10 Replies Latest reply on Feb 7, 2012 12:48 PM by Drew Fustini

    Rookie Project: Inline IR/Bluetooth volume knob


      So let me start by warning that I am a rookie to these forums and ive only done menial work in the hobby so far. Also, sorry in advance for the long post haha


      I want to get into making some of my own electronics as a little hobby, and this seems like a good site to start on haha

      In case I come off the wrong way,  I would never ask anyone to hold my hand and tell me exactly how to do this. All I am asking is to be pointed in the right direction. I can probably figure out the first project I am going to mention by reading the forums and doing some research, but it’s the second project that I really cant figure out how to start. Needless to say, the second project is something I really want to do haha


      I have a nice entertainment center in my room, but I have some issues with my speakers. I don’t need speakers that are really good, so I picked up a set of some cheap cyber acoustics. Im no audiophile, so these sound great to me! (at least a lot better than the speakers built into my tv). I have them plugged into the audio ouput on my TV so anything I do on it (media center, xbox360, wii) plays through the speakers that are hooked up to it. The problem is my old Samsung LCD doesn’t change the volume on the external speakers when I change the volume on the tv.


      I have an IR dongle rigged from an old xbox dvd dongle kit. It works great and i can adjust the volume comfortably with my remote when im using my media center, but not for anything else. I would very much like my volume to be controllable from afar no matter what im doing. right now i change volume from the wired volume knob my speakers came with. I like it, its not a big deal, but im a perfectionist and I want to learn how to make things


      Basically, I want to make an inline volume knob to replace the one I already have, obviously making it better. I was thinking of making one from scratch, with a built in IR receiver. This way, I can control the volume by turning the dial, and also make the knob think the dial has moved one way or another  with a remote. That would solve my tiny little dilemma!

      Of course I really don’t know where to start, and for some reason i haven’t found anything online to point me in the right direction. As long as its possible to do, Im sure ill figure it out eventually though.


      The problem is that  I keep coming up with new things to add into my project, which caused my project to split into two different ones! My first project I want to add a headphone and aux jack on the knob, which shouldn’t be too difficult. I was even thinking of adding some LED lights to it (the one I am using now is lit up, and I love that!)

      Perhaps that’s an easy project… but I want to do something even better! I wish I could take that knob around the room with me, like lie in bed with it by my side while I watch a movie. So my second project is to make a wireless knob with IR capabilities. Only thing is, I want to use Bluetooth… sounds ridiculous, im sure, but for what I want to do i think thats my answer.


      I want to be able to plug in any set of headphones I have to the wirelesss knob, basically turning any headphones I have into wireless (kind of). I want to have a knob that can receive audio and send commands (and maybe even send audio) to a Bluetooth controller that handles all the volume changes. This controller would also be able to receive IR signals and change volume that way as well. The controller would take in the output of my tv as its source, manipulate volume, then pass it through to my speakers. The controller will look nice, and have a volume knob and mute button as well as headphones and aux jacks. The knob itself will obviously be battery powered, but I would like to allow it to charge via usb or the Bluetooth controller (which will have power from the wall). I would definitely want to have lights on it so I can find it at night and a hold button that would keep it from working but keep the lights on.


      I am interested in doing the first project, but I really want to try to do the Bluetooth one. Ive never been one for baby steps haha. Like I said earlier, im not asking any of you to hold my hand. I am simply asking for your opinion on this project (for instance, is it practical? Is it possible to do yet such a pain that it wouldn’t be worth it even for the learning experience?) and for a finger in the right direction. Thank you in advance for your help. I spent some time drawing up some barbaric plans that are a little more detailed than what I just said. Thanks again!



      project 1.jpg

      Volume Knob:

      - rotate freely left and right to control the volume

                      - although it will keep turning, volume will cease to go higher or lower at certain levels.

      - A hole would be cut out in the middle of the knob for a mute button

                      - Mute button would not rotate with knob.

