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Pure Sine Wave Inverter, Using IC 555

The proposed circuit generates accurately spaced PWM pulses which imitates a sine wave very closely and thus can be considered as good as its sine wave counter part design.

 Here we use  two stages for creating the required  PWM pulses, the stage comprising the ICs 741 and the other comprising the IC 555. Let’s learn the whole concept in details.

How the Circuit Functions – The PWM Stage

The circuit diagram of the proposed pure sine wave inverter can be understood with the following points:
The two op amps are basically arranged to generate the required sample source voltages for the IC 555. 
The couple of outputs from this stage is responsible for the generation of square waves and triangular waves.

pure sine wave inverter circuit

The second stage which is actually the heart of the circuit consists of the IC 555. Here the IC is wired in a monostable mode with the square waves from the op amp stage applied to its trigger pin #2 and the triangular waves applied to its control voltage pin # 5.

The square wave input triggers the monostable to generate a chain of pulses at the output where as the triangular signal modulates the width of this output square wave pulses.
The output from the IC 555 now follows the “instructions” from the op amp stage and optimizes its output in response to the two input signals, producing the sine equivalent PWM pulses.
Now it’s just a matter of appropriately feeding the PWM pulses to the output stages of an inverter consisting of the output devices, the transformer and the battery.
The Output Stage

pure sine wave inverter circuit power transistor stage

The above PWM output is applied to the output stage as shown in the figure.
Transistors T1 and T2 receive the PWM pulses at their bases and switch the battery voltage into the transformer winding according to the duty cycles of the PWM optimized waveform.

Expected PWM waveform from the above circuit
The other two transistors make sure that the conduction of T1 and T2 takes place in tandem, that is alternately so that the output o from the transformer generates one complete AC cycle with the two halves of the PWM pulses.

Parts List for the proposed homemade pure sine wave inverter circuit
R1, R2, R3, R8, R9, R10 = 10K,
R7 = 8K2,
R11, R14, R15, R16 = 1K,
R12, R13 = 33 Ohms 5 Watt,
R4 = 1M preset,
R5 = 150 K preset,
R6 = 1K5
C1 = 0.1 uF,
C2 = 100 pF,
IC1 = TL 072,
 IC2 = 555,
T1, T2 = BDY29,
T5, T6 = TIP 127,
T3, T4 = TIP122
Transformer = 12 – 0 – 12 V, 200 Watts,
Battery = 12 volts, 100 AH.


  1. hi swagatam…can u give a circuit of a small ups which we can connect to a cordless phone or wifi internet set; the problem i am facing is that during the interim period when power goes, and invertor takes over, the call drops from the cordless phone; even the wifi stops working and the screen on the computer goes blank…the internet connection breaks.

  2. Hi Sunjay,
    Thanks, Yes I'll surely design it for you, just give me a day's time, I'll inform you when it get's published.

    I am not getting notified about the posted comments, I will have to check why this is happening.

  3. Hola Swagatam una cosa como regular la frecuencia y el voltaje de salida en este inversor..gracias desde rep dominicana y que hay que hacer para aumentarlo de potencia

  4. Hi Swagatam

    Thanks for all cool and very good modified square wave inverter diagrams, love it. I think now you are almost achieving a true inverter/ UPS working however now it only lacks a single 'Error Correction' feature. 220V is actually load dependent i.e. if configured 220V for 100W but suddenly load is increased to 500W then voltage will drop. Is it possible to check for 220V AC regulation, perhaps some configuration to input 220 back and check for it, not sure.

    Many thanks and regards


  5. Thanks Sam, Yes, I am trying to figure out a Error correction circuit through LED/LDR opto coupler feedback method, hopefully I'll publish it soon once it's done.

    Thanks for keeping me inspired


  6. Hello Swagatam As regular frequency and output voltage .. This inverter REP thanks Dominican and I have to do for performance enhancement

  7. Dear swagatam,

    your circuit is amazing and i loved it.Actually i want to design a 500 watts pure sine wave inverter with power mosfets like irfp260, irfp540. Please help me regarding which mosfets to be used in place of existing transistors in your circuit, battery specifications and transformer ratings.

