LED as a Light Sensor and more....

Recently got interested in the use of a normal LED as a light sensor. Its amazing, but there seems to be some conspiracy on the part of the electronics professionals, in keeping this interesting and wonderful physical phenomenon, hidden from public. Or is it ignorance?

Just take a normal voltmeter (or a digital multimeter) and connect the two terminals of any (say red) LED to the voltmeter. Cover the LED with your hands and note the voltage on the voltmeter. It should read close to 0. Now expose this LED to bright light. What do you observe?


The only book that talks about this is by Forrest Mims.

We just published a Design Idea in EDN on this topic.

The natural extension to the idea of LED as a touch sensor, is to use commonly available 5x7 or 8x8 LED matrix displays as a touch panel. We have been toying with this idea for some time now and have made some interesting progress. Its not very straight forward, but we are getting there...



Dhananjay Gadre

Travelogger: A Gadget to Record and Document Your Travel Memories

I just came back from a small trip to Manali and Kullu. While there, we also visited Rohtang Pass (Altitude: 4000 meters) and Manikarn. Manikarn has hot water springs and we cooked rice and potatoes in the boiling water (temperature: about 95 degrees Celsius).

On the way to Rohtang on the second day of our trip, there was a small mishap. We lost our beloved Nikon Coolpix 4100 digital camera. I guess at that altitude with very low oxygen levels, I wasnt as sharp to realize when the camera slipped off my shoulders. The loss was a little damper to an otherwise wonderful trip.

But, there was a bright side to the loss. It made me think of a device that would help travellers to record and document their travels. Here is what I had wrote on 24th October 2006, at the back of a restaurant bill:

I have always faced this problem while travelling: The desire to take notes of what ever is happenning, correlate the photos I take and maybe even add more information... but Once its over, I feel too lazy to do anything...

Here is a technology solution:


A battery powered portable device with a camera, a microphone, memory storage using SD card or something similar, temperature sensor, humidity sensor, optional GPS.

Camera is similar to the ones in mobile phones these days. Not too fancy. Fixed focus, hands off operation.

The user wears the camera on a headband. The mic is used to record travel anecdotes, travel related information as it happens.. in the form of a running commentary. Intermittently, a time stamp is also taken, as he user dictates into the mic. The speech stored on the SD card is interspersed with images, temperature, humidy readings etc. Similarly, user coordinates can also be recorded if GPS unit available and stored.

Eventually, all the information stored on the SD card is downloaded onto the PC and a speech to text program is used to convert to text. Interspersed with temperature, humidity, coordinate information and photographs, a custom PC software converts all data in to a HTML webpage!

Thus in the end, you have a Travel-Log.


I was really excited about my idea and on the first opportunity I got to get online, I talked to Anurag.

And he started laughing. He told me, I was reinventing something! Turns out that Microsoft has put in big bucks on a similar (OK, I overshot a lil bit) project titled MyLifeBits, pioneered by Gordon Bell, Jim Gemmell and others. They added a camera component to this project. The camera, Sensecam, is also developed in a Microsoft lab.

It is interesting to note that the MyLifeBits project has its genesis in the Memex Device, that was described in the July 1945 article in The Atlantic Monthly, titled "As We May Think" by Vannevar Bush. No relation to the American president Bush apparently.


The upshot is that my idea of a Travelogger is very similar to the one being pursued by other people, except for the speech to text part that I am rooting for, in my device.

A few students from the current batch of ECE students at NSIT have now decided to pursue this as part of their B.Tech. final year project. I dont see any glitch in its implementation. By great coincidence, I have the major part, a CMOS Camera module, required for this project.

Dhananjay Gadre

PS: While in Manali, you rely upon Yash Pal (cell number: 09816271899) to drive you around in his cosy lil Maruti Alto. Highly recommended for his promptness and reasonable charges.

Brain Waves for Control

When I wrote the AVR Book , I added a figure (seen on the left), to show how in remote future, you might be able to download programs in a Microcontroller.

How naive I was!

