13 Online Shops for Buying Electronic Components in India

 Image courtesy: www.techieinfocenter.com

Are you a newbie or student who wants to explore the world of electronics? Are you a hobbyist or maker who loves to tinker with electronics? Are you a practicing electronics engineer or a hands-on researcher? If your answer to any of the above questions is yes, you need to buy different types of electronics components and printed circuit boards for your projects. They may range from the most basic resistors and capacitors to highly specialized integrated circuits, sensors and development boards. 

Unless you stay in one of the metro cities of India, you will find it hard to get many of these components. Even if you stay in a metro, some components are hard to find. But thanks to the internet, we have many online shops to buy electronic parts from. I've listed 13 options here. Although I've bought from some of them, I haven't bought from all of them. I've included websites that I know people get stuff from. 

1. Free samples

Who does not like freebies? Some companies are generous enough to provide samples of their components either through their websites or if you politely request them stating your purpose and requirement. E.g. TI, Cypress, Allegro. There might be many more. If you're a student, many companies have designated personnel for university relations who can be approached.  

The rest of the list is about online destinations where you BUY the components and boards. 

[Pay in Indian Rupees]

2. Element14 www.element14.com
Formerly Farnell electronics, Element14 is one of the biggest online stores for electronic components. They charge pretty high particularly for small numbers. However, they are sometimes the only option for hard-to-find components and are highly reliable. You might need to have TIN number to buy from them. I was able to get around that problem when I bought from them a few years back.

3. Kits 'n' Spares www.kitsnspares.com
Kits 'n' Spares is a subsidiary of Element14 catering to non-industrial costumers. They sell a wide variety of Do-It-Yourself electronics projects and hobby kits.

4. Nex Robotics www.nex-robotics.com
Nex Robotix is a spin-off from IIT Bombay that intends to cater to the robotics and embedded systems community. However, many of their products are useful for any electronics enthusiast. I've bought some nice stepper motors and breakout boards from them.

5. Explore Labs www.explorelabs.com 
This Jodhpur based startup calls itself "an opensource playground" and stocks a diverse range of DIY electronics kits. They are an authorized distributor for Sparkfun Electronics in India. 

6. ProtoCentral www.protocentral.com
This Bangalore based company sells DIY electronics kits and is another authorized distributor for Sparkfun Electronics in India. They ship worldwide.

7. Tenet Technetronics www.tenettech.com
Tenet Technetronics is yet another Bangalore based online store for electronics hobbysists and engineers.

8. NSK Electronics www.nskelectronics.com
NSK is the third Bangalore based entry on the list. Their SP road shop is hugely popular with localites and also has an online store.

9. OnlineTPS www.onlinetps.com
OnlineTPS is a Bhopal based online provider of electronics components and boards.

10. Ventor Technologies www.ventor.co.in
Ventor Technologies is a Kolkata based online shop for electronics components and boards.

11. rhydoLABZ www.rhydolabz.com
This Kochi based online store is known as the Sparkfun of India and ships worldwide.

DangerousPrototypes visited and blogged about ProtoCentral, Tenet Technetronics, NSK Electronics, and rhydoLABZ during their India Global Geek Tour 2012.

[Pay in US Dollars]

If you can afford to pay in dollars for something that isn't available anywhere else, try the following two international biggies.

12. DigiKey www.digikey.com

13. Mouser www.mouser.com

I hope this was useful. Let me know of your personal experiences with them and also if you know of other reliable online stores. I expect the list to grow with time. Happy soldering!

_____________________________________________________________________________

Reader suggestions

14. Aliexpress www.aliexpress.com [Suggested by Syam Krishnan]
While Element14 requires TIN number, Aliexpress is better suited for personal orders. Go to the "Electronic components and supplies" category on their website. 

15. Digibay www.digibay.in [Suggested by John F Xavier]
John found some affordable modules at their site.

16. Robokits www.robokits.co.in [Suggested by John F Xavier]
John bought servo and stepper motors from them.

17. DNA Technology www.dnatechindia.com [Suggested by Anonymous]

18. Hacktronics India www.hacktronics.co.in [Suggested by Abhijit Kshirsagar]

19. eNTesla India www.entesla.com [Suggested by Sudish Menon]

_____________________________________________________________________________ 

Discovered later

20. Project Point www.projectpoint.in

The PhD Experience

Yesterday I gave a talk titled "The PhD Experience: Lessons learnt in five and half years." I narrated my personal experiences, thoughts and the lessons I learnt while pursuing a PhD at the Department of Electronic Systems Engineering, Indian Institute of Science. 