    Hope to here from you soon.waiting for your reply.


    • Hi Bharadwaj,

      Thanks, it's my pleasure.
      You can refer the datasheets of the respective devices and select the one which is able to handle more than 40 amps of current.
      Battery should be rated at around 150 AH and the transformer input winding should be rated at 500 watts or more.


  8. thanks swagatam for your quick reply. Actually i want to develop your PWM based simple sine wave inverter for my home purpose, i have few more doubts, hope you can spare your time for me.

    My doubts regarding

    1. Any simulation software available to test theoretically? ( like proteus )
    2. this circuit already implemented practically? ( theoretically 1000 % it works)
    3. i want to use this inverter for fans,computers,light loads, is this ok with this design or any other problems there?if yes please specify.

    Well again thanks for your reply to my previous doubts.


  9. Here in your design total six transistors are there, for 500 watts to handle 40 amps current we replace these six transistors with mosfets or some of them only?


  10. My final doubts for today,

    1.how much time this circuit can handle the load ( say at half load ) continuously without any damage. ( imagine battery is full and can supply a long time back up means amperes hours is more like 200AH or even more )

    2. Total operating life of this circuit.

    3. Please post PCB layout of this circuit if available or suggest me how to do.

    Briefly about me

    I am studying my engineering ( third year )Actually i want to design a best low cost inverter for my home, i referred a lot of websites in net, all are giving square wave inverter with different wattages and i studied drawbacks of square wave inverters like over heating of fans, reducing fan speed , well good for lighing. After lot of search i found your blog in Google search, i am very happy to see a PWM based inverter with only analog components without using little complexed Microcontrollers, but here in your blog you solved my problem by posting a low cost design.

    Thanks for your publishings,


  11. Hi Bhardwaj,

    Here are the answers to your questions:

    All thses circuits are based on my personal assumptions and simulation only and has never been tested practically.

    The best way to test it is by making it practically and not through any software.

    Being a sine wave concept, this circuit should support all types of appliances.

    Only T1 and T2 are associated with power handling, remaining are the driver transistors only, so T1 and T2 needs to be replaced with the mosfets, may be two in parallel for each channel.

    If the components are optimally calculated, the unit can run for many hours without degrading at all.

    I appreciate and thank you for your interest in the subject, however I would like to caution you regarding the results, because the circuit has not been tested practically.
    Build it step by step, first go for a smaller model and gradually modify it for the intended high power application.

    PCB can be designed only after the circuit is tested roughly and successfully.

    Thanks and Regards.

  12. thanks for the clarifications,

    i have few more ideas got in my mind after seeing your circuit for different applications.

    1. For example if we connect a 230v AC single phase motor ( medium sized motor ) at the output of the inverter, if we vary the pot (freq) value from min to max, the motor speed varies or not. otherwise i want to vary the motor speed through changing the inverter parameters.Any option is there for this application?

    2. I seen some other inverter circuits previously ( square wave type ), they are using a capacitor at inverter output or even an inductor in series. i think placing a capacitor at inverter output reduces ripples and we get even more smoothen sine wave, if yes please specify capacitor value for 500 watts.

    3. I want to make a solar panel ( say for power up a single fan ) and i don't have any idea regarding solar panels except that little basics theoretically but practically i am zero. please help me in this if it is possible practically to make a solar panel.


  13. thanks for your quick reply.

    Actually i want to connect a 230v Ac motor at output of inverter and i want to vary the speed of motor from min to max manually only like varying POT or any suitable one by manually only, what type of circuit i have to use ? motor rating 230v Ac ( medium sized motor )


  14. Actually after seeing your design i got an idea to design a electric bicycle, so my idea is to use this inverter to drive a 230V AC motor which is connected to cycle, and for changing the cycle speed say from 0% to 50 % speed or like that range, i must control the power delivered to the motor. Say motor speed depends on frequency so if we change the frequency, we can change the motor speed or any other option is there for controlling the motor speed, please let me know.


