SIMPLE POOR MAN'S INVERTER [100-150 watts]

 DESCRIPTION: In this blog we clearly mentioned the steps from priciple of an Inverter to how to construct a simple 100-150 watts  inverter which is capable to drive 3 CFL BULBS & a FAN (or) 1 TUBE LIGHT & a FAN (which are basic necessities of a modern man ).Our video posted in this blog will really helpful to you.In our video we explained every concept including circuit construction & its operation is demonstrated practically.VIDEO contains ...

• What are do's & don'ts while constructing an inverter.
• Problems we faced during design.
• How to check damaged components in circuit.
• & many more.... 

              Some important points we missed in video are included in this blog.So read every point carefully.

                                      " WISH U ALL THE BEST.... "                                          

PRINCIPLE :  DC  power to AC power.

  If 12 V input dc is given from battery, output of inverter circuit  will be 230 V.

BASIC NECESSITIES: 1.Battery.

                                                            2.Circuit.

                                                            3.Transformer.

1.BATTERY: 

    -WHY? to provide DC input to the inverter circuit.

    -WHAT? car battery or auto battery or any other battery with capacity >20 Ah [30 Ah,40 Ah,70 Ah---] can be used to provide input supply.

    -WHY TO USE >20 Ah.

                  Ah= am-pear hour (It indicates how many amps of current drawn by circuit for 1 hour.)

   power = voltage*current

                  P=V*I

    Our inverter capacity is 100 watts=P.
    Input Dc voltage =12v.
        So,from above formula current is 
       I=P/V=100/12=8.3 AMPS/HOUR
   It means our circuit  draws 8.3 amperes of current  per 1 hour.So we have to provide a battery of 8.3Ah.But here there is a practical problem .when inverter is turned ON it draws high start up current i.e approximately 10 A/hr.This is more than battery capacity (8.3A/hr).So,inverter doesn't work that is why choose >20Ah,these are commonly available in market.

• The second reason is to get more backup hours.If battery is more capacity your inverter works for long hours.

2.CIRCUIT:

    COMPONENTS:

    Ic used : CD4047-1
    R=19 k ohms
    R1=R2=220 ohms
   C=0.22uf,C1=1000uf/16(or)25v
    Zenor diode-2( any code )
    C2=104pf( not necessary to use ).
     MOSFETS = Q1,Q2 (N-Channel only)

AIM OF IC-CD4047:

              To generate square wave output of 50-60 Hz frequency.Because house hold devices work at that frequency.

FREQUENCY CALCULATION:

      frequency generated by IC is calculated as follows. 

frequency(f) = 1/4.4 RC ( This formula differs for every IC's)
f= 1/4.4*19*1000*0.22*10^(-6)
 f=54.37
  approx f=50HZ
               R1&R2 resistors are used for certain voltage drop in them. So,Mosfets doesn't get damaged.You can also use 100 ohms in place of 220 ohms.

WAVE FORMS :

   CD 4047 IC generates two wave forms of opposite polarities across 10 th & 11th  pins.

                                                                                                                                                        
               These wave forms are switched by mosfets setup Q1 & Q2 and given to transformer primary.   

• IMPORTANT POINT: Square wave is combination of DC + AC voltage .So if you see multimeter reading across 10th or 11th pin it shows 6V Ac value.To see DC component value put your multimeter in DC voltage.

     

1000uf CAPACITOR USE: ( Black capacitor in circuit)

 -It smooths output waveforms.
 -It acts as a reservoir of charge.It means even if battery connection is removed inverter works for some time.(it's demonstrated in video practically)

MOSFETS:  These are used for switching purpose .Every mosfet has certain tolerance rating it is mentioned below.

* steel body above MOSFET acts as DRAIN.

MOSFETS TOLERANCE  RATING:

    IRF3205: 115 watts.

    IRFZ44 :80 watts.

    IRF540N: 150watts.

    P55NF06: 60watts.

     we used IRF540N in circuit.

WORKING:

•  Mosfets ON for -ve pulse because in inverter we use only N-channel mosfets.
• Transfomer doesn't work for P-channel.
• From circuit diagram ,if Q1 is ON Q2 will be OFF & viceversa.In this way switching process is done.

Why we connected 2 mosfets parallel in circuit ?

       When excess load is placed on output side.Mosfets share current equally & hence reduce risk of damage.

• By increasing number of mosfets inverter wattage can be increased.It does'nt mean you can turn your 150 watt circuit to 200 watts or above.It mean, Generally you can put load only up to mosfet tolerance capacity( for example if mosfet capacity is 80 watts you can put only 80watts of load but not above).By placing 2 mosfets(80 watts) in parallel you can now put load more than 80 watts.Thus we increased inverter capacity.
• Use heat sinks to protect mosfets from overheating.
• We should use only one kind of mosfets in circuit.so,that switching will be uniform,i.e you can't use a IRF540N & IRFZ44N in circuit.

3.TRANSFORMER:
         Only center tapped step up transformer is preferred for making inverter.The main aim of transformer is to step up low AC voltage to high AC voltage.

                   Primary Side Rating: 12V-0-12V  or 09-0-09 or 06-0-06                 
                   Secondary Side Rating:         300V,230V,120V or 80V

                                              

   IMPORTANT POINTS:

• We should put only 70% load on transformer.Because there will be no ideal Transformers which can show 100% efficiency,Some power losses occurs. For example. If your transformer is 100 watts capacity, only 70% i.e-70 watts of loads should be placed.

