Simple Doxygen templates

Reblogged from JustChecking's Weblog On All:

This is a follow-up to previous tutorial, Simple guide to basic Doxygen usage. Here are few simple templates that you might use for documenting your source; easiest use is with e.g. Visual Assist X, or any other tool that allows you to add predefined templates to your source code. I use these template with VAX and shortcut set to “/*!”, with short descriptive names, thus I don’t need to remember many shortcuts and have all at reach of 3 key-clicks. And we finish off with a small list of simple tips. …

Bluetooth Controlled RGB LED strip

RGB LED strips such as this are available for a low price.They are generally bundled with a IR controller and a power supply to power the LEDs and to change the color ,display various colour sequences etc.The IR Receiver is  similiar to those used in TV and requires line-of-sight for reliable operation . I wanted the strip to be Controllable via a PC or a Mobile Phone.So I decided to make my own RGB LED strip Controller and to enable wireless control  i used Bluetooth technology.The device can be controlled using a PC or a mobile phone with Bluetooth having a suitable graphical  user interface.

The Hardware needed for this build is pretty simple and uses commonly found devices and may be salvaged from old electronics.

1. Atmega8L-8PU 8-bit AVR microcontroller
2. LM1117-3.3 3.3V LDO regulator
3. IRF640 N-Channel MOSFET(salvaged from an old Uninterrupted Power Supply-Thanks Kushal for that Dead UPS! )
4. Connecting wires ,Berg strips,etc.
5. 12v 1A+Wall wart.

The Firmware for the ATmega8L micrcontroller was developed with Arduino 0023 and also with Arduino 1.0 (Can be downloaded for your OS of choice from HERE).The GUI for the Windows PC was Developed using the GTK+ toolkit using the python bindings available via pyGTK(Get it from here).The GUI was designed for running on nokia s60 devices using  pyS60.

The arduino Firmware

The arduino is an awesome prototyping platform.Churning out prototypes from Ideas is very fast since all the hardware and other functions are pretty much abstracted out and only the Application Logic needs to be implemented.

The Firmware performs the following basic functions.Handle the communication routines,Control the LED brightness for each of the Colors RED,GREEN and BLUE and also be able to display the various sequences of colors of light.

I have a Arduino Duemilanove that came with an Atmega328P processor onboard.The Atmega 328P would have been an overkill for this project so i decided to replace it with an Atmega8L.The mega8 has only 3 v/s 6 PWM  channels and 8K v/s 32K of flash program memory of the mega328.To verify the firmware I set up a simple testbench with three LEDs one each of RED GREEN and BLUE LEDs plugged into a breadboard connected to the Digital pins 9,10,11 of the arduino.These Correspond to the PWM Pins on the atmega8. The Communications with the controller was tested with the standard serial port given by the FTDI interface of the arduino.

Once The test bench was setup I could move on to Actually Writing the Firmware.The Setup section consists of all the PWM pins being set as Output and the Serial Port opened to Communicate at 9600 Baud.The Main while Loop has a Non-blocking delay section in which the Functions are updated at a User changeable delay.The more the delay the more slowly the color transition takes place and viz.This is necessary because if a delay is not present then the transitions would be so fast that it would appear as if the LEDs are blinking.I have NOT used the default delay function of the arduino library because of it blocking nature(Here’s a good article about Non-blocking code).The delay would block the processor by executing a number of instructions with a known execution time to get the specified time delay and only then execute the next instruction.This blocking delay would cause problems when data arrives at the serial port and the processor is busy executing the delay.Hence the data will be missed by the processor or will be processed only when the delay loop completes execution thus introducing lags between the user giving input and the suitable function being executed.Non-blocking Delay is hence used to prevent these problems and to provide reliable communication.And Precisely for this reason I have avoided Blocking codes in my Firmware.

The CellPhone GUI

The Cellphone GUI is a  pyS60 script with five consecutive dialog boxes for mode selection,red value,green value,blue value and the update delay value  respectively.The mode selection selects one of three modes.Mode 0 is the default mode  will fire up if no bluetooth device is connected for control .In this mode the entire colour spectrum is traversed starting from red end of the spectrum.The transition goes on in a infinte loop.Mode 2 is a mode where each color namely Red,Green,Blue and White Respectively “breathe” i.e. the intensity of each color goes from zero to maximum and back to zero.Check out the Video to see it in action.The Mode three is the Color Chooser Mode. In this mode the User can choose the color.Set the value of the respective color from 0 for completely off to 255 for fully bright.

