In this Instructable we'll take a look at the inner workings of the in line remote. We will then create a larger remote that will fit inside of an Altoids Smalls tin.
- Expendable or broken set of iPhone/ iPod Touch Ear Buds with Remote
- Altoids Smalls tin
- 3 small push buttons
- 1/8" stereo jack
- small Perfboard
- pair of right angle headers
- small rubber grommet
- Soldering iron
- Wire cutters/strippers
- Razor blade
- Small torch or lighter
- Sanding block with 150 grip sand paper
- Jeweler's file set.
Step 1: Inside the Remote
After hours of research and experimenting, with my limit knowledge, i have no idea how it all works. What i could find online seams to indicate that the circuit board in the remote triggers the iPhone/iPod into excepting various signals between the Ground and Control/Mic wires. I do know that the Play/Pause/Skip button shorts the Control/Mic wire to Ground. But if you connect a TRRS jack up to the phone, start up some music, and short the Control/Mic wire to the Ground wire, nothing happens. But if you short those wire at the remote you will trigger the iPod to ply/pause/skip. As for how the circuit triggers volume control i have no idea.
Here is what i do know. When the headphones are plugged in there is about 1.9V DC on the Control/Mic and Ground wires. When the cable is not connected to anything there is about 0.87 Ohms on the wires. When the Volume + button is pressed the resistance drops to 0.85 Ohms. When the Volume - is pressed the resistance drops to 0.86 Ohms. That doesn't really mean much since there is more going on there then a couple of resistors. From what i can make out there is 1 transistor on the board and an IC with 6 leads.
So to keep things simple we will used the existing board and just extend the buttons on the board to our larger push buttons.
Step 2: Laying Out the Perfboard
We need to desolder the remote circuit board from the ear buds. Be sure to make a note of which contacts are the ground and control. Also make a note of which wires from the ear buds where soldered to those contacts. Don't just go off my pictures. Mine came from a pair of Sony ear buds and your's may be oriented differently. Just know which one is ground and which one is the control.
To help make it easier to connect the circuit to the perfboard we'll use a pair of right angle headers soldered to the ground and control points. After solding the header glue them securely to the board. The SMD traces are very small and will rip off the board very easily. Now we'll remove the spacer to allow the circuit to sit as close to the perfboard as possible.
Now we can lay out the components and see how they will fit in the tin. Make sure you have enough room for the 1/8" stereo jack to fit. When we do the final assembly the board will be raised up from the bottom of the tin so the buttons can protrude through the top.
Now we very carefully desolder the contact pads from the board so we can solder wires that will run to our push buttons. Using a peice of ribbon cable we very carefully solder the wires to the button contacts. The common trace for all the buttons leads to the control wire. With the wires in place we'll glue them down so we don't rip the traces off the board.
Step 3: Wiring and Soldering
Now before we can connect the TRRS and 1/8" stereo jacks we need to prepare the Altoids Smalls tin.
Step 4: Preparing the Altoids Smalls Tin
For the TRRS wire you will need a small rubber grommet to protect the wire from the sharp edges of the tin. So you drill bit selection will be based on that grommet. For me i used an 11/64" drill bit and my round jeweler's file to clean up the edges. Then we can pop the grommet in place.
Now we need to measure out where the button holes will go. Then using a 9/64" bit we can drill out the hole. Since its hard to get the line up of the holes just right you will want to test fit the buttons into the holes and use your files to make adjustments as needed.
I came to realize it would be best to mount the board to the top of the tin. But the board was in the way of the tin closing. So we need to trim some more off the sides. I trimmed off 2 rows worth on the hing side and trimmed 1 row off the opposite side. I also trimmed some off the top. This leaves plenty of clearance for the tin to close and room to secure the board to the tin with Hot Glue.
If you like to have a good finished product then now is the time to paint your box.
Step 5: Final Assembly
Now we need to strip the wires and go back to our notes where we marked which wire goes where. As with most ear buds the wires have a very thin plastic coating on them rather then rubber insulation. You can use a lighter or small torch to help burn the plastic off. Be carefull the wires are thin enough a common lighter can melt the. Some time the residue left behind needs to be scraped off. After cleaning the wires off give them a bit of solder.You may want to use a Multi meter to verify which wire goes to which part of the TRRS plug. Refer back to step 1 for the picture of the TRRS plug and which rings go to what. Now we solder the ground and control wires to the remote circuit. Next we will solder the right and left channel to the 1/8" stereo jack as well as the ground.
Now we can mount the 1/8 in stereo jack and Glue the board into the top. Close it all up and your ready to rock with your favorite headphones.