Monday, January 23, 2017

Arduino Pro Mini : Identifying Voltage and Frequency

Why Arduino pro mini
Arduino pro mini board has almost all features of Arduino Uno except the programming interface. After programming, the programming interface components become redundant and not useful in most of the cases. In Any system, the rule of thump holds good "More the complexity, more the problems". Arduino pro mini provides the minimal set of components
Arduino mini comes in 5v/16Mz or 3.3v/8Mz forms.
How to identify Voltage and frequency.
Very straight forward method is to measure it straight. Connect a supply voltage upto 12 to "RAW" input compared to ground ("GND") and measure the voltage available at VCC compared to ground.
Another approach is to read labels on voltage regulator and resonator (oscillator ).
Below image shows the components.
You may need a lens to read this.
The voltage regulator IC has a label  "S8PE". this corresponds to 5v
The label on the Oscillator reads like "Ag". Anything starting with "A" corresponds to 16Mz.
Those Oscillator starting with "8" is an indication of 8Mz

KBAA3.3/5 Selectable
Generally, If the Oscillator is 16Mz, the voltage will be 5v

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:

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

Webm parameters
Webm to ffmpeg parameter mapping

Saturday, November 6, 2010

Power Amplifier using TOSHIBA TA 8210

This Single IC Power amplifier (2 Channel) designed for Car Stereo Applications.
Single IC is capable of driving 20W per channel.
Beauty of this IC is it require very less external components. Not even coupling capacitors are not required for output.

Full Data Sheet is available from Toshiba's site.
If  TA 8210 is not available in your electronic shop. there are couple of known equivalent : KIA6210 and KA22103. They are pin to pin compatible.

There are few alternatives which you can consider from TOSHIBA. but they are not equivalents.
TA 8205   (18 watts x 2channles)
TA 8254   (45 watts x 2 channels)
TA 8776   (35 watts x 4 channels)

Last weekend i completely overhauled my car stereo to have only this IC
(just as a power amplifier for my portable MP3 player)
See below video of the same:

Tuesday, October 16, 2007

Evaporative Air Cooler's Pump Controler - Energy Saver

For me, a normal air cooler is a mandatory equipment for surviving the hot summer. This common-man's AC is working on few basic principles (heat is comsumed from air for vapourization of water and air becomes cooler since the latent heat of vaporization of water is very high) but it is a great equipment for common-man. A locally made cooler is normally available for Rs. 2500/- ($55).
I got a new cooler last week, as a electronics enthusiasist, i verified the power consumption and i was shocked by the mesurements. the blower motor is consuming around 300W. and power factor was also very poor. The motor was heating up and i was not able to touch it if it operates for 5 minutes and it was making too much noice also. i decided to replace the motor with a normal table-fan's (i used my bajaj BT-05 for this). The power consumption came down to below 50W!.
In addition to blower motor, the air cooler got another one for pumping the water. but unfortunately i did not get a right replacement for that motor. But i have another justification that it is taking below 100W. Meanwhile, i noticed another big wastage. onces the grills of the cooler is wet, then there is no point in pumping the water to wet the grill again until the wetness reduces. Normally 1/10 of the pump's effort is waisted. so we need a mechanism to switch on the pump periodically so that the grill is always wet.
I picked up a small relay for Rs.20 ($0.5) from a local electronic shop which is normally used in computer monitors and TV sets. it operates on 12V DC. and it to very low rating. so that it can directly driven by the output of the IC 555. You know 555 is capable of loads upto 200mA. i verified that the internal impedence of the relay is high that it takes less than 20mA to operate. i even connected a LED is series with the relay.

here is the diagram!

The simple timer circute with 555 is more than sufficient. The circute i used for my cooler is shown above. Everything is worked perfect. i have few snaps of the assembly (please see below).

With current value of resistor and capacitor (as per diagram), the relay switches on the motor for 30 sec in every 5 minutes.

This simple circut reduces the power consumption to 1/10 th.
You belive it or not! it is working perfectly.

I am attaching few snaps of the assmebled board and my air cooler working with that.