  15. if 12 or 24v DC motor can drive the Bicycle load? if yes please give me the motor specifications, it has to drive at least 70 kg load – i mean body weight of a cycle rider.

  16. i think 230v AC motor can drive large loads even two persons on cycle. if it is possible with DC motor 12v or 24v for a single person please give motor specs



  17. ok thanks for your help regarding inverter design, i will take care of electric bicycles and get back to you after implementation with results. Hope i have to do before the end of feb and tell you the results. thanks for your support.


  18. Is it ok to use high frequency toroid core transformer wound for 660Hz or must stay at 60Hz? Idea is to increase efficiency but I could be wrong .

  19. Very interesting circuit. On your output transformer you have an arrow pointing to battery positive, is this because this is a centre tap, or are you using a 2-in 2-out transformer? Thanks. Your site is getting very good!!

    • Hi,

      Thank you very much for reading and appreciating my blog!

      The transformer is a center tap type and therefore the center tap wire needs to be connected to the battery positive.


  20. hi swagatam we got a project of designing the sine wave inverter can you help me this regaed i had accessed to your post of sine wave inverter but i need some extra information

    • Hi,

      Most of the inverter designs presented in this blog have not been tested practically and are based on my assumptions only.
      If you have sufficient faith in the given explanations, you may proceed with them, I'll try my best to help you with the proceedings.


  21. Hi swagatam i got a 25AH battery, can i use it in this system, or there are some components changes that i need to do? if they are can u help outline the changes to me please.

    • Hi Okafor,

      Yes you may use it, but are you sure you have sufficient basic knowledge to build this circuit?
      I would recommend some other similar circuit for you.


  22. man i know how to build it electronics is my hobby, by the way which one do u recomend for me. the problem i have with this one; is that i dont have access to all the component like the ic 555 or the ic TL072. are they subtitutes to this components Mr Swagatam

  23. thanks i am waiting on the resistors i ordered to start building i have a question i have a 24 volts 400 watts dc motor and i need some help on building a speed controller for it i will appreciate your help.

  24. Hi, sir how are you? you are really grate person,which are helping other people, now a days I am working on HHO gas producing from tab water, but the problem is that my rectifier circuit was heat up after few second, my power supply is 12v DC and 2 Amps. can you solve my problem?

  25. hi sir,
    i think both driver transistors are configured the same,which will create a short circuit in the pus=pull stage

    • Hi Micaiah,

      R5 is for adjusting the square wave modification or the PWM, while R10 may be adjusted for getting the required frequency.

      All these should be measured using a good oscilloscope.

  26. hi sir,
    am very sorry for not checking the circuit well before commenting, i thought the signals were all coming from pin3 of the 555 i.c.
    it is right because pin2 and 3 are out of phase based on the operation mode of the i.c.
    thanks for the reply.

    • OK, not a problem….

      Pin2 generates PWM, Pin3 is responsible for clocking the output transistors.

      T3 and T4, makes sure that the clock from pin3 are made out of phase to the output transistors.

    • G'day Mr Swagatam ???
      Designing high power sine wave 230V power inverters is quite a bit more involved than the simple circuits you have drawn here. Pure sinewave inverters usually use a dc to dc converter feed to an output stage consisting of several power FET's in parallel push-pull arrangement. The drive to such a high power output stage is usually a sinewave digitally formed under a micro-controller which of course looks after all other aspects of the inverter.
      This is why such 3-6 KVA inverters are better bought commercially. Silicon Chip in Australia produced a design for a 2 KVA pure sine wave inverter and it was quite complex, cost more to build than buying one.
      I have been an electronics tech now for over 40 years and have much experience in most areas of electronics. If you want a high power 230V 50 Htz inverter, buy one out of China, you honestly can't build one cheaper.

      Regards Rob Scott

    • G'day to you Mr.Robert,

      Yes I know that and agree with you.

      I have just tried to introduce my concepts here and would like to know how these circuits would actually perform practically, especially the waveforms….I am not much worried about the power output because that entirely will depend on the selection of the transformer, output devices and the battery.
      I believe my sine wave concepts presented in this blog would at least produce waveforms better than flat square waves.

