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At this time I will share about the series used in the usb to charge battery. Issued voltage 4.7 Volt to 5 Volt DC suitable for battery charge the phone, as well as other batteries.  Below is a circuit where the voltage is removed the usb on the computer will be strengthened by several components so that the voltage used to charge batteries more powerful and filtered, and will make it more durable and long lasting. Part List : R1 = 1 K R2 = 330 R R3 = 4K7 R4 = 300 R R5 = 27R D1 = 4.7 volt zener /1W C1 = 100uF/16V Q1 = BC548 Q2 = BC558A

24v DC is a very popular voltage used in industrial settings. This hobby circuit below was designed to accept four different 24v DC alarm input signals, which are then used to drive a single low power beeper. The beeper is a magnetic type with its own oscillator/driver. The four diodes form an “OR” gate so any one of the four inputs will cause the beeper to make noise. A CMOS version of the popular 555 timer is used to strobe the beeper on and off at about 1Hz.   Copyright: Discover Circuits

A simple NiCd battery charger powered by solar cells. A solar cell panel or an array of solar cells can charge a battery at more than 80 % efficiency provided the available voltage exceeds the ‘fully charged’ battery voltage by the drop across one diode, which is simply inserted between the solar cell array and the battery. Adding a step-down regulator enables a solar cell array to charge battery packs with various terminal voltages at optimum rates and with efficiencies approaching those of the regulator itself. However, the IC must then operate in an unorthodox fashion (a.k.a. ‘Elektor mode’) regulating the flow of charge current in such a way that the solar array output voltage remains near the level required for peak power transfer. Here, the MAX639 regulates its input voltage instead of its output voltage as is more customary (but less interesting). Solar-Powered High Efficiency Battery Charger Circuit Diagram The input voltage is supplied by twelve amorphous solar cells with a mi...

This small and bright LED lamp is telephone line powered, means it uses the power of our telephone line. There are about -40v to -50v at telephone line, LM317T is used to adjust them according to our demand. 12 white LEDs of 5mm dia is used in this lamp, are all in series to compensate the voltage. Out of four wires of telephone only red and green is of our interest. This telephone line powered LED lamp is small, efficient and bright; one can also be use this for study or desk lamp. Schematic: Telephone Line Operated LED Lamp Components Required: BR2----------------------Bridge Rectifire U2------------------------LM617T or LM317L R3-------------------------270 ohm 1/2watt R4-------------------------6.8k ohm 12 white LEDs

Ultra-low current drawing 1.5V battery supply This circuit is usable as a Night Lamp when a wall mains socket is not available to plug-in an ever running small neon lamp device. In order to ensure minimum battery consumption, one 1.5V cell is used, and a simple voltage doubler drives a pulsating ultra-bright LED: current drawing is less than 500µA. An optional Photo resistor will switch-off the circuit in daylight or when room lamps illuminate, allowing further current economy. This device will run for about 3 months continuously on an ordinary AA sized cell or for around 6 months on an alkaline type cell but, adding the Photo resistor circuitry, running time will be doubled or, very likely, triplicated. Battery Powered Night Lamp Circuit Diagram Parts: R1,R2___________1M 1/4W Resistors R3_____________47K 1/4W Resistor (optional: see Notes) R4____________Photo resistor (any type, optional: see Notes) C1____________100nF 63V Polyester Capacitor C2____________220µF 25V Electrolytic Capac...

Here is a low-cost Electronic Circuit Project of Portable Battery Powered USB Charger Circuit . This circuit is able to charge your PDAs, Ipods, Mp3 players and any device that plug in to a computer USB to charge. If you fit this circuit in a small box with a 9V battery then it will become a portable emergency USB charger. Low-Cost Portable Battery Powered USB Charger Circuit Diagram: The schematic is so simple using only few components so you can make this circuit in some minutes if all parts available with you. The circuit is using low dropout regulator IC LM7805 which is easily available in the market and it is also very cheap. The circuit takes voltage from 9V battery and step down the voltage in to a DC 5V output.