Mobile Cellphone Battery Charger

Charging of the cellphone battery is a big problem while travelling 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 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 pen cells gives sufficient current (1.8A) to charge the battery connected across the output terminals.

Circuit Diagram :

Mobile Cellphone Battery Charger Circuit Diagram

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 EFY 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.

Author :  Mohan kumar  Copyright : www.efymag.com

Read More..

Mobile Phone Battery Charger Circuit Diagram

Small and portable unit, Can be assembled on veroboard

Mobile phone chargers available in the market are quite expensive. The circuit presented here comes as a low-cost alternative to charge mobile telephones/battery packs with a rating of 7.2 volts, such as Nokia 6110/6150.

Circuit diagram:

 Mobile Phone Battery Charger Circuit Diagram

Parts	Description
R1	1K
R2	47R
R3	10R
R4	47R
C1	1000uF-25V
D1	LEDs any color
D2	LEDs any color
D3	LEDs any color
D4	1N4007
D5	1N4007
Ic1	LM7806
T1	9VAC Xformer 250mA
BR1	Diode bridge 1A

 

Circuit Operation:

The 220-240V AC mains supply is down-converted to 9V AC by transformer T1. The transformer output is rectified by BR1 and the positive DC supply is directly connected to the charger’s output contact, while the negative terminal is connected through current limiting resistor R2. D2 works as a power indicator with R1 serving as the current limiter and D3 indicates the charging status. During the charging period, about 3 volts drop occurs across R2, which turns on D3 through R3.

An external DC supply source (for instance, from a vehicle battery) can also be used to energies the charger, where R4, after polarity protection diode D5, limits the input current to a safe value. The 3-terminal positive voltage regulator LM7806 (IC1) provides a constant voltage output of 7.8V DC since D1 connected between the common terminal (pin 2) and ground rail of IC1 raises the output voltage to 7.8V DC. D1 also serves as a power indicator for the external DC supply. After constructing the circuit on a veroboard, enclose it in a suitable cabinet. A small heat sink is recommended for IC1.

Source :www.extremecircuits.net

Read More..

Car Mobile Phone Charger Circuit

Cellphone battery charging process when were done traveling is a big problem. Because when traveling source of power supply is generally difficult to find. If you turn on your phone then the battery continuously over time will run out within a period of five to six hours and eventually mobile phones unusable. Here is described a series of simple charger that will increase battery life two to three hours.

In principle, the charger uses a series of Limited Voltage Current Source. Generally requires cellphone battery voltage 3.6 - 6 volts DC and currents 180-200 mA to perform the charging process. Cellphone battery usually consists of three NiCd battery cells, and each cell has a voltage of 1.2 volts potential. At the speed - average low flows required to charge mobile phone battery about - about 100mA.

In this series there is a 12V voltage source consists of 8 regular battery cells (each cell 1.5 Volt) able to supply current at 1.8 A which is connected with output terminals.

The circuit is also able to monitor the battery voltage level which is in charge. And will automatically cut off the charging process when the output terminal detects a certain battery voltage level predetermined. Timer IC NE555 is used to charge and monitor the voltage level in the battery, Pin 5 (IC1) as the control voltage using a reference voltage zener voltage 5.6Volt. Voltage at Pin 6 as the threshold set by VR1 and the voltage at Pin 2 as the trigger is set by VR2.

When the cellphone battery is connected in series (the Charging Process) applied voltage on PIN2 (IC1) as a trigger would be below the value 1 / 3 Vcc and will cause the Flip-Flop in IC1 will ON and on Pin 3 (IC1) will be high (Cause transistor T1 saturation.). When the battery is full (Full Charge) then the voltage will rise and the voltage on the PIN2 (IC1) will be above the level of trigger point threshold. This will cause the Flip Flop OFF and the output will be low (transistor T1 causes the cutoff) and indirectly also the charging process will stop.

Pin 6 (Threshold IC1) is set at 2 / 3 Vcc by using VR1, transistors T1 which is used to increase the charging current. R3 value is very important to provide the charging current, by setting the value of R3 to 39 ohms then the charging current supplied approximately 180mA. This circuit can be built on any type of PCB (General Purpose PCB) for the calibration process using the DC voltage level cutoff Variable Power Supply. Connect the output terminal circuit with Variable DC Power Supply and set on 7 volts. Adjust VR1 in middle position and slowly adjust VR2 until LED1 OFF, this indicates Low Output. LED1 should turn on when the DC Variable Power Supply voltage is reduced below 5V. LED1 Status flame shown in the table below. Closed circuit with plastic casing and use a suitable connector for connecting to the Battery for Mobile.

Read More..