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Cheap Keyboard ---> sequencer modification
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stolenfat



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PostPosted: Wed Jul 18, 2012 8:01 pm    Post subject: Cheap Keyboard ---> sequencer modification
Subject description: ...there must be a better way
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Howdy guys! I need some help brain storming an idea and would love to pick the minds of the community once again. It's been a long while since i've posted here but i know this place is full of extremely creative and helpful people.

I had an idea to add a programmable sequencer to a cheap keyboard. I was hoping it would be as simple as connecting a 4017 decade counter to the keyboard matrix and hopefully upon receiving a +V jolt at the appropriate node it would trigger that key for the duration of the voltage.

...But its not.

Apparently the keyboard acts as just as i thought.... a matrix. where pin 1 to pin A makes one note and pin 1 to pin B makes another note.... pin 2 to pin A makes a third... ect for 32 notes.

What would be an elegant way to activate the matrix connections based on a voltage output from the 4017 that could be patched to a bay of 32 notes, one for each key and still trigger them?

So far my only idea is to use a bunch of vactrols or optoisolators ICs to be activated from a voltage pulse via the 4017 to bridge the gap in the keyboard's note matrix.

Any other ideas? Mine should theoretically work... so does any one have any suggestions for larger maybe 16 pin optoisolator ics? Some research has led me to try a batch of LTV-847 ics.... any experience with them?


thanks!

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MusicMan11712



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PostPosted: Wed Jul 18, 2012 8:45 pm    Post subject: Re: Cheap Keyboard ---> sequencer modification
Subject description: ...there must be a better way
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stolenfat wrote:
I had an idea to add a programmable sequencer to a cheap keyboard. I was hoping it would be as simple as connecting a 4017 decade counter to the keyboard matrix and hopefully upon receiving a +V jolt at the appropriate node it would trigger that key for the duration of the voltage.

...But its not.

Apparently the keyboard acts as just as i thought.... a matrix. where pin 1 to pin A makes one note and pin 1 to pin B makes another note.... pin 2 to pin A makes a third... etc for 32 notes.
I am new to understanding and tapping into keyboard matrix logic. (See http://electro-music.com/forum/topic-54441.html where I have a number of links related to keyboard matrixes.) Where as I was interested in taking the output of the matrix and plugging that into the Arduino, your project is to tap into the matrix in order to trigger the keyboard's sound engine.

The keys on my keyboard are just switches. If you keyboard works the same way, I assume all you need to do is just have your sequencer close the switches to play patterns.

As I said, this is new to me, so I look forward to reading your progress and solution. (Out of curiosity, what keyboard are you modifying?)

Steve
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elmegil



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PostPosted: Wed Jul 18, 2012 8:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

How many keys on your keyboard? (n/m I see, 32) How were you planning on choosing which keys to activate?
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stolenfat



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PostPosted: Thu Jul 19, 2012 12:02 am    Post subject: Reply with quote  Mark this post and the followings unread

i imagined an interface with a bunch of output terminals from each of the 4017 steps which would simply be sending V+. (im thinking of using 8 or 4 of the chips outputs)

those out put terminals could be patched into a bay of 32 possible jacks which would connect the keyboard matrix to play the key associated with the jack when it received V+ from the 4017.

i think the only way to do this would be to use relays... yuck... or optoisolator (vactrol) ICs


i'll have to test my idea, but it should work theoretically and if so, many cheap little keyboards could be modded like this to become little melody sequencers.

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stolenfat



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PostPosted: Thu Jul 19, 2012 12:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey mods!
This might be a better topic for the lunetta subforum since the brains and guts of this idea is pretty lofi and will be utilizing mostly cmos chips!


Also, a cmos 4066 could be used instead of a collection of opto-isolators?

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richardc64



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PostPosted: Thu Jul 19, 2012 2:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

stolenfat wrote:
Also, a cmos 4066 could be used instead of a collection of opto-isolators?


Absolutely!

Quote:
i think the only way to do this would be to use relays... yuck... or optoisolator (vactrol) ICs


Sentence needs another "yuck" after "vactrol."

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Blue Hell
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PostPosted: Fri Jul 20, 2012 7:49 am    Post subject: Reply with quote  Mark this post and the followings unread

Maybe have a look at CMOS matrix switches like they were once used in telephony.

But it needs not be analog .. so prolly you could use some digital bus buffers too provided they have a tri state output and an enable input ... depends a bit on the actual matrix layout what would be handy and if additional diodes would be needed.

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Uncle Krunkus
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PostPosted: Fri Jul 20, 2012 3:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sounds more and more like it would be easier and more reliable to decode the keyboard matrix in the way it was intended, and then process beyond that.
Not that I fully understand how a matrix keyboard is decoded. I suppose on many cheap, simple keyboards, this would all go on inside 1 chip. Is this the main issue? (ie replicating just the decode section) or am I missing something?
It could be a good thing for me (and you) to study the way Ray Wilson did his matrix keyboard to CV+Gate.

