IMPORTANT = This operation needs root access.So you have to root your phone before you do this,and I am not responsible if your phone gets damaged during the operation.
You all know that most of Android phones does not power on or start(boot) when the wall charger is connected like the iPhones.
This might be a problem if you going to use an Android device for some dedicated work.For example if you want to put a tablet in your car dash like here , and your car cuts off electricity when ignition turned off, you have to be able to start your tablet when charger is connected.
Step 1: Finding Necessary Files
When they are switched off,every but every android phone shows a charging animation on their screen. Like in the photo above. Our starting point is this. We are gonna edit the file which is responsible for creating this charging animation.
The hardest part is finding the file.Most of system files are stored under "/system/bin/" path. And we are going to search through these files.
On most of samsung devices , the file name which is responsible for battery animation contains "lpm" keyword.I had tried on two different Samsung devices the file name was "lpm". To make sure it is , change the file name like "lpm23" and turn off the phone. After phone turned off connect the wall charger and if you don't see a battery animation this means you found your file. If you still see a battery animation it means you failed and you should continue to search the files for battery animation.
Step 2: Editing the File
I suppose that you already found your file and ready to edit.
*Just open the file with a root supported browser.
*Delete all of the lines
*Add these lines:
After adding these lines, save it and turn off your phone.
Connect it to a charger and taadaaaa :D you should see your phone is turning on.
Here is mine :
Step 3: Final
For more info and comments visit : http://developwear.com/blog/2014/07/03/autobootstart-android-when-charger-is-connected/