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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
CGS VCO PW Pot
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Audent



Joined: Dec 19, 2007
Posts: 24
Location: oh-hi-oh

PostPosted: Mon Jun 15, 2009 10:41 pm    Post subject: CGS VCO PW Pot Reply with quote  Mark this post and the followings unread

Hello all...

I'm currently building a couple of full-featured CGS VCO's and although I've figured out most of the panel wiring, I cannot seem to determine how to wire up the pulse width pot.

I'm not terribly good at figuring these things out...but im wondering if i need to tie into the PWM input somehow and wire up a pot with a +V input?

can anyone help me on this?

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andrewF



Joined: Dec 29, 2006
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Location: australia
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PostPosted: Tue Jun 16, 2009 12:11 am    Post subject: Reply with quote  Mark this post and the followings unread

hi
I have never actually installed a pot on the PWM of my CGS VCOs....but if i did i would copy the circuitry for the 'division' pot on the CGS VC Divider

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

wire up +V thru a 1k resistor to the switch of your jack. then wire the jack to a 20k-100k pot. wiper of the pot goes to PWM input. bottom tab of the pot to ground.

this way, if nothing is plugged in, you can set the PWM manually with the pot. If you plug in a CV signal, the pot becomes an attenuator to set the 'strength' of your CV signal.
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zthee



Joined: Feb 20, 2008
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PostPosted: Tue Jun 16, 2009 1:27 am    Post subject: Reply with quote  Mark this post and the followings unread

I wired mine with +15V at one end and -15V at the other and then thru a 330K resistor to the PW pad. So the pot goes from approx 10% to 90% PW.

The incoming signal into the TL072 (that act as a comparator) is AC coupled - so it goes from -2.5V to +2.5V (approx). So the pot need so be able to go from - to +, else you'll only get modulation from 50% to 100% PW...

As Andrew suggests you could have a switching jack for it all - but make sure you put the 330K resistor between the pot and the jack and not between the jack and the pad!

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Audent



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PostPosted: Thu Jun 25, 2009 7:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the replies!

this should keep me moving along...panels are almost done, so i'm trying to prepare all the wiring now. what a job!

i'm sure there will be more questions to come! Laughing

banana

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