voltage controlled resistors

[Harry Bissell]

Its an optical encoder... it uses an LED and phototransistors. There are usually
two detectors that sense little slots in a disk... the slots are 90 degrees out
of phase.. so this way direction can be encoded. Counters accumulate the number
of pulses.

They make encoders that look like pots... also mechanical encoders that have
contacts...
Don't have any circuits off hand but if you search the web under "optical
encoder" or "Mechanical encoder" and check out "Bourns" and "Grayhill" you will
get some app noptes...

H^)

Uros Milicevic wrote:

> ----- Original Message -----
> From: Magnus Danielson <cfmd at swipnet.se>
> To: <t02e at hotmail.com>
> Cc: <synth-diy at mailhost.bpa.nl>
> Sent: Monday, February 14, 2000 8:59 PM
> Subject: Re: voltage controlled resistors
>
> > From: "walter carpenter" <t02e at hotmail.com>
> > Subject: voltage controlled resistors
> > Date: Sun, 13 Feb 2000 20:19:13 PST
> >
> > > This might be a stupid idea, but has anyone ever built a simple "voltage
> > > controlled resistor" that, with a switch, could override a
> potentiometer? is
> > > this possible? it would be nice to have lfo's controlling as many things
> as
> > > possible :)
> >
> > Hm. This really sounds like something you would build with OTAs. One or
> > possibly two OTAs in a gyrator setting should be an interesting thing. For
> > most settings will a single OTA be suiteable, but if you need both ends of
> the
> > resistor to "float" and push/pull current I think a little more advanced
> tricks
> > have to be used. Hmm...
> >
> > Cheers,
> > Magnus
> Or you can use discrete OTAs or you can use fet transistor . It depends for
> what you need it .
> I think ( I'm not an expert so I may be wrong ) it is best to designe
> circuit with VC in mind and not to apply VC to nonVC circuit ( I'have
> feeling that you want to change pot with VCresistance
> Usualy circuit can be much simpler if you use Vc from the start ( this is
> IMHO ) . If you need to change existing circuit and you need it badly maybe
> someone from the list ( I'm not pretending of being capable of doing that )
> could do it for you .OTOH I realy should not speak
> in other people name .
> When we are talkin about resistors and pots could someone give me some info
> ( or point me out where to get info ) on motion tracking device ( what a
> terrible description ) from mouse
> Im refering to two pot look-a-likes that tracks motion of rubber ball . Im
> shure it is light based
> and that it uses descrete logic but what is sensor for light ( it certanly
> dont need  LDR ) ? Voltages , suply voltages , circuit layout ?
> Thanks in advance
>
> Uros