Also the Update delay can be set in milliseconds.This is used for setting the Delay Between Each color transition.the more the dealy the more slower will be the colour change. An update delay of around 5 to 20 milliseconds has a pleasing effect.

[Screenshot]The Pys60 Script Running on my S60 3rd Edition Nokia N78.

The PC GUI.

The PC gui was created Using PyGTK and UImanager Tools for GUI Creation. The PC GUI runs well on Windows (and probably also on Linux).I have tested it on my Windows Seven Home Premium 64-bit laptop .For Running the Application on Linux Small Amount of changes will have to be made ,Like changing the serial port label(on linux the PORT variable would be something like  dev/ttyUSB0) etc. But other than that it would work fine on linux too.The GUI has three sliders for Color selection and a Bunch of radio Buttons for Mode selection.The Sliders are active only in the color selection mode.Check out the Source code included in the Zip file attached

[Screenshot]The Python Gui running on A win7 Home Premium x64 Machine

Hardware Design

the Hardware basically consists of a Atmega8L Microcontroller (with an Arduino Bootloader on-board which i have  included in the sources.zip file) and three  IRF640 N-channel MOSFETs ,One Each for Driving Each  Color on the RGB LED strip .There’s also Lm1117 3.3V power regulator for powering up the Logic and a Berg connector for connecting the RX,TX,GND and VCC lines of the Bluetooth Module with the Atmega.I did Not make a schematic since i did not want to etch a PCB.Instead i just built the entire circuit on a perf-board and used flexible wire to build the circuit.The Entire Circuit is designed to be powered by an 12V DC Supply.I checked the Power  Consumption of the entire circuit with a Multimeter and it was found to be around 1Amp.I used a 12v 2 Amp SMPS based supply.

I made My prototype on a perfboard here’s a Pic of the Top Side.

And the Bottom Side

Working on a PCB using toner tranfer technique to finalise the prototype. All the Python Source Codes and the Hardware schematics and the Layout Diagrams in Eagle Format are included in the attached Zip File .Feedback is appreciated!(Note:a ULN2803 and a 7805 are some extra components on the PCB shown above that i tried out during testing.But are not necessary in this circuit).

Here are some pics of the project in action.

Download all the required Source codes and the hardware design files from here.

Adding Bluetooth To your Microcontroller projects

Bluetooth has become Ubiqutios these days Bluetooth Wireless technology is present is Most mobile phones today as well as in laptops and in desktop PCs.And If your PC or laptop doesn’t have it then you can get a Bluetooth USB dongle for cheap!

Wouldn’t it be interesting if your mobile phones /PCs could talk to your Micro-controller Projects??

Lets find out how to add Bluetooth capability easily to your existing Micro-controller projects with out many hardware or software changes.

Bluetooth has many ‘profiles’ for communication with various kinds of devices.The profile in which we will be interested in is the Serial Port Profile or SPP for short.This profile simply emulates a standard Serial port over a wireless bluetooth link.

I was working on a arduino project and wanted to eliminate the wired connection to the arduino form my laptop.The laptop had a GUI running which sent data over a serial COM port to the arduino.I got a Bluetooth module from Lamington road,Mumbai for around 850 INR. You could find it for less on ebay or something.The model number of the bluetooth module is AUBTM-20 .Its  a Class 2 Bluetooth SPP module (Class 2 meaning that its range is around 10 meters/ 30 feet).

I added a relimate connector to make it easy to connect it a breadboard or to connect jumper wires.I had the following connections on the module taken to the connectorGND,VCC and the RX and TX connections of the serial port.

Step one : Test the module

Just power up the Bluetooth module(I Fed in power to the Bluetooth Module from the 3.3v output of my arduino ) and scan the bluetooth devices on your PC/laptop.If everything’s done correctly you will be able to find a bluetooth device named AUBTM-20 or something simliar.You will be asked for a pairing code in case of the above model (AUBTM-20)it is 8888 but it might be different if you are using a bluetooth module from another vendor.On my WINDOWS 7 Laptop it showed up as “AUBTM-20″ under devices and printers.

