About me

Rajendra Bhatt is currently employed by Science Systems and Applications, Inc. in Hampton, VA as a contract research scientist to support the Clouds and Earth’s Radiant Energy System (CERES) project at the NASA Langley Research Center. His research involves studying the long-term stability and calibration of various geostationary and low-earth orbiting satellite sensors. Apart from his work and family commitments, he enjoys educating people about microcontrollers and DIY electronics through blogging.

How did you get into electronics/ engineering and when did you start?

It is hard to recall exactly when I first became interested in electronics as it started at an early age. I was born and raised in a small town located in the far-western region of Nepal. There was a radio and TV repairing workshop (actually it is still there) right next to our house. That’s the place where I first became acquainted with basic electronics components. The guy who ran that shop was very kind and welcoming. I liked watching him fixing various kinds of electronic gadgets. At the age of ten, I was already handy with a soldering iron and could easily replace broken electronics parts from a circuit board. I enjoyed tearing apart radios and tape recorders and building fun projects with their parts. One of the very first things I made was an audio amplifier using TBA810 IC, which I used for many years with my portable cassette player. In later years, my older brother and I made an FM transmitter microphone that had a range of about 300 ft. My brother broad-casted songs by playing a cassette player in front of the microphone and I would run to our neighbor’s house to tell them that there was a new radio station that played nonstop songs. I surprised them by predicting correctly what song would be played next. That was so much fun. Although I didn’t fully understand the involved physics, I enjoyed playing around with electronics more than anything else. So I would say, I didn’t choose to be an electrical engineer, it chose me.

After finishing my high school, I joined Institute of Engineering, Lalitpur, Nepal to study engineering. I graduated in 2002 with a bachelor’s degree in electronics engineering. Then I worked at the RADAR and RDPS division of Tribhuvan international airport, Kathmandu, Nepal, as a technical officer. I had a great time working with the RADAR team at the airport. In 2007 I moved to the United States to get my M.S. degree in Electrical Engineering from South Dakota State University (SDSU), Brookings. My research at SDSU involved post-launch calibration of Landsat series satellite sensors. The project was funded jointly by USGS and NASA. I graduated in the early 2009 and since then I have been employed by Science Systems and Applications, Inc. (SSAI) as a contract scientist to NASA Langley Research Center (LaRC) in Hampton, Virginia.

Can you tell us about your work at NASA LaRC?

My task involves monitoring the radiometric stability of various geostationary and sun-synchronous earth observing satellite sensors during their operational lifetime. Satellite sensors are calibrated very precisely and accurately in lab prior to their launch. However, once they get into orbits their characteristics change with use and as their components age. My job is to develop post-launch calibration techniques to correct for any artifacts in the received satellite data that may have been introduced due to the degradation of the sensors and on-board electronics. This is required to ensure that any variability observed in the satellite data is natural and is not caused by the instruments. This helps other scientists to do climatic studies more accurately.

What are your favorite hardware tools that you use?

A reliable multimeter and a good temperature-controlled soldering station have always been my favorite tools. I am also a fan of mikroElektronika’s PIC development boards which I use most often to develop my microcontroller based projects. These boards come with a built-in programmer and an in-circuit debugger, which greatly reduces the total development time.

What are your favorite software tools that you use?

At work I use IDL a lot for processing satellite data. At home, mikroC Pro for PIC is my favorite C compiler for developing firmware for PIC microcontrollers. Recently, I have started learning DesignSpark, which is an open source tool for schematic capture and PCB layout. I am liking it so far.

What is the hardest/trickiest bug you have ever fixed?

Bugs are an inevitable part of any kind of project. Sometimes they could turn into a lesson. My three other friends and I were once making a home monitoring and remote control system for our undergraduate engineering project. It was a device through which you could control household appliances remotely by dialing the home telephone. Meanwhile, it also informed the user about any critical situations at home, such as if somebody broke into your house, or there was a fire, smoke, etc, by dialing to his cell phone or to a land-line number stored in the system memory. A bunch of electromechanical relays were used in the project for switching 220 V AC appliances on and off. Everything worked well except that when a relay switch was turned ON, the microcontroller got reset. We thought this could be a glitch in the power supply caused by switching of the relays. Every IC on the board had already got a decoupling capacitor across its power supply lines. So we added more capacitors in the filter part of the power supply unit but it didn’t help. Later we tried using separate power supply units for the relays and the controller board, and that didn’t work either. We were tired working on it for hours and so we called it a day. The next day we came in with a fresh mind and tried couple different things. We found that the problem occurred only when an AC load was connected to the relay terminals. If the load is disconnected, the relay switches on and off perfectly without reseting the microcontroller. We immediately realized that it was an electromagnetic interference (EMI) issue. The relay contacts switching the external AC load was actually putting a big EMI hit on the system causing the microcontroller to reset. We then connected a simple RC snubber network across the relay contacts to suppress the voltage spikes and the problem got solved.

