50 Watts Inverter Circuit

A 50 watt inverter might look quite trivial, but it can serve some useful purposes to you. When outdoors, this small power house can be used for operating small electronic gadgets, soldering iron, table top radios, incandescent lights, fans etc.

Let’s learn how to build this homemade 50 watt inverter unit, beginning with a brief description regarding the circuit diagram and its functioning:

Circuit Description

The circuit may be understood with the following points:

Referring to the figure, transistors T1 and T2 along with the other R1, R2, R3 R4, C1 and C2 together form a simple astable multivibrator (AMV) circuit. A multivibrator circuit basically is composed of two symmetrical half stages, here its formed by the left and the right hand side transistor stages which conduct in tandem or in simple words the left and the right stages conduct alternately in a kind of a perpetual “motion”, generating a continuous flip flop action.

The above action is responsible of creating the required oscillations for our inverter circuit. The frequency of the oscillation is directly proportional to the values of the capacitors or/and the resistors at the base of each transistor.

Lowering the values of the capacitors increases the frequency while increasing the values of the resistors decreases the frequency and vice versa. Here the values are chosen so as to produce a stable frequency of 50 Hz.

Readers, who wish to alter the frequency to 60 Hz, may easily do it by just changing the capacitor values appropriately.

Transistors T2 and T3 are placed at the two output arms of the AMV circuit. These are high gain; high current Darlington paired transistors, used as the output devices for the present configuration.

The frequency from the AMV is fed to the base of T2 and T3 alternately which in turn switch the transformer secondary winding, dumping the entire battery power in the transformer winding.

This results in a fast magnetic induction switching across the transformer windings, resulting the required the mains voltage at the output of the transformer.

Parts Required

You will require the following components for making this 50 watt homemade inverter circuit:

R1, R2 = 100K,

R3, R4 = 330 Ohms,

R5, R6 = 470 Ohms, 2 Watt,
R7, R8 = 22 Ohms, 5 Watt

C1, C2 = 0.22 uF, Ceramic Disc,
D1, D2 = 1N5402 or 1N5408

T1, T2 = 8050,

T3, T4 = BC316,
T5, T6 = 2N3055 (TO-220)

General purpose PCB = cut into the desired size, approximately 5 by 4 inches should suffice.

Battery: 12 volts, Current not less than 10 AH.

Transformer = 9 – 0 – 9 volts, 5 Amps, Output winding may be 220 V or 120 volts as per your country specifications

Sundries: Metallic box, fuse holder, connecting cords, sockets etc

 

Testing and Setting Up the Circuit

After you finish making the above explained inverter circuit, you may do the testing of the unit in the following manner:

Initially do not connect the transformer or battery to the circuit.

Using a small DC power supply power the circuit.

If everything is done rightly, the circuit should start oscillating at the rated frequency of 50 Hz.

You can check this by connecting the prods of a frequency meter across T3’s or T4’s collector and the ground. The positive of the prod should go to the collector of the transistor.

If you don’t own a frequency meter, never mind, you do a rough checking by connecting a headphone pin across the above explained terminals of the circuit. If you hear a loud humming sound, will prove that your circuit is generating the required frequency output.

Now it’s time to integrate the battery and the transformer to the above circuit.

Connect everything as shown in the figure.

Connect a 40 watt incandescent lamp  at the output of the transformer. And switch ON the battery to the circuit.

The bulb will immediately come ON brightly…..your homemade 50 watt inverrer is ready and may be used as desired by for powering many small appliances whenever required.

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Mobile phone call indicator

Purpose
This circuit can be used to escape from the nuisance of mobile phone rings when you are at home. This circuit will give a visual indication if placed near a mobile phone even if the ringer is deactivated. This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED.

The device must be placed a few centimeters from the cellular phone, so its sensor coil L1 can detect the field emitted by the phone receiver during an incoming call.

Device operation

When a call is coming to the mobile phone, the transmitter inside it becomes activated. The  frequency of the transmitter is around 900MHz.The  coil L1 picks up these oscillations by induction and feds it to the base of Q1. This makes the transistor Q1 activated.Since the Collector of Q1 is connected to the pin 2 of IC1 (NE555) , the IC1 is triggered to make the LED connected at  its output pin (pin 3) to blink. The blinking of the LED is the indication of incoming call.

The signal detected by the sensor coil is amplified by transistor Q1 and drives the monostable input pin of IC1. The IC's output voltage is doubled by C2 & D2 in order to drive the high-efficiency ultra-bright LED at a suitable peak-voltage.

Note:

• Stand-by current drawing is less than 200µA, therefore a power on/off switch is unnecessary.
• Sensitivity of this circuit depends on the sensor coil type.
• L1 can be made by winding 130 to 150 turns of 0.2 mm. enameled wire on a 5 cm. diameter former (e.g. a can). Remove the coil from the former and wind it with insulating tape, thus obtaining a stand-alone coil.
• A commercial 10mH miniature inductor, usually sold in the form of a tiny rectangular plastic box, can be used satisfactorily but with lower sensitivity.
• IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less.
• Any Schottky-barrier type diode can be used in place of the 1N5819: the BAT46 type is a very good choice.

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