      Any way thanks very much, I appreciate your knowledge and experience, and you are welcome to my blog for presenting your expertise to the many needy hobbyists.

      Best Regards

  27. Respected Swagatam Sir,
    First of all i appreciate your work for sharing such simple inverter circuit idea with us , But my doubt is that can we directly couple Squre wave and PWM output to output stage of inverter shown in above diagram or do we need optical isolation or something for protecting pwm generator circuit from high power inverter circuit ? if we do need then what you would suggest ?
    And What is the Vcc value for PWM generation circuit ?

    • Hi SSN,

      Thanks very much!

      The PWM pulses and the 50Hz pulses are well buffered by the associated resistors and the transistors, so there's no danger to the ICs from getting damaged.
      The Vcc value is 12V, which may be directly derived from the battery itself, provided a 12V battery is used.


  28. hi,i just go through the circuit,can u just tell me how i can get the constant voltage at output and can we convert these transistors into mosfets as power device to save the space.

    Vimesh Sharma

    • Constant voltage cannot be achieved from this circuit, it will require addition of further stages.

      T1 and T2 can be replaced with mosfets with a 10K resistor connected across their gates and ground.

  29. Swagath Sir, can we use the UPS board for powering 2 fan and two tube light with adequate battery backup say 100AH or car Battery

    • If the particular UPS board and the transformer is rated at 250 watts or more only then you can use it for powering 2 fans and two tube lights, otherwise just increasing the battery power will not work.

  30. dear Swagath, i want a circuit design for the following, can you please design it for me?
    i have 50 No.of 5mm white LED, 1 No.of 12V/2AH transformer and 1 No.of 7AH zebronics battery (computer ups battery) by using this i want to make a emergency light which will work on both AC & DC and also it should turn on when the Main power is absent.

    • Connect the 220 volt tap to mains and check the output volts from the remaining taps in some sequential order, this will help you track the voltages of the respective taps.

  31. hellow Swagatam…

    i want to know if i use 2n3055 transistor instead of BDY29…
    then what will the max output power of inverter..?(neglecting transformer perameters).

    how much less power i will get by using 2n3055

    • You may get 50% less power with 2N3055 compared to BDY29.

      2N3055 will switch max 10 to 12 amps, multiply this with the number of devices on one channel and 12V.

  32. hi mr. swagatam the sqare wave from pin#2 going to T1 AND T2 is negative! what reaction will it cause¿ does it turn off the PWM pulses and the transistor so it wont conduct? correct me if im wrong…


    • Hi Mr Roger,

      Yes it does turn of the PWM, but actually it's for keeping the PWM pulses connected at 50Hz frequency or at the rate of the square wave pulses.


  33. hiiiiiiiiiiii

    anyone can upload 5kva dc-ac inverter please… i would like design my own inverter.
    so anyone can upload the circuit diagram it's the part help to me

  34. I am looking at buying a commercial inverter and you seem to know about them. Most commercial ones are rated in output Watts. I assume they have a maximum output current they can deliver. So if, for example, the load is 0.1 PF and the inverter is rated at 300W, the actual (current limted) maximum power it can deliver is 30W. Is my logic correct?

  35. helo sir. I am a lover of self development in electronics from nigeria. i read d computation u did to construct a transformer but what am confused about the way u selected the gauge of the wire. cos i want to use the method to build a 5KVA UPS. i will be glad if u can shed more light on it. thanks

    • The article is based on the information gathered from one of the books, it's not written by me, so I won't be able to help you much in this regard.

      The gauge is probably selected with the help of the given tables and their corresponding values.

  36. hi brother. will it be possible for you to design me a 12v 40 amp pulse width modulator. really in need but could not find it localy.

    thanks bro



  37. Al Salam A'likum
    i want to ask some questions:
    1- the first stage in the draw the ic1 output is pin 2 square wave and pin3 is pwm output but you write (The couple of outputs from this stage is responsible for the generation of square waves and triangular waves.) is this amistake in the draw or i have wrong understand?
    2- for the T1, T2 = BDY29, is there another one i can use instead of it? also the same for IC1 = TL 072
    3- what does (Transformer = 12 – 0 – 12 V) ?

