Dynamo-LED based cycle safety light

Sanjay & Pratap

This is the second post in the series of building more practical circuit applications that children can use in their daily life and show their friends and family. The first post was here, Cycle Safety light – C3STREAM Land Designs (auraauro.com)

The cycle safety light in the previous post relied on a 9-V battery which runs out or has to be recharged. Ashwin, a friend of Ajay (who built the previous application) decided to go one better than his friend and get rid of the battery altogether. To this end, he relied on a DC motor to generate the power to light up an LED.

The fact that a DC motor when mechanically rotated generates a voltage was known to the kids. They took advantage of this fact to use the rotation of the bicycle wheel on a vertical axis to rotate a DC motor on a horizontal axis. See the pictures to see how he accomplished this. He fixed a wheel of the required diameter to the DC motor axle. The diameter is such that it touches the bicycle wheel at a single point along both their circumferences. Thus, when the bicycle wheel rotates, it rotates the DC motor as well. Pretty ingenious isn’t it? God, these kids are creative.

Take a look at the pictures and the video which is the final demonstration. Pratap and I helped the kids a bit, mostly with materials and some muscle with lifting the bike, rotating the wheel, and holding the torch lights. But this was the kids’ brainchild through and through. He and I were just the laborer and the quartermaster. I think what we have here is a local and practical implementation of what the government is trying to achieve via the Atal Tinkering Labs.

At the end of the day, my heart was filled with bursting. There is so much joy in these things. Why did it take me so long to discover this sort of Joy?