Because, it seems controlling gadgets with brainwaves is not so futuristic afterall! A company called IBVA Technologies (Interactive Brainwave Visual Analyzer) has been in the business of creating hardware and software for many computer platforms, to use Brainwaves to control other programs on the computer, or other gadgets. And they have been doing this for a long time now.

Awesome!

Hope to see this technology being made available more easily so that it can be used in day to day applications.

Dhananjay Gadre

Chumby: The Hacker's Dream Machine

Chumby Industries makes these Chumby Devices. Chumby heralds a new dawn for open source hardware and software. The complete package is availble for anyone to customize the gadget.

The device isnt for sale yet, but the company is targetting a US$150 or less for this crafty contraption. The feature are:

* 266 MHz ARM controller (the MX21 by Freescale)
* 32 MB SDRAM running at 133 MHz bus speed
* 64 MB NAND FLASH ROM
* 320x240 3.5" TFT LCD with PWM-controlled LED backlighting
* Stereo 2W speakers
* Headphone output
* Ambient light sensor
* Bend sensor (to pick up when you squeeze the chumby)
* Two USB 2.0 ports, one on the main board and one on the outerware electronics
* WiFi connectivity via a USB dongle plugged into the main board
* Circuitry to detect the presence of wall adapter power and auto-fallback to backup battery power
* Switching power supply network that can eat between 6V and 14V
* Available microphone input on the chumbilical bus
* Available SPI bus on the chumbilical bus
* Serial debug port set to 115200 8N1.

And it runs embedded Linux.

As it is, Chumby isnt targeted as a portable device. More like a bedside,
grid-powered device.

Chumby has a hardware support package that offers:

* Support for the ADXL3XX series of pin-compatible accelerometers (3-axis and 2-axis versions available)
* Up to 6 available 12-bit analog inputs
* Limited support for servo motor drivers (1-high resolution driver, and 3 low-res drivers)
* 8x 3.3V-compatible digital inputs
* 8x 5.0V-swing digital outputs
* 8x 1-A DC motor driver channels (can be configured for high or low side driving to make an H-bridge configuration), with support for motor voltages between 5.5V and 24.5V
* A small prototyping area for you to add on quick hacks


Truely, a Hacker's Dream.

Dhananjay V. Gadre

The Fab Lab Initiative

The Fab Lab program is an educational outreach initiative of the Massachusetts Institute of Technology's Center for Bits and Atmos (CBA). The CBA is directed by Professor Neil Gershenfeld, who in 2004 was named to the "Scientific American 50" the magazine's annual list of leaders in science and technology.

Currently, Fab lab operates in rural India, Norway, Ghana, Costa Rica, South Africa and Boston. More Fab labs are being considered. Each Fab lab owns a group of off the shelf industrial-grade fabrication and electronics tools, wrapped in open source software and programs written by the folks at the Center for Bits and Atoms. The list of the tools is interesting.


The idea behind a Fab lab is to provide a rapid prototyping platform so as to encourage local entrepreneurs to take their own ideas from the drawing board to prototypes to starting local micro businesses. This effort is backed by an international consortium of engineers to hel solve problems and offer design solutions to the local community.

One of the interesting projects to come out of the Fab Lab initiative, is the Internet 0 project, by Neil and his team. Internet 0 has profound implications for networking small devices for home and offices for control and data acquisition. A more detailed description appeared in the October 2004 edition of the Scientific American.

I came to know about Fab Lab after I found that they use my AVR book in their program. Since then there have been frequent interactions between me and Neil Gershenfeld. Hopefully a Fab Lab would open in Delhi soon.



Dhananjay V. Gadre

Write Only Memory

Although its way past all fools day, I recently discovered Bob Pease's article on the origins of the Write Only Memory.

Check out the data sheet of Write Only Memory for some real fun.


Dhananjay V. Gadre

AVR2006 Contest - An Update

Atmel corporation and Circuit Cellar have organized the AVR2006 Design Contest.

The contest has been on for quite some time now. The chip and development tools samples have been exhausted which indicates the utter popularity of this family of controllers as well as the popularity of Circuit Cellar contests!

The last date of submission of entries has now been extended to August 16, 2006. The participants can design using any of the following AVR components: AT90CAN128,AT90CAN32, ATmega32, ATmega16, ATmega168, ATmega169, ATmega88, ATtiny85, AT90PWM2, AT90PWM3, ATmega48, ATtiny45, ATtiny25 and ATtiny13.