Right Click on the device name in the devices and printers folder under the hardware tab .You will find a Standard Serial over Bluetooth Link and the COM port number writeen in brackets. Note down the COM port number.This completes the Basic test.

Step Two: Verify The COM link.

you will need to verify if you are able to send and receive data over the serial port to be able to use the device in your project for that. I used the FT232RL USB to serial converter chip on-board the arduino. But remember to remove the ATmega processor chip from the socket.(You’re out of luck if you have one of those SMD versions of the arduino .In this case you will need to get hold of a 3.3V power source such as the lm1117-3.3 and a FT232RL breakout board from here or here ) before you connect the bluetooth module to the arduino. Now Connect the RX line of the Bluetooth module to the TX line of the FT232RL module or you arduino DIgital Pin 1 and the TX line to the RX line of the  module or to that of the arduino.

Now open a terminal application such as TeraTerm (You can download it from here) select the serial port on which you connect your arduino/FT232 module(you can get the com port number of the FTDI device in the device manager under COM ports -> USB serial Port).Open a terminal with the COM port number of the The FTDI device and set the baud rate to 9600 ,8bit -data,Parity- none,1 -stop bit,Flow control -None.

Now open another COM port,this time with the for the serial COM port of your bluetooth device that you had noted down in the first step. The settings of this COM port will also be the same as above FTDI device. IF all the connections are proper and the link is established then anything you type in the FTDI COM terminal should appear on the Bluetooth COM terminal and vice-versa

The +CON:1 is something that the Bluetooth module gives out on the COM port whenever a device is connected .This Proves that the device can successfully communicate over the serial port

Step Three: Finally connecting the Bluetooth module to the Micro-controller.

Here’s a quick arduino script to verify everything’s fine .

void setup() {
  Serial.begin(9600);      // open the serial port at 9600 bps:
}

void loop() {
    if( byte( Serial.read() == 'a' )) {
        Serial.print("\nHey!");       // print Hey
    }
}

Just open the arduino IDE and open the serial terminal.Set the COM port number that you noted down in the First Step and the baud rate to 9600. Just type an “a” without the quotes  in the terminal and you should get a reply with a ‘Hey!’.A word of caution the Bluetooth module works at the CMOS voltage range of 3.3V and can take only upto 3.7v max so while interfacing with TTL level devices such as the ATmega8/168/328 of the arduino level conversion will be required (check out this app note from NXP).I chose to use the 3.3v Level Atmega8L instead since the device can work at 3.3V no level conversion would be required.This is the final device that i made uses the LM1117-3.3 as the power regulator to regulate the 12v from the wall wart.

For microcontrollers such as LPC1768 and LPC2148 which run at 3.3v levels no level conversion or modification would be required at all.All that would be needed to be done is to connect the rx,tx and the ground lines of the Microcontroller to the Bluetooth module and you would have  a Bluetooth enabled microcontroller project!

The board was first designed with the Atmega8 then i added the 3.3v regulator and switched over to the Atmega8L.The Mosfets and other devices onboard are for another project that i’m currently working on.Will Post about the project in my next post.Post in the Comments below what you think about it !

LPC1768 – Sending a Byte output to a port

Just  a Simple code snippet that allows you to send a byte over a 8-bit wide parallel bus when using 32 bit devices such as those based on the ARM architecture.

While programming AVRs this usually would suffice to send a BYTE over a parallel 8-bit wide port.Here’s an avr-gcc example

PORTC = data;

But with the a 32-bit microcontroller For example the LPC1768 from NXP.

Each port is 32 bits wide and in order to send  a byte over an 8-bit section of the 32 bit wide ports

a write to the PIN register of the respective port doesnt work.The Arm cortex-m3 has registers called SET,CLR,MASK and PIN for each of the ports.The purpose of the registers is pretty obvious and for more info refer to the datasheet of the LPC1768 .

now in order to send an 8 bit data over a section of the port beginning at byte number 19

LPC_GPIO2->FIOSET |= (data << 19);

data ^= 0xFF;

LPC_GPIO2->FIOCLR |= (data << 19);

sends the data over the 8 bit section of port 2 beginning from pin 19 to pin 26 of the LPC1768.

