Adjustable Speaker


#1

Dear all,

I am working on a project that uses a prebuilt bluetooth speaker module. Originally I was going to use an arduino to just fire a relay that would turn the module on and off, but I was wondering if anyone knew if it would be possible to use transistors to adjust the speaker volume using PWM in the same way you would for an LED strip?

Thanks.
Josh


#2

PWM will make a heck of a mess of your audio…

But there ARE digital potentiometers available.


#3

Thank you! Can you recommend any?

Thanks


#4

You’ll have to do a bit of research.

Work out the values of the physical volume controls your speaker module needs, then check your favorite parts supplier.

Then you basically use the digital one in place of the physical ones, add power & control from your choice of micro-controller.

One example: http://www.learningaboutelectronics.com/Articles/MCP4131-digital-potentiometer-circuit.php


#5

Ok thank you for the help @Tinker!


#6

Can you post the module you are using?


#7


Its a very off the shelf sort of kit designed for education


#8

It looks like that kit would only adjust volume (amplification) via the Bluetooth protocol. I don’t see any provisions for physical volume control. So your phone volume would control the speaker volume. Are you trying to bypass that and add physical “local” volume?

Check out this kit:


https://www.ebay.com/itm/Hifi-12V-CSR8645-APT-X-Bluetooth-4-0-Receiver-Board-for-Car-Amplifier-Speaker/232684226548
It doesn’t have an amplifier but I’m sure you could find one easily. This would add play/pause/back/next/mute; and you could even add a microphone to take calls with.


#9

That looks great! So do you just pull the pins on the side high for a certain amount of time for the extra control (for example: volume up pin pulled high for 10ms to increase the volume by 1 step)?


#10

That is correct. You could probably use transistors if you want and have one microcontroller control another… Not really sure your end goal - keep in mind that a phone linked via BT will already have direct control over the audio; and this can still allow for “local” control. I have two of these modules wired inside of OEM car stereos to add a bluetooth “line in”.


#11

I have ordered two for testing.
My end goal is actually a birthday present for my sister, a speaker system that can connect to the TV in her bedroom and also to the bluetooth module.
I am a little confused as to why I would use transistors and not just an arduino digital pin (with a common ground)?