This Battery Charger Electronic circuit Project An LM317 voltage regulator is configured as a constant-current source. It is used to supply the 50 mA charging current to S01-S06, an array of AA-cell battery holders. Each of the battery holders is wired in series with an LED and its associated shunt resistor.

Battery charger using LM317 Circuit Diagram:

 When the battery holder contains a battery, the LED glows during charging. Each battery holder/LED combination is paralleled by a 5.1-volt Zener diode. If the battery holder is empty, the Zener conducts the current around the holder.

A timing circuit prevents overcharging. When power is applied to the circuit, timing is initiated by IC2, a CD4541 oscillator/programmable timer. The output of IC2 is fed to Ql. When that output is high, the transistor is on, and the charging circuit is completed. When the output is low, the transistor is off, and the path to ground is interrupted.

This is Dry Cell Battery Charger Circuit. That can use charger battery get that about 12 hour. When apply to power supply 9 volt the equipment that fix in the circuit use for size battery AA. If use the size C or D should devalue of Resistor RX down be 68ohm and should not lead battery come to serial while voltage in cell battery lower 1.6V.

This is the cell phone shield circuit which can be used as mobile charger. Give protection to your cell phone from unexpected use or theft working with this easy circuit. It is able to produce a loud chirping sound when someone tries to take away the mobile handset. The added function is that the circuit also operates as being a mobile charger.

Cell Phone Shield with Charger:


The circuit is powered by a step-down transformer X1 with rectifier diodes D1 and D2 and filter capacitor C1. Regulator IC 7812 (IC1) together with noise filter capacitors C2 and C3 gives regulated power source. The cell phone shield circuit uses two NE555 timer ICs: One as being a very simple astable multivibrator (IC2) and then the 2nd as being a monostable multivibrator (IC3). The astable multivibrator has timing resistors R1 and R2 but no timing capacitor since it operates with stray capacitance. Its pins 6 and 2 are directly joined to a safeguarding shield built up of 10cm×10cm copper-clad board.

The inherent stray capacitance of the circuit is enough to supplied an output frequency of about 25 kHz with R1 and R2. This arrangement gives better sensitivity and allows the circuit with hand capacitance effect. Output pulses from the oscillator are immediately assigned to trigger pin 2 of the monostable multivibrator. The monostable utilizes a low-value capacitor C6, resistors R3 and preset VR1 for timing.

The output frequency of the monostable multivibrator is altered utilizing preset/trimmer VR1 such that it is slightly less than that of the astable multivibrator. This makes the circuit standby, as soon as there is no hand capacitance present. So in the standby mode, the astable’s output is going to be low. This tends to make the trigger input of monostable become low and output become high.

The warning indicator buzzer and LED1 are joined such that they come to be active only when the output of the monostable multivibrator sinks current. During the standby state, the LED1 continues to be “off” and also the buzzer is silent. As someone attempts to take the cell phone from the defending shield, his hand comes close to the shield or makes contact with the shield, which introduces hand capacitance within the circuit. Because of this, the astable’s frequency changes, which makes the trigger pin of the monostable become low and its output oscillates. This generates chirping sound from the buzzer and also makes the LED1 blink.
The circuit can even be utilized as being a mobile charger. It delivers output of 6V at 180 mA through regulator IC 7806 (IC4) and resistor R5 for charging the cell phone. Diode D3 defends the output from polarity reversal.

The circuit could be wired on a general PCB. Enclose it inside a appropriate case with provision for charger output leads. Produce the protective shield making use of 10cm×10cm copper-clad board or aluminium sheet. Hook it up towards the circuit working with a 15cm plastic wire. Leads of all capacitors ought to be short.


Fine-tune VR1 little by little working with a plastic screwdriver until eventually the buzzer stops sounding. Get the hand nearby to the shield and fine-tune VR1 right up until the buzzer sounds. With trial-and-error method, set it up for the highest level of sensitivity such that as shortly the hand comes close to the shield, the buzzer begins chirpring and also the LED blinks. As an alternative to applying the copper cladding for shield, a metallic cell phone holder can be utilized as being the shield.

This is 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.

Simple Solar-Powered High Efficiency Charger:


Here, the MAX639 regulates its input voltage instead of its output voltage as is more customary (but less interesting). The input voltage is supplied by twelve amorphous solar cells with a minimum surface area of 100 cm2. Returning to the circuit, potential divider R2/R3 disables the internal regulating loop by holding the V-FB (voltage feedback) terminal low, while divider R1/R2+R3 enables LBI (low battery input) to sense a decrease in the solar array output voltage. The resulting deviation from the solar cells’ peak output power causes LBO (low battery output) to pull SHDN (shutdown) low and consequently disable the chip. LBI then senses a rising input voltage, LBO goes high and the pulsating control maintains maximum power transfer to the NiCd cells.

Current limiting inside the MAX639 creates a ‘ceiling’ of 200 mA for I out. Up to five NiCd cells may be connected in series to the charger output. When ‘on’ the regulator chip passes current from pin 6 to pin 5 through an internal switch representing a resistance of less than 1 ohm. Benefiting from the regulator’s low quiescent current (10 microamps typical) and high efficiency (85 %), the circuit can deliver four times more power than the single-diode configuration usually found in simple solar chargers. Coil L1 is a 100-µH suppressor choke rated for 600 mA.

There are many ways of battery charging but constant-current charging, in particular,  is a popular method for lead-acid and Ni-Cd batteries. In this circuit, the battery  is charged with a constant current that is generally  one-tenth of the  battery capacity in ampere-hours. So for a 4.5Ah battery, constant charging current would be 450 mA.