Little cheap keyboard plays itself

droffset

This isn't the keyboard I was describing to Tonewill, by the way, that one's coming next.

Anyway this is just a little idea I've been playing with that you might enjoy. I'm using Lunetta techniques to help bend a toy. First let's get to know the victim:

It's the simplest keyboard I could find, i think i got it for a dollar. The IC is a blobby one, so i focused on learning the basics of keyboard matrices.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Pretty simple, there are groups of buttons, then items within each group.
When you press a key, you're connecting a group and an item and the blobby IC plays it's note.

So how to hack this baby to make it play itself? Here's the plan:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

The main job is done by 4052, which is a dual multiplexer. Its big brother 4051 is used quite often in Lunetta machines but I thought I'd give this one a try. This chip can act as a group of analog switches to connect data lines together. Connect four inputs on each side, use logic signals at the A and B pins to select which channels get to the output for each of the two muxes. Connect those two outputs and you're basically rubbing wires together.

And here's what it sounds like. Because I used just a few ICs it's pretty repetitive, so had to turn knobs and change connections to make it do something interesting.

Need to think of better ways to make the 4052's connections have more variety.

Selfplayingcheapo01 by droffset

droffset · Posted: Sun Aug 30, 2009 4:59 am Post subject:

Instead of using two halves of a 4052 the setup no has an additional 4051 to handle the note selection, while half of the 4052 is still selecting which group of notes to select from.

Selfplayingcheapo02 by droffset

I think i destroyed the circuit, or at least the built in wiring, need to resolder tons of stuff. The bend circuit is more complex than the little crappy thing it's meant for, but the sounds coming out are pretty cool for what it is.

sizone · Posted: Sun Aug 30, 2009 8:09 am Post subject:

HELL YES!

A tiny bit of advice, cob based, made in china toy keyboards break. I must have gone though 4 of these things so far
http://www.flickr.com/photos/xelent/2820763166/
If it's not working don't bother resoldering stuff or troubleshooting it (with the above example, for instance, I swear the hot glue that tacks the components to the board is an integral part of the signal path). Instead, try to haggle a bulk discount for 5 or 10 of the things. They will break, no matter how careful you are, once the case is opened the crap out fuse is lit. So view them the same way you'd view bic lighters or toilet paper: disposable.

Inventor · Posted: Sun Aug 30, 2009 9:24 am Post subject:

droffset, you are always into the coolest stuff! nicely done!

Les

droffset · Posted: Sun Aug 30, 2009 4:56 pm Post subject:

Thanks Les ! Just filling in the time until all my drum synth parts get in.

Sizone, good advice. It's hard to let go (even just this little thing.) But it's worth it because an expanded version of this idea will go into the KE-5 .

But the big difference will be....polyphony!

stolenfat · Posted: Wed Sep 02, 2009 6:00 pm Post subject:

i've had some success using 40106 oscillators with little toys, and definitely not in the form of 'bending', maybe 'intelligent bending'? lol

I hooked up the audio out put of the toy inline with some RC oscillators from a 40106 and was VERY pleasantly surprised with the results.

I'd love to see what others would do with this idea, theoretically the technique i thought could be applied to almost anything. With zero bending.

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You might remember a post a while back i had about designing op amp filters while drunk... and you guessed it my problems came from being drunk, but thats the project i was talking about.
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sizone · Posted: Wed Sep 02, 2009 9:07 pm Post subject:

Imma coin a new term 'cause I'm hip like that: "Circuit Blending"

stolenfat · Posted: Thu Sep 03, 2009 3:48 pm Post subject:

droffset · Posted: Thu Sep 03, 2009 4:51 pm Post subject:

sizone · Posted: Sat Sep 05, 2009 8:36 pm Post subject:

I just lost a ton of stuff in a hdd crash, but this little guy was discovered in the wreckage (originally posted on Ryk's forum also precrash)

Basic resonant l/p filter. Works o.k. (no voltage control though). If you stuff it with a 358 it'll work off a single or dual supply (though dual works much better). If you use sockets, you can swap out capacitors until the cows (NZ, ummm, sheep) come home.

genericfilter.bmp

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electri-fire · Posted: Fri Sep 11, 2009 7:15 am Post subject:

electri-fire · Posted: Fri Sep 11, 2009 7:39 am Post subject:

droffset · Posted: Fri Sep 11, 2009 5:17 pm Post subject:

Thanks for the info guys,

I've found that the complexity of my CMOS circuitblend circuits is a bit silly in terms of the amount of ICs needed, but the act of design and implementation is sort of gratifying for me because I feel like I've learned a few concepts well enough to riff on them. With a microcontroller I'd have to be at a computer writing code, here I can use my hands.

I have the KE-5 already half bent and there are wires everywhere, hopefully the self-playing circuit and some pots will fit. Trying to stuff as much bendy goodness into the existing chassis without removing speakers or adding moogy panels. (I'm not against those ideas, it's just a personal challenge.)

It's a funny balance between features I'd really like to have and what there's actually space/time to implement.

Trying hard to enjoy the 4052s, but it ain't easy when you can't control the two muxes seperately.