Panning over 4 audio-channels using only 1 pot ?

[watchjohn]

.

Hi,

It`s a little difficult to explain:


I have 4 audiochannels (mono)

I have 1 amplifier to make them audible

I want to use only 1 potmeter to mix/pan them
to the amplifier.

Lets say these are the 4 channels

1...2...3...4

Ideally i like to be able to "pan" over the channels
to hear mostly one channel, either 1...2...3...or 4
(while the other channels should be much weaker)

So if i adjust for max volume of channel 1
then channel 2,3,4 should be muchweaker
slightly moving the pot towards another channel
should change the output in the same way.

When to pot is at channel 2...then the other channels
are much weaker...etc

pot between 2 channels gives both of them at half strength
...etc


Same as having a pan control for 2 channels (stereo)
where you can "pan" from the left to the right channel
Instead of 2 channels i now have 4 channels.

I like to be able to do it with only 1 (single channel)
digital potmeter (under uP control)

Yes i know i could do it with 4 digital pots
but i dont want that.

How to do it with only 1 pot ?
...maybe i could have somekind of resistor-bridge ?

Thanks in advance !


WatchJohn

 

[watchjohn]

.

Hello again,


> "The world's first 10 kg (22 lb) 'wristwatch"

Believe it or not...but i have most of the device
already designed..and it is indeed the size of
a wristwatch...not even that redicioulous big
currently i think it will be 40mm Diameter x 18 mm High

Fortunately i realised that this forum is not a closed
group...meaning that if i would show my design it
would be to easy to copy...before it is even finished
A simple wristwatch-detector search on google will
imidiatly show this thread.

Not much i can do when it is on the market later
but for now i will have to keep a low profile.




> "Think your market is 10% of the millionaires (CEO etc)

Wow ! ...i wish that was true...any idea how many units
that would be...MILLIONS !

Seriously...the market is large enough...do a Google
for "Bugdetector" or "Spyshop" or "Countersurveillance"
and see the huge amounts of websites selling them.

Most of them are crap and cant do what they tell you,
specially the high frequency-range up to 6 or even 14 Ghz.

I have opened a lot of them and some of those "6 Ghz" units
contain 2.5 Ghz amplifiers ! (frontend)
They use only 1 telescopic-antenna for the whole range
from 100 khz to 6 ghz...wich can´t be serious.

Mine is wearable...better quality...better looking and
with a higher James Bond-sexappeal

Yes it will be in the higher price-range

But i have no doubts of its potential

Wanna invest or join ? ... show the money !




> "The big problem of invertors is marketing"

Yes i agree..usually inventors are not great salesman
i´m a designer...designing for someone else.

The idea of a wristwatch-style bugdetector is good
and very new...and very usefull.

It´s not only usable as a bugdetector but also
as a so called "elektrosmog" detector wich will warn
you for large levels from GSM and Cellphone-masts...etc
There´s a lot on that on the internet.
Advantage would be that you now always have it with you.

Every one that uses a bug-detector or a
elektrosmog-detector will immidiatly want
my wristwatch unit...provided it works just as good
and it will...even better...since i have added some features
that will make it better...without complicating it.

So it will almost sell itself...when sold trough the
same channels as the other older units.



> " SPI, I2C, 3 wire interfacing, bus...etc

Yes thanks...i have seen it all...and thinking of it
Maybe i´ll included that in a next "pro" model
since i now realise that adjusting/mixing the signals
might be a to-difficult feature for a beginner.



> " One guy turned the atomic-clock into a wristwatch....."



For less then 50$ you get a radio-controlled wristwatch
that listens to a radio-signal from 500 miles away
why cant i make a very very much simpler bug-detector
inside a watch...no problemo:

http://tinyurl.com/36ap3t

Here´s a Wristwatch-TV...1000 times more complicated
then a bugdetector:

http://tinyurl.com/yoeqml

I can understand your sceptism...but that is probably
because you don´t realise that a basic bugdetector-circuit
is really very simple and small.
I have found some very small but very capable chips that
will make it much better without making it to big at all.

A very small PIC (10 x 10 mm microprocessor)
will do most of the work.

I´m asking questions on this forum only to perfect
my design and get the most out of it...but the basics
is peanuts to built inside a wristwatch.

For your entertainmaint...check out these amazing watches from Japan:

http://www.tokyoflash.com/watches2.html

> " You won't need the "panning" feature.
> " A simple selector would do
> " Bands will overlap

Yes...a 5 position switch( 4 bands + all) will do.
And indeed the individual bands will (have to) overlap.

