Organize and Share your Electronics the way you want. Sign-Up for a free account now. It takes only 30 seconds!

Solar Cell Phone Charger

Solar Cell Phone Charger

This little gadget uses a small 3 volt solar cell to charge a 6 volt NiCad battery pack which, in turn, may be used to charge many models of cell phones and other portable devices. The circuit scavenges energy from the solar cell by keeping it loaded near 1.5 volts and trickle charges the internal battery pack with current pulses.
The simple circuit isn’t the most efficient possible but it manages a respectable 70% at 100 mA from the cell and 30% when the cell is providing only 25 mA which is actually pretty good without going to a lot more trouble or using more exotic components.

Here is how it works:
When the voltage on the emitter of Q1 rises a little over 1.5 volts, both transistors turn on quickly, snapping on due to the positive feedback through R5 and C2. The current increases in L1 through Q2 until the voltage across the cell drops somewhat below 1.5 volts. The circuit then switches off quickly and the voltage on the collector of Q2 jumps up, turning on D1, allowing the inductor current to flow into the battery. Once the inductor has discharged into the battery, the process starts over. The circuit can charge higher voltage batteries without any circuit changes since the voltage will jump up quite high on the collector when the transistors turn off. The circuit should not be operated without a battery attached. For a little more efficiency, increase R5 in proportion to the voltage increase on the battery. (For example, double R5 for charging a 12 volt battery.) A NiCad battery was chosen because they are particularly forgiving of overcharging, simply converting the excess current into heat.

Visit Here for more.

 

More Articles to Read

Estimating Power for ADSP-BF561 Blackfin® Processors
Estimating Power for ADSP-BF561 Blackfin® Processors
Teach Your Arduino to Switch Itself Off!
Teach Your Arduino to Switch Itself Off!
Control a tracked robot with your mind (or joystick)
Control a tracked robot with your mind (or joystick)
A 400W (1kW Peak) 100A electronic load using linear MOSFETs
A 400W (1kW Peak) 100A electronic load using linear MOSFETs
Shirt Pocket Transceiver with the Si5351 and OLED
Shirt Pocket Transceiver with the Si5351 and OLED
All metal C930e webcam
All metal C930e webcam
The Soldering Tools That Make Your Life Easier
The Soldering Tools That Make Your Life Easier
App note: Operation evaluation of ultra low ON resistance MOSFET supporting quick charge for 1 c ...
App note: Operation evaluation of ultra low ON resistance MOSFET supporting quick charge for 1 cell Lithium ion battery protection
Synthesized Sidetone
Synthesized Sidetone
App note: Application precautions: Power MOSFET application notes
App note: Application precautions: Power MOSFET application notes

Top




Shares