Monday, November 28, 2011

Hacking Nokia Charger

My Charger for Nokia mobile stopped working yesterday.
so decided to give a try to fix the problem.

In the initial inspection itself i found that the very first stage (high voltage bridge rectifier) is not getting supply. Noticed that there is a very low resistance just before the bridge which is burned off. but there should be some reason for it to burn.

Then noticed that there are 2 electrolytic capacitors immediately after the bridge, and they are bit bulged out. they are rated as  4.4micro fared 400v. but size was too small for that rating. so it is very evident that Nokia charger fitted with an over rated capacitors which is suffering from internal short circuit.

Now bigger challenge is where can i get a replacement for this high rated capacitors!?
its not a big problem, i had a collection of burned out CFL lamps. every CFL lamp is equiped with such a bridge and a high voltage capacitor. so i pulled out one of such capacitors and and replaced it in the charger.

(I had an accident that i burned 2 diodes also in the testing, giving a mild explosion. but that also i could able to replace from discarded CFL ballast.)

Then i kept worrying where will i get a replacement for the burned out low resistances. since the resistors are rated very low, i decided to take a chance by short circuiting it. this OK because it is the first stage of conversion from AC line to high voltage DC. in fact resistors don't make any sense in this stage.

Then i went for a final testing and found that it is working like a charm.

Here is the overall experiment in nutshell:


Saturday, March 19, 2011

Encoding Movies into webm format

Get FFmepg with webm support:
you can get the lastest nightly builds of ffmpeg fromfirefogg site:
http://firefogg.org/nightly/

download the executable for your platform.
(linux, windows, mac are supported)

Start encoding:
simple command is like:
ffmpeg -i MVI_6646.AVI -b 600k -aq 60 MVI_6646.webm

Bit more Advanced
ffmpeg -y -i MOV003.3gp -threads 0 -f webm -vcodec libvpx -g 250 -qmin 10 -qmax 42 -rc_buf_aggressivity 1 -vb 800k -acodec libvorbis -aq 0 MOV003.webm

Use VP9 and Opus for encoding
ffmpeg -i 00019.MTS -c:v libvpx-vp9 -crf 10 -threads 1 -speed 0 -tile-columns 0 -frame-parallel 0 -auto-alt-ref 1 -lag-in-frames 25 -g 9999 -aq-mode 0 -c:a libopus -b:a 64k -f webm out.web
References:
Webm parameters
Webm to ffmpeg parameter mapping