1.First the pins corresponding to all the ones present in the 8-bit data are set.

2.The data is exored with FF.This sets all the zeroes in the data to ones and all the ones to zeroes

3.Then the data containing the ones in place where the original data had zeroes is used to clear the port.Hence only those pins corresponding to the Zeroes in the data are cleared.

 

 

Steps to include Indian Rupee Symbol Font in MS word applications

Recently the indian rupee joined the elite league of currencies that have their own unique symbol. The symbol is a combination of the devanagri ‘ra’ and also symbolises the roman letter R. the two stokes signifies the tricolour and the progress of the nation. here’s how u can use it in your emails and word documents.

Given below are the steps to use the new Indian Rupee Symbol as a Font in your word applications:

1.       Download the attached font Rupee.ttf or Rupee_Foradian.ttf
2.       Copy the font and paste it in “Fonts” folder in Control Panel.
3.       Open any Microsoft Office application (For E.g., Microsoft Office Word). (See Figure 1.a)
4.       Select the font type as Rupee or Rupee Foradian.
5.       Click on ` (Grave accent) symbol. This key is just above “tab” button in your keyboard. (See figure 2)
6.       You can see the new Rupee symbol in your office application.

Figure 1.a. Rupee Symbol in MS word

Figure 1.b. Rupee Symbol in Gmail application

Figure2. Grave Accent Symbol

Limitations:

The “Rupee.ttf” font is necessary to view the currency symbol. So as long as the new symbol is not encoded in to Unicode font by default,

we cant use the symbol universally.

Thanks to Foradian Technologies for giving these fonts as a free download to public

make a PCB yourself

Making  a printed circuit board (PCB).

• First cut the copper clad board to size required.
• Sand the surface of the board to remove the layer of copper oxide that is formed due to the reaction of the copper with the oxygen in the air.
• 
• Once the copper surface is shiny and clean avoid touching the surface of the copper.
• Eaglecad or ORCad may be used to design the schematic and the pcb design .
• Take a mirror image of the pcb design while using the CAM processor to generate the Gerber files .
• The gerber files maybe viewed online at www.circuitpeople.com or the .eps file maybe viewed offline using the .eps viewer  take a lazer printout of the pcb layout using. this printout will be the mirror image of the actual pcb layout .
• Since during the transfer process the mirror image of the actual image will be transferred.
• Now cutout the actual PCB layout on the transperency. this will be the toner transfer
• .
• Lightly wipe the toner layer of the toner transfer with a peice of cloth and the surface of the cleaned copper clad. This will ensure that there is no dust or grime between the toner surface and the copper.
• Place the transfer on top of the cleaned copper clad board.
• Secure the layout in place with the help of a peice of tape or some glue.
• Using a hot clothes iron heat the toner transfer so that the toner layer from the tranfer is transferred onto the copper.(set the iron to the highest temperature possible…usually the cotton settings)
• Iron the transperency gently.
• 
• Don’t put too much pressure on the clothes iron else the toner will smudge. too little pressure and the toner wont be transferred at all.
• Once you think the toner is stuck to the copper turn off the iron. let it cool down to the ambient temperature.
• 
• Peel off the transperency if you got it right then you will see that almost all the toner has been transferred to the copper surface.
• The toner layer will form the etch resist.
• 
• Now the copper clad can be put into the etching tank. ferric chloride maybe used as the etchant. although muriatic acid maybe used too.
• 
• Gently ‘move’ the copper clad board through the FeCl3 solution.
• Once all the unwanted copper has been removed clean the PCB under running water.
• 
• Remove the layer of the toner with some sand paper or a solvent such as acetone.
• 
• If the PCB is meant for surface mount components then the PCB might require drilling.
• After the drilling is over. tin the copper surface to protect and increase the conductivity of the copper tracks.

References:

http://www.riccibitti.com/pcb/pcb.htm

http://www.qsl.net/vk5cu/

http://www.fullnet.com/~tomg/gooteepc.htm

http://www.youritronics.com/diy-printed-circuit-board-using-photo-etching-method/

http://hackaday.com/2008/07/28/how-to-etch-a-single-sided-pcb/

Made a Big Muff Pi….check it out…..my guitarist buddies are checking out the stuff!

