An enterprising B.E. project in tune with the environment

We all think that cell phones have become an integral part of our lives. While, that assumption by itself is questionable, a group of six COEP students have built a mobile charger using a completely renewable source of energy. Not only have they won the first firze at Techfest for their efforts, but they have also demonstrated that sustainable and renewable sources of energy can be tapped at a personal level. The following is an article from Times of India's 'Pune Mirror' which tells us about this group....

POWER WALK
This mobile charger is truly mobile. Six COEP students have built a device that can charge your cellphone battery while you take a walk
ARUNDHATI RANADE
Now your regular 20-minute morning walk can also help in recharging your cellphone battery. Don’t miss a step. It’s true! A team of six students from College of Engineering, Pune (COEP) has made this possible for those who are always on the run. Isha Nag, Aditya Nanavaty, Rushikesh Pande, Shachi Pande (all third-year production engineering students) and Sarvesh Patil, Tejas Narasimhan (second year students from the same stream) teamed up for the venture. The portable walk-in charger that they have made works on energy produced while you walk and within 20 minutes your cellphone battery could get fully charged.
WINNERS ALL
Their device bagged the first prize in the recently-concluded Tech Fest at IIT Bombay. Tejas said, “Our task at Techfest was to construct a device which uses only renewable sources of energy to produce at least 3 watts of electric power. And it was for this that we got the prize.” But even before giving in their entry for this national competition, the team was working on manufacturing an easy-to-use portable charger which uses alternative source of energy.
THE DEVICE
The device they made comprises a small spring coil attached to belts. This compact device has a single casing enclosing all necessary components along with the charging circuit with an output power of around 3.5 W. A brief walk of 20 minutes (not necessarily a constant walk) could give you a fully-charged mobile battery.
PATENT IN THE PIPELINE
The COEP team has already applied for a patent for their walk-in charger. “We have applied for the provisional patent now. During the Mumbai Techfest, some venture capitalists such as DGlight and Mellagro approached us and expressed interest in our device,” Isha said. When asked if they are ready for its commercial launch, the team expressed full confidence. According to them, the production cost of the charger is around Rs 250. “With a much more attractive and portable design on a commercial level, it could be available for Rs 350 as per our calculations,” she added.
DESIGN DETAILS
While talking about the device’s manufacturing details, Shachi and Rushikesh said, “The spring design was the crucial part of the device. We tried the device with a tin outer cover earlier. But it took whole of last week to design it to make it more attractive.” They did all the experimentation in COEP’s workshop. “The material was provided by the college which supported us throughout the venture,” they said.
CHARGE-ON!
A single pencil cell costs about Rs. 7. A walk ‘n’ charge device would generate as much energy as a AA battery in 21 minutes. If it is used for one hour daily, it would recover its cost in less than 12 days A 20 minute walk charges your cell phone for a day’s usage. It can fit in your pocket Not only mobile but could be used to charge other electronic devices such as i-pods, PMPs, GPS devices, Digital cameras The spring has a guarantee of eight years!
FUNDAMENTALS
Basic principle behind the device is similar to that of a generator or a dynamo.
A DYNAMO In simplest terms, a dynamo is an electric motor run in reverse, instead of spending energy, it saves energy. A dynamo uses magnets spinning in a metal coil to spin a shaft.The spinning shaft in turn, causes the same magnets to rotate in the coil.This generates an electric current.
WALK ‘N’ CHARGE The mobile charger uses the oscillatory movement of your legs.This is converted into rotations by a pulley onto the shaft. Repositioning of the shaft and pulley is done with the use of a prestressed coil spring.
HOW DOES IT WORK? 1 Dynamo: Captures the rhythmic movement of both legs and turns it into a rotary motion
2 Retractable string: Can be pulled out from the device to connect both legs
3 Circuit: Attached to a rechargable battery that gets charged when you walk