    • hello,

      "couple of outputs" was referred to the opamp circuit not the 555 circuit.

      you can use mosfets in place of BDY29.

      you may use any good standard opamps in place of A1 and A2.

      12-0-12 means three wire transformer (center tap) with this rating.

  38. Hello sir,
    we are looking for a circuit diagram for 5 level cascaded h-bridge inverter with driver circuit. please post it for us

  39. yes sir u say r4 is for the amplitude of the wave form how can i know which position to set the pot if it's half way or all the way around for the precise wave form cause im from the carribean we don't hav those type of meters to check.

  40. Greetings,

    The waveform image doesnt make sense with regards to the circuit. If one square wave pulse + relevant triangular position is required to generate 1 PWM outpur pulse and that same square wave is used to alternate T1 and T2, then why does the image show a set of 11 PWM pulses for each half of the square wave?

    • Thanks!

      I think you are correct.

      R14 and R16 should be connected to the triangle pulses, and not to the square wave pulses, because the square wave generation has no relation with the PWMs.

  41. hi swagatam, this is sekhar.
    i want a inverter circuit diagram to run fan (80watt) with low cost. i observed a circuit readily available in the market with 40watt. cfl bulb circuit with a cost of Rs.-50 /- only. can we design a circuit cost of Rs.100/- to Rs. 150/- is it possible. if possible can u send the circuit diagram please help thanks & regards.

  42. hi, first good job. I'm going to build it because in Egypt power goes out too much if you follow the news but is there an alternative for the BDY29 transistor as I cant find it. thanks in advance. is it going to work practically?

  43. hi sir, the 555 timer can only modulate at 0-5V. but sine wave is -2.5 to 2.5v. Which device in the circuit causes the negative swing of the sine wave?


    • Hi Roger,

      the transformer is responsible for delivering the negative cycles, because it's a center tap and the two half winding are pulled in opposite directions which produces the required positive and negative cycles.

  44. Hi, I am Vignesh, an electronics hobbyist. Please suggest some pure sine wave inverter circuits that does not incorporate any PWM pulses from your blog.

    Thank You..

  45. A horizontal S ( as you said ) resembling a square wave is there in my multimeter. But when i am connecting the leads b/w secondary terminals of a 15 V ac transformer no readings is showing on putting this range. I think the transformer doesn't change the input frequency since it is a power transformet….. Is my way of taking frequency reading is ok sir ???'

    • yes it's the square wave symbol which is assigned for measuring frequency.
      The transformer secondary should definitely show a 50Hz frequency on the meter when the above range is selected.

      Your meter frequency range could be faulty or the prods are not making contact.

  46. hello Swagatam,
    i think your circuit is wrong. R14 and R15 should not be connected to square wave. in one of the comment it is said to connect to the triangular wave output.
    How it works? there is no alternating wave at 50hz frequency.

    • T6 switches T1/T2 simultaneously with the PWM pulses, while T3/T4 make sure that T1/T2 conduct alternately at 50Hz rate individually (100 times per second together alternately), it's as simple as that.

  47. It is very interesting the idea of different inverter design from your blog.
    I have following some doubts
    1). What may be the specifications of the battery ( Ah and V ) being used with a 300 W transformer to support a maximum load of 300 W ?
    2). Can you please point out a modification to any pwm inverter like this to facilitate the feature of automatic load regulation. I found a similar one in your article (posted 6 days before ), but didn't seem like satisfying the requirement.

    I think it only shutts off the ac out when the voltage rises a specified limit (say 230 V ). It doesn't stabilize the voltage at 230V at varying loads.

  48. Sir If i am gonna construct a PWM type of inverter, i have to use 24 V instead of 12 V along with a 230V/12-0-12 V transformer. Am i right ?
    I am using the series configuration of two 12 V battery banks each of which is a parallel configuration of two 12 V 20 Ah sealed lead accid batteries, thereby getting an overall specification of 24V 40 Ah.
    Now my second question is whethet this will be enough to support the required load, since by calculation Ah=900/24 =37.5 ?
    I think it will support atleast 250W for the same time period.

