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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Single bus keyboard stripboard layout
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henq



Joined: Nov 29, 2006
Posts: 23
Location: holland

PostPosted: Sat Jan 27, 2007 4:14 am    Post subject: Reply with quote  Mark this post and the followings unread

hmm, my camera got broken and i still have to get a new one...
but i'll try to get some pics soon.

ill check all the switches, and maybe i can get them all to 190 ohm by soldering some resistors to them...

thanks for the reply.
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Uncle Krunkus
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PostPosted: Sat Jan 27, 2007 5:53 am    Post subject: Reply with quote  Mark this post and the followings unread

If there aren't resistors already in series with those switches, then there's something seriously wrong with them. A closed switch shouldn't read anymore than 2-3 ohms, (and that would be the resistance of the meter leads! Very Happy )
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henq



Joined: Nov 29, 2006
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Location: holland

PostPosted: Sat Jan 27, 2007 8:13 am    Post subject: Reply with quote  Mark this post and the followings unread

i just went out to get a new camera, as soon as the battery is charged, ill take some pics...

but i'm already guessing i had better chosen the matrix decoder thing...
anyway, if that is the case, i'm going to convert an old guitar into a single bus synth controller anyway, so i can still use the circuit.

i just opted for this one because i thought it would be easyer to make, and there was a stripboard layout for it and not for the matrix decoder (hint Wink )
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Blue Hell
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PostPosted: Sat Jan 27, 2007 9:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
If there aren't resistors already in series with those switches, then there's something seriously wrong with them. A closed switch shouldn't read anymore than 2-3 ohms, (and that would be the resistance of the meter leads! Very Happy )


Don't know for sure, but maybe, when it has rubber contacts, the on resistance could be pretty shitty.

I don't know how the keyboard circuit is constructed, but when it's a resistor chain where the contacts just have to select a tap and give the voltage to a high impedance sample and hold a bad on resistance might not matter too much. (links Exclamation we need more links here Smile )

When the keyboard is set up in a matrix some serious trace hacking might be needed.

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henq



Joined: Nov 29, 2006
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PostPosted: Sat Jan 27, 2007 11:27 am    Post subject: Reply with quote  Mark this post and the followings unread

ok, so yeah, they are rubber switches, and inside them (i hoped it was visible on the pic) there is a tiny black cylinder, that connects two metal thingies then the buton is pushed...


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henq



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PostPosted: Sat Jan 27, 2007 11:33 am    Post subject: Reply with quote  Mark this post and the followings unread

this was my initial plan, but i guess this wont work, some switches have 260 ohms, some 85 ohms when closed, i hope that is no problem for the matrix thing...


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henq



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PostPosted: Sat Jan 27, 2007 11:38 am    Post subject: Reply with quote  Mark this post and the followings unread

this might give you an impresion of what the whole thing looks like...


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Uncle Krunkus
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PostPosted: Sat Jan 27, 2007 4:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Don't know for sure, but maybe, when it has rubber contacts, the on resistance could be pretty shitty.

I don't know how the keyboard circuit is constructed, but when it's a resistor chain where the contacts just have to select a tap and give the voltage to a high impedance sample and hold a bad on resistance might not matter too much.)


Now that I've seen it, I agree with Jan on both these points.

So,..... clear each switch from any outside connections, run a common connection to each switch, and loop a chain of 100R resistors across points which connect to the common. And,..... see what happens. If there's a problem, you may be able to increase the input impedance of the S&H, and the option of pulling it all off and trying the matrix solution is still there.

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Blue Hell
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PostPosted: Sat Jan 27, 2007 4:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Now that I've seen it, I agree with Jan on both these points.


Me too Laughing

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henq



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PostPosted: Sun Jan 28, 2007 2:51 am    Post subject: Reply with quote  Mark this post and the followings unread

it was a 4 octave keyboard that i cut to be 3 ovtaves, so i'll try with the spare octave first...

but i think it could never be in tune, because the resistance of each button is different...
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Uncle Krunkus
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PostPosted: Sun Jan 28, 2007 4:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Like Jan pointed out, if the input impedance of the S&H chip is sufficiently high, the voltage potential at that point of the resistor chain will be correctly carried across the resistance of the switch.
Trust us, we're doctors! Laughing

(Well,... Jan's a doctor, I'm just an inturn, but I do like chopping things up to see if I can put them back together.
"Uncle!...
Uncle!!....
I need another brain for my experiments!!"
"Yes master!......
I think I need one too!")

