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 Forum index » DIY Hardware and Software » Musical Interfaces
How to Wire Keyboard to 555 Timer?
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samp



Joined: Oct 15, 2016
Posts: 13
Location: Australia

PostPosted: Sat Oct 15, 2016 7:48 am    Post subject: How to Wire Keyboard to 555 Timer?
Subject description: Triggering an Oscillator With a Keyboard
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Hi,

I have recently ripped the keyboard out of an old Kawai organ and would like to use it as a part of this circuit (see attached).

I understand how this circuit is played with a stylus from the 555's pin 3 out, but am having trouble replacing this with the organ keyboard (see photos). I've tried connecting the bus (green wire?) to pin 3 and a single key's wire to pin 2, but with no results.

Is this something to do with CV?

Any suggested schematics/links would be appreciated.

Thanks,
Sam


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MusicMan11712



Joined: Aug 08, 2009
Posts: 1009
Location: Out scouting . . .

PostPosted: Sat Oct 15, 2016 2:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

[removed for personal reasons]
Last edited by MusicMan11712 on Tue Nov 15, 2016 10:18 pm; edited 2 times in total
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gdavis



Joined: Feb 27, 2013
Posts: 359
Location: San Diego
Audio files: 1

PostPosted: Sat Oct 15, 2016 5:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Did you meter the keyboard to see if it actually works the way you think?

Assuming it actually connects one wire for each key to a bus wire, you'd need to connect the key wire to is corresponding pad in your circuit instead of pin two. Each pad creates a different resistance between pins 2 and 3 which controls the pitch. Connecting it directly to pin 2 eliminates all the resistance so the pitch is probably above the audible range.

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My synth build blog: http://gndsynth.blogspot.com/
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samp



Joined: Oct 15, 2016
Posts: 13
Location: Australia

PostPosted: Sat Oct 15, 2016 8:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your help! I'll have a look.
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Cfish



Joined: Feb 24, 2016
Posts: 451
Location: Indiana

PostPosted: Sun Oct 16, 2016 3:55 am    Post subject: Reply with quote  Mark this post and the followings unread

That is the exact circuit that got me really interested about 7 years ago. I did the same thing you are doing. I used an organ keybed that happened to be single buss. I was lucky enough to have an easy keybed to use. I just had to place a resistor between each corisponding key wire. Basicly make the keys be wired like the key and stylus section of your schematic. Stylus wire ties to the buss of the keybed.

Only problem is if you hit 2 keys

I had the forethought to use 100 ohm 1% resistors in the resistor chain, because that was what every volt per octave keyboard circuit I could find used.
It does not tune this circuit correctly. However
The keybed I use to control my home built modular synth is that exact . Keyboard and resistor chain setup I built for this project back then.

Is a thread on here called easy analog synth project. That was sort of the next step after this project. Was a lot more musically usable. I still use that project in one of my bass pedal sets


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samp



Joined: Oct 15, 2016
Posts: 13
Location: Australia

PostPosted: Mon Oct 17, 2016 7:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Woo! Got it working! Thanks Cfish -nice synth by the way.

Turns out the first two keys I was testing are broken.

Definitely going to try the bass pedals next.
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