    • Arun, increasing voltage will decrease the current requirement of the inveter, this the only advantage of using higher voltage trafo and batt, it has no connection with a PWM type or any ordinary design, you can incorporate higher voltage concept in any design…..however for full bride designs you will require a single winding while for center tapped you will require a center tapped trafo.

      making series batery connections will not yield double AH, the AH will stick to 20AH only.

  49. Hello sir,
    Can you please describe me what section of the circuit is making the pure sine wave..i meant that what section is responsible for pure sine wave?
    thank you!

    • Hi Bro, how are you? Hope you and your family all going well.

      I am preparing to build this inverter (the 3’rd one after succeeding builder the 400 Watts inverter design circuit from your other post and the 1 KVA H-bridge with 4 N Channels mosfets).

      Before I starting to build this one, could you please advise me to the following questions:
      1. What is the closest value of the resistor + preset P1 to achieve the best amplitude setting; if I substitute it’s with 220K preset instead of 10K resistor + 1M preset as of your design (I have no 1M preset ready in hand). I still not own oscillator/frequency meter, so it would be helpful for me also if you can give me some indicator of voltage measurement at some important points.
      2. I want replace the BDY29 with IRF3205 N-Channel mosfets and feed the gates voltage with 18 Volts supply line from an additional voltage doubling stage. So the TIP127 and TIP 122 can be replaced with ordinary small transistors such as BC547 and BC557 accordingly. I think doing this would become much more efficient. Do you think it’s could make sense?
      3. Can I use 741 OpAmps instead of TL072?

      Thanks a lot for your support.

      Best regards,

    • Hi Bro,great to hear from you back!

      According to me all that you have asked makes sense.

      Use IRF540 instead as these would be easier to obtain.

      for the opamps you can use two opamps from the IC LM324, will be much suitable.

      I am not sure about the preset set up values you will have to check them out through practical assessments.

      Do everything extremely carefully and step wise only that could lead you to success.

    • Thanks for your fast response Bro,

      I think I’ll postpone building this project, since without any parameter measurements at some important points and without oscilloscope is difficult for me to achieve the correct results, especially to your unusual design like this.
      My understanding to your design is that you use the first OpAmps for astable-multivibrator which output (square wave) to be fed to the second OpAmps which is designed as Integrator, from where the triangular waveform output will be used to superimpose or chops the PWM output of the 555 IC.
      Could you please explain me why you fed back this triangular output to the 1’st OpAmps also?

      From your expert views, Is it possible to convert a sinewave produced from a Bubba oscillator or any other oscillator stage, which output swing at about +20 Volts and -20 Volts and frequency of about 50-60 HZ, which directly fed to flip-flop switch the NPN and PNP power transistors alternately without any driver IC?

      Thanks Bro, I have learned a lot from you.
      Best regards,

    • Hi Bro, sorry me again.

      Actually I have build the driver stage tomorrow with 500K variable resistor for adjusting the amplitude that I borrowed from my other finish project.
      First I just connected the 10K resistor with it and measured the output of pin 2 from IC 555. Then I add another 510K resistor to the other end of potentio and measured again these output. But I could not sensed any fluctuated swing although the frequency preset (I used 220K preset instead of 150K) has been varied from zero to max. The voltage coming out from IC 555 pin 2 was at about 7 to 8 Volts, while at pin 3 vary from 4.5 Volts to 9.5 volts (with various preset setting).

      Regards, Ferry

    • Hi Bro,

      The opamp circuit is a standard design which I borrowed from the datasheet of the opamp, so I cannot say much about its configuration, it must be correct since it's designed by the experts.

      BJTs or mosfets will never respond to sine waves directly, because each counterpart will swing to the highest voltage as soon as the saturation limit is reached which will result in a square wave output from the devices, and not sine wave.