The key question that I try to address is, "What are the processes and tasks that get the best out of a researcher?" Considering the researcher as a system, I discuss the inputs (information and experiences), outputs (hardware, software, knowledge) and processes of this system. The presentation is targeted primarily at present and prospective graduate students. However, anybody with an interest in learning and productivity might resonate with aspects of the talk.

Here's the video of the talk [video credits: Abhijit Kshirsagar]

The pdf file of my presentation is available here.

P.S. During the talk, I mentioned the importance of developing verb vocabulary.

The Thesis Whisperer has compiled a useful verb cheat sheet that is available here.

Learning How to Learn

This blog post is a course assignment for the Coursera MOOC titled "Learning How to Learn" taught by Prof Barbara Oakley and Prof Terrance Sejnowski, University of California, San Diego. Here I discuss my ideas and experiences with three of the learning techniques mentioned in the course: (1) Switching between focused and diffuse mode of thinking, (2) Memory: spaced repetition and associations, and (3) Interleaving.

1. Focused and diffuse mode of thinking

The pinball analogy described by Prof Barbara Oakley is a very elegant way of conveying how the focused and diffuse mode of thinking work.

Depiction of focused and diffuse mode of thinking in Prof Barbara Oakley's lecture.

[Source: http://projectfidgetyfingers.blogspot.in/2015/01/how-to-be-creative-switching-between.html]

The importance of playing ping-pong between these two modes in cementing the learning cannot be over-emphasized. Several accomplished people have vouched for it. Prof Arindam Ghosh at the Indian Institute of Science is a renowned scientist in the field of low-temperature nano-electronics. I happened to be team mates with him in the institute cricket team and once did an interview of him where he stressed the importance of playing sports. "Sport rejuvenates the mind. In research or, for that matter, any profession that involves a fair deal of thought, it is very easy to get stuck in a thinking loop. Sports helps break that loop so that you can start your thought process afresh, from a new perspective", he avers. You can read the full interview here.

I've come up with my own analogy to illustrate the importance of switching between the focused and diffuse modes. Picture a fly trying to escape out of a car banging against the glass window. The window is half open but the fly is pushing away at the closed part of the window duped by its transparency. Its trying really hard in its focused approach to get out of the car. But no amount of pushing and buzzing against the glass will solve the fly's problem. What it needs to do is to back away from the glass (akin to going into a relaxed diffuse mode) and come back at it a few inches from where it had approached earlier and voila! It's an open window. The problem is solved, the fly is free.


2. Memory: Spaced Repetition and Associations

I tend to browse and read about a diverse range of subjects. In the process of looking up new information all the time, I might not repeat what I already learnt and hence tend to forget many of the things that I learn. On the contrary, when it comes to identifying plants along with their common and scientific names and their key features, I found that I had a very good memory. The key difference that I noticed was that of spaced repetition. Every time I take a walk in the campus to and from my laboratory, I notice these plants and recall their names while observing them. This routine of recall and spaced repetition helped cement the details of these plants in my mind. I now intend to use the same technique in other aspects of my learning.

Another common problem that I had was to frequently forget where I parked my bicycle possibly because I'm absent minded, not paying attention while I'm parking. Lately, I started leveraging my good plant memory for solving this problem. Every time I park my bicycle, I notice the nearest tree. By building this association, the next time I'm looking for the bike I just have to recall the tree and I find my bike!

3. Interleaving

Prof Barbara Oakley stresses the importance of interleaving one's learning using various techniques and from various perspectives. This helps in gaining a better understanding and in better retention of the material. An interleaving technique that I often use and that has helped me in learning various subjects is what I call "Repeated Classification" of the material. I shall illustrate this technique in the following paragraphs.

Number based classification

After having studied a chapter or several chapters of a book on a subject XYZ, I try to cull out all the numbers mentioned in the text and put them together in a list called "XYZ in numbers." E.g. recently I attended a colloquium by Prof Arnab Rai Choudhuri titled "The mysterious magnetic personality of our sun." I distilled out the numbers he presented at various points of the talk as follows.

The sun in numbers:
Surface temperature of sun = 6000K
Temperature at sunspots = 3000-4500K
Temperature of corona discharge = 1,000,000K
Strength of the sun's poloidal magnetic field = 0.3T
Strength of the magnetic field at sunspots = 10T
Time taken by the sun to complete one rotation about its own axis = 27 days
Time period of the sunspot cycles = 11 years
Time period of the polar magnetic field reversals = 22 years

Time based classification: (when)
Another form of classification is based on the historical timeline of events pertaining to a field of study. Systematically listing down the years of occurrence of significant events provides a sense of how a particular field evolved and creates a storyline that makes it easier to grasp the complete picture. Call it the "Timeline of XYZ."

