Idea Log

a record of ideas I've come up with

hacking bluetooth headphones by adding a 3.5mm headphone jack

bluetooth_headphones_openSo i go through ear buds like crazy.  Cheap ones last me two weeks to a month, high end ones last me 6-12 month.  I though this may be because of snags. So i bought a cheap set of bluetooth headphones.  It lasted around 90 days.  the hardware works fine, but the wires to the ear buds wore out.

I liked the functionality of the bluetooth thing so i decided to add a headphone jack to it so i can plug in any headphones i want.



  • bluetooth head phones
  • 3.5mm TRRS(4-pole) headphone jack



  • opening it up
  • removing the ear bud wires
  • drilled holes for the headphone jack
  • soldered wires from board to jack
    • [R+] to [right]
    • [R-] to [ground]
    • [L+] to [left]
  • added so glue to re-enforce the wires contacts
  • closed it up and added some glue to hold it together
  • plug in a set of headphones
  • zip tie excess wire from plug to buds



  • test with 3-pole and 4-pole headphone jacks before closing it up
  • use thin wire so it doesn’t pull off the PCB, I used 30AWG wire wrap wire.
  • be careful not to pull off contact from PCB.  I used super glue to re-enforce contact


Useful info:

from  CableChick
Example of a 3.5mm TRRS 4-pole cellphone headphone jack, from mklec



Software security through sandboxing

The idea of sandboxing software is not a new one, and probably my idea has been descussed, but I’ll put it out there anyway.  It works like this.  Current software is installed pretty much anywhere it wishes and has access to any part of your hard dive, all your files, and hardware.  This allows it to the software to

  • access your web browser history,
  • emails,
  • possibly passwords.
  • record any keystroke one your keyboard,[2]
  • turn on you mic and record every thing you say,
  • turn on your webcam and record without you ever the wiser.
  • It also has access to the Internet and can send any of this data anywhere.
  • O ya and it can encrypt all your files, delete the originals and send you a message saying if you don’t send money, they wont let you access your files ever again. [1]

All of this has been done before in the past and many legitimate software still record and send out some of this data for ‘statistical’ purposes.  A sandbox installs a piece of software in seperate area, and imaginary box, that isolates its self from direct access to the operating system, hard drive, etc.  My proposal is this.  modify the OS to sandbox any installed software, and durring installation or first run, have it pop-up an check-box window to show what you want it to have access to.  It can list all the software’s requirements, optional, etc.  Similar to you Google play apps displays what an installed app can do, but more complete and check boxes for yes/no access.  This way you know what it can and cant do, and deny specific things.  Examples.

  • Output sound
  • change volume contoll
  • access mic
  • access camera
  • access full harddive, documents folder, home folder, or sandboxed folder in home or docs
  • full screen access
  • change display resolution
  • access usb
  • access net
  • run in background
  • a bunch more, but you get the idea.

So thats the idea.



Laptop batteries with longer lifespans

I have taken apart a bunch of failed laptop batteries to harvest the lithium-ion/polymer batteries for random projects.  By doing this i have noticed that often only one cell out of many has failed, and often even the failing one can be saved.  Lithium-ion battery cells are considered ‘dead’ if the voltage goes below 2V. “The Li-Ion cell
should never be allowed to drop below about 2.4V, or an internal chemical reaction will
occur where one of the battery electrodes can oxidize (corrode) through a process
which can not be reversed by recharging. If this occurs, battery capacity will be lost
(and the cell may be completely destroyed)”.[1] So if one cell becomes dead the whole battery pack is useless.  If there are 4 cells in the battery pack, and one cell is bad, 3/4 are still useful.   I think most users would be happy if they could continue to use a battery with 3/4 the charge, rather than having to buy a new battery pack each time one cell dies.

My idea is two parts.  First is attempt to recover the ‘dead’ cell.  Second is bypass the dead cell.

Idea one:  Recovery a dead cell. I have found that i can recover most dead cells, by applying a small current until the 2V is reached, then charging like normal.  I am no expert on the chemistry of the cells, by lithium-ion batteries are volatile so this may be dangerous.  I havnt had any problems but there could be a good reason cells below 2V are considered dead.  To impliment this, it wouldnt take to much circuity to add this to a battery pack.  Adding a small increase in parts cost and probably no increase in battery size.

Idea two:  Bypass a dead cell.  There is no reason a dead cell couldn’t be bypassed.  This would lower the max/min voltage of the pack.  for example a 4-cell pack has a max voltage of 16.8V(4.2×4), average voltage of 14.8V(3.7×4) and a min voltage of 12V(3×4).  With one dead cell this would cause the voltages(max/ave/min to be 12.6V/11.1V/9V.  If you applied this to the same laptop it probably wouldn’t work, however this can be solved using two methods.  First and most effective is to have the laptop accept the lower voltages when a cell is bypassed.  When the power comes out of the battery if goes through a DC-DC converter to lower the voltages to usable levels(usually 12V/5V/3.3V) for the laptops devices.  If that converter is designed to accept voltages of a wider range, it can easily use batteries with bypassed cells.  Another method for allowing the use of bypassed cell is putting a DC-DC converter in the battery pack.  This would make the pack larger and less efficient but would allow the pack to be used on an unmodified laptop.  Ether way the bypass circuit would increase the size of the battery pack’s circuits and the cost of added parts.  The circuity accounts for about 1%(estimated) of the battery packs volume.  The bypass circuitry would probably double the size of the circuity.  Adding a DC-DC converter to the pack would increase the size by 10%(guess), and lower the efficiency by 5%(guess).

Using ether of these ideas will increase the battery packs lifespan significantly saving users a lot of money, and hassle with dead batteries.

Example laptop battery.  Although there are 6-cells they are actually 3- sets of 2 cells in parallel, so with respect to voltage, it is the equivalent of 3-cell




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