      Again I would say that without an oscilloscope it would extremely difficult to judge whether the circuit's producing the correct required outputs, so I think an oscilloscope is a must for a design as complex as the above one.

    • Thanks for your reply Bro, I agreed with you. I'll take a break with this project.
      Btw, I read your other post of inverter circuit using 556 IC, I'll study it first and read your discussion with other readers about all aspects that might be encountered while building this. See you there in the near next days.

      Best regards, Ferry

  50. hi sir, I beg to back the scheme pwm led dimmer that works on mains voltage 6 volts. because most pwm led dimmer that I found, almost all the work on the main voltage 5v, 9v and 12v. Hopefully you can help me.Thanks

  51. Dear sir,
    I made this circuit but it didn't work, I checked it 10 times with my friends and found no error in pcb and all parts work. is this circuit really working have you made it??? I made the circuit on Proteus circuit simulation but it didn't work also, thanks in advance.

    • Dear Omar, you cannot just make any circuit directly and entirely as it is shown and hope for success. That's not the way to go.

      You will need to make each stage separately, check it separately and then proceed identically for the the remaining stages also.

      The above circuit may have some minor faults which can be easily traced and rectified.

      Did you check and confirm the frequency generating stages separately with an oscilloscope???

      Did you check the output stages separately?

      Proceed in the above manner you will definitely find the circuit working.

  52. Please Engineer Swagatam ,
    What a great opportunity to link up a gain? I have been struggling to post my comments on your BLOGSPORT but all in vain
    Thanks, am very happy a successfully circuit I built which is " pure sine wave Inverter circuit"
    And there are so many Interesting circuits from this site i need to build very soon

  53. Dear Swagatam,
    Am ever grateful for your dedication to all electronic hobbyist around the world.
    Engineer , my pure sine wave inverter i built is perfectly working , but still i need to be well versed about the following points :
    1)How to measure or between which two points should read 200HZ and 500HZ
    2) My oscillator outputs is between 8 to 9v AC when 12.8 dc is applied at the input is this ok? And what is the suppose voltage in particular for this case?
    3) What is the transformer output(secondary coil)
    I will be grateful to receive a feedback from you thanks.

    • Dear Kaluya, thanks!

      The oscillator output voltage should read 50% of the supply due to 50% duty cycle, for 12.8V supply it should show around 6,4V

      The transformer output will be as per your requirement, 120V or 220V

      pls provide me the link of the design you have built.

  54. Kaluya Moses
    Sep 26 (5 days ago)

    to Swagatam
    Hi Engineer Swagatam,
    Thanks for the quick reply, I understood the two questions i asked for a helped right a part from the two points where should i press "my negative and positive probes" in order to adjust and get 200HZ and 500HZKaluya Moses
    Sep 26 (5 days ago)

    to Swagatam
    Hi Engineer Swagatam,
    Thanks for the quick reply, I understood the two questions i asked for a helped right a part from the two points where should i press "my negative and positive probes" in order to adjust and get 200HZ and 500HZKaluya Moses
    Sep 26 (5 days ago)

    to Swagatam
    Hi Engineer Swagatam,
    Thanks for the quick reply, I understood the two questions i asked for a helped right a part from the two points where should i press "my negative and positive probes" in order to adjust and get 200HZ and 500HZ pure sine wave inverter circuit schematic it is the one which is using 3 ICS (555) and CD 4017BE so please help me engineer.

    • it'll depend on the wattage of the transformer and the battery AH, and also the output power transistor current handling capacity….these parameters can be increased to any limits for obtaining any desired power from the inverter.

  55. hello engr.
    pls i have an idea iv been pondering on. its a method, i think, pure sine wave inverter circuits can be designed. i need to discuss it with an expereienced person thats why im contacting you. pls how can one discuss privately with you. may be your facebook or whatsapp handle or emial will do.
    thanks for your anticipated reply.

  56. ok then. here is what i think.

    from my understanding of inverter operation, there is a unit to create d alternating pulses from a dc source, den this signal is fed to a tx for amplification to d desired voltage level….now d unit that creates this pulses determines if its a pure sinewave or modified or even square wave inverter.