Spatial classification: (where)
Making a list of places and the associated events is another handy way of classifying. Marking the places on map is even better. This can provide insights on how geographically diverse or concentrated the development of a particular field has been. Call it the "XYZ map."

People based classification: (who)
List down the names of all the people associated with the field of study, preferably along with their significant contributions and quotes. Here's a list of the people who appeared in the 'Learning How to Learn' course lectures and interview videos along with a memorable quote or key take-way from each of them:

Dr Barbara Oakley: "Do not just FOLLOW your passions. Instead, BROADEN your passions."

Dr Terrance Sejnowski: "Unfortunately, there is no instruction manual for the brain."

Dr Robert Bilder: "Disagreeability can spark creativity."

Daphne Gray-Grant: "Do not edit while writing!"

Benny Lewis: "Why children learn language easily is because they are not afraid of making mistakes."

Dr Norman Fortenberry: "Multi-mode input is critical for learning."

Scott Young: "Learn a language by immersing yourself in it."

Amy Alkon: "Fast reading tip: approach a book like a buffet; do not eat everything!"

Dr Robert Gamache: "Study every subject everyday, even if it is for only 10 min"

Dr Keith Devlin: "Switching from one task to another is when one is most likely to fall into the procrastination trap."

Dr Richard Felder: "Don't wait for that 'block of time' to get things done. Do the task in short bursts with whatever time slots are available."

Dr Rebecca Brent: "Give your subconscious an assignment."

John G Maguire: "The secret to good writing is objects, not ideas."

Kalid Azad: "The ADEPT method of learning: Analogy, Diagram, Example, Plain English, Technical Description."

While we looked at questions like how many, how much, when, where and who, several other ways of classification are possible using 'what' based questions. E.g. classifications based on techniques, methods, objectives, products, types, resources etc. There are no limitations to how many different ways you can classify the material and play with it providing various insightful perspectives. It is down to your own imagination. Happy learning!

Bicycle power

A few months back, Deepak Malani asked me about the torque and power requirements of a bicycle so as to get an idea of the required ratings of an electric motor that can be retrofitted in the bicycle. So I went about doing some back of the envelope calculations taking into account rolling friction, aerodynamic drag and inclines. Here's a simple MATLAB/octave script I wrote to carry out the calculations.

The following assumptions were made:

• The transmission (pedal-sprocket-chain assembly) is 100% efficient. Note that practical efficiencies are in the range of 96-98%
• The rider plus bike system is moving at a constant velocity
• There is no headwind, tailwind or crosswind

Plugging in some typical values for the parameters, a 65 kg rider on a 15 kg bike moving at 15 kmph on a level road (no incline), does mechanical work at a rate of 60 Watts. He/she would need to put in a torque of about 10 Nm into the pedals (assuming a gear ratio of 2).

You can use the script for plugging in various values of the parameters and compute the torque and power requirements under those conditions. Note that at even a couple of degrees of upward incline, the torque required to overcome gravity dominates over that required to overcome rolling friction and aerodynamic drag.

The computations in the script are for a constant speed. However, the rating of the motor needs to take into account the worst case scenario which would typically be an acceleration or even a constant speed climb up a specified incline.

A few points to note:

• Coefficient of rolling friction (Crr) could vary between 0.0021 to 0.017 [1]
• Aerodynamic drag coefficient (Cdr) could vary between 0.65 to 1.1 [1]
• Gear ratio (GR) could be anywhere between 1.75 to 4 [2]
• The gear ratio (GR) and wheel radius (Rw) effect only the torque requirement but not the power requirement
• For electric bikes with hub motors, GR=1

References:
[1] Stetler, Energy Efficiency of Bicycle Transportation
[2] V. Ryan, The Basics - Gear Ratio
[3] Ashburn, The Physics of Moving a Bike
[4] Cycling Aerodynamics & CdA - A Primer

What's in a name?

This one is one of my favorite Richard Feynman anecdotes. [Quoted from http://www.vigyanprasar.gov.in/scientists/RichardPFeynman/RichardPFeynman.htm]

Feynman's father Melville Feynman encouraged his son's fascination with science in all possible ways. While not pushing in any particular direction his father would explain things about the way the world worked. Melville taught his son at a very early age 'the difference between knowing the name of something and knowing something'. To quote one of Richard's oft-quoted anecdotes about his father: "See that bird?" he says. "It's a Spencer's warbler (I knew he didn't know the real name)". "Well, in Italian, it's a Chutto Lapittida. In Portuguese, it's a Bom da Peida. In Chinese it's a Chung-Iong-tah, and in Japanese it's a Katano Takeda. You can know the name of the bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird. You'll only know about humans in different places, and what they call the bird. So let's look at the birds and see what it's doing - that's what counts!" 

