Wireless Systems Design

Human Power Charges Handsets

Have you ever seen those emergency-radio products that receive power from a hand-crank mechanism? Well, now the same type of mechanism is available for mobile phones. The FreeCharge hails from a company called FreePlay. Essentially, it converts human mechanical energy into electricity.

FreeCharge is a fully functional energy source for mobile phones. It incorporates a winding handle to power a handset anytime and anywhere (See Photo). As a generic unit, the FreeCharge is customized for major brand families through the use of an adapter module. That module utilizes the relevant connectors to allow charging from an AC/DC adapter. It also supplies power to the handset.

The product incorporates the following: a winder handle; gearbox; alternator; rectification; power conditioning; intermediate battery storage cells; an energy-effort-input charge indicator; and a power-output socket. The internal battery can be charged by the human-powered alternator or an AC/DC adapter. Energy is stored in the internal battery. It can be supplied to the mobile phone upon demand.

At the heart of this device is a crank-driven alternator. It measures 54 mm in diameter with a height of 11 mm. As a miniaturized electric machine, it makes the most of input torque from the user by generating more current from less winding. Even small-muscled users can produce a useful amount of energy. The FreeCharge also limits the long-term wear and tear on the cranking mechanism by more muscular users. A high-power density keeps the alternator's size in check without sacrificing the amount of current that's put out by the tiny dynamo.

The adapter module provides the interface between the mobile phone and the charger unit. Brand-specific power-delivery protocols are formed by the electronics that are contained within the adapter module. That module is situated at one end of the power cord. To form one unit, the power cord attaches to the charger's body. The adapter DC input socket also is incorporated into the adapter module.

If an average input effort is applied for 45 sec., the device will permit a call that lasts between 4 and 5 min. (depending on the mobile phone used). It will provide several hours of standby time. The FreeCharge is equipped with a light-emitting-diode (LED) effort-input charge indicator. The optimal winding input energy is reached as the LED illuminates. If the user exerts more effort, however, more energy is supplied to the mobile phone. Talk times are then extended proportionately.

If the FreeCharge is energized while it's attached to the handset, the generated electricity charges the handset battery as well as its internal battery. The casing employs co-molding techniques to provide an inlayed, rubberized soft-touch feature. This feature enhances the product's usability and ruggedness.

The adapter-module range will cover about 80% of the current installed base. It will expand appropriately as new mobile phones are introduced in the marketplace. The suggested retail price of FreeCharge is $65.

FreePlay Ltd.
Unit 12, Montague Industrial Park, Montague Dr., Montague Gardens 7441, South Africa; +27 21 551 2002, FAX: +27 21 551 2096, www.freeplay.net.

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