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Analog Logic pulldown resistor question

Analog Logic pulldown resistor question

2008-04-07 by andrewlistmayer

Hi. I'm building a clone of the buchla 281 function generator which is
basically a set of voltage controlled attack-release generators where
each pair has an extra OR output. I have chosen to replace this OR
output with a CGS Analog Logic Board so I can also have the AND
function and external inputs.

Please see my panel layout here:
http://electro-music.com/forum/phpbb-files/buchla_v5_183.jpg

See the little knob in the middle? That and the 8 jacks below it
comprise the analog logic section of the module. The pot is a dual
gang and controls how much of envelope generator B goes into input 1
of the AND and how much of EG B goes into input 1 of the OR. Now my
question is: When this pot is turned all the way off, will the fact
that the inputs are then connected to ground interfere with the
pulldown resistors that turn off unused inputs to the logic module? Or
is it just the same as no input?

Re: Analog Logic pulldown resistor question

2008-04-07 by sasami@hotkey.net.au

>pulldown resistors that turn off unused inputs to the logic module? Or
>is it just the same as no input?

Assuming I am reading this right, It will be the same as being connected to
an output pushing out 0V. i.e. 0V will become your minimum in one gate, and
the maximum in the other.
_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: Analog Logic pulldown resistor question

2008-04-08 by andrewlistmayer

--- In cgs_synth@yahoogroups.com, sasami@... wrote:
Show quoted textHide quoted text
>
> >pulldown resistors that turn off unused inputs to the logic module? Or
> >is it just the same as no input?
>
> Assuming I am reading this right, It will be the same as being
connected to
> an output pushing out 0V. i.e. 0V will become your minimum in one
gate, and
> the maximum in the other.

Ok thanks, I think I get it, though I am a little confused about how
it differentiates between a 0v input and nothing connected at all. You
are saying that if no cable is connected a to a certain logic input,
it will automatically shut off, but if a cable is connected supplying
0v it will take that as an input(and the output, by default if it is
the AND gate), and it is the same case when a
potentiometer which is closed(and tied to ground) is connected to it?

Re: Analog Logic pulldown resistor question

2008-04-08 by sasami@hotkey.net.au

It will limit the AND gate output to 0V. If another input goes lower than
0V, the output will also go lower, but it will never go above 0V.
Show quoted textHide quoted text
>So, say If I have two signals patched into inputs 2 and 3 of the AND
>gate, and the attenuator that feeds the envelope generator output into
>input 1 is turned all the way down(thereby connecting that input to
>ground) will that input put 0V into the logic element, rendering it
>ineffective, or will it turn itself off, allowing the AND gate to
>process the other 2 signals properly? Thanks, and sorry for being bad
>at explaining things.
>
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>
_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: Analog Logic pulldown resistor question

2008-04-08 by sasami@hotkey.net.au

When there is nothing connected to an input to the AND gate, the pull-up
resistor will pull that input up to +10V. If you plug in something connected
to ground, the input is now at 0V instead of +10V.
Show quoted textHide quoted text
>--- In cgs_synth@yahoogroups.com, sasami@... wrote:
>>
>> >pulldown resistors that turn off unused inputs to the logic module? Or
>> >is it just the same as no input?
>>
>> Assuming I am reading this right, It will be the same as being
>connected to
>> an output pushing out 0V. i.e. 0V will become your minimum in one
>gate, and
>> the maximum in the other.
>
>Ok thanks, I think I get it, though I am a little confused about how
>it differentiates between a 0v input and nothing connected at all. You
>are saying that if no cable is connected a to a certain logic input,
>it will automatically shut off, but if a cable is connected supplying
>0v it will take that as an input(and the output, by default if it is
>the AND gate), and it is the same case when a
>potentiometer which is closed(and tied to ground) is connected to it?
>
>
>------------------------------------
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>Yahoo! Groups Links
>
>
>
>
_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: Analog Logic pulldown resistor question

2008-04-08 by andrewlistmayer

Ahh, I see now. Thank you very much. I will just need a switch to
break the connection.
Show quoted textHide quoted text
--- In cgs_synth@yahoogroups.com, sasami@... wrote:
>
> When there is nothing connected to an input to the AND gate, the pull-up
> resistor will pull that input up to +10V. If you plug in something
connected
> to ground, the input is now at 0V instead of +10V.
>
>
>
> >--- In cgs_synth@yahoogroups.com, sasami@ wrote:
> >>
> >> >pulldown resistors that turn off unused inputs to the logic
module? Or
> >> >is it just the same as no input?
> >>
> >> Assuming I am reading this right, It will be the same as being
> >connected to
> >> an output pushing out 0V. i.e. 0V will become your minimum in one
> >gate, and
> >> the maximum in the other.
> >
> >Ok thanks, I think I get it, though I am a little confused about how
> >it differentiates between a 0v input and nothing connected at all. You
> >are saying that if no cable is connected a to a certain logic input,
> >it will automatically shut off, but if a cable is connected supplying
> >0v it will take that as an input(and the output, by default if it is
> >the AND gate), and it is the same case when a
> >potentiometer which is closed(and tied to ground) is connected to it?
> >
> >
> >------------------------------------
> >
> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> >Yahoo! Groups Links
> >
> >
> >
> >
> _______________________________________________________________________
> Ken Stone sasami@...
> Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>

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