Savel brain dump in English!

I bought a new toy – GPS receiver (WBT300). It’s very simple  with USB and Bluetooth ports. I do not need it at all, but it’s very curious to play.

Some Chinese software is provided with this device. It shows already decoded information.  I checked, that coordinates remain quite stable. However, sometimes it’s seems to the device, that it goes somewhere at 0.16km/h speed. 

I was disappointed in height showing results. The height of my room varies from 60 till 170 m above sea level. I thought, that my house is stably fastened to the ground.

I haven’t demounted this device yet, but theoretically it should has some receiver, transmitter and RS232-USB adapter. The idee fixe appeared to bypass this USB port…

By the way, if you install virtual COM port of Windows,  the Hyper terminal program will help you to see all data “flowing” out of the device. Here is a sample:

$GPGSA,A,3,25,20,02,04,,,,,,,,,3.5,2.8,2.1*3E
$GPGSV,3,1,12,25,67,177,25,23,39,086,19,20,11,140,20,02,35,276,38*7C
$GPGSV,3,2,12,16,27,057,,29,06,344,17,27,49,200,14,13,83,064,13*75
$GPGSV,3,3,12,04,30,232,29,06,04,011,,08,19,208,,10,13,308,*75
$GPRMC,183101.000,A,5453.5577,N,02356.2293,E,0.00,214.57,120208,,,A*67
$GPGGA,183101.000,5453.5577,N,02356.2293,E,1,04,2.8,66.1,M,28.9,M,,0000*65
$GPGSA,A,3,25,20,02,04,,,,,,,,,3.5,2.8,2.1*3E
$GPGSV,3,1,12,25,67,177,25,23,39,086,19,20,11,140,19,02,35,276,38*76
$GPGSV,3,2,12,16,27,057,,29,06,344,16,27,49,200,14,13,83,064,12*75
$GPGSV,3,3,12,04,30,232,29,06,04,011,,08,19,208,,10,13,308,*75
$GPRMC,183102.000,A,5453.5577,N,02356.2293,E,0.00,214.57,120208,,,A*64
$GPGGA,183102.000,5453.5577,N,02356.2293,E,1,04

Smarter people can identify the place and time of the experiment from that rubbish. I also understood several rows. But others remain mysterious.

Here I introduce Dread to you. Her nickname is “Skurokas”. 

Click here for more details: http://www.gwaten.com/. 🙂

To light blue and white light-emitting diodes (LEDs) the voltage of 3V is required. By the way, white LED is the same as blue LED with additional luminophore inside. This luminophore is activated by blue light and lights up. Finally it lights as white.

What to do if you wish to connect a white or blue LED to a simple AA or AAA battery or even worse to the dead battery? It’s very simple. It’s enough to assemble a self generator on one transistor and the LED will light. That’s a real sample:

On the Internet this scheme is often called “Joule Thief”. Though the idea of self generation is well known and used in various strange devices.

What do you need for repeating the experiment? A simple transistor firstly. I used the transistor NPN 2N3904.  Secondly, you need 1K resistor  and  a small transformer wound on a ferrite ring. The ring can be very small, as device is not very powerful. My ring has 2 x 30 winds of thin copper wire.

Wind the transformer as follows: take 1m of  thin wire and fold it in half. So you have two wires. Wind them on the ring simultaneously. When the ring is wound, crop and tin each end of the wires. Connect the beginning of one wind to the end of the other wind and to the positive post of a battery. (Check with a tester or in any other way if the connection was made correctly. You can use coloured wires, it will be easier to recognize them).  The second wire of the transformer should be connected to the resistor, the third – to the collector. Connect Led’s anode (+) to the same collector and free end of the resistor to transistor base (to the central leg). Transistor emitter and LED’s cathode (-) should be connected to the negative post of the battery.

 Scheme is here:

Theoretical remarks (untested).

You can use PNP transistor, but it will be necessary to reverse emitter with collector, anode with cathode and to connect the power supply in opposite way. You can also use old Russian germanium transistors. Then the device will work more stable at low voltage. Such device could be powered from “primary power sources” as lemons or apples with two different wires inside… 🙂

I adapted the collimator of the higher quality. The voltage 250 mA is enough to light a match. And there is no need to hold it long.