The moral of the story was whenever you feel stumped, don’t burn yourself out by over thinking the problem. Take a little break and come back to your project. You will have a completely new perspective of the problem which will help you discover a solution more quickly.

Do you have any tricks up your sleeve?

I don’t have any special tricks other than I try to keep things as simple as possible. Whenever I start working on a new project, I first make a paper drawn circuit prototype of it. Then I split the whole application into smaller modules, each of which is supposed to do a specific task. I work on one module at a time and when it’s finished, I test it by providing simulated inputs. I make sure that every module is working correctly before I put them together. This greatly reduces the debugging time because you are dealing with a lesser number of variables at a time.

What has been your favorite project?

I have enjoyed every projects I worked on but the more exciting moments came from the ones that I did as a teenager. One such project was a two way intercom that I made when I was a kid. We lived in an incomplete two storey house which had two bedrooms on the first floor and a small kitchen on the second floor. There was a staircase to get to the second floor but it was not covered on the top and you could see the sky while climbing up the stairs. In rainy days, you needed an umbrella to make an up-down trip. My mom spent most of her time in the kitchen and she called us from the kitchen window when dinner got ready. But if it were raining outside it would be hard for us to hear her calling us and she bothered herself to walk downstairs in the rain. So I made a two way intercom circuit using parts from an old broken cassette player and set it up to connect the kitchen with one of the bedrooms. I still remember my mom’s happy face after I showed her how to use it. I had a moment of great satisfaction after addressing my mom’s little problem.

Do you have any note-worthy engineering experiences?

When I was twelve my older brother (he studied physics) explained to me why a crow sitting on a 220 V transmission line does not get an electrical shock. After listening to his reasoning I asked, “Would I be safe then if I stand high on a wooden chair and touch a live wire?”. He stared at me and said, “Don’t even think about trying that!” There were a few cases of fatal electrocution in the town before because of the poor insulation and grounding in the houses. So electricity was a great fear of danger and that’s why power outlets and switches were located higher on walls to avoid kids from reaching them. But it made a perfect sense to me that current requires a complete conducting path to flow, and if I only touch one wire of the mains supply by standing on a wooden table, there shouldn’t be any current flow through my body, as the loop is incomplete. I wanted to try it but I was little afraid to do it alone. Neither would I be allowed to do this under somebody’s supervision. But if I could verify it that would be something fun to show to my faint-hearted friends. Finally I decided to try it alone. One day when nobody was home, I stood upon a wooden chair holding on one hand an insulated copper wire carrying 220V. The insulation at the tip of the wire was stripped off. First, I touched the tip with an electrical tester screwdriver and the light didn’t glow. Knock on wood! Then I quickly moved my other hand through it touching it slightly for a moment. I instantly realized that the theory was right. Then I hold the naked tip completely in my hand with full confidence. I was so excited that I lost my balance and fell off the chair. I landed on my back holding the wire tip in my hand. Oh yes, that was the biggest electrical shock I have ever had in my life.

What are you currently working on apart from your day job?

Apart from my day work, I like writing blogs about electronics tutorials and projects. Last year I started my own blog site named Embedded Lab (see link at the end), which has become my biggest hobby project now. This blog is my attempt to provide free comprehensive resources on microcontrollers and their use in embedded systems. It has been very well received so far, and I have got some strong positive feedback from the readers of my blog. Two months ago, I got an email from a 75 years old retired electrical engineer who mentioned that he is referring my tutorials to educate himself about microcontrollers. It was very encouraging and made me feel good that in some way I am contributing to the community. I am also working on a couple of new hardware projects that I will be publishing on Embedded Lab. One of which is an open source pulse oximeter using discrete components and a microcontroller.

What is on your bookself?

Designing Embedded Hardware by John Catsoulis, The Feynman Lectures on Physics, TTL logic data book, C Programming Language by Brian W. Kernighan and Dennis M. Ritchie, and a bunch of printed datasheets.

What do you see as the main challenges for embedded systems in future?

While there has been great progress in the embedded systems technology in the last two decades, some challenges involved in the design part have remained very much the same. For example, increased performance and low power consumption have always been two opposing forces. Although the modern processors yield a lot more performance per watt than the previous generation chips, but the processing demand has also gone up drastically with new embedded applications. Therefore, I think increased performance at reduced power consumption and cost will continue to drive innovation in the embedded systems research.

Besides, ensuring security in embedded systems is another challenge. Embedded devices have become a necessity in almost every aspect of our daily lives. With growing number of financial transactions happening over handheld devices, the security requirements in embedded systems have also become critical. However, implementing full-fledged security protocols on resource-constrained (in both power and performance) embedded systems still remains a challenge.

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