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Simple Arduino Modified Sine Wave Inverter Circuit

In this post we are going to construct a modified sine wave inverter using Arduino. We will explore the methodology of the proposed sine wave inverter and finally, we will take a look at simulated output of this inverter.


By Girish Radhakrishnan

Inverters saved us from short term power cuts at home, industries and emergency rooms. The quality of power of delivered by inverters vary depending on what kind of inverter is used. Inverters are classified into three types: square wave, modified sine wave and pure sine wave inverters.

A square wave inverter has poor quality output and contains lot of harmonic noise which may not suitable for many electronic gadgets. Its wave form goes up and down peak. But, resistive loads such as incandescent bulbs, heater and some devices which employees SMPS don’t exhibit problem with square wave inverters.

A modified sine wave or modified square wave to be precise can run most of the electronic gadgets without much issue.

The wave form goes peak up and come down to zero volt and stays for some interval and goes negative peak and come back to zero volt and cycle repeats. It has harmonic noise but not as bad as square wave and can be filtered easily. This design is used in most of the inexpensive inverters.

A pure sine wave inverter has most sophisticated design and expensive one. It can run all electronic devices including inductive loads such as motors which have problems in operating with other mentioned designs. It has no harmonics and wave form is smooth sinusoidal.

By now you know the basic difference between sine, modified sine and square wave inverters.

 In this project we are constructing an inverter which can deliver output equivalent to sine wave inverter.
The circuit can be understood better by given block diagram below:



The proposed design consists of an Arduino which generates 50Hz constant square wave. An IC 555 chopper circuit generates high frequency pulse.

The actual chopping of these two signals is done by IC 7408, which is AND gate. The mixed signal is fed to gate of MOSFET. The frequency of IC 555 can be varied for adjusting the output voltage by tuning the variable resistor.

Circuit Diagram:



  Simple Arduino Sine Wave Inverter Circuit


The constant 50Hz square wave is generated across pin #7 and pin #8 of Arduino. This flip-flop signal is fed to pin #1 and pin #4 of IC 7408. These two pins are of two different AND gates.

The high frequency chopping signal is fed to pin #2 and #5. The AND gate allows only when two inputs are high, since the Arduino frequency output is lower and IC555 higher, we get chopped signal at the corresponding gate output.

The chopped output is fed to MOSFET with a current limiting resistor for limiting the gate capacitor charging rate.  A 12V 15A or higher rated transformer can be used if you need higher wattage output.

A 400V metal oxide varistor is utilized across the output for suppressing initial high voltage surge while turning on the inverter; it could be several hundreds of volts in magnitude.

A 9V regulator is used for arduino as constant voltage source. A 1000uF or higher capacitance can be used at battery input for smooth starting and to protect the inverter from sudden voltage fluctuations.

Chopper circuit:





The chopper circuit is simple variable frequency generator, and the circuit is self-explanatory.
Now let’s see how well the frequency from Arduino is chopped by high frequency generator circuit to achieve sine wave equivalent.


   
The above simulation describes the output from arduino. It’s a simple and stable 50Hz signal.



The above simulation shows the wave form after chopping the constant 50Hz signal. The width of the chopping ratio can be adjusted by tuning the variable resistor and which also determine the output voltage.

The above chopped signal may not look like sine wave. A real sine wave inverter’s chopped wave form increase and decrease exponentially across x-axis. But begin a simple design the chopping frequency stay constant and good enough to run most of electronic gadgets. 

Program for Arduino:

//-------------Program developed by R.Girish-----------//
int out1 = 8;
int out2 = 7;
void setup()
{
pinMode(out1,OUTPUT);
pinMode(out2,OUTPUT);
}
void loop()
{
digitalWrite(out2,LOW);
digitalWrite(out1,HIGH);
delay(10);
digitalWrite(out1,LOW);
digitalWrite(out2,HIGH);
delay(10);
}
//-------------Program developed by R.Girish----------//




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31 comments:

  1. Sir I have a LED light which has 60 LED's in it the converter driving it is all burnt, the sticker on the converter specifies output 3V DC input 220V AC, can you please help me build one from scratch, its a very small circuit with few Resistance total 6 one electrolytic capacitor, 4 diodes and a Polyester PF.