DIWALI PROJECT – LED luminaire

Happy diwali to all!!!

Last week i was alone at home since my parents had gone out to attend a marriage in mangalore.I was alone at home for about 10 days and had no college since there was our college ‘techfest’.i dont like attending ‘techfests’ on a shoestring budget,like the one in our college!!.there only a few things which fit into my definition of tech there!

So I was alone & bored and to get rid of my boredom and loneliness i wanted to do some fun project.i had a few hundred bucks with me,and i had an old luminaire (called jhoomer in hindi)-it had those bayonet mounted so called ‘zero watt’ incandescent bulbs. I consider incandescents a thing of the past as they are very inefficient and are energy guzzlers-they waste a lot of energy as heat.Infact they generate much more heat than they produce light!!!So i thought that replacing the incandescents with power LEDs which consume lower power and produce much more light.Also the light is much more soothing to the eye.

I went to the electronics heaven of mumbai-lamington road.with my friend Vijay to get some 1 watt LEDs.In my previous posts i have written about these LEDs and how to drive them.I got six 1 watt LEDs since my luminiare had six ‘arm’s.i could simply hook these leds to a wall wart of about 12 volts and a current rating of about 600 ma.hook it up in two parallel rows of three series LEDs .each LED requires a voltage drop of about 3.4v and a current of 300ma.that totals to about 10.2 volts and 600ma total power required. simple eh?? but that’s not the case these led are much more complicated devices as mentioned in the past posts.They require a constant regulated supply for stable and reliable operation. With the correct type of supply a long life can be expected of these LEDs.Usually these LEDs are rated for about 10,000 to 100,000 hours of operation.Thats miles ahead of the current fluorescent and incandescent technologies.

So i had to make the power supply for these LEDs so as to ensure reliable operation.I had a few LM3404 samples i had received from National semiconductor lying around.Its a buck converter based constant current source LED driver.It has an internal MOSFET capable to switch up an amp of current. requires very few external components for operation.Hence is ideal for my project.Also since it’s switching based device it has very high efficiency.So my objective of going green is fulfilled too.The rest of the components used have been salvaged from old electronics-old PC SMPS,old nokia charger,cordless phones,TV video games,FM radio,DVD writer etc.I firmly beleive in recycling!!.

Now i checked out the datasheet of the LM3404,there were a lot of formulae and stuff on how to calculate the values of the various components used in the circuit.I found it difficult to get the accurate values of these components .I was also not too sure about the values being accurate. so i tried out the webench tools from National Semiconductor.These are great free tools from national which help in designing circuits based on their ICs.registration is required to use these tools which is also free. now on the webench designer page for LM3404 there were fields for the forward voltage of the LEDs,forward current,etc.I had no exact values for my LEDs since the guy whom i brought it from just referred to the as chinese made 1w led.So i assumed that it would be having a forward voltage of 3.4v and a current of 350ma.To confirm my assumption i had to check these specs with my multimeter.the volatge across the LED was 3.18v @133ma and 3.32v @210ma.I used a constant current supply mentioned in my provious post on power LEDs to check the voltage across the led.These values also help in determining the Rdyanmic-the dynamic resistance of the LED also known as ESR(equivalent series resistance).usually it is 1-2 ohms for power LEDs. In my case it was 1.81 ohms.The ESR can be calculated by measuring the increase in forward voltage drop dividedby the increase in current. For example, if the forward voltage drop increases by from 3.5V to 3.55V (a 50mV increase) when the forward current goes from 10mA to 20mA (a 10mA increase), the ESR will be 50 mV/10mA=5 ohms.I’ll be using a 12volt-1amp Wall wart from a deceased cordless phone as power souce for the LED driver cicuit.Take a printout of the circuit designed by the webench designer,as you’ll be needing it for further reference.here’s mine. there are 2 strings of three LEDs in parallel at the output block.