    What if a true sinewave motor(mini ac generator) is used to produce this signal and then this sinwave signal is used to switch some power mosfets appropriately wouldn't that be a better way of producing a pure sinwave inverter?

    are my assumptions practical? shed some light on this please.


  57. Dear sir,
    I have a pc ups rated at 600va
    i measured the o/p volt it says 180v@2.2amps.

    I wish to use a ceiling fan and i tried by connecting it, it works well. fan runs for about 20 mins. with noise
    my question is that what circuit should i use at the o/p of the ups in order to reduce the noise from fan,
    Also, tell me where does ceiling fans' wattage range.

    • Dear Sherwin,

      try putting a 0.22uF/400V capacitor across the output of the inverter mains and check if the noise gets reduced, a coil can be also included in series with one of the terminals of the output for improving the effect.

    • Hi Nguyen, this circuit is a complex circuit and will require a step wise verification, checking, adjustments and tweaking, etc it cannot be built and operated at one shot.

      did you check the confirm the various stages first??

  58. dears
    I am of the similar stuff. Can you introduce yourself. Are you trustworthy enough to handle confidential research and development circuits from us to check with your resources as intellectual asset sharing. We are ready to pay if you have adequate infrastructure and fund to construct or simulate the circuit in orcad and check the credibility of my personal designs. I have one site launched for sharing it.
    equipment designer since 1982

  59. i want to use fet in place of T1 & T2 hw wil go abt it?and can i use d pwm out into d power stage of another inverter.cn there b any modification to av a steady 220volt like d sg3525 & sg3524.?cn dis b added to d sg3525 inverter to get a better sin wave output?tnx.

  60. tnk u sir bt am confused.d circuit u recommended for steady voltage says d 1N4148 diodes should go to d gates of d fet and u said i should fix d 1N4148 ends to pin5 of d 555.dnt knw which to do.tnx

    • pin5 is an alternate suggestion.

      in that case the 1N4148 could be eliminated and the collector connected directly with pin5 of the IC 555 via a 100 ohm resistor

  61. Hi sirji!
    I am Indonesian.
    I am newbie in electro. but i was read many articles those you've posted and i interest to build it from a basically.
    But sir, i have a confuse;
    1st. As i see in the circuit, R12 and R13 are 33 ohm 5 watts.
    But i have a mistake, it's couldn't to find in my town.
    I just only find 0.33 in value of 5 watt.
    Can i replace it with these 0.33?

    2nd. can i replace the T1 an T2 by 2N3055 and what value that i'll get in wattage?

    3rd. if i replace by it, what value of base resistors can i use?

    Thank you for answer sir.

    *Fadly Muslim

    • Hi Fadly,

      you can use 3nos of 100 ohm 2 watt in parallel for achieving the 33 ohm value…I hope 100 ohm/2 watt or 3 watt will be easily available in your area, yes T1/T2 can be replaced with 2N3055

      the base resistor can be the same, that is 33 ohm, if more power is required then you could reduce them a bit more to 22 ohms or 20 ohms.

  62. Finally i have finished it circuit, i made it with 2 transistors, 2n3055 that i use in tandem.

    I think, i have placed every parts like in the schema and as like you referenced to me.

    But i confuse, i don't have a battery at 100 amps and a trafo CT 12-0-12, 10 amps yet. and i want to try my first project.

    In my home i have only a trafo 12-0-12 at 3 amps, and a battery 12v 5 amps.
    Can i try it circuit by using them?

    I hope you don't bored by my questions, sir. 🙂

    • I appreciate it but sorry that's not the right way to proceed, you should build the various stages first and confirm them using proper test equipment.

      first test whether the opamps are generating the intended waveforms or not, then check the 555 response to these waveforms.

      once these are confirmed then you can integrate the relevant inputs with your power transistor stage….and do more related tests before going for the final results

  63. Lord blessings swagatam like this. I wanted to ask you if this circuit can be output to the transformer with mosfet transistors and how can I do it. I commented that I am still working on the inverter with the cd4013. a cordial greeting

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