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Arjun Sarwal - intern, OLPC

Email : arjun at laptop dot org

IRC  : arjs on #olpc, #sugar, #olpc-devel

Website :

Demonstrating Measure Activity during the learning workshop. (Image credits: isforinsects)

Areas of involvement

Check out Measure

Please see the Measure page and help us develop educational activities and content. Also give your feedback on how the Activity can be improved.

Cow Power

Have a look at the alternative power solution that we are trying to develop for the pilot project in Mumbai Cow Power and give your feedback

Medical Applications

If you are interested in developing medical applications around the XO, or are a Doctor/Biologist who can help us with perspectives, please join the "Library" mailing list and also add your name in the volunteers section of the health page

Things I am working on these days

  • Learning how to configure school server, doing customization and other XO related tricks etc
  • Working on developing Measure Activity and re-organizing related wiki pages
  • Keyboard related bugs
  • OLPC Public Health push

Hand crank

Summary of my experience with the present crank --

  • The crank is rated 15V 1.5A
  • Cranking at the rated rpm of about 130 rpm would give one the rated current output. This is when the green LED on the crank will glow.
  • Cranking at rpms below that would give us lesser rpm hence less current, which would require more time to charge. Charging at 130 rpm would require 3 hours to charge and charging at a slower rate, would need more time to charge.
  • Initially cranking would be easy, but one would experience a slight jerk when the orange light on the laptop turns on. This indicates that actual charging has begun. Cranking would be much harder now. This is because now mechanical energy of our muscles is getting converted to electrical energy. Note that energy is always conserved (in fact lost in the conversion) and can only be converted from one form to another.
  • Specifications are not given properly . See ticket on Trac
  • Cranking is difficult. It is hard and the crank length is short. It is thus tiresome to charge the laptop with the current design of the crank.

My suggestions for improvement --

I believe in the general concept of the crank and believe that with appropriate modifications it would lead to better usability and using experience.

  • Increasing the gearing ratio of the crank. Which would be slower rotation of the crank would lead to electric current being generated from the dynamo
  • Increasing the length of the crank. Increasing the gearing ratio as given above would increase the input torque. However increasing the length of the crank would offset this effect (as the force length would become longer)
  • An idea to test out these ideas would be to organize a competition amongst college students to build a hand crank to charge the laptop

Quotations I like

  • "People today are too busy in complicated things, they forget that there can be simple solutions too" --Unknown
  • "When the going gets tough, just keep going" --Unknown
  • "First they ignore you, then they laugh at you, then they fight you, then you win." - Mahatma Gandhi
  • The "I have a dream..." speech:


I see children across my street without access to education and I want to change that

I've been lucky to have gone to school and had access to education. However I've grown up in an environment where I've seen children around me made to work, not having access to teachers or books, children just dreaming of a place called school. My association with OLPC is my chance to change that, and more. (New Delhi, India)