Searching \ for 'Digital volume control' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=digital+volume+control
Search entire site for: 'Digital volume control'.

Truncated match.
PICList Thread
'Digital volume control'
1999\03\14@055326 by ry (Nahum Tchernihhovsky)

flavicon
face
Hi folks,
Does any one have an idea how to control volume of an analog amplifier
digitaly using a PIC

Nahum Tchernihovsky
Visonic Ltd.
spam_OUTcherry.nTakeThisOuTspamvisonic.com

1999\03\14@092948 by Bob Drzyzgula

flavicon
face
On Sun, Mar 14, 1999 at 01:01:34PM +0200, Cherry  (Nahum Tchernihhovsky) wrote:
> Hi folks,
> Does any one have an idea how to control volume of an analog amplifier
> digitaly using a PIC
>
> Nahum Tchernihovsky
> Visonic Ltd.
> .....cherry.nKILLspamspam@spam@visonic.com

Digital pots? E.g. those from Dallas?

http://www.dalsemi.com/Prod_info/Dig_Pots/index.html

--Bob

--
============================================================
Bob Drzyzgula                             It's not a problem
bobspamKILLspamdrzyzgula.org                until something bad happens
============================================================

1999\03\14@110056 by Brian Aase

flavicon
face
Attach it to a Crystal Semi CS3310.  Works great.

> Hi folks,
> Does any one have an idea how to control volume of an analog amplifier
> digitaly using a PIC
>
> Nahum Tchernihovsky
> Visonic Ltd.
> .....cherry.nKILLspamspam.....visonic.com
>

1999\03\14@120232 by Jim Paul

picon face
I have a couple of ideas.  1. use a 1-2-4-8 resistor ladder at the output of
4 I-O pins,
and use the resulting voltage to control the bias point of an active
attenuator, or more
simply, number 2.., use an I-O pin to control a digital pot used as a volume
control.
Digital pots are made by several mfg's, but I am most familiar with Dallas
Semi.
parts.  You can get them in 10K, 50K and 100K resistances.  I believe you
also have
a choice of linear taper and audio taper.  You'll want the audio taper
probably.
You might be able to get them from digikey, but I went through a Dallas
Semi. Mfg.
Rep in Dallas.  I don't remember his name and I can't find the business
card.  I'll
keep searching though.  You might try the Dallas Semi Web Site for a Disty
or Mfg.
Rep. near you.   Hope this helps.

Regards,

 Jim
----Original Message-----
From: Cherry (Nahum Tchernihhovsky) <EraseMEcherry.nspam_OUTspamTakeThisOuTVISONIC.COM>
To: PICLISTspamspam_OUTMITVMA.MIT.EDU <@spam@PICLISTKILLspamspamMITVMA.MIT.EDU>
Date: Sunday, March 14, 1999 4:50 AM
Subject: Digital volume control


>Hi folks,
>Does any one have an idea how to control volume of an analog amplifier
>digitaly using a PIC
>
>Nahum Tchernihovsky
>Visonic Ltd.
>KILLspamcherry.nKILLspamspamvisonic.com

1999\03\14@121927 by Marc
flavicon
face
> Does any one have an idea how to control volume of an analog amplifier
> digitaly using a PIC

There exist digital pots, you supply the value either direct, or via
a bus interface (SPI, I2C).  XICOR makes them for example.

If you're out for a minimum components phone quality PIC circuit, try
a divider like this:

  in ----+
         |
        Rin
         |
         +---+---+---+------------ OpAmp
         |   |   |   |
         R1  R2  R3  R4
         |   |   |   |
 RA0 ----+   |   |   |
 RA1 --------+   |   |
 RA2 ------------+   |
 RA3 ----------------+

You can leave the port pins floating, or pull them down. With proper
chosen R values, you can select up to 16 volume levels (and have a
little bit of digital noise, too :)

(Make sure your input signal does not exceed 0-5V, for example
decouple it and bias it at 2.5V, and decouple it again right before
the OpAmp if you need it DC-free).

1999\03\14@125125 by ry (Nahum Tchernihhovsky)

flavicon
face
Thank you Jim,
I am not mean using one of the standard digital potentiometers that are
manufactured by some companies and are too expensive for our purpose. I am
looking for a cheap solution in the range of several cents (transistor+,
etc.) any how thank you and all the others for your efforts and I am still
looking for an idea to make it simple and cheap.

