# 3 phase SPWM using arduino mega . My target fundamental frequency is 60Hz with a switching frequency of 1980Hz **URL:** \ **Category:** Programming\ **Created:** [March 2, 2023, 6:35pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999 "2023-03-02T18:35:38Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![taet17](https://avatars.discourse-cdn.com/v4/letter/t/b5e925/32.png) [@taet17](https://forum.arduino.cc/u/taet17)\ **Post date:** [March 2, 2023, 6:35pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/1 "2023-03-02T18:35:38Z")
I have the code below that does SPWM but problem is it has a frequency of 50Hz and I don't know how to change the frequency to the desired 60Hz . And I don't know how to incorporate my switching frequency of 4000Hz. The code: ```cpp int i = 0; int j = 0; int k = 0; int x = 0; int y = 0; int z = 0; int OK = 0; int OK1 = 0; int OK2 = 0; int OK3 = 0; int OK4 = 0; int sinPWM[] = { 1, 2, 5, 7, 10, 12, 15, 17, 19, 22, 24, 27, 30, 32, 34, 37, 39, 42, 44, 47, 49, 52, 54, 57, 59, 61, 64, 66, 69, 71, 73, 76, 78, 80, 83, 85, 88, 90, 92, 94, 97, 99, 101, 103, 106, 108, 110, 113, 115, 117, 119, 121, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164, 166, 168, 169, 171, 173, 175, 177, 178, 180, 182, 184, 185, 187, 188, 190, 192, 193, 195, 196, 198, 199, 201, 202, 204, 205, 207, 208, 209, 211, 212, 213, 215, 216, 217, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 237, 238, 239, 240, 240, 241, 242, 242, 243, 243, 244, 244, 245, 245, 246, 246, 247, 247, 247, 248, 248, 248, 248, 249, 249, 249, 249, 249, 255, 255, 255, 255, 249, 249, 249, 249, 249, 248, 248, 248, 248, 247, 247, 247, 246, 246, 245, 245, 244, 244, 243, 243, 242, 242, 241, 240, 240, 239, 238, 237, 237, 236, 235, 234, 233, 232, 231, 230, 229, 228, 227, 226, 225, 224, 223, 222, 221, 220, 219, 217, 216, 215, 213, 212, 211, 209, 208, 207, 205, 204, 202, 201, 199, 198, 196, 195, 193, 192, 190, 188, 187, 185, 184, 182, 180, 178, 177, 175, 173, 171, 169, 168, 166, 164, 162, 160, 158, 156, 154, 152, 150, 148, 146, 144, 142, 140, 138, 136, 134, 132, 130, 128, 126, 124, 121, 119, 117, 115, 113, 110, 108, 106, 103, 101, 99, 97, 94, 92, 90, 88, 85, 83, 80, 78, 76, 73, 71, 69, 66, 64, 61, 59, 57, 54, 52, 49, 47, 44, 42, 39, 37, 34, 32, 30, 27, 24, 22, 19, 17, 15, 12, 10, 7, 5, 2, 1}; void setup() { Serial.begin(9600); pinMode(4, OUTPUT); // Phase A negative half cycle pinMode(13, OUTPUT); // Phase A positive half cycle pinMode(9, OUTPUT); // Phase B negative half cycle pinMode(10, OUTPUT); // Phase B positive half cycle pinMode(2, OUTPUT); // Phase C negative half cycle pinMode(3, OUTPUT); pinMode(5, OUTPUT); // Phase C positive half cycle cli(); // stop interrupts TCCR0A = 0; // reset the value TCCR0B = 0; // reset the value TCNT0 = 0; // reset the value // 0b allow me to write bits in binary TCCR0A = 0b10100001; // phase correct pwm mode TCCR0B = 0b00000001; // no prescaler TCCR2A = 0; // reset the value TCCR2B = 0; // reset the value TCNT2 = 0; // reset the value // 0b allow me to write bits in binary TCCR2A = 0b10100001; // phase correct pwm mode TCCR2B = 0b00000001; // no prescaler TCCR3A = 0; // reset the value TCCR3B = 0; // reset the value TCNT3 = 0; // reset the value // 0b allow me to write bits in binary TCCR3A = 0b10100001; // phase correct pwm mode TCCR3B = 0b00000001; // no prescaler TCCR1A = 0; // reset the value TCCR1B = 0; // reset the value TCNT1 = 0; // reset the value OCR1A = 509; // compare match value TCCR1B = 0b00001001; // WGM12 bit is 1 for CTC mode and no prescaler TIMSK1 |= (1 << OCIE1A); // enable interrupts sei(); // stop interrupts } ISR(TIMER1_COMPA_vect) { // interrupt when timer 1 match with OCR1A value if (i > 313 && OK == 0) { // final value from vector for pin 13 i = 0; // go to first value of vector OK = 1; // enable pin 4 } if (i > 313 && OK == 1) { // final value from vector for pin 4 i = 0; // go to firs value of vector OK = 0; // enable pin 13 } x = sinPWM[i]; // x take the value from vector corresponding to position i(i // is zero indexed) i = i + 1; // go to the next position if (OK == 0) { OCR0B = 0; // make pin 4 0 OCR0A = x; // enable pin 13 to corresponding duty cycle } if (OK == 1) { OCR0A = 0; // make pin 13 0 OCR0B = x; // enable pin 4 to corresponding duty cycle } if ((i == 209) || OK1 == 1) { // if i equal with 209 enable second signal OK1 = 1; // mantain if function if (j > 313 && OK2 == 0) { // final value from vector for pin 10 j = 0; // go to first value of vector OK2 = 1; // enable pin 9 } if (j > 313 && OK2 == 1) { // final value from vector for pin 9 j = 0; // go to firs value of vector OK2 = 0; // enable pin 10 } y = sinPWM[j]; // y take the value from vector corresponding to position // j(j is zero indexed) j = j + 1; // go to the next position if (OK2 == 0) { OCR2B = 0; // make pin 9 0 OCR2A = y; // enable pin 10 to corresponding duty cycle } if (OK2 == 1) { OCR2A = 0; // make pin 10 0 OCR2B = y; // enable pin 9 to corresponding duty cycle } } if ((j == 209) || OK3 == 1) { // if j equal with 209 enable third signal OK3 = 1; // mantain if function if (k > 313 && OK4 == 0) { // final value from vector for pin 5 k = 0; // go to first value of vector OK4 = 1; // enable pin 2 } if (k > 313 && OK4 == 1) { // final value from vector for pin 2 k = 0; // go to firs value of vector OK4 = 0; // enable pin 5 } z = sinPWM[k]; // z take the value from vector corresponding to position // k(k is zero indexed) k = k + 1; // go to the next position if (OK4 == 0) { OCR3B = 0; // make pin 2 0 OCR3A = z; // enable pin 5 to corresponding duty cycle } if (OK4 == 1) { OCR3A = 0; // make pin 5 0 OCR3B = z; // enable pin 2 to corresponding duty cycle } } } void loop() { } ``` ---
**Author:** ![pylon](https://avatars.discourse-cdn.com/v4/letter/p/59ef9b/32.png) [@pylon](https://forum.arduino.cc/u/pylon)\ **Post date:** [March 3, 2023, 6:48pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/2 "2023-03-03T18:48:25Z")
You get about 60Hz if you change this line: ```arduino OCR1A = 509; // compare match value ``` to ```arduino OCR1A = 425; // compare match value ``` > [@taet17](#): > > And I don't know how to incorporate my switching frequency of 4000Hz. What do you mean by "switching frequency"? The PWM frequency in the code is a bit more the 31kHz and will be above 37kHz after above change. If you want it to be 4kHz you won't get a smooth sinus any more and it will change almost the complete sketch. Why do you think you need that? ---
**Author:** ![taet17](https://avatars.discourse-cdn.com/v4/letter/t/b5e925/32.png) [@taet17](https://forum.arduino.cc/u/taet17)\ **Post date:** [March 3, 2023, 7:39pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/3 "2023-03-03T19:39:28Z")
For SPWM isn’t I compare the triangular waveform with a switching frequency of 4kHz to sine wave with 60 Hz hence the switching frequency of 4kHz. And it won’t be a good sine wave output but I have a filter at the output to filter the harmonics so 4kHz was ideal for my situation. On the note of the 4kHz , when you check in my code I have a lookup table for sine , isn’t that one somehow related to the switching frequency since the values in the table are varying gate pulses . I will change my frequency to 60 Hz . Thank you ---
**Author:** ![xfpd](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/xfpd/32/1120236_2.png) [@xfpd](https://forum.arduino.cc/u/xfpd)\ **Post date:** [March 3, 2023, 8:30pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/4 "2023-03-03T20:30:43Z")
> [@pylon](#): > > "switching frequency"? PWM for VFD. ---
**Author:** ![pylon](https://avatars.discourse-cdn.com/v4/letter/p/59ef9b/32.png) [@pylon](https://forum.arduino.cc/u/pylon)\ **Post date:** [March 6, 2023, 7:34pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/5 "2023-03-06T19:34:45Z")
> [@taet17](#): > > For SPWM isn’t I compare the triangular waveform with a switching frequency of 4kHz to sine wave with 60 Hz hence the switching frequency of 4kHz. PWM has a rectangular waveform so the answer is no. I also have no clue where the 4kHz are coming from, you can use any PWM frequency significantly higher than the sine wave frequency to get that effect given the driven component accepts PWM or a corresponding smoothening circuit is used. > [@taet17](#): > > On the note of the 4kHz , when you check in my code I have a lookup table for sine , isn’t that one somehow related to the switching frequency since the values in the table are varying gate pulses . If the switching frequency is the PWM frequency: yes, it is related but that code doesn't produce a 4 kHz frequency. As you can see the the sine table has 314 entries and shows one half wave, so the actual PWM frequency has to be 628 times higher than the sine wave frequency. The PWM frequencies are 31.4kHz and 37.7kHz. ---
**Author:** ![taet17](https://avatars.discourse-cdn.com/v4/letter/t/b5e925/32.png) [@taet17](https://forum.arduino.cc/u/taet17)\ **Post date:** [March 6, 2023, 7:51pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/6 "2023-