Power supply failure alarm circuit

This is very useful circuit for you.Because through this circuit we will be able to know about a power failure.Here We have done some modification,its nothing but this circuit doesnt want an extra power supply for the alarm circuit.Because after the power failure alarm circuit doesnt operate with out power,But here we have attached a capacitor so through that after the power failure this capacitor can operate the alarm circuit.After giving 5V to 15V power.Then tune VR1 till alarm goes on position to off position

Mini Auto Charger Fan Circuit

This circuit is called the auto circuit which can use any electronic device

to operate it automatically. To make this circuit the cost is very

low. Any interested student can make it very easily. The main component

of this circuit is transistor. Its operation is very easy. 

The main purpose of this is to operate a charger fan

where need 6volt battery. This circuit is mainly needed when the main

power is OFF. That is called load shedding. Because at the time of  load shedding , 6volt battery operate the fan automatically.

You don’t have need to ON the switch of the fan or OFF the fan switch.

Only relay work this as a switch. The charging system is also

automatically. On the other big matter is that no over charge is

occurred of the battery. So the life time of the battery is increased. 

Component:

1.      Transistor ( npn ) – 2N2222, BC547

2.      Zener Diode - 6.8V

3.      Diode

4.       Relay - 6V

5.      Resistor – 1K, 100Ω

6.      Rechargeable Battery - 6V

7.      Fan - 6V

8.      Power supply - 6V

Operation:

This circuit is three section, input section and output section. 2N2222 transistor is used to control relay. BC547

transistor is used to control output section using relay. Zener diode

and a diode connect with BC547 transistor base as a series connection.

Zener diode always controls battery charge. It zener voltage is 6.8V which can’t overcome battery voltage.

When

power supply voltage is applied to the 2N2222 transistor base the

transistor is on. So the relay is ON relatively the output circuit is

OFF. Inverse will occurs when power supply voltage is OFF. When 2N2222 transistor

is ON then relay active only battery charging, relay deactivate the

fan. Zener diode always keeps battery voltage full (6volt).

Advantages:

1.      Need not switch ON/OFF.

2.      It depends on AC power supply come or gone.

3.      This circuit is used when you are sleeping.

4.      Easy to make

5.      Cost is very low

6.      Components are few.

7.      Battery can’t over charge.

8.      Overall efficiency is 78%.

9.      Not you, only relay can do your work.

10.  The circuit is a small project for all students.

FM Tuning Indicator Circuit

Here is an add on circuit to your FM radio for precise tuning of stations. Usually an LED indicator is provided in FM radio to see whether the station is tuned or not. But it is difficult to see the precise tuning points since the variation in the LED brightness cannot be detected easily. This circuit solves the problem.
Circuit diagram :

Precise  FM Tuning Indicator Circuit Diagram

The circuit uses the Op Amp IC CA3140 as a differential amplifier to sense the voltage level between the terminals of the tuning LED. The output of IC1 drives two LEDs one Red and one Green to indicate whether the station is precisely tuned or not. If both LEDs remain off, it indicates precise tuning. If anyone LED is on, it indicates that tuning is not precise. If both LEDs remain on, it indicates that there is no signal.
First tune the FM receiver in a station having strong signal. The tuning LED will light brilliantly. Then connect point A and B to the soldering points of the tuning LED observing polarity. Adjust VR till both the Red and Green LEDs turn off. Slowly change the tuning knob position. Any one LED will light up. So the circuit is working. Now glue the wiper of VR using adhesive to prevent its position change. Disconnect the tuning LED from the board. Now the circuit is ready to use. Power for the circuit can be obtained from the power supply of FM radio.

How to Build a100 Watt Pure Sine Wave Inverter Circuit

The circuit provided in this article shows you a simple way of building a useful liitle inverter thats easy to build and yet provides the features of a pure sine wave inverter. The circuit can be easily modified for getting higher outputs.
Let’s begin the discussion about how to build a 120 Volt, 100 watt sine wave inverter, by first learning it’s circuit functioning details:

The circuit can be basically divided in to two stages viz: the oscillator stage and the power output stage.

Oscillator Stage:

Please refer the detailed explanation about this stage in this article.

The power output stage:

Looking at the circuit diagram we can see that the entire configuration is fundamentally made up of three sections.

The input stage consisting of T1 and T2 form a discrete differential amplifier, responsible for boosting the low amplitude input signal from the sine generator.


The driver stage consists of T4 as the main component whose collector is connected to the emitter of T3.

The configuration quite replicates an adjustable zener diode and is used for settling the quiescent current of the circuit.

A full fledged output stage comprising Darlington transistors T7 and T8 forms the final stage of the circuit after the driver stage.

The above three stages are integrated with each other to form a perfect high power sine wave inverter circuit.

The best feature of the circuit is its high input impedance, around 100K which helps to keep the input sine waveform shape intact and distortion free.

The design is pretty straightforward and will not pose any problems if built correctly as per the circuit diagram and the provided instructions.

Battery Power

As we all know that the biggest drawback with sine wave inverters is its RED HOT output devices, which drastically reduces the over all efficiency of the system.
This can be avoided by increasing the input battery voltage up to the maximum possible tolerable limits of the devices.

This will help to reduce the current requirements of the circuit and thus help to keep the devices cooler. The approach will also help to increase the efficiency of the system.

Here, the voltage can be increased up to 48 volts plus/minus by connecting eight small sized 12 volt batteries in series as shown in the figure.

The batteries can be 12 V, 7 AH type each and may be tied in series for getting the required supply for the inverter circuit.








The TRANSFORMER is a made to order type, with an input winding of 48 – 0 – 48 V, 3 Amps, output is 120V, 1 Amp.

Once this is done, you can rest assured of a clean, hassle free pure sine wave output that may be used for powering ANY electrical gadget, even your computer.


Adjusting the Preset


The preset P1 may be used to optimize the sine waveform at the output and also to increase the output power to optimal levels.

Another power output stage is shown below using MOSFETs, which may be used in conjunction with the above discussed sine generator circuit for making a 150 watts high power pure sine wave inverter.























Parts List

R1 = 100K

R2 = 100K

R3 = 2K

R4,5,6,7 = 33 E

R8 = 3K3,

R9 = 1K PRESET,

R10,11,12,13 = 1K2,

R14,15 = 470E,

R16 = 3K3,

R17 = 470E,

R18,19,21,24 = 12E,

R22 = 220, 5 WATT

R20,25 = 220E,

R23 = 56E, 5 WATTS

R26 = 5E6, ½ WATT

C1 = 2.2uF, PPC,

C2 = 1n,

C3 = 330pF,

C6 = 0.1uF, mkt,

T1 = BC547B 2nos. matched pair

T2 = BC557B 2nos. matched pair

T3 = BC557B,

T4 = BC547B,

T7,9 = TIP32,

T5,6,8 = TIP31,

T10 = IRF9540,

T11 = IRF540,

Oscillator Parts List

R1 = 14K3 (12K1),

R2, R3, R4, R7, R8 = 1K,

R5, R6 = 2K2 (1K9),

R9 = 20K

C1, C2 = 1µF, TANT.

C3 = 2µF, TANT (TWO 1µF IN PARALLEL)

IC = 324