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stolenfat



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PostPosted: Fri Jul 20, 2012 4:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

http://youtu.be/5o5m3wl3Oac

heres a video i took last night of my idea. I try to explain whats going on.

I figured in order to make this work well, i'd have to connect lots of wires to the active nodes in the matrix and just kinda hard 'trail and error' process through all the possible combinations to find the right note i want to activate.

Thinking about keyboard logic sounds like a pretty good idea... any chips to study?

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richardc64



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PostPosted: Fri Jul 20, 2012 6:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:

It could be a good thing for me (and you) to study the way Ray Wilson did his matrix keyboard to CV+Gate.


I used to recommend that. Try this:
http://pcbheaven.com/wikipages/How_Key_Matrices_Works/

One advantage to using analog switches to interface to a digital matrix is you won't have to be concerned with which end connects to an output and which to an input, since the analog switch is bidirectional.

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elmegil



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PostPosted: Fri Jul 20, 2012 10:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm still kind of confused by how you would "rewire" it. In other words, you can wire a given output of the 4017 to a given key with the 4066. Now, how do I make it operate a different key? A sequencer with a fixed set of 10 notes doesn't seem very interesting, so that can't be what you mean....
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JingleJoe



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PostPosted: Sat Jul 21, 2012 8:17 am    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
I'm still kind of confused by how you would "rewire" it. In other words, you can wire a given output of the 4017 to a given key with the 4066. Now, how do I make it operate a different key?

'NARNER PLUGS! Very Happy

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elmegil



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PostPosted: Sat Jul 21, 2012 9:23 am    Post subject: Reply with quote  Mark this post and the followings unread

so bring the keyboard control bits out to banana jacks and then rewire it. Ok Smile
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stolenfat



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PostPosted: Sat Jul 21, 2012 6:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

exactly.
untill i dive into keyboard matrix logic, i think the best idea is 8 4066's to cover all 32 keys along side a 32 point patch bay to connect to the 4017.

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elmegil



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PostPosted: Sat Jul 21, 2012 10:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Using stacking bananas, if you have sufficient current to drive multiple 4066's, you could sequence chords that way Smile
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wmonk



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PostPosted: Sun Jul 22, 2012 4:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Why a 4017? Sure it is an easy way to get a simple one direction sequencer, but I think there are quite a few other chips around that would be better to use here, including a switch for direction changes Cool
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MusicMan11712



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PostPosted: Sun Jul 22, 2012 6:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for posting the video--it gives a clearer idea of what you are doing. I have a few questions:
(1) In the keyboard does the keyboard matrix connect to a processor?
(2) If so, how many leads are used to make the 32 different tones?
(3) Where are you connecting each lead from your circuit into the cheap keyboard?

Part of what I am trying to understand is why you need 32 connections.

(4) Does the cheap keyboard have a brand (and possibly a model)?
(5) Do the keys of the keyboard also trigger the notes while your circuit is running?
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richardc64



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PostPosted: Sun Jul 22, 2012 8:22 am    Post subject: Reply with quote  Mark this post and the followings unread

stolenfat wrote:
exactly.
untill i dive into keyboard matrix logic, i think the best idea is 8 4066's to cover all 32 keys along side a 32 point patch bay to connect to the 4017.

This would be somewhat parts-intensive but would also be the most straightforward method. To do it any other way would require first determining the exact configuration of the cheap keyboard matrix: that is how many rows, how many columns and which are inputs and which are outputs.

Although it's reasonable to assume that 32keys = 8x4, nothing can be assumed. I've seen instruments where the matrix was broken up into groups of half-octaves of keys -- 6x some number (+1 for the top or bottom note). Another possibility is full octaves of 12xn. (See picsynth's PICSynth http://electro-music.com/forum/viewtopic.php?highlight=picsynth&t=52755) Furthemore, any controlling buttons or switches the instrument has may also be part of the matrix, "before" or "after" the keys' crosspoints or even interspersed within groups of keys. (Early Casios were like that, using an 8x9 matrix! Rolling Eyes )

Eight 4066s doesn't seem so bad, to me, but I do agree that a 4017 might not be the best choice for sequencing the thing. Good enough for a first effort or proof-of-concept, perhaps.

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stolenfat



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PostPosted: Sat Jul 28, 2012 12:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

I read there is a better way to drive the whole thing other than a 4017? What method/chip were you referring to?

So far I've been able to set up a proto-surface design with components mounted into a cardboard surface (untill i get something better) that allows me to connect the 10 voltage pulses to the keyboard matrix.

The matrix idea isnt to hard to understand, but deducing how its sets up in the keyboard was getting time consuming so i took a break from it for a few days. but planning to jump back into it soon.

To answer some questions posted earlier:
Quote:
(1) In the keyboard does the keyboard matrix connect to a processor?

Im not 100% sure since i've walked away from the project for a few days, but i think the keyboard only has 1 main cpu chip to which all the matrix leads run to via a thin ribbon strip.
Quote:
(2) If so, how many leads are used to make the 32 different tones?

