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Old 19th June 2011, 03:52 PM   #1
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Default Microcontoller control over CMoy volume.

So I'm looking for an easy/cheap way to achieve volume control over a cmoy via a microcontroller (right now I'm prolly going to use an arduino pro mini, but thats not set in stone).

Simply put I need an easy drop in for the cmoy's potentiometer. I know there are digital pots but I hear that many of them introduce zipper noise when changing levels. So far I'm looking at the DS1802 but its a bit pricy compared to the rest of the amp section.

Would something like this be a simple drop-in, where I connect the wiper pin where the physical pot's wiper went. Any problems with this scenario, this is not a hi-fi project so I don't need audiophile quality (and cost).

For reference, the cmoy is just one part of my project and the whole deal is controlled via IR + uC. It generally won't be powered off often so memory settings are unneeded and super precise change isnt needed, I probably won't need to change volume all that often.
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Old 21st June 2011, 05:43 PM   #2
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Originally Posted by jtavrisov View Post
So far I'm looking at the DS1802 but its a bit pricy compared to the rest of the amp section.
The fine thing about it is that you can save on the ĶC, because the DS1802 can also be controlled through two pushbuttons.

Originally Posted by jtavrisov View Post
Would something like this be a simple drop-in, where I connect the wiper pin where the physical pot's wiper went.
If you've always done it like that, then it's probably wrong. (Henry Ford)
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Old 23rd June 2011, 03:57 PM   #3
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If you are going to use MCU control, why not look at texas instruments' chips made specificaly for this job, some even have volume control, you just need to add the commands from your MCU.
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Old 29th June 2011, 06:28 PM   #4
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Location: Budapest
Or maybe you could use TDA7309 from ST.
There are free samples available.
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Old 29th June 2011, 07:07 PM   #5
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or maybe you can use a weird idea of mine, I want to try it out but have no time these days but anyways here it goes,This induces no noise to the audio line..

it uses 2 chips, a 555 timer ic and a 4017 decade counter ic,
the 555 feeds in clock to the 4017,

something like this

the last diagram in circut, one button advances the count, the other reduces the count..

each output pin of the 4017 triggers a transistor with a different resistor value..

the emitter of the transistors are joined together powering an led,

now as the count ascends or you press the + button, the sequence starts

the first transistors resistor value should be so that it ascends as the pin count increases.

like output 1 10% of led brightness
output 2 20% of led brigtness and so on till 10 pins...

the led has to be enclosed in a small tubing alongside a LDR which is inline the audio signal.. So what happens here as the led glows brighter ldr conducts more of audio signal to cmoy amp and so you got a volume control..

the total circuit will work with voltages as low as 5volt, but hey you are going to use a cmoy with mostly 2x9v cells so power is no problem..
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Old 2nd July 2011, 03:48 AM   #6
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Join Date: Jun 2011
Thanks for the replies guys but I got a sample for the DS1802 to try out. I've run into some problems and I think I found a problem in my design. Right now I'm using an aruduino uno as I'm breadboarding.

So the cmoy circuit uses a voltage divider circuit to create a +/- 9V power supply. The ground ive been using for everything has then been the mid-point of that circuit. However the VCC pin and GND pins on the digi-pot are powered from the arduino's voltage regulator, being 5v from a 0V ground. The low side of the potentiometer is connected to the virtual ground. The datasheet lists two ground, analog ground and digital ground. I'm not to sure what the difference between them would be but I'm thinking the discrepancies between my grounds is causing problems.

Unplugging the GND and AGND from the digi-pot actually plays sounds although noisy, hooking them up in any fashion leads to just noise. Its an easy fix but I wanted to know if that sounds right.
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