                      - May consider a 2 second hold on the mute button for it to work if it gets pressed too easily

      - On the side of the knob would be 2 female 3.5mm stereo jacks. One for headphones, one for aux

                      - When headphone jack is plugged in, the audio will stop being sent to the speakers

                      - When plugged in, the aux device will replace the normal source

      - Knob would have a built in programmable IR receiver to control various volume functions via a universal remote (in my case, a harmony remote with a learning function)

                      - when a signal is received, the knob will adjust the volume as if you turned it manually

      - Knob gets its power from the wall

      - May consider throwing some LED lights on it for fun, in which case I would need to add an on/off switch.


      Main Adapter:

      - Designed for better cable management.

      - Has a male 3.5mm stereo plug that would plug into the output on the source for input.

                      - This input would pass through the knob, then back to the main adapter again.

                                      - This allows the knob to control the volume before being sent to the speakers

                      - The main adapter has a female 3.5mm jack for speaker output that feeds from the knob output





      project 2.png

      Same functionality as the other project, this time using Bluetooth instead of wires.


      Master Bluetooth controller:

      -passes audio from the source to the speakers, adjusting the volume in the process.

      - connects via Bluetooth to the Bluetooth volume knob

                      - knob tells the controller how to adjust the volume

                      - knob sends aux input to the Bluetooth controller (might consider removing feature)

                      - controller sends audio feed to knob for headphones when needed

      -    Has a built in programmable IR sensor that allows an IR remote to control volume like the knob

      - Has a volume knob on it that spins freely left or right, controlling volume only up to and down to certain levels.  Also has a mute button. This is important in case you run out of batteries in the knob and lose your remote

                      - Knob and button both light up via LEDs

      - Has a 3.5mm female stereo jack for aux. When plugged in, aux replaces  the regular input source and/or the knobs aux source.

      - Has a 3.5mm female stereo jack for headphones. When plugged in, the speakers become muted. Headphones can be used from both the controller’s jack and the knob’s jack at the same time


      Bluetooth Knob:

      - Sends Bluetooth commands to controller for volume control

      - Receives audio input via Bluetooth for 3.5mm headphone jack

                      - Speakers become muted if headphone is plugged in

      - Sends audio via Bluetooth from aux jack. (might consider removing this feature)

                      - replaces the normal source when the aux is plugged in

                      - if aux is plugged in on controller as well as the knob, the aux on the knob will not play

      - Knob spins freely left or right controlling volume only up to and down to certain levels

      - hole cut out in center of knob for mute button. Mute button does not rotate with knob.

                      - may consider requiring  user to hold mute button for 2 seconds  if its too easily  pressed.

      - Lights up via LEDS when on

      - Has an off switch on bottom to save batteries.

      - Hold button on side to prevent accidental use while keeping the LED lights on.

      - Battery powered. Not sure what kind of battery required yet. If rechargeable, then a charging port would be added to that it could charge via the Bluetooth controller and/or wall

        • Re: Rookie Project: Inline IR/Bluetooth volume knob
          Drew Fustini

          Hello and welcome to element14


          I think your project is quite interesting.  I have a similar need where my I have external computer speakers connected to my cable box.  Unfortunately, I have no way to control the volume with a remote as I do with the builtin TV speakers.  I'm glad you posted as I had not been thinking that I should bother to figure out a solution.


          I like your idea of an inline volume control with remote control.  I noticed there is a kit from Ramsey that might be useful:


          MK163 - IR Stereo Volume Control Board Kit



          If you'd rather build it from the ground up, then I think that the Arduino prototyping platform would be a good way to go.  Do you have any microcontroller experience?


          The Arduino could interface with a digital potentiometer to adjust the audio volume.  There are several tutorials I can point to if interested.  Also, there are several good tutorials on how to do IR remote control of the Arduino.


          As for Bluetooth, if I understand correctly, then this would to interface the volume knob with the master controller?  Is that because you like RF as it doesn't require line of sight like IR?  I think you'd be better off using a different RF protocol as Bluetooth modules tend to be more pricey.  A cheaper alternative would be XBee (aka ZigBee).  There are many great tutorials for interfacing with Arduino.