The ATxxPWM are the newer parts from Atmel, targeted towards designing lighting and motor controls and have integrated D/A converter and power factor correction.

As usual, a heavy response is expected for this contest. Although the participants would miss designing with the new PicoPower AVR devices which were introduced after the contest was thrown open.

Happy Designing...

Dhananjay V. Gadre

The Ubiquitous Remote Control

I recently came across an article (thanks to Anurag Chugh for the link) in the March 2006 issue IEEE Spectrum, by Rober W. Lucky, titled Remote Control. A remote control is one piece of ubiquitious, mundane hardware that you take for granted. One is likely to own a multiple of these devices, for a variety of consumer entertainment electronics.

Bob explains his encounter with a remote-less, bargain price HDTV Tuner and how he set about getting a "Universal Remote" to work with the tuner. I was curious to know more details of all the websites dedicated to remote controls and I contacted him. It turns out that many many brands of remote controls are available, but all of them are made by a single manufacturer! Hi-fi Remote is one of the most popular websites dedicated to remote controls, provides a wealth of inside information.

Dhananjay V. Gadre

The Truth about Windows Embedded Students Challenge (WESC) 2006 Finals Projects

Microsoft Corporation sponsored an international competition, titled Windows Embedded Student Challenge 2006. This contest was first organised in 2004 and has been held ever since. Due to the involvement of Microsoft, the competition attracts huge interest from the student community.

As part of the contest, the organizers (Microsoft Corporation) propose a theme for the competition and expects participating team to design and build projects in line with the theme. To help the design and implementation, it provides free hardware and software tools. The hardware platform is an x86 derived single board computer, called Ebox. The software tools includes the Windows CE RTOS development suite.

Participants are expected to design their projects around the Ebox and WinCE RTOS.

This year around 230 teams sent proposals to the organizers, out of which 200 teams were selected and were provided with the abovementioned tools.

Out of these 200 teams, about 185 teams sent final reports which were evaluated by a team of judges to select the top 30 projects. The list of these top 30 teams together with their reports is available here.

This year, the theme for the contest was "Preserving, Protecting and Enhancing the Environment".

The teams are supposed to follow eligibility rules as listed on the Windows Challenge website. One assumes that teams that do not meet the eligibility criterion, will be inelligible? Or so I thought.

Also, since this is a Microsoft spondored project, it is obvious that Microsoft's motive is to try and popularize the use of WInCE RTOS amongst the student community. The choice of Ebox is only to allow the operation of WInCE RTOS. It could as well have been any other hardware platform.

It is therefore natural to expect that a participant would develop a project that would justify the use of Ebox and WinCE RTOS. Or am I too naive to assume that?

It is worthwhile to note that the Ebox is a serious piece of hardware. It is an Vortex86 200 Mhz processor based, small foorprint embedded system with a serial port, a parallel port, 3 USB ports, an ethernet port, AV'97 audio, PS2 mouse and keyboard ports, VGA port. The Ebox consumes about 10W of power in active mode.

I was a mentor to a team from NSIT, which in my opinion implemented a wonderful project (which btw, is being patented now). Unfortunately, the judges did not deem the project as worthy of selection in the final 30 list.

My team brought to my notice that some of the teams did not meet the eligibility criterion. They also mentioned that many projects seemed very trivial for an Ebox. Many infact do not need any RTOS at all.

I then decided to read all the reports and make an assessment about such projects, which, in my opinion do not justify the use of an EBox and WinCE RTOS. My brief report about such projects is available here.

Read it for yourself and make your own judgement and decide if these selected project deserve to be in top 30 by any measurement metrics? If you would like to read my team's report for comparison sake or otherwise, send me a mail at dvgadre@gmail.com and I will be more than glad to mail you a copy.

I have brought this to the notice of the organizers of WESC'06 but they have decided to ignore my feedback and go ahead with the contest as per the schedule.

I guess its bye bye future Microsoft contests, as far as I am concerned.


Dhananjay V. Gadre