Nahum (cherry)
Visonic Ltd.
RemoveMEcherry.nTakeThisOuTspamvisonic.com




Jim Paul <spamBeGonejamespspamBeGonespamINTERTEX.NET> on 14/03/99 18:55:59

Please respond to pic microcontroller discussion list
     <TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU>

To:   RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU
cc:    (bcc: Nachum Tchernichovski/Visonic Ltd.)
Subject:  Re: Digital volume control




I have a couple of ideas.  1. use a 1-2-4-8 resistor ladder at the output
of
4 I-O pins,
and use the resulting voltage to control the bias point of an active
attenuator, or more
simply, number 2.., use an I-O pin to control a digital pot used as a
volume
control.
Digital pots are made by several mfg's, but I am most familiar with Dallas
Semi.
parts.  You can get them in 10K, 50K and 100K resistances.  I believe you
also have
a choice of linear taper and audio taper.  You'll want the audio taper
probably.
You might be able to get them from digikey, but I went through a Dallas
Semi. Mfg.
Rep in Dallas.  I don't remember his name and I can't find the business
card.  I'll
keep searching though.  You might try the Dallas Semi Web Site for a Disty
or Mfg.
Rep. near you.   Hope this helps.

Regards,

 Jim
----Original Message-----
From: Cherry (Nahum Tchernihhovsky) <cherry.nEraseMEspam.....VISONIC.COM>
To: EraseMEPICLISTspamMITVMA.MIT.EDU <RemoveMEPICLISTEraseMEspamEraseMEMITVMA.MIT.EDU>
Date: Sunday, March 14, 1999 4:50 AM
Subject: Digital volume control


>Hi folks,
>Does any one have an idea how to control volume of an analog amplifier
>digitaly using a PIC
>
>Nahum Tchernihovsky
>Visonic Ltd.
>RemoveMEcherry.nspam_OUTspamKILLspamvisonic.com

1999\03\14@125740 by ry (Nahum Tchernihhovsky)

flavicon
face
Thank you Marc,
Nice idea. That's exactly the type of solution I am looking for. Is there
any idea using PWM for instance?

Cherry (Nahum Tchernihovsky)




Marc <RemoveMEmarcTakeThisOuTspamspamAARGH.FRANKEN.DE> on 14/03/99 16:28:55

Please respond to pic microcontroller discussion list
     <EraseMEPICLISTspamspamspamBeGoneMITVMA.MIT.EDU>

To:   RemoveMEPICLISTKILLspamspamMITVMA.MIT.EDU
cc:    (bcc: Nachum Tchernichovski/Visonic Ltd.)
Subject:  Re: Digital volume control




> Does any one have an idea how to control volume of an analog amplifier
> digitaly using a PIC

There exist digital pots, you supply the value either direct, or via
a bus interface (SPI, I2C).  XICOR makes them for example.

If you're out for a minimum components phone quality PIC circuit, try
a divider like this:

  in ----+
         |
        Rin
         |
         +---+---+---+------------ OpAmp
         |   |   |   |
         R1  R2  R3  R4
         |   |   |   |
 RA0 ----+   |   |   |
 RA1 --------+   |   |
 RA2 ------------+   |
 RA3 ----------------+

You can leave the port pins floating, or pull them down. With proper
chosen R values, you can select up to 16 volume levels (and have a
little bit of digital noise, too :)

(Make sure your input signal does not exceed 0-5V, for example
decouple it and bias it at 2.5V, and decouple it again right before
the OpAmp if you need it DC-free).

1999\03\14@130748 by Sean Breheny

face picon face
At 08:05 PM 3/14/99 +0200, you wrote:
>Thank you Marc,
>Nice idea. That's exactly the type of solution I am looking for. Is there
>any idea using PWM for instance?

I was sorta wondering that myself. I have never tried it,but what about
using a PIC pin to periodically short the signal on the amp's input to
ground,and then use a low pass filter on he input as well to make the
response roll off way below the PWM frequency?

It may be somewhat difficult to generate PWM that fast and still have
enough time left over in your PIC to get other things done.

Of course,the sound quality can't be expected to be great if you do a trick
like this.

>
>Cherry (Nahum Tchernihovsky)


Sean

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
shb7STOPspamspamspam_OUTcornell.edu ICQ #: 3329174

1999\03\14@135434 by Mike Morrin

flavicon
face
At 08:05 pm 14/03/99 +0200, Cherry  (Nahum Tchernihhovsky) wrote:
>Thank you Marc,
>Nice idea. That's exactly the type of solution I am looking for. Is there
>any idea using PWM for instance?

If the amplitude of the signal you are working with is less than about
10mV, you can shunt it with a forward biassed diode and pwm (and smooth)
the supply for the current through the diode.  The attenuation varies a bit
with temperature etc, but you can get distortion below 5% over a 30 or 40db
control range.

{Quote hidden}

For this design to work, you need to tri-state the pins, or put diodes in
series.

regasrds,

Mike

1999\03\14@164906 by Marc

flavicon
face
> If the amplitude of the signal you are working with is less than about
> 10mV, you can shunt it with a forward biassed diode and pwm (and smooth)
> the supply for the current through the diode.  The attenuation varies a bit
> with temperature etc, but you can get distortion below 5% over a 30 or 40db
> control range.

How would the schematic look like for this idea?

1999\03\14@174725 by Keith Doxey

flavicon
face
Hi All,

Like many others in this list, I like to reverse engineer products to see
what makes them tick and to learn new techniques for my own projects.
Several years ago I was the station engineer on a community radio station
that we set up for 3 experimental broadcasts to see if there was a need for
a community station in our area. (There was but the license went to our
competitors.....but thats a different story).