          Finally, just a tip since you are new to element14, I think your post might be more relevant for the "Open Source Hardware" or "Embedded Systems" groups.   You can move this discussion thread if you'd like by clicking on "Move discussion" under the "Actions" box on the upper right hand side.  You might also want to create blog under your account to post about your progress - I'll definitely be interested to see how your design evolves.




          • Re: Rookie Project: Inline IR/Bluetooth volume knob



            I admire your enthusiasm, it nearly matches my own! I know exactly how you feel regarding the way a project grows, I guess you have an inventors soul. Do not try to stifle it!


            Your project is entirely possible, wether or not it is practical is something you should not worry about, as you are making it to use yourself.


            I have designed a Bluetooth speaker for my garden shelter, you can connect with a bluetooth phone and play what you like, I am hoping to have time to redesign and add a playlist feature.


            Take a look at some Bluetooth modules...search google for small form factor Bluetooth pcb modules like the MDCS51B class 2 module.


            Also it might help to draw yourself a flowchart, It will help your mind to focus, and will allow you to break the system down into smaller steps.


            Take each step at a time, and write down everything in your project notebook.


            And then when you need help, you will be able to ask for it in a more concise manner.


            Good Luck!

              • Re: Rookie Project: Inline IR/Bluetooth volume knob
                Drew Fustini

                As an aside, thanks for the comment on the Bluetooth module.  I've only used and seen modules which do SPP (like from SparkFun).  I really like that this one has A2DP.  Curious, what type of processor did you use in the project?

                • Re: Rookie Project: Inline IR/Bluetooth volume knob

                  Hello again everyone! Thanks for the replies, sorry it took so long for me to look at them ><


                  As for Bluetooth, if I understand correctly, then this would to interface the volume knob with the master controller?  Is that because you like RF as it doesn't require line of sight like IR?  I think you'd be better off using a different RF protocol as Bluetooth modules tend to be more pricey.  A cheaper alternative would be XBee (aka ZigBee).  There are many great tutorials for interfacing with Arduino.


                  Yes, the volume knob would interface with the master controller. It would send commands and allow audio to be streamed between the two devices. Because of the streaming audio, I was thinking bluetooth would be the best option. I didn't even know bluetooth was an RF protocol and i didnt think to look into another one of those. (despite anything the master controller will also have an IR sensor for basic remote controls). Thanks for the tips Drew! I will definitely be looking into the arduino. Also, sorry for the noob post in the wrong area, ill move that after i make this post.


                  I admire your enthusiasm, it nearly matches my own! I know exactly how  you feel regarding the way a project grows, I guess you have an  inventors soul. Do not try to stifle it!

                  Aha thanks for the support, means alot to me really! And thanks for the tips as well!


                  You really sparked my interest in solving my own volume control need

                  Well then, glad to be of service haha! Hopefully you are successful in solving your issue as well! keep me posted! ill be keeping a blog of my progress when i start just as you suggested.


                  I am really impressed by the community here, ill reply later this week when i have a plan ready!

                    • Re: Rookie Project: Inline IR/Bluetooth volume knob

                      Hey all, just a quick reply with what I have thought of so far.


                      I thought some more about using RF to transmit audio, then i realized... DUH! Im already doing that!!!!

                      I had a set of very unconfortable, now discontinued radioshack wireless headphones that operated on the 2.4ghz range. I hated the headphones, so i bought some more comfortable ones that operated on the same range. Both of these headphone packages were very cheap and not really meant for home entertainment systems. They each came with a portable transmitter that ran on batteries that would plug into a device via the headphone jack.


                      The portable transmitters both worked perfectly for my needs except for one issue: they could only run on batteries. I was not able to plug the power to the transmitter and have it transmit at the same time, which means that i would have to constantly recharge the batteries and turn the device off to save the charge i made. All i wanted to do was have the transmitter plugged into my tv transmitting at all times, getting its power from the outlet.