The collimator was tore out from a copier. It’s quite good, that you can precisely focus the laser beam by turning a screw. You minimize the power and focus the laser beam till minmum. It it impossible to notice that the laser beam is minimized when everything around is light due to full power.

Video: DVD with New Collimator (Xvid, ~1Mb).

I tried to turn “a laser arrow” to the sky, but the beam gone into nonexistence. But it was perfectly visible on all the nearest objects. I tried to make some photos, but they came out so so…

After digital “processing “:

Youtube version:

Older lazeriniai postai.

At last I finished (2008.02) my torchlight project. I was looking quite a long time for good LED driver. When I found driver chip, I’ve lost all my white LEDs. So I used white LEDs from bad USB web cameras’. There are 4 LEDs in one web camera. I dissasembled several ones and collected 12 (in last edition 16) bright white LEDs.

baltų šviesos diodų projektą.

Here is last PCB test before finishing assembly:

I compared light output using simple cheap incandescent bulb, but powered from one Liion battery. Bulb is 2.4V and 0.75A. As it was powered from 4…3.7V source, output power is much more. And it was very hot- plastic details near lamp melted.

“Light power” comparison:

Conclusions:

After comparing both types of the lamp I can definetely tell, that LEDs are better in case of energy use. But only if LEDs are connected using special driver chip. Cheap China torches are made without any driver and are not very good for advanced use. Looking from spent money, the situation may be different. LED driver chips and custom hardware is expensive. Another advantage using drivers chips is that light power is constant during all liftime of battery.

Continue reading →

This is not up to date post (post date 2008.02)

I rescanned DVB-T channels using areal antena and found some new stations. As my antenna is quite big I am receiving TV stations from some near cities. I find new transponder at 778MHz. Maybe it is TEO? During tests all channels were uncoded. Now I need card to view.
Some changes in free to air channels. Also, picture size is smaller. Size is reduced from 720×576 to 544×576. But bandwidth is same, so overall quality is same. Also, less CPU power is needed to decode TV programs. Maybe size is changed because cheap TV tuners are with very “thin” CPU.

The are only 3 channels in 786Mhz…

Screenshots:

More cropped pictures: Continue reading →

Maybe you noticed, that new home cinema systems, LCD/Plasma screens, receivers have very small amplifiers. Physically small. But the power output is quite big. And there is no big, heavy heatsinks on these devices. And no big transformers. At a first glance I thought that all this output power is represented in “Chinese wats”. But in this case, the wats are real. And these devices are using “digital” D-class amplifiers.

What a hell is D-Class amplifier? It is old-new invention- digital amplifier. “Digital” means only one bit 🙂 The analog output is made using pulse width modulation (PWM) output. Some sound is converted to digital form using CPU ar special chips and this PWM sygnal is fed to powerfull MOSFETS. Real DAC conversion is made on small inductors near the output.

Here is image of one such amp:

I removed small heatsink from the top of chips. There is no need for big heatsinks as efficiency of such amp is about 90% (acording datasheet).

Here is closeup of the PCB. Note the size of SMD resistors and compare to the size of the chips. Chip is TAS5111 and TAS5112 made by Texas Instruments.

TAS5111 is buwoofer driver. Output of the chip is 70W RMS (@ 0,2% THD+N), 95dB dynamic range. And all this for single polarity 30V PSU (3.3V for logic). Other chip, TAS5112 is stereo amp (two channels) 2 x 50W (@ 0,2% THD+N).

The principle of operation is very simple. PWM sygnal from sound processor is fed to the chip. The chip is driving output mosfets in H-Bridge connection. As there are two PWM channels, the output is connected in full bridge. The chip is full of various protection circuits. All DAC is made on quite small 10uH coils (blue cylinders on PCB).

All amp is 6+1. Total 370W RMS from board sized like a CD box. Heat sink need to sink only 40W of heat during max load!

This particular board is damaged, I didn’t examined what is bad is this PCB, I picked up this PCB for weblog ilustration only.