Showing posts with label Saturday Special. Show all posts
Showing posts with label Saturday Special. Show all posts

Saturday, 3 September 2011

Now Charge your Mobile Phone with your sweet voice

Scientists have come up with a way to harness the energy in sound waves to power electronic gadgets :

Early prototypes harnessing new phone-charging technology require users to scream into their cell phone in order to boost their batteries, but future designs should have a better balance between decibels and power. Photo: Mango Productions/CORBIS SEE ALL 38 PHOTOS
Normally, chatting aimlessly is a surefire way to wind up with a dead cellphone battery. But researchers at South Korea's Sungkyunkwan University have discovered a technique that could use the sound of your voice to charge your phone. Here, a brief guide:



Can you really power a cellphone by talking into it?
In theory, yes. Although for now you really have to shout to give your battery much of a boost. A prototype needed 100 decibels — the equivalent of noisy traffic or a jet passing overhead — to generate 50 millivolts of electricity. That's enough to give a smartphone battery a lift, but far from the 5 to 12 volts needed to properly charge the typical mobile device. So don't expect to find voice-charged phones in stores any time soon. But the lead researcher, Sang-Woo Kim of Sungkyunkwan University's nanotechnology institute, is confident that tinkering with the design will make this technology more practical.

How does it work?
The scientists trapped nano-scale strands of zinc oxide between two flexible electrodes. Incoming sound waves hit a sound-absorbing pad on top of the device, causing the tiny zinc wires to compress and release. The movement generates a tiny electrical current. And your voice isn't the only sound the nanogenerator can convert into power. Music or any background noise, such as the sound of traffic, will also work.

Would this only work with phones?
No, there are plenty of other possible applications. The same technology, once perfected, also could be used to recharge electric cars by tapping into the energy in traffic noise. Sound-insulating walls along highways also could trap and store the sound of passing vehicles, both reducing noise levels and capturing wasted energy.

Is sound the only untapped source of electricity out there?
Hardly. As the hunt for alternative energy intensifies, "energy scavenging" is becoming a hot pursuit. In two of Tokyo's busiest subway stations, scientists are using power-absorbing floor tiles that store energy generated every time a passenger steps on them. Researchers have also figured out how to use the human heartbeat to charge MP3 players. "Our nanogenerators are poised to change lives in the future," says Zhong Lin Wang of Georgia Institute of Technology, whose team harnessed the energy of the human heart using nanowires so small that 500 could fit in a human hair. "Their potential is only limited by one's imagination."

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CREATE YOUR OWN MOBILE CHARGER IN HOME


            Charging of the cellphone battery is a big problem while traveling as power supply source is not generally accessible. If you keep your cellphone switched on continuously, its battery will go flat within five to six hours, making the cellphone useless. A fully charged battery becomes necessary especially when your distance from the nearest relay station increases. Here’s a simple charger that replenishes the cellphone battery within two to three hours. Basically, the charger is a current-limited limited voltage source. Generally, cellphone battery packs require 3.6-6V DC and 180- 200mA current for charging. These usually contain three NiCd cells, each having 1.2V rating. Current of 100mA is sufficient for charging the cellphone battery at a slow rate. A 12V battery containing eight pin cells gives sufficient current (1.8A) to charge the battery connected across the output terminals. The circuit also monitors the voltage level of the battery. It automatically cuts off the charging process when its output terminal voltage increases above the predetermined voltage level.


                  Timer IC NE555 is used to charge and monitor the voltage level in the battery. Control voltage pin 5 of IC1 is provided with a reference voltage of 5.6V by zener diode ZD1. Threshold pin 6 is supplied with a voltage set by VR1 and trigger pin 2 is supplied with a voltage set by VR2. When the discharged cellphone battery is connected to the circuit, the voltage given to trigger pin 2 of IC1 is below 1/3Vcc and hence the flip-flop in the IC is switched on to take output pin 3 high. When the battery is fully charged, the output terminal voltage increases the voltage at pin 2 of IC1 above the trigger point threshold. This switches off the flip-flop and the output goes low to terminate the charging process. Threshold pin 6 of IC1 is referenced at 2/3Vcc set by VR1. Transistor T1 is used to enhance the charging current. Value of R3 is critical in providing the required current for charging. With the given value of 39-ohm the charging current is around 180 mA. The circuit can be constructed on a small general purpose PCB. For calibration of cut-off voltage level, use a variable DC power source. Connect the output terminals of the circuit to the variable power supply set at 7V. Adjust VR1 in the middle position and slowly adjust VR2 until LED1 goes off, indicating low output. LED1 should turn on when the voltage of the variable power supply reduces below 5V. Enclose the circuit in a small plastic case and use suitable connector for connecting to the cellphone battery.
Note : At lab, the circuit was tested with a Motorola make cellphone battery rated at 3.6V, 320 mAH. In place of 5.6V zener, a 3.3V zener diode was used. The charging current measured was about 200 mA.The status of LED1 is shown in the table.

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