let’s start building the circuit now.The LM3404 chip was in a PSOP-8(power small outline package-8 pins)package.The SMD package is very tiny and i had to refer some sites to learn how to solder SMDs at home.The whole chip is just a couple of mm in width and in length!!I had to handle these using tweezers.First I placed the chip on a bare pcb coated with the ink from a permenent marker.

then i drew a few lines between the leads of the chip using the pointed end of one leg of the tweezer as shown.this exposes the copper of the pcb.Here the chip acts as the stencil.the chip can be held in place using an end of a toothpick.

extend the lines further and widen these lines if possible,to allow for use of thru hole components.now prepare the etching solution.I prefer ferric chloride. hold the pcb by means of a ‘holder’ i hav made one out of thick laminated copper wire.dip it into the etching soln.keep stirring continously.sometimes heating may also be required for speeding up the process.after the etching is done and all the bare copper is removed, remove the marker ink using acetone(sold as nail paint remover). your pcb is ready. check for any short circuits between the various parts of the pcb usin multimeter.i kept a small patch of copper shorted with the ground under the pcb to act as a heatsink since this chip has a powerpad at the bottom which is grounded.this power pad help dissipate heat as well as increase the sink/source capability of the chip.

first of all hold the chip in place using a tootpick on the prepared PCB. solder just the pin no.1.this helps to keep the chip in place.now now solder the pin no.8. now the rest of the pin are soldered by placing a blob of solder on all the four pins on one side .then the blob maybe sucked out using desoldering braid which leaves only the required quantity of solder on the pad.the process is repeated on the other side as well. check for the continuity between the pads and the pins by a multimeter,once confirmed.proceed to soldering the other components.

slightly bend the legs of the thru hole components then tin them.then solder these components over the

now try applying a thin layer of solder over the pcb.this helps in increasing the current carrying capacity of the pcb as well as to prevent oxidation of the copper.solder the components on the pcb as shown.a thin sticky layer of slag was formed on the pcb while soldering.this can be easily removed by rubbing a peice of cotton soaked in acetone.

i use this technique to ‘surface mount’ thru hole devices.this technique is great for prototyping.this method can also be used for ‘permanentizing’ the circuit. heres the completed circuit. before testing the circuit do remember to remove the slag as i can form a capacitor between the pins.this stray capacitance can damage the circuit and lead to malfunction and i learnt this the hard way.I had to sacrifice a IC to this stray capacitance .

the led driver circuit is ready now.

Now these LEDs cary a huge amount of power for their size.They generate some heat so heat sinking is required to prevent any damage due to overheating.I got some small heatsinks that could fit in the bulbholders themselves so there’s no need to reengineer the LED mount.the LEDs were ‘stuck’ to the heatsinks by means of heats ink compound.a small container of this thermal compound would suffice and the cost just 10 bucks.i would suggest polishing the surface of the heatsink before applying the thermal paste.It is not necessary though.Just to be on the safer side i polished the surface of the heatsink with some sand paper.a very small amount of thermal paste is applied on the heatsink.so as to form a very thin layer. the LED is the placed on the heatsink and a small amount of force may be applied so as to place the LED firmly in place.this step is repated for all the leds.

i managed to squeeze the LEDs fitted with the heatsink into the bayonet mountings of the incandescent bulb.this made my job of mounting the LEDs a bit easy.a lot of improvisation might be needed here.i also rewired the whole Luminaire. since the wire was old and was oxidised. i connected the each set of 3 LEDs in series. this gave me 2 strings of 3 series LEDs. i connected these two strings in parallel. i first tested the circuit with the 12v out from an computer SMPS.the yellow wire from the SMPS is the +12v while the black wire is the ground. the test was sucessfull so i proceeded to mounting the circuit.i attached a barrel plug connector to driver circuit so as to allow the connection of a standard wall wart supply. i used a 12v-1amp adapter that was used as a supply for a cordless phone. i mounted the circuit on the wallwart itself with some insulation tape.the supply for the adapter is given from the mains .after testing the circuit for another hour to check the stability i reassembled the luminaire and hung it back up on the ceiling.

