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 Forum index » DIY Hardware and Software » The layout factory
basic volt per octave keyboard schematics
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Grumble



Joined: Nov 23, 2015
Posts: 721
Location: Netherlands
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PostPosted: Sat Nov 19, 2016 1:51 am    Post subject: Reply with quote  Mark this post and the followings unread

One of my favo sites when it comes to calculation of schematics behavoural calculations is THIS site.

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PHOBoS



Joined: Jan 14, 2010
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Location: Moon Base
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PostPosted: Sat Nov 19, 2016 5:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I have also a bunch of zener diodes of many values.Which do i pick and how do i connect it?
You need a 10.0V zenerdiode and a resistor, 1K will probably do but you could experiment a little. Connect the cathode of the zenerdiode
to GND, the anode to the resistor and the other side of the resistor to -12V. The point where the diode and resistor are connected will be
your -10V reference voltage.

Quote:
Now,looking for a definitive solution.I only have LM 317,(positive regulator), but not the LM 337 which will do the job from what i've heard.
That actually made me think of another method last night but it is a bit over the top for this purpose. Use the LM317 to create a +10v
voltage and then use an opamp configured as a inverting amplifier with a gain of x1 to invert it to -10V.

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Cfish



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

PostPosted: Sat Nov 19, 2016 5:18 am    Post subject: Reply with quote  Mark this post and the followings unread

extremly useful link grumble.


Edit. That would be a great link in the (fun useful tips thread)
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alanwilder81



Joined: Sep 03, 2016
Posts: 325
Location: italy

PostPosted: Sat Nov 19, 2016 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Grumble Smile
designing and calculating things for now is a bit over my head, but this site will come handy in the future


to Phobos,

i've come across a website where they describe the inverting opamp method you mention to change the voltage polarity,Now you confirm it works.
I will also try the zener diodes thing.Good to know different approaches to get this matter around Smile
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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Sat Nov 19, 2016 6:15 am    Post subject: Reply with quote  Mark this post and the followings unread

to Cfish
i can confirm that the keyboard circuits works decently.The VCO i used for testing it tracks ok.It s only three octaves but hey. Enough for a little monophonic analog synth.
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Grumble



Joined: Nov 23, 2015
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Location: Netherlands
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PostPosted: Sat Nov 19, 2016 9:49 am    Post subject: Reply with quote  Mark this post and the followings unread

But why do you want -10volt? you could just as easily put a resistor of 10k in series with the potmeter of 1k and connect it with the -12volt.
This resistor will prevent the -input of the opamp being directly connected to -12volt if you happen to turn the potmeter to 0 ohm.
Usualy opamps dislike to have the inputs connected to the power supply (pos. nor neg.) and the resistor prevents that from happening.
It may not be very stable, but you can play anyways.
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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Sun Nov 20, 2016 6:51 am    Post subject: Reply with quote  Mark this post and the followings unread

i want -10 V because in the schematics its specified so
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Grumble



Joined: Nov 23, 2015
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PostPosted: Sun Nov 20, 2016 9:23 am    Post subject: Reply with quote  Mark this post and the followings unread

There is no law against changing diagrams to ones likings, in fact it realy helps you in understanding whats going on...
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alanwilder81



Joined: Sep 03, 2016
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Location: italy

PostPosted: Sun Nov 20, 2016 9:47 am    Post subject: Reply with quote  Mark this post and the followings unread

tweaking diagrams is well over my head.So,for the moment i'm settling for working with what's there and trying to wrap my head around that. Cool Cool
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alanwilder81



Joined: Sep 03, 2016
Posts: 325
Location: italy

PostPosted: Sun Nov 20, 2016 3:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

to Phobos,

excellent trick, i got my steady -10 V reference voltage Smile
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Cfish



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

PostPosted: Sun Dec 04, 2016 6:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

So, experimenting with the yousynth schematic on here has led me to try to add basic trigger to the original schematic that has grown along the way.

Looks like it should work


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