    All is burnt so badly no value can be identified.

    ReplyDelete
    Replies
    1. Ajay, according to me 3 LEDs cannot be driven through a 3V supply.

      anyway you can try the following circuit, make sure the LEDs are connected in series

      http://www.homemade-circuits.com/2012/04/how-to-make-led-bulb-circuit.html

      Delete
  2. How to program an arduino board and can I do this project without arduino and chopper.

    ReplyDelete
    Replies
    1. I have explained many sinewave inverter circuits without MCU in this website, you can easily search them through the search box....

      Delete
    2. Sir on your website, I never found a search box let me know where it is?

      Delete
    3. there are two of them....one at top right and the other at bottom footer left

      Delete
  3. Hello SWAGATAM . Thanks for another helpful Post, how much wattage can i get with this design and how to design it with a charging circuit for 260AH battery . actually few months ago i have loss my modified sine wave inverter, now i want to make a new one with batter equipment's or if i sent you my old inverter circuit pictures with fault detail's for diagnose it burnt the MOSFET within a day some time it happens after a week i have checked many components and found good

    ReplyDelete
    Replies
    1. Thanks Mir, You can try the above inverter design or some other design which are explained in this website

      Charger circuit can be built separately, you can make the following for your specific application

      http://www.homemade-circuits.com/2011/12/high-current-10-to-20-amp-automatic.html

      the wattage of any inverter will depend on its mosfet, transformer power rating and the battery AH rating....you can increase these parameters appropriately for achieving any desired wattage from a given inverter design.

      Delete
  4. https://www.dropbox.com/s/lpur0269jaomykp/Untitled.png?dl=0

    check out the result.
    is this okay?
    i complie the code and simulated to proteus.,

    ReplyDelete
    Replies
    1. please explain what exactly you are trying to achieve....the image only shows a mosfet/trafo stage with a square wave output...

      Delete
    2. i did create the circuit above including the chopper and the Arduino compiled with code.,,.
      that image shows the output from the transformer., and i can see is that most likely not a sine-wave., i tried to varied the variable resistor but having same waveform output.,

      Delete
    3. I would suggest you build it practically and then check the output with a scope...because simulation may not be always right.

      Delete
  5. Hi M. Swagatam. I think Arduino, alone, is able to generate the modulated signal shown on the 2nd oscilloscope image. No 555, no add. gate. What is your opinion ? Arduino must have one (or more) counter and certainly a prescaler, as many small µ controlers have. Or maybe the freq. is too high ? It doesn't look more than 1kHz. Thx for your huge work and informative site.

    ReplyDelete
    Replies
    1. Hi Mr. Rafu, that's not correct. You can check out the following article for seeing the waveform generated by an ordinary 555 IC circuit

      http://www.homemade-circuits.com/2013/10/modified-sine-wave-inverter-circuit.html

      Delete
    2. the second waveform image above has 16 pillars on each block...multiplying it with 50Hz gives 800 so it's pretty close to 1000 Hz

      Delete
  6. i have just create a simulation of this circuit Plz check it and advice for improvement. also tell me the transformer detail plz then i will make it :

    https://drive.google.com/drive/folders/0B3ugaS2dUPGmQkcybmRvTk1tbVU?usp=sharing

    ReplyDelete
    Replies
    1. I will forward the message to Mr.Girish,

      your question will be answered soon...

      Delete
  7. Hi MIR,

    Please share wave form from your simulation.

    The transformer is 12-0-12V if you can't find in your simulator no problem (try similar specification), you have to focus on wave form than output voltage. when you try the circuit practically, you will get correct voltage.


