main circuit is based on the Roland M181 keyboard, with a few tweaks, additions and modifications.
All the individual components have been built and tested, I have done up a new pcb with everything (except the ribbon) incorporated onto one board, but of course I have no money at the moment to get some boards made,
I did manage to get some panels made, once I get everything mounted in them, I'll post another pic.

AndyR1960:
I like your keyboard design, I was planning on doing something very similar for mine, I have some 3/4" pine boards here, so if it ever warms up a bit, I'll go out to the shop and start mocking up a prototype, in the mean time, I have been very busy working on my cnc engraver.
I did a couple test runs with it, and it is working perfectly, I am just waiting for some proper engraving bits, then I can try doing some panels, and stop paying FPE their ridiculous prices.
It has enough travel to do a 12'x 18" panel.


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3 axis CNC Engraver/Milling machine
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Dragon's Lair



Joined: Dec 29, 2006
Posts: 185
Location: Nakusp BC, Canada
Audio files: 1

PostPosted: Wed Dec 26, 2012 9:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well the weather warmed up enough to get out to the shop and cut some boards, and mock up a case.
Generally, this is what the keyboard will look like, dimensions are 36"x 10"x 3.75" high (at the back)
It needs a bit of tweaking, before finalizing the design, mostly to eliminate the visible screws.
I added a 6 pin din plug to the rear panel, that way the keyboard can be powered from my dotcom system, or alternatively I can put a power supply into the keyboard case, and use it to power a medium sized dotcom system.
I have also been thinking of hinging the top panel (with the ribbon) to allow easy access to the electronics inside.
One question, would you rather have the jacks on the back, or on the top?

Now to order some nice hardwood planks (and a new saw blade)


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Dragon's Lair



Joined: Dec 29, 2006
Posts: 185
Location: Nakusp BC, Canada
Audio files: 1

PostPosted: Fri Dec 28, 2012 11:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

I opted for a complete re-style, I took out the power supply and put in a board to convert a 20vac wallwort to +/- 15 and 5v, this let me cut the cabinet down a bit, the dimensions are 36"x 9"x 3" (3.5 for the end cheeks)
With a 20vac 2amp wallwort there is enough power for a 22 space dotcom studio or portable case.
I also hinged the top, which makes it a lot easier to adjust/scale the keyboard.
Once I can find a reliable source for the keybeds and pitch/mod wheels, I was planning on building and selling complete units, I am also planning on offering stand alone CV and Midi Ribbon controllers, I am hoping to have prototypes made up by mid February.

Now for some sanding and staining, then a few coats of varnish.


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Dragon's Lair



Joined: Dec 29, 2006
Posts: 185
Location: Nakusp BC, Canada
Audio files: 1

PostPosted: Sat Dec 29, 2012 9:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Stained and varnished...


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