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Blue Hell
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PostPosted: Sun Jan 28, 2007 6:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
Trust us, we're doctors! Laughing


OMG Shocked

Laughing

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henq



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PostPosted: Sun Jan 28, 2007 9:30 am    Post subject: Reply with quote  Mark this post and the followings unread

ill give it a go.
(first i have to get 2 more ICs in the mail, and find some time)

i wish i knew a bit more about impedance...
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Uncle Krunkus
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PostPosted: Sun Jan 28, 2007 4:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

A bit of background info; -
Impedance is AC resistance. Sounds simple, but AC has many possible frequencies, and impedance is dependant on the frequency of the signal. So a certain component, or group of components, has an impedance of X ohms @ Y Hz. The same component will have a different impedance if you change the frequency of the signal across it.

Now, Jan and I are talking about the impedance of the Op-Amp in this circuit, because Op-Amps are often used for AC applications. In this situation however, the op-amp is buffering a DC voltage from the resistor chain. So it would be just as useful to speak of the op-amp's input resistance.
If it's relatively low (1K-5K), the resistance of the switch would effectively be part of a voltage divider, and would have a big impact on the buffered DC level coming out of the op-amp. If it is relatively high (5M-10M) then the 100 or so ohms of each switch will only have a tiny part of the signal dropped across them (.002%) and the rest will be accurately buffered by the op-amp.

Does that help?

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henq



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PostPosted: Sun Jan 28, 2007 10:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
...

Does that help?


i think it does...
at least i understand it a little, i'm not sure if i can implement this knowledge, but tomorrow i think i'll have some time to look at the circuit again.
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Ohmu



Joined: Jul 30, 2009
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PostPosted: Sun Aug 23, 2009 11:17 am    Post subject: Reply with quote  Mark this post and the followings unread

What kind of keyboard we have to use with the single bus?
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Uncle Krunkus
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PostPosted: Sun Aug 23, 2009 4:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

A single bus keyboard! Very Happy
In other words, there needs to be a common connection to all keys, (single bus) and each key needs another connection which is shorted to the common bus when pressed.

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Ohmu



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PostPosted: Mon Aug 24, 2009 1:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Thank for yout answer but is there a model/mark in particulary?
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Uncle Krunkus
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PostPosted: Mon Aug 24, 2009 6:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Sorry, I don't know.
I made one with an old organ keyboard. Smile

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mikebike



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PostPosted: Fri Apr 16, 2010 3:23 pm    Post subject: firtst post! Reply with quote  Mark this post and the followings unread

hey everyone!

long time lurker, firrst time poster

where is V+, V-, earth?

where do the key switches conect? the bus from the keyboard?
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El Mop



Joined: Aug 20, 2012
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PostPosted: Tue Oct 02, 2012 11:21 am    Post subject: Reply with quote  Mark this post and the followings unread

I thought this layout had been made from this:
Posted Image, might have been reduced in size. Click Image to view fullscreen.
But since it doesn´t seem to fit and the fact that this post is from 2005,
maybe there had been something changed meanwhile?!

Anyway, can I anyone send me the right values for this layout?

Thank you

@mikebike
V+, V- and ground can be found on the left side in the middle (There are signs for +/- and ground).
There are two points in the layout labeled "Busbar" and "Ladder", where you connect the keyboard.
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El Mop



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PostPosted: Thu Oct 04, 2012 6:48 am    Post subject: Reply with quote  Mark this post and the followings unread

The link didn´t work, now it does.
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El Mop



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PostPosted: Sat Oct 06, 2012 5:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Nobody knows anything about this?
Don´t believe it!
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El Mop



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PostPosted: Thu Oct 11, 2012 1:59 am    Post subject: Reply with quote  Mark this post and the followings unread

If the schematic of this layout doesn´t exist and the even the creator of this layout doesn´t seem to know anything about it, this layout is pretty much useless, isn´t it?
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El Mop



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PostPosted: Sat Nov 10, 2012 7:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Found the schematic today by accident.
But by now it´s too late... Sad

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.
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