    The chopped wave form shown in the article is from the GATE of the MOSFETs and not from the transformer. Two wave form from both MOSFETs is merged together(in the simulator), this what look like when you practically try on oscilloscope.

    I used "multisim" for simulation which is not arduino oriented, but I have used function generator in place of arduino, I excluded transformer and rest if the circuit is same.

    Don't always trust simulator they give incorrect results some time. When I tried it was giving error in during simulation and the culprit was transformer. The transformer was not optimized well in the software, so it forced me to exclude transformer. If you try it practically I am very sure that it works fine.

    Regards

    ReplyDelete
    Replies
    1. https://drive.google.com/drive/folders/0B3ugaS2dUPGmQkcybmRvTk1tbVU?usp=sharing

      Girish Radhakrishnan Thanks for your prompt reply and also Thanks for Swagatam Majumdar . i have attached the wave form from my simulator Ch A+B is from transformer output and C+D is from IC7408.

      i don't have a oscilloscope to try it practically but ill try it in few days and pls advice me which MOSFET is Suitable for a 1000 Watts output and you are using an Arduino so can you make it more functional more powerful like builtin battery charger LED's indications etc.

      Warm Regards.

      Delete
    2. Hi,
      your simulation is correct, it may not look like a sine wave.
      If you want to know how chopped square wave match the properties of sine wave, take a look at this:

      http://www.homemade-circuits.com/2013/04/how-to-modify-square-wave-inverter-into.html

      MOSFET suitable for handling 1000W load: MOSFET RFP50N06, but i am not sure is it commonly available, (or) you can connect MOSFETs in parallel to achieve the same.

      You must add automatic voltage correction circuit to your inverter for 1000W loads, which is explained in this post:

      http://www.homemade-circuits.com/2013/10/modified-sine-wave-inverter-circuit.html

      I am not sure weather it will work with this project and I am not sure weather simulator help to verify this.

      Regards



      Delete
  8. hi,
    since this is an arduino. we can add more features like checking the battery for low voltage., but the question is., how can we check the battery voltage while the inverter having an high power laod.??

    ReplyDelete
  9. Hi kikiloaw,

    Yes it is possible! Different functions must written into single program and one function should not create bugs for another function.

    Regards

    ReplyDelete
    Replies
    1. i am confuse checking the exact voltage of the battery since the inverter is in load. the battery will eventually drop voltage. i know checking the voltage but no load in present. so how we can do while this inverter is working on load?

      Delete
    2. Hi kilkiloaw,
      The battery voltage must be monitored while inverter is working.

      Delete
    3. When pulling high currents from batteries, the voltage should be monitored on-load. As an example, the ideal cutoff point for a 12VDC car battery would probably be about 10 VDC ON LOAD ! Measuring voltage off load doesn't give as accurate an idea of available power with lead/acid batteries (and some other types) because the battery will always try to restore to its nominal voltage or a bit above. Performing some experiments whilst taking measurements of voltage and current should lead to a clear understanding of the best monitoring choices for any given type of battery. Hope this helps.

      Delete
  10. Hi, i tried to simulate this but when i chop my square wave with the high frequency waveform from the 555 timer, i am only chopping either the positive portion or the negative portion. So how do I get the 2nd diagram shown in this page? Do I have to add up both the waveform to get that?

    ReplyDelete
    Replies
    1. Hi, only the positives are chopped, the negatives are at 0V, and therefore are not relevant.

      The last diagram refers to the output from the transformer, where both the half cycles can be seen due to the push pull action at the primary side of the transformer.

      Delete
  11. Hi,
    According to the given Arduino program it has error in frequency the total time period is 20ms+20ms=40ms
    so,frequency=1/40ms=25Hz

    ReplyDelete
    Replies
    1. dividing 1 by 50 gives 20ms per cycle, that's 10ms high, 10ms low

      you can change it to 10ms instead

      Delete
    2. Hi sir,

      Yes it is 10ms, please modify delay(20); to delay(10); in two places.

      Regards

      Delete

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