DIY MIDI Keyboard (Remodeling!) - diyAudio
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Old 22nd November 2011, 01:53 AM   #1
Clopay is offline Clopay  United States
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Default DIY MIDI Keyboard (Remodeling!)

Greetings to you DIYers,

I've done quite a bit of searching over the past few days on this topic, but haven't come across anything quite like what I'm aiming for. Well, I have, but it was in Italian. Then I remembered how much awesomeness/insight there is on this forum, so I thought I'd give it a try.

I'm aiming to build a MIDI Keyboard (or remodel into a new one, using parts from an old one). There was another thread here about a DIY MIDI Keyboard, but that was regarding the physical construction specifications of a MIDI keyboard. I'm aiming to simplify an existing one that's in pieces and barely workable condition.

A friend of mine gave me a Casio WK 1630 MIDI keyboard to fix, as it wasn't working, which I quickly fixed.. This specific keyboard is a synth/controller, with 76 velocity sensitive keys, MIDI in/out, two sets of speakers (lots of weight!!) programmed piano samples, and all of this other fancy stuff I'm not looking to use. I'm aiming to take these parts and incorporate it into a MIDI controller. All I'd have to do is make an enclosure-most likely out of wood-and transfer the necessary brains right over.

I'd like this keyboard that I intend to make include all 76 velocity sensitive keys with a MIDI out. Tone/mod wheel would be nice, but I'll tackle the basics to start. This Casio has a great deal of features I'm not looking to utilize, so I thought it'd be a brilliant idea to carefully de-solder as much as I can, so it's mostly in pieces right now.

Any knowledge on the inner workings of a MIDI micro controller? I'm aware this keyboard will utilize the Casio's diode-matrix keys, which will be decoded by a V/Hz chip. I get that; however, as it is velocity sensitive, two switches/key are required, which I don't understand. Does each pair of switches for the keys get decoded by the V/Hz IC chip before it is analyzed for the time difference? Any knowledge, advice, schematics, or prior experience would be greatly appreciated. I really look forward to seeing what you guys have to say.

P.S. The Casio obviously was fully MIDI capable as it was before, I'm jut looking to simplify it and make it smaller (the keyboard is HUGE!). That means it's got everything I need to remodel a new one, I'm just not sure how to properly hijack the existing circuitry.

Thanks!
Clopay
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Old 22nd November 2011, 05:15 AM   #2
benb is offline benb  United States
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A V/Hz chip? What's that?

The key scanning and timing gets done by a microprocessor, and that's all you need to know unless you're going to write your own code to do it.

Your question presumes that you CAN separate the keyboard keypress/velocity-read and MIDI output circuitry from the rest in this thing, and I'm not sure that's possible. These things were designed to be mass-produced, not necessarily to be modular or easily hacked up.
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Old 22nd November 2011, 05:26 AM   #3
Clopay is offline Clopay  United States
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benb,

A V/Hz chip is a nickname for the chip (or sometimes multiple chips) that decodes the verticle/horizontal (row/column) information from a diode-matrix layout, which is the circuitry mapping used for the keys on this Casio keyboard. This information, I believe, is then fed to another microprocessor which converts it into MIDI information.

I suppose that'd be a better question to ask as well - if anyone knows whether or not this is possible. I mean, I'd detached a good amount of the components and had it still fully midi functional. I can really only imagine I'd need a few jumper wires, maybe some resistors here and there.

Thanks for the quick reply as well. I'm looking forward to hearing what everyone's got to say.

Clopay
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Old 22nd November 2011, 01:46 PM   #4
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Sounds like you are re-inventing the wheel here, if you pardon me saying so. Many dedicated controllers are available at very little cost to do that job, and probanly better, since Casio MIDI is not quite standard and also, it probably won't give you multiple zone control. Since you have gotten this far with this one, I can understand wanting to continue. Your keyscan processor is probably already outputting MIDI and would only require the buffer section, also present here if there is a MIDI output jack. If not, MIDI is no more that a current loop (5 volt, ~20ma) driving an LED on the receiving equipments opto-isolated input. Finding this data stream would be easiest with the schematic. Good luck!
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Old 22nd November 2011, 04:03 PM   #5
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you can possibly find more specific information on your keyboard on organforum.com, the construction and repair set of topics, the midi forum. The moderator won't reset the defaults to show the threads beyond one day old, so everytime you visit you will have to do it yourself unless you become a member.
Velocity sensitive keyboards come in 3 flavors, form C hard contacts (SPDT), two form A contacts (NO) and conductive rubber contacts. I don't know exactly how the rubber contacts work as they usually come with a built in multifunction IC that does everything, or not. Hard contact you can buy encoders sense the velocity. I have looked at the midi-boutique one, and it is hard coded for form C, and has a poorly discussed "parallel" contact function that might be two form A but who knows. Kinkennon's free software for the $40 PIC 128 input PCB does not do velocity. (kinkennon.com)
Hard contact keyboards are also separated into matrix encoded ones, like 8 x 8 for 61 keys, or straight units with 61 inputs, x 2 for the velocity of course. Matrix encoders are cheaper but have a bad reputation for some reason. Read picothinker's "Midi basics" thread on organforum, it is so good it should be a sticky thread but it isn't. He has been around since year one.
I suspect rubber contact units use AC signals and some sort of frequency detect, but nobody has worked on those but you. I hate them, rubber deteriorates with age and the reliability of old versions of these is so high that a hard contact Rogers organ is worth minimum $5000 here, whereas the rubber contact version goes for $500. Probably because the rubber one is already broken when it hits craigslist. If rubber keyboards were so great you would see old ones on the stage, whereas most of the ones you see on TV appear to be under 10 years old. Learning a new set of button push skills every 10 years strikes me as ****.
I don't know anybody that has actually bought from midi boutique, so do more research before actually spending money with them. I'm looking at adding midi to palladium contact Hammond organs, and mb is the only outfit I have found so far that does velocity. Hammonds are dual form A.
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Last edited by indianajo; 22nd November 2011 at 04:11 PM.
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Old 23rd November 2011, 12:08 AM   #6
Enzo is offline Enzo  United States
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I'd agree you are trying to re-invent the wheel. If the thing is a MIDI controller, then it ALREADY is what you want to build. If the Casio has features you don;t want, just don't wire them in. The old one may be HUGE, but that is only the case, the little circuit board isn;t HUGE. Just move the keybed and works into whatever you want. Don't want amp and speakers? Fine, leave them out. DOn;t want accompaniment features? Just don;t wire up the buttons that start them. Don't want the sound generation? OK< leave out the audio sections. If that is on the same board as the MIDI, then merely leave out the wires to the audio stuff. GOing to want to put patch changes on MIDI? I bet the panel buttons already can do that.
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Old 5th June 2013, 12:09 PM   #7
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Default Hello IndianaJo

Hey Joe,
If you're still around and working on the Hammond/MIDI project I'd love to chat with you. Let me know, Bruce
bnelson218@yahoo.com
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