That is exactly why continious panning might give
a better indication of the frequency of
an unknown transmitter.

Lets say the received frequency is right on a overlap,
on the edges of 2 bands. (in between the two)

In that case if i pan/tune for max reception...then
i would see (on the freq-tune-indicator) that the max
signal would be right in-between those 2 bands.

On a wristwatch-style scale...a circle of 20 LED´s wich
i have already anyway (to show the signal-strength)
i could then have a scale from 1 Mhz to 10 Ghz
and get a more finer indication showing that in-between frequency.

Also i thought with continious-panning to have a better way
of "peaking" (wanted) or "notching" (unwanted) signals.



> " Bugs transmit data in encrypted form,
> " so the audible signal won't be legible.

Yes there are some around,
and yes these are not legible.

But these are usually not in the hands of the
greater public...these are just a very low percentage.

By far most are not encrypted !

But that doesn´t really matter anyway since this is a:

-----------------------
!! bug-DETECTOR !!
-----------------------

wich purpose is...to DETECT bugs...nomatter if i can
actually decode the contents.
All i want to know is: " IS THERE A BUG ? "
i can then find it´s (hidden) location
by moving the detector across the area
while observing the signal-strength.

I can then remove that bug...or take some other action.

The audio from the speaker will be of great help
to have some sort of identification of what i´m
actually receiving...also after a while you will
exactly know wich kind of signals are not harming.

There´s 100´s of bugdetectors on the market,
none of them can decode the contents of digital encrypted
or freq-hopping bugs (or cellphones)
But they don´t have to...in order to find such bug.

Yes i would hear garbled voices or digital pulses
but that doesn´t matter...as long as i am warned
and able to find the bug.

The contents would be your own voice anyway



> "Digital pots that have zero-crossing detectors.

Yes that would help,

Another point would be the choise between
volatile or non-volatile digital-pot.

Non-volatile remembers the slider position
when power is switched off...and come back
in the last position used.

In case of uP control the uP could remember that position.



> " A quad digital-pot will probably take up less space

Yes agree.


Check out "Maxim" who probably make the largest range
of digital pots...up to 6 pots in one single chip.

http://tinyurl.com/2v5pzr

Thanks all !


WatchJohn

 

[itsmoked]

Sounds like a fun project John! I never considered something along those lines. Nice post too. A star.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[IRstuff]

High end bugs don't continuously broadcast, specifically to avoid detection by standard RF detection methods.

They buffer the data and squirt them at periodic intervals to minimize their RF footprint. This also makes it harder to trigger a transmission with extraneous sounds.

TTFN

FAQ731-376

 

[watchjohn]

.

IRstuff said:

> "High end bugs don't continuously broadcast,
> "specifically to avoid detection by standard
> "RF detection methods.


Yep...those are called "Burst-transmitters"

Just as with digital or encrypted bugs...these
are not common available or in use by the greater
public.

BUT...they are detectable...with a little more effort.

They will transmit in regular intervals
those intervals depend on the storage-capacity
of the internal memory...and the sample-rate used

The duration of the "burst" depends on how much
(compressed) voice has to be transmitted.

For example a 1 hour conversation could be compressed
to 5 minutes or less.

Like that there could be a 5 minute transmission
of compressed sound...occuring every hour.

Above is just a rough an example and many other schemes
are imagineable.


So in the above example there would be a 5 min transmission
every hour...a bug-detector will receive that and show
it´s signal-strength and let you hear the sound of whatever
such burst-transmission sounds like.

If you would hear such burst-transmission on a regular base
you could be alert...specially if you have reasons for believing that you could be bugged.

During such burst-transmission you could walk around the
room and try to find a point with substantial higher
signal-level...that point might be the hiding-place
of the burst-transmission.

If no clear "hotspot" can be found...then the transmission
might come from outside...and poses no threat.

Now a problem with most wideband-detectors is that
they don´t have a squelch...meaning that you would hear
annoying background-noise as long as there is no strong (local)signal.

Yes they sometimes have a gain-adjuster.
but that is not the same you will still hear
background noise.

My solution is to have a adjustable squelch
it will activate the audio/speaker and led-bar meter only
when the received level is above the squelch-level.
Such squelch will also save on battery-power.

Instead of received-audio you could also have a
"tone-level-indicator" wich is a pulsing tone
the faster it pulses the higher the signal-level.

You could also have a little vibrator (pager-motor)
...it vibrates every time the adjustable squelch opens.

Other (expensive)detection-equipment exists
but we are talking low-end wideband-detector here.


WatchJohn