                      That just wouldnt do, so of course i made a little mod I opened up the old transmitter and took out the batteries. after making sure it would be safe, i soldered the positive and negative leads on the board for the battery to the leads that came from the outlet. Then i disconnected the wires that fed the outlet power to the batteries for charging so that the transmitter wouldnt think it was charging when plugged in, and instead thought it was running on batteries. the result: a perfect rf audio transmitter for my needs


                      So in other words, I already have an rf transmitter for headphones. If I wanted to make it so that the knob could recieve that signal and send it to any headphones, all i would need is an rf reciever module to integrate into the knob. After doing some thinking, ive decided this to be impractical since i already have a set of working wireless headphones, so for now I am going to scrap that idea out of my project (although i may add the functionality at a later time)


                      Now my project has become much simpler. I want a wireless volume control wheel (it has to be a knob/wheel cuz i like that style best) that controls the volume via an inline volume controller.


                      From drews first post, I took a gander at this: http://www.vellemanusa.com/products/view/?id=521414 (the mk164 ir volume control).


                      I think this would work nicely for my project! I would take the transmitter and put a pot on it that would cause it to send an IR signal to the reciever whenever i moved it left or right, and then put a button somewhere that would allow for a mute and a switch that would put the device on hold, stoping it from sending signals to the reciever yet allowing the blue leds im going to throw on it to glow. And of course, an on/off switch on the botton to conserve battery.


                      My concern is, would the ir signal respond quickly enough? I would like to emulate the same kind of control that my current volume wheel has. For instance, would the volume level change fluidly even if i turn the knob fairly quickly? It is this concern that is making me consider RF for the communication (in which case I would need an rf transmitter and reciever. the RF reciever would be rigged into the IR reciever to make it think it has recieved an IR signal every time the RF reciever picks something up. The knob would use RF transmitter instead of the IR one)


                      while looking things up, I found many tutorials on converting a wireless mouse into a volume knob. I thought that was a really good idea! The problem with this is that it would only change the volume on my computer. Im going to look more into allowing the mouse to send its signals to my inline controller.


                      Another thought that i think would be pretty nifty would be an LED bar strip velcroed/glued to my tv. The led bar would display blocks to portray the volume level, just like you would see on the tv normally! I could wire the led bar into the controller so that whenever the volume changes, the led bar responds by lighting up and changing the number of bars accordingling, then dimming after a few seconds. I could put this bar behind a piece of translucent grey/dark grey plastic to make it look nice.

                      • Re: Rookie Project: Inline IR/Bluetooth volume knob
                        Drew Fustini

                        Hi Evocator, glad to see your mod worked and your ideas are progressing.  If you get the Velleman volume controller, then I think you could make an IR controller with a dial. 


                        One idea would be to get the MK162 2-channel remote and control it with another microcontroller (let's say an Arduino) which has a rotary encoder attached.  The MK162 does come with a simple microcontroller already, a PIC12, which controls the IR emitter.  If you had the source code and the ability to program it, then you could probably just modify it to use a rotary encoder directly.


                        However, it would be easier to use a secondary microcontroller like an Arduino.  Instead of placing the push buttons on the MK162, wires would go from those pads to the Arduino.  The Arduino could then trigger the remote to change volume up or down.  The Arduino would do so based on input from a rotary encoder.  Here's an Arduino example on SparkFun: http://www.sparkfun.com/products/9117


                        This might all sound a bit bulky but you can save alot of space by constructing your own Arduino circuit on a perfboard using a kit like the Mintduino:




                        or using a small Arduino clone like the Arduino Nano:




                        or the Pro Mini:





                        Alternatively, you could just use the MK162 remote to figure out the IR coding scheme and then integrate the IR emitter into the Arduino.  This would make for even a nicer package.  If you have access to a digital scope or logic analyzer then that should be doable.  Adafruit has a great tutorial on this:




                        (BTW, if you happen to be in the market for a logic analyzer, I highly recommend the Saleae Logic: http://www.saleae.com/Logic)