I'm trying to avoid soldering 64 total connections (2 runs to connect all 32 notes) And will spend some time trying to work out how i can do the mod cleanly and efficiently. Hopefully I might be able to get it down to half that and still using the 4066s to make the connections. 64 wires would be the ultimate brute force method.
Quote:
(3) Where are you connecting each lead from your circuit into the cheap keyboard?

The ribbon wires have large solder gobs where they connect from the actual keyboard pcb to the main brain pcb. I thought i would solder there?
Quote:
(4) Does the cheap keyboard have a brand (and possibly a model)?

Yamaha Pss-80
Quote:
(5) Do the keys of the keyboard also trigger the notes while your circuit is running?

Theoretically yes! But do to its condition atm, being all opened up and all, its hard to trigger the keys... as long as i dont max out the polyphony it should!

One thing i was thinking about was adding a pwm module so i could control the length of the voltage steps into the 4066s and therefore 'gate' or control the lengths of the steps.

I had thought about forking the step out puts to multiple jacks to sequence chords and hope to include it into the final design.

Gotta run, more to come.

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MusicMan11712



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PostPosted: Sat Jul 28, 2012 6:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

stolenfat wrote:
The matrix idea isnt to hard to understand, but deducing how its sets up in the keyboard was getting time consuming so i took a break from it for a few days. but planning to jump back into it soon.
[snip]
I'm trying to avoid soldering 64 total connections (2 runs to connect all 32 notes) And will spend some time trying to work out how i can do the mod cleanly and efficiently. Hopefully I might be able to get it down to half that and still using the 4066s to make the connections. 64 wires would be the ultimate brute force method.
[snip]
Yamaha Pss-80

Thanks for the replies. It seems there are a number of people who circuit bent the PSS-80. In one forum, someone wrote, "Just started MIDIfying my PSS-80 last night. Definitely looks like a scan-low configuration with a 6/6 keyboard matrix." http://forum.highlyliquid.com/archive/forums.html/t-112.html Perhaps this might help you design something without using 64 wires. Again, I have never tapped into a cheap keyboard's sound engine, but perhaps you can build your note triggering circuit to do what the keyboard matrix does, only from your sequencer. Maybe others with more DYI experience than I have can comment on whether or not this would be possible.
Steve
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stolenfat



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PostPosted: Tue Jul 31, 2012 9:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Definitely looks like a scan-low configuration with a 6/6 keyboard matrix

It is a 6 by 6 keyboard matrix, verified last night.

I think as far as my control logic will go, I feel like i'd like to keep it simple so it's more standardly musical. If i really wanted to get crazy i'll just patch into my other wild lunetta logic synth but I think for stand alone purposes bit sequences limited to themes of 2, 4, and 8 will do me well and will aid the modifications approachability to other people beyond it's creator.

I'm starting with a single clock source that will be hard fed into a divider (cmos 4040). The divider out puts will be limited to 6 (to save on space) and will be patchable into a pair of 4017 with a total of 8 output stages each. The 4017s will also have an option to sync clock sources or to stay independent of each other. (Im considering adding a reset input for the 4017s but i think a 3 way switch setting the count limit to 2, 4, or 8 will be best.)

At this point the stages of the dual 4017s can be patched into the 32 4066 control inputs that will toggle the keyboard matrix.

Its definitely a tough call not to add crazy logic gates and multiplexers to increase the weirdness/randomness of it all but i want my friends who have no idea about binary logic to be able to play it with it instantly.

Currently designing the layout and drilling holes ect.

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stolenfat



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PostPosted: Wed Aug 01, 2012 3:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

made a panel today


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stolenfat



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PostPosted: Fri Aug 03, 2012 3:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

would any one out there know where i could find a schematic of the yamaha ps-80? I'd like to know where it's internal clock is coming from so i can try to manipulate it with my trigger pulses.

I could possibly poke and prod and try to find it the old fashion way but if some one knows, it might speed things up a bit.

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magnusvon



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PostPosted: Fri Aug 03, 2012 4:07 pm    Post subject: Geared motors, heavy duty (ish) Reply with quote  Mark this post and the followings unread

Hey guys/gals

I am building a rotary sequencer, and I need to find a geared motor that will be able to spin a wheel steadily despite intermittent physical resistance to the wheel (from it contacting on an uneven surface.)

Does anyone know any things i could find that might have a geared motor in them? I don't have the money to buy a 50 dollar one from digikey.

Also, I figured I could control the speed using some kind of pulse width modulation. Would a CMOS IC be the right thing to use to supply the motor?

Thanks!

m
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JingleJoe



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PostPosted: Fri Aug 03, 2012 6:10 pm    Post subject: Re: Geared motors, heavy duty (ish) Reply with quote  Mark this post and the followings unread

magnusvon wrote:

Also, I figured I could control the speed using some kind of pulse width modulation. Would a CMOS IC be the right thing to use to supply the motor?

Thanks!

m

No, it would be much better to make your sequencer with an IC, also that's the most archaic method for making a sequencer ever Smile I'm not saying don't try it, it would be fun and rather spiffing, but completely and utterly obsolete.

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