I've seen so many people - when they realize they haven't understood something correctly - trying to push their way through arguments and discussions using some high-sounding technical jargon. That's what we can call the Spencer's-warbler-syndrome. When reason fails, vocabulary takes over! My only suggestion, admit your mistake and move on.

My experiments with toothpaste - II

In part one, we looked at the ubiquitous tube and arrived at an approximate formula for its volume. We had neglected the effect of the increasing major axis on the volume and had taken it as a constant. Here, we shall try to be more accurate by including this tapering as well in our analysis.

For the elliptical cross section of the tube, let the major axis taper linearly from 2R to 3.14R as you move from the bottom of the tube to the top as shown above. The expression for the semi major axis 'a' at any vertical distance 'x' from the top is given by:

The expression for the semi minor axis 'b' at any vertical distance 'x' from the top is given by:

The volume of the tube can be obtained by the following integration.

Substituting the expressions for 'a' and 'b' and working out the integral we get

which is greater than the result obtained earlier.

Applying the result:

For the toothpaste tube under consideration in part one (R=1.6cm, h=13.8cm), the new formula gives a volume of 66.6 ml. Taking a correction factor of 1.5 to account for the bulging profile as opposed to a triangular one, we get a volume of about 100 ml. The choice of an appropriate correction factor is a matter of debate though. For a net weight of 150 gm, the density of the toothpaste would be 1.5 gm/ml as opposed to the earlier result of 2.5 gm/ml. This new result seems more in agreement with literature which says that typically it's in the range of 1.2-1.6 gm/ml.

Thanks to Raghunandan for pointing out an alternative approach to calculating the density of toothpaste coming from the chemical composition data.

Caveat:

Strictly speaking it is not correct to say that both major axis as well as minor axis taper linearly. Whatever be the values of 'a' and 'b', they have to satisfy the constraint that the perimeter of the ellipse has to equal 2 x pi x R (Since our tube was actually formed by pinching one end of a cylindrical tube). Hence, the moment you say that either 'a' or 'b' tapers linearly, the other has to taper non-linearly. But so far as an approximate calculation is concerned we shall not worry about this constraint.

My experiments with toothpaste - I

Brushing my teeth on a Sunday morning I glanced upon the new toothpaste tube and wondered what's the volume of the paste in it. So many of our daily use pastes and gels - toothpastes, shaving creams, face-washes, ointments and many others - come in this weird shape that I don't have a name for. Let me call it the tube. The mensuration tables we all studied in school gave us the formulae for the volumes of common shapes such as cube, cuboid, sphere, cylinder, cone etc. But they didn't talk about this ubiquitous shape!

If you look at the horizontal cross section of a right circular cone, it starts out with a big circle at the bottom and as you move up, the circle becomes smaller and smaller till you finally reach a point. The cross section of the tube also starts out with a circle, but as you move up, one of the two principal axes of the circle starts shrinking (minor axis) while the other starts increasing (major axis). You end up with flatter and flatter ellipses finally reaching a line segment of length 3.14xR when the ellipse is completely flattened out at the top. 

Let us assume that the tube tapers off linearly and hence it should look like a triangle from the side view as shown above. Another simplifying assumption is to neglect the effect of the increasing major axis, hence taking it as a constant. As per this assumption the major axis stays at 2R throughout. In other words, the semi-major axis stays at R throughout. (A more accurate analysis taking into account the tapering of the major axis can be found in part two)

The volume of the elemental ellipse of thickness 'dx' located at a distance 'x' from the top is given by,

We get the total volume of the tube by integrating the above elemental volume for 'x' varying from 0 to h,

That's an intuitively pleasing result because it tells us that the volume of the tube is in between the volume of a cone and that of a cylinder having the same base radius and height.

Applying the result:

For the toothpaste tube I was using, R=1.6 cm and h=13.8 cm which gives a volume of about 55.5 ml as per the formula derived above. Since the tube is brand new, it's likely to have a bulging profile as opposed to the triangular one assumed above. So, the volume would actually be slightly larger than the calculated value. Let's take it as 60 ml. The net weight marked on the tube is 150 gm. Hence the density of the paste is (150 gm)/(60 ml) = 2.5 gm/ml, that's two and a half times the density of water.

No wonder, however small amount of toothpaste you put into water, it's bound to sink!