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Showing posts from 2010

Installing Android on a Virtual Machine running inside Windows using VirtualBox

Operating System: Windows 7 Ultimate 64 bit Download VirtualBox (filename: VirtualBox-4.0.0-69151-Win.exe) from Download a ISO image of Android-x86 built for installation on a virtual machine (filename: froyo-vm-20100812) from   Install Virtualbox. Download "VM VirtualBox Extension Pack" (filename:Oracle_VM_VirtualBox_Extension_Pack-4.0.0-69151.vbox-extpack) from Install "VM VirtualBox Extension Pack" by double clicking on the file. Start VirtualBox Create a new Virtual Machine named "Android-x86-froyo" for OS "Linux" and Version "Linux 2.6" with RAM as 256 MB and dynamically growing IDE (not SCSI) Harddisk of 2 GB Capacity. Enable both the serial ports (COM1 and COM2) but leave them in "Disconnected" mode. To the above Virtual Machine, attach "froyo-vm-20100812.iso" as CD image to the IDE co

Setting up toolchain for developing applications for Android on a Windows PC

Operating System: Windows 7 Ultimate 64 bit Download "Java Platform,Standard Edition JDK" (filename: jdk-6u23-windows-i586.exe) from When asked to select the platform, select "Windows" and not "Windows x64" because we want the 32 bit software and not the 64 bit one eventhough our OS is 64 bit. No special installation instruction, just keep clicking next on the installation wizard dialog boxes that pop up. Download "Eclipse IDE for Java Developers" (filename: from Use the 32 bit Eclipse eventhough your OS is 64 bit. Extract the folder "eclipse" from within to C:\ Rename this "eclipse" folder to "eclipseandroid" in case you want to distinguish it from other installations of eclipse. Run C:\eclipseandroid\eclipse.exe Rename the workspace path

50 Hz AC Mains

So the waveform collection wouldnt be complete without the 50Hz AC Mains . Since the oscilloscope I am currently using is USB powered PC based, it can't handle high voltages such as the 230 Volts AC/Hz available in India. So I stuck my probes onto the secondary of a AC/DC step down adapter.. ..connected the oscilloscope to my laptop and observed the waveform and more specifically, its frequency: Just to be safe, I operated the laptop on battery and disconnected the laptop charger from the mains. Next I loaded the AC/DC adapter with a 47 ohms resistor... .. and observed the signal (note the distortion): If you are wondering if (and why) the utility frequency ever changes then the following articles would interest you: Wikipedia article on "Utility Frequency" Increase AC mains frequency? Accuracy and stability of the 50 Hz mains frequency

10 Mbps Ethernet

Waveforms of signal on a 10 Mbps Ethernet CAT5 cable (captured differentially on the RX+ and RX- wires): For the info regarding how I managed to captured this waveform have a look at the usenet discussion here and the supporting info here . Click on the image below to know how I forced my network card to operate in 10 Mbps mode only:

Dual-Tone Multi-Frequency

Whenever we press the keys on our touchtone landline phones, it transmits two sine waves simultaneously. The interface at your telephone exchange recognizes the frequencies of both of these waves and hence identifies the key pressed. This is known as Dual-tone multi-frequency signaling . The various combinations of the frequencies of each of the keys are as below: DTMF Frequencies in Hertz       KEY  FREQ1    FREQ2         1    697    1209 2    697    1336 3    697    1477 A    697    1633         4    770    1209 5    770    1336 6    770    1477 B    770    1633         7    852    1209 8    852    1336 9    852    1477 C    852    1633         *    941    1209 0    941    1336 #    941    1477 D    941    1633 Here are how the waveform of DTMF signals corresponding to various key presses look like: Digit 0 Digit 1 Digit 2 Digit 3 Digit 4 Digit 5 Digit 6 Digit 7 Digit 8 Digit 9 Hash (#) Asterix (*) And here is what the FF


Here is a printout of screen capture of A and B signals of an RS485 Bus as captured on an oscilloscope (Agilent 54621A). The RS485 Bus usually consists of a twisted pair cable connected to an RS485 Transceiver. In the case, below, a twisted pair cable has not been used - the signals were directly observed at the A and B pins of DS75176 loaded by a 120 ohm resistor and biased by two 560 ohm resistors. The bus is bein operated in half-duplex mode. DS75176 (which is equivalent to MAX485 ) was connected to the UART of Atmega8 AVR Microcontroller. The data being transmitted were the characters: 'a' '0' '1' '2' 'K' 'Q' - in that order. The UART frame format is 8-N-1 and the baud rate is 38.4 kbps. The signals A and B were captured on two different channels both referenced to the common system ground. This waveform was captured while me and my classmates were working on our final year project at the end of our undergraduate engineering cour


