I need a help with DC to AC converter ( pure sine )

[Ahmad_k]

I found my mistake. I forgot to clear the flag PIR1.1 on each overflow of timer1 and now the signal has very good sinewave shape   

But another problem was found when i tried to modify the lookup table within the program to control the feedback from output  . I dont know why but the frequency is changed each time i change the lookuptable.

[iphone]

Ahmad_K,

I just run your DSN file ... just working as you said but once I compile to hex code, one message appear ( not error message ... just warning/advice message)

Just FYI

[Ahmad_k]

This is not an error if you run the program, a pure sinewave will be on the output but when i change the Factor "/4" in line 65 and 70 the frequency change. I think that the divide function took a lot of time that's why the frequency change, i will try using another PIC maybe the 18 series, or if SOHEL will give me any idea to solve this problem, i dont need any source code sohel, but an idea of controling the output amplitude via the feedback.

[sam_des]

Hello Ahmad_k,

Yes, your guess is correct. PIC takes lot of time for divide.  Simply scale your table so that, you don't need to divide, rather do shifting.

e.g. Sine Table generated as 128 * sin(x), x from 0->180 degrees

At run time you can calculate Pulse Width as (A * Sine table(i)) >> 7, where A is amplitude your feedback alogirthm calculated. Note that multiplication must be done before Division.
For PIC14, not having 'mul', you will have to bear with Slow Software Calculation, try to implement that multiplication inline in assembly.

Also, if you are building actual hardware, make sure you put checks on Max & Min. Pulse Width that can be used by PWM.

Try Arithmatic Waveform Synthesis - You can generate Waveform of any Freqeuncy + Shape + Amplitude.

regrads,

sam_des

[tAhm1D]

u Can also use pic16f676. r u know another way make pwm using timer1. some sample with pic16f84. how they did it? f84 have any pwm ?

Hi Sohel,
Yes it can be done with 16F676. I have studied your schematic and found out the following:
You have used Full Bridge circuit and used 6.4 KHz modulated frequency with pic Microcontroller for creating sinewave with 12v dc having 50 Hz carrier frequency.
Before the Mosfet gate, the modulating frequency is demodulated with RC Low Pass Filter and pulse of 50Hz carrier frequency of sine wave shape is applied to the Mosfet gate so that the Big Linear Iron Core Transformer see 50Hz sinewave in the primary side and produce 220v sinewave AC in the output.

Please put your comment regarding my observation and if you put some light regarding the modality of RC Low pass filter, it will be easier for me to make the sinewave inverter with Linear Transformer.

I made modified sine wave inverter with Ferrite Core with 400 VA with 90% efficiency. My modality is to made 12v Dc to 270v Dc with ETD39 Ferrite Core with SG3525 pwm ic and push-pull topology. Then making that 270v Dc to 220v AC with Full Bridge Topology with Pic 12F675. Then I made the the Battery Charger with another ETD 39 Ferrite Core and Top Switch and max. current output of the charger is 10A. Now I am trying to make Switch Mode Pure Sine wave inverter with Pic 18F1320.

If you kindly put some light on RC Low Pass Filter as I assume that you have used it in your circuit, I can try for Linear Sine wave Inverter.
With Thanks.

[sohel]

please search microchip and sonsivri u will find  pure sun light on ur project, i am busy on learning a Small "C" With flavour HI-TECH and MICROCHIP., IF u can light on it not for sun light. please help me.

[[email protected]]

Hello Ahmad_k

i want code and schematic for the above pls help me.

[rajudp]

there is  a new reference design available at microchip site http://www.microchip.com/offlineups

[Jehan]

Microchip has a new application note for DSP based UPS, this use all digital technique

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en543189

[rajudp]

here is 16f72 ASM file

http://www.mediafire.com/file/yyfz4y1mmmn/pic16f72.rar

Regrds

Please give the password for download

[king]

Hi!

I have generated 3 sine waves using Proton and PIC16f876A (Xtal= 20MHZ)  and currently these three waves are not 120 degree apart from each other but two are of same phase and one is 180 degree out of phase.Out of three sine waves two has been produced using HPWM and the third one using Software PWM which has same frequency as HPWM (19.56 KHZ), Now the problem which i am facing is that the sine wave produced using software pwm is not pure as other two produced by HPWM and also the peak voltage is different from HPWM Sine waves, i have attached the screen shots, Proteus file, and HEX file.Please do help me in solving this problem. Any kind of help will be highly appreciated.

Yellow = Phase 1
Pink = Phase 2 (180 Deg out of phase)
Green = Phase 3 (Produced using Software by the help of T1mer1)


Also Phase1 and Phase2 can be used in making single phase Sine Wave Inverter.Please Reply Soon

Regards

King

[PilotPTK]

King,

Switch to a uC that has 3 HWPWM Modules.

Software PWM.. in a word.. sucks.  The Rising/Falling edges are not as sharp and the freq/duty will not be as exact as HW.

The PIC16F767 is usually a good choice for an inexpensive part with 3 HWPWM modules - I use it often.

[king]

Hi!
No Pilotpk, this is possible to generate Three Phase using PIC18F452 because if you see An843 of microchip then in there Application Note they have generated Three Phases using PIC18F452 with the help of Timer so i think little hard work would be needed to do this task and then all problems will be solved and if i will try to switch on 3HPWM channel PIC then it is not locally available in our market, i have to import it so this is one of the second issue. On the contrary i have find out one thing that if we modify the lookup table then the edges will be sharp like other two waves and I am still working on it.

Regards,

King