We hired a signal processor to optimise the signal we were broadcasting. I
spent several hours reading and inwardly digesting the manual that came with
it (sad I know but...) and learnt several things.

The relevant bit to this topic was that its automatic gain control was done
by PWM chopping the signal going through it. I cant remember the exact
details but the frequency of the PWM was MUCH higher than the required audio
bandwidth and basically varied its duty cycle to increase/decrease the gain.
The comments Sean made about the sound quality are probably quite correct if
the PWM frequency is too low, but this was a piece of Professional Broadcast
equipment so the sound was of the utmost importance. I had forgotten about
this until the topic came up but I may try and find time to experiment a
little.

I have succesfully used the Dallas DS1802 and will be publishing a project
for a Digital Volume Control on my website shortly. I have to admit that the
PWM approach appeals to me greatly as the DS1802 is not exactly cheap when
compared to a CMOS switch.

Hope that helps

Keith

Keith Doxey
http://www.btinternet.com/~krazy.keith
Krazy Keith's World of DIY HomeAutomation


> {Original Message removed}

1999\03\14@180419 by Dwayne Reid

flavicon
face
>If you're out for a minimum components phone quality PIC circuit, try
>a divider like this:
>
>   in ----+                VCC
>          |                 |
>         Rin              Rbias
>          |                 |
>          +---+---+---+-----+------- OpAmp
>          |   |   |   |     |
>          R1  R2  R3  R4  Rbias
>          |   |   |   |     |
>  RA0 ----+   |   |   |    GND
>  RA1 --------+   |   |
>  RA2 ------------+   |
>  RA3 ----------------+

This works best with a '71 or other PIC with an a/d convertor.  Use port RA,
turn off the a/d (reduce noise), configure the inputs as analog, write all
zeros to port RA (clrf RA), then manipulate the TRIS register to select
which resistors need to be grounded.

You want to use an analog pin so that it can live safely at the bias level
of 2.5V (with all pins open circuit).  Note that the bias level is going to
change as you turn on the different pins, but that doesn't matter to the
PIC.  What is more of a concern is the large 'thump' you get as that bias
level changes.  If you can live with it, this is about as low cost as you
can get.

dwayne


Dwayne Reid   <spamBeGonedwaynerSTOPspamspamEraseMEplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(403) 489-3199 voice          (403) 487-6397 fax

Celebrating 15 years of Engineering Innovation (1984 - 1999)

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Do NOT send unsolicited commercial email to this email address.
My posting messages to Usenet neither grants consent to receive
unsolicited commercial email nor is intended to solicit commercial
email.

1999\03\14@184157 by Gerhard Fiedler

picon face
At 22:44 03/14/99 +0000, Keith Doxey wrote:
>The relevant bit to this topic was that its automatic gain control was done
>by PWM chopping the signal going through it. I cant remember the exact
>details but the frequency of the PWM was MUCH higher than the required audio
>bandwidth and basically varied its duty cycle to increase/decrease the gain.
>The comments Sean made about the sound quality are probably quite correct if
>the PWM frequency is too low, but this was a piece of Professional Broadcast
>equipment so the sound was of the utmost importance. I had forgotten about
>this until the topic came up but I may try and find time to experiment a
>little.

i would guess that in order to get low on distortion, you'd have to be at
least 10 times the highest audio frequency with the pwm frequency.

ge

1999\03\15@165051 by Graeme Smith

flavicon
face
How about using a resistor ladder....

Powered by your PIC.

as you turn on more pins, (or use a decoder to turn on more pins to expand
the range) it reduces the resistance, thus increasing the amperage flowing
into the analog device. You get a discrete (Stepped) volume control for
the cost of a few resistors. Depending on which resistors you use, you can
set the circuit to have a linear, or logarythmic gain...

you might then feed the result, through a transistor to get more gain.


GRAEME SMITH                         email: KILLspamgrysmithspamBeGonespamfreenet.edmonton.ab.ca
YMCA Edmonton

Address has changed with little warning!
(I moved across the hall! :) )

Email will remain constant... at least for now.


On Sun, 14 Mar 1999, Cherry  (Nahum Tchernihhovsky) wrote:

{Quote hidden}

1999\03\15@192137 by marcel

flavicon
face
You could try pwm to a light bulb or led which is optically connected to an ldr
photo sensitive resistor
Marcel
Amsterdam
Marc wrote:

> > If the amplitude of the signal you are working with is less than about
> > 10mV, you can shunt it with a forward biassed diode and pwm (and smooth)
> > the supply for the current through the diode.  The attenuation varies a bit
> > with temperature etc, but you can get distortion below 5% over a 30 or 40db
> > control range.
>
> How would the schematic look like for this idea?

More... (looser matching)
- Last day of these posts
- In 1999 , 2000 only
- Today
- New search...