Innovative Project Ideas

Battery Charger Circuit Using SCR

The battery is charged with small amount of AC voltage or DC voltage. So if you want to charge your battery with AC source then should follow these steps, we need first limit the large AC voltage, need to filter the AC voltage to remove the noise, regulate and get the constant voltage and then give the resulting voltage to the battery for charging. Once charging is completed the circuit should automatically turned off.

The AC source is given to the step down transformer which converts the large AC source into limited AC source, filter the AC voltage and remove the noise and then give that voltage to the SCR where it will rectify the AC and give the resulting voltage to the battery for charging.

Circuit Diagram Explanation:

The AC main voltage is given to the step down transformer the voltage should be down to 20V approx. the step down voltage is given to the SCR for rectification and SCR rectifies AC main voltage. This rectified voltage is used to charge battery.

When the battery connecter to the charging circuit, the battery will not be dead completely and it will get discharged this will give the forward bias voltage to the transistor through the diode D2 and resistor R7 which will get turned on. When the transistor is turned on the SCR will get off.

When the battery voltage is dropped the forward bias will be decreased and transistor gets turned off. When the transistor is turned off automatically the diode D1 and resistor R3 will get the current to the gate of the SCR, this will triggers the SCR and gets conduct. SCR will rectifies the AC input voltage and give to the battery through Resistor R6.

This will charge the battery when the voltage drop in the battery decreases the forward bias current also gets increased to the transistor when the battery is completely charged the Transistor Q1 will be again turned on and turned off the SCR.

Auto Night Lamp Using High Power LED

Auto Night Lamp Using High Power LEDs is a circuit which turns ON the LED lights interfaced to it at night time and it turns OFF the lights automatically when it is day. Usage of LEDs is growing day by day due to the advantages they provide compared to the conventional filament bulbs or fluorescent lamps. They provide good quality of white light with a better intensity compared to others. They also consume less power compared to their alternatives. These are the advantages which the LEDs encourage us to use them compared to their alternatives.

In this article, we shall see the circuit and the working of turning on or off of high power LEDs with light intensity. The element which is used for sensing light in the circuit is the light dependent resistor. The resistance of the light dependent resistor depends on the light incident on it. If the intensity of light incident on it is more, then the resistance of the circuit decreases. If the intensity of light incident on it decreases, then the resistance of the device increases. We are making use of this property of the light dependent resistor to detect the light and thereby operate the LEDs. We are arranging twenty five light emitting diodes in an array such that five LEDs are in series and five such series LEDs are arranged in parallel.

The transistors are used in saturation mode. They are used as electronic switches in this mode. The transistor BC547 is a general purpose NPN transistor which is used to further switch the LEDs. This is a power transistor with a heat sink. The heat sink helps the transistor to dissipate the generated heat into air so that the transistor can handle higher power loads than it can do without the heat sink.

The entire circuit along with the LEDs is powered by a 12V DC power supply. A battery based DC power supply is usually preferred. However, you can use a ac rectified and regulated power supply.

The LEDs used in the circuit are high powered white LEDs. The intensity of light produced by these LEDs equals an ordinary fluorescent bulb. The lighting produced is sufficient for reading or to do any other daily activity. The circuit can be assembled on a printed circuit board with all the components neatly arranged and the LEDs placed in order. Try to place the LEDs maintaining a distance of about 1 cm between the LEDs so that the the lighting will be well distributed in your room.