How to observe Spectrograms of various signals or latest pop/techno songs: Buy a Nokia phone - specially the ones like Nokia 5800 or Nokia X6 or any other which are labelled "comes with music" or "music unlimited" Install the nokia support software on your computer - especially the Ovi Player Validate your music coupon and download a few songs from using Ovi Player. This is completely legal. Install Winamp 2.95 (older version). You can get it from here . Start Winamp, go to preferences, set the visualization plug-in to "Spectrum Analyzer + Voiceprint" which is present in the "Nullsoft Tiny Fullscreen 2001" Library Load the song in winamp, play it and press "Ctrl+Shift+K" to watch the live spectrogram of the song. The Spectrogram is updated from left to right. Press "Esc" key to get out of fullscreen mode. If you want to see the voiceprint of your voice, "add a URL" to playlist and type "

Frequency Modulation

Here's a GIF Animation of the modulating signal (top) and the corresponding frequency modulated signal (bottom) captured on an analog Cathode Ray Oscilloscope. The modulating signal is a very low frequency sine wave fed from signal generator to an ICL8038 FSK trainer kit. You can see the frequency of the carrier wave change as the voltage level of the modulating signal changes slowly. The video was shot using a digital camera. The location is VESIT, Mumbai's Communications Laboratory. Here's how the GIF animation was created on a Windows based PC using free tools: The video was originally in .MOV (Quicktime) format. It was converted to uncompressed AVI using Rad Tools (free version of QuickTime must be installed on your system before you can convert the MOV to AVI). The uncompressed AVI was then loaded into VirtualDub and Image Sequence of a selected duration of video was exported. This particular time period of the video consisted of a seque

Electroluminescent Strips

Electroluminescent strips are available in all shapes and sizes. They can even be cut to whatever shape is required as long as the end terminals are left unscathed. These strips find use as backlight for watches and other devices having LCDs. High voltage AC signal is required to turn on an EL Display and special drivers are available to achieve this. Typical AC voltages applied to the EL display are 50V to 250 VPK-PK, with a frequency of 50Hz to 1KHz. The current consumption depends on the area of the display - a display having an area of a few (< 5) square inches would draw somewhere around few tens of (< 100) microamperes. So the job of the driver is to essentially draw a few tens of milliamperes at 3.3/5.0 volts DC and convert it to around 100Vp-p AC at a few hundred hertz and supplying a few tens of microamperes of current. Information Regarding ELs: History LuminousFilm EL Wire FAQ EL Driver ICs from Micrel ( Application Note ) EL Driver ICs from Supertex Dr

Inside Electret Microphone

Electret Microphones come in all kind of sizes. Let us look inside three of these: Type 1 Type 2 Type 3 Few useful links explaining the construstion and use of Electret Microphones: HyperPhysics WM-60a , WM-61a microphone modification SparkFun Powering Microphones   History Hosiden MEMS enables multi-microphone consumer products (Article in EDN, Photo of Electret Microphone Schematic) These Microphones are available in Mumbai, India from Visha Electronics Corporation

Breakout Boards

So what do you do if you want to assemble a prototype of a project based on an IC which is only available in Surface Mount Package like one of these? You make use of an appropriate Breakout Board (BoB). Lets look at some of these: Quad Flat Package ( QFP )| upto 64 Pins | 0.8mm Pitch Quad Flat Package ( QFP )| upto 160 Pins | 0.5mm Pitch Quad Flat Package ( QFP )| upto 160 Pins | 0.65mm Pitch Shrink Small Outline Package ( SSOP )| upto 40 Pins | 0.65mm Pitch Small Outlined Integrated Circuit ( SOIC )| upto 28 Pins | 1.27mm Pitch All the above breakout boards are available in Mumbai, India from Visha Electronics Corporation Make sure that before you solder your IC to the breakout board, you do remove the extra tinning from the tracks using a soldering iron and copper desoldering braid as shown in the photo below. Use of soldering paste while doing this is recommended. This will flatten the tracks and the you would be able to easily and accurately position the SMD I