                   Similarly, If 500W transformer only 350W load  should be placed.

• You can use UPS transformer also as inverter transformer.While using UPS transformer ignore additional wires on primary side .Consider only 3 wires,One is transformer center wire which is connected to battery + ve terminal & other two wires are which connects to 2 Mosfets in UPS circuit.Some wires are ignored because UPS transformer is basically a charging Transformer,Battery of the UPS gets charged using these additional wires.In case of inverter operation you don't require these wires so we ignored.
  
            IMAGE OF UPS TRANSFORMER PRIMARY WINDINGS
• In the above image you can ignore wires connected to WHITE CLIP .The RED WIRE should be connected to battery +ve terminal,BLUE & WHITE wires are connected to Drain terminals of mosfets.
  

                     IMAGE OF UPS TRANSFORMER SECONDARY WINDINGS 

• In secondary windings BLACK WIRE is -ve .Every other wire generates different voltages 230v,120v etc.these act as +ve wire.Use Black & 230V generating wire as Output terminals of transformer.

• To check whether transformer is working or not ,connect secondary sides of it to AC MAINS (230V) and check voltage on primary side it should be equal to your transformer primary rating (12-0-12 or 09-0-09 or 06-0-06 ).

OUR INVERTER PROPERTIES:

• * You can hear little noise from ceiling fan while running on this inverter because of square wave output from transformer.It is not a SINE WAVE.Its not a problem.Practically it is very difficult to design a pure sine wave inverter.
• Our inverter is not connected to mains so to charge the battery of inverter you can use SOLAR PANEL or construct an additional circuit using bridge rectifier to charge battery from AC MAINS.

ADDITIONAL PROTECTION TO CIRCUIT:

         -Placing zenor diodes across mosfets as shown in circuit diagram  protect mosfets from excess voltage.
         -At input side place a fuse of 10 Amp or above range to protect circuit or place PN junction diode across input as shown in circuit.

PROBLEMS WE FACED DURING THE DESIGN: 

1. We intially tried to design this circuit in computer & verify output wave forms using softwares MATLAB,SIMULINK,PROTEUS & AVR.But all components used in circuit are not available in these softwares.We even tried to make SIMULATION using  near by value components but did'nt get good results.So we suggest not to use softwares ,go doing  practical it saves your huge time.
2. We tried to make inverter using IC'S 555 timer,SG3524,SG3525 but only CD4047 given better results.Other IC's are giving 230V out put not giving required current.For an inverter not only voltage current is also very important.
3.  IC'S gets damaged with simple wrong connections so avoid them.Use IC base so you can replace damaged IC with new one.
4. While replacing IC's remove battery connection. 
5. Sometimes if IC gets damaged you don't get output voltage at this time mosfets gets over heated.so,don't touch mosfets diectly.
6. Don't use duplicate mosfets they may damage your circuit.Its better if you use mosfets of same branch code.BRANCH CODE is the code you find below mosfet number.Every manufacture company has its own branch code.For example consider IRFZ44N mosfet.All IRFZ44N working will be same but branch code may differ.Some times this may cause little problem.So try to use mosfets with same branch code.

HOW TO CHECK MOSFET DAMAGED OR NOT?

          You can check mosfet using a multimeter by putting it in buzzer mode. Check whether GATE-DRAIN  & DRAIN-SOURCE  junctions are shorted or not .If they are shorted you can hear Buzzer sound this indicates mosfet is damaged.(Demonstrated practically in our video....)

        

*If anyone of above junction is shorted then also mosfet is damaged.

SOME SUGGESTIONS:

• Don't use bread boards because they can't tolerate heat.Use only PCB board.
• Be careful at transformer output.Because of 230V.
• To know whether your connections are correct.Check the voltage across Drain pins of mosfets before connecting drains to transformer primary.It should show 0.12 - 0.13 V Ac value.(input power supply is ON)
• If you are interested to  know the internal operation of every component ,download corresponding Data sheet from GOOGLE.
• To get basic knowledge on  INVERTERS operation & working .We suggest you to go through the following link containing 3 pages data sheet. ( http://www.dos4ever.com/battery/inverter.pdf )

HOW MANY HOURS YOUR INVERTER RUN?

•  It depends on your battery capacity.Number of back up hours can be calculated using the formula  

     NO.OF.BACK UP HOURS = ( BATTERY CAPACITY * INPUT VOLTAGE )/TOTAL LOAD    
Example calculation :    
 We used 70Ah battery 
 input voltage is 12 V
 If 100 watts load is placed. 
BUH( Back up hours ) = 70*12/100 = 8.4 Hours. 

OUR ACHIEVEMENTS: 

• We attached a solar panel of 100W capacity and turned our circuit in to a NANO SOLAR INVERTER.
• We demonstrated this project on occasion of our college technical fest SKOPOS-15 and got good response.We were appreciated by our college management & HOD's , Judges.

(A local news paper article regarding our project on 27th MARCH 2015 ) 

•   To link solar panel with inverter circuit you must place a converter box in between them.Due to time constraint we did'nt prepared converter circuit.We wish readers of this blog to work on converter circuit.