Note:i was unable to upload the photos of soldering the through hole components on the SMD pcb due to some technical glitches.sorry for the incompleteness.will upload the pics as soon as possible.Also thanks to mandar for staying up late until the wee hours of morning and for that can of redbull which helped me stay up that late

philips she-9500 reviews

I was desperately in need of a good pair of in-ear earphones for a long time since my JVC FX-33 marshmallows went kaput a few months ago.So I got myself a new philips she-9500 from the tech haven of mumbai aka lamington road for about 750 INR a couple of days ago. I had done quite a bit of research before buying these earphones.Here’s the review.

First of all i’m no hardcore audiophile,but the audio quality is a top priority to me and i can’t bear to hear the bassless music from the silly nokia earphones bundled with my nokia n78.I a huge linkin park fan and i can hear linkin park all day long!!. The philips earphones are very good VFM earphones. The transperent blister package it came in contains the following.

1. the earphones themselves(length-60cm)
2. a 60 cm long extender cable
3. a carrying pouch
4. a small earphones box
5. a couple of extra pairs of rubber tips of different sizes(small,medium,large).

For 750 bucks thats more than enough i think.I was contempalting maybe a creative or maybe a sony before finally settling on the philips one. There are various models in the 500-1000Rs. range from creative,sony and panasonic.But the best thing i found about these earphones during my pre-purcahse reasearch was that these earphones have great bass.This is very much evident from the bass vents present at the back of the earphones.I had also found many good comments on these earphones on various forums.Although there were even comments that suggested that these earphones lacked the ‘meatiness’ in the bass range.

Now about the construction of these earphones.The earphones are built solidly enough but can’t say the same about the cord though. The wire has a slight rubbery texture and is very thin a looks flimsy. Although the wire feels much stronger than it looks.The plugs are all 24k gold plated. Even the extender cable has the connectors gold plated. My experience suggests that this gold plating tends to wear off with use.The rubber cups provided have a soft feel to them and are of good quality.The manage to have the right balance between providing good isolation and providing comfort.I can wear these earbuds for hours without feeling any discomfort,or any itchy feeling,the earbuds are so comfortable that i tend to forget that i have even worn them.This was not my case with the JVC marshmallows. The memory foam insulation provided with those earbuds was good at providin isolation,but comfort was not one of its strong points.I have read many comments on various forums such head-fi.org,iaudiophile,etc that the assymetric cable length of these earphones as being ‘clumsy’. I consider this feature as a plus point. this makes wearing these earphones even more comfortable.

Now,for the audio quality department.these earphones have a very decent audio quality. Altough i had expected more. But i guess that the comfort does come at a price.The isolation is not what i would get from my marshmallows.I think the isolation provided by the jvc was unbeatable.The complete sealing of this earphones is compromised due to the bass vents present at the rear i think.The bass is more pronounced due to this.Hence it’s like a necessary evil!!The bass and treble felt rich. The midrange was so-so. One major drawback of these earbuds is that the sound crackles when the eq settings are fiddled with,especially the bass booster setting. I had to change the default nokia bass booster settings reducing the bass range pointer to a level slightly above default.But one thing that i noticed was that the sound at the default settings itself was good enough and no bass booster setting were needed,even a bassophile like me could do away with the bass booster settings.This was not the case with the jvc marshmallows. There was no severe distortion even when all the eq settings were kept very high.So go for the SHE9500 earphones only if are willing to do away with the eq settings altogether.This was one major dissapointment i had with these earbuds.I’m very much fond of fiddling with the eq settings and i always keep the bass at a very high level.

to sum it all up

PROS

1. great vfm,cant beat the performance at this price point,even the creative ep630 costs 800 bucks and has much inferior bass(very boomy and hollow) altough it can handle high eq settings.
2. The asymmetric cable length.
3. Extremly comfortable.
4. Comes with great carrying box,pouch.
5. Ideal for use with mobile phones,since the cable is of short length without the extender,can be directly connected to the handsfree port of your mobile.can be used with mp3 player with the extender cable.(a nifty feature indeed).
6. Good bass for the price.

CONS

1. The cord is very thin,could have been of much better quality(one thing i liked very much about my jvc FX-33 was that the cable was very solidly built and was very thick and storng,certainly not a strong point of the SHE9500).
2. The sound quality could have been much better,the midrange is a weak point.But the price is a much stronger point here which influences me.
3. The chrome tends to attract a lot of attention. but thats pro right?But i think that the earphones should blend in which this earphones certainly dont.certainly could have been better without the chrome!

Isolation not very good.That might sometimes be a lifesaver,while walking on the streets listening to music it is necessary that you hear outside sounds and thus might prevent accidents.

These earphones are ideal if you are on a shoestring budget and are looking for a good pair of earbuds. for the price the sound and comfort is great.The cable with the extender is great for use with mobile phones having the remote for music player. If you have a flexible budget go for the sennheiser cx180,or maybe philips SHE9501,or the sonys they have much better sound quality but the price too is greater

High efficiency portable gadget charger

In my earlier post i had made a gadget charger which could charge your mobile phone,ipod,or other gadgets.It was based on a rather simple chip -the humble 7805. Now lets move a step further and make a more efficient emergency charger. this charger is based on the lt1302 from linear technology. I had got as samples from linear.com samples service two lt1302 ics .the datasheet provided very promising numbers efficiency reaching nearly 87%!! wow!!!!that’s great.That means more charge gets into your gadget.

The IC is a boost converter IC .As the name suggests it boosts the input voltage.It forms a very simple switching mode power supply. From the datasheet i found that it can operate down to voltages as low as 2v.That means we will can use two 1.5v alkaline or 1.2v ni-mh rechargeablesas the power source(as the cells discharge their voltage falls below the rated volatge,Ni-mhs usually discharge down to 1.0 v per cell before they need a recharge).Now what exactly is a boost converter??? . A boost converter is a form of a smps.It’s basic circuit is as follows.

Basic boost converter

source:wikipedia

To understand better try wikipedia.what it basically does is it employs an inductor to store energy from supply as the switch switches on and off rapidly.This switching on-off happens at a very high frequency upto 310 khz in this case.The switch in the SMPS of your PC is usually a MOSFET or an IGBT.These devices can handle a huge amount of power i.e. upto 50A constant current and 200A transients!!.These devices have very low on state resistances usually 0.015-0.018Ω hence the power losses across these devices are less.A simple BC547 NPN transistor can handle upto a few hundred mA hence in comparison these devices have very high power rating.These switches are turned on-off by means of an oscillator connected to a comparator which takes feedback and adjusts the frequency accordingly.Thus modifying the pulse width depending upon the power requirement. This is called pulse width modulation.

Enough basics.Back to our project now.All the switches,pwm comparators, etc are built right into the lt1302. a few external components are required such as a schotthy diode(warning do not use 1N400 series diodes they are designed to work at low frequencies and hence will not work.),power inductor(I salvaged mine from an old printer), a few caps and resistors,Oh and a perf board or pcb to mount them all.

Here’s the schematic.

schematic for gadget charger using Lt1302.

The input capacitors are present for the noise suppresion. now when the circuit is given the supply the switch is off which charges the inductor through the sw pin now the switch turns on then the energey stored in the inductor along with the energy from the supply are fed to the output. the 220uf o/p smoothing capacitor is present for smoothing the output. the capacitor iaverages the output. a gives a good consistent output. The inductor should usually have very low dc resistance to reduce copper losses. The inductor should have a rated current of at least 2A. checkout the ones from coiltronics and coil craft.The output maybe connected to a usb female jack to charge your usb device such as a mp3 player or in my case it’s the nokia 2.5mm male charging connector.

This charger has higher efficiency also the output of this circuit is 600ma max. so this can charge your device pretty quickly. my nokia n78 charges from near empty to full in about 2 hrs.compare that to a standard wall charger which takes 1.5 hrs for a full charge.Thats pretty good for a portable charger i think. I use 2100mAh Ni-Mh rechargeables as the power source.they last me for more than one full charge..the batteries and the inductors do get very hot when in use.you can leave the batteries in the circuit itsel when not in use since the quienscent or “housekeeping” currrent of this circuit is about a few hundred microAmps but this will drain the batteries eventually ,or better still you may include an on/off switch with the battery holder .i wrapped the whole circuit in insulation tape to protect it and increase the ruggedness.i did not find the inductor the correct value so i tied two inductors in parallel to get the desired value.Inductors in parallel are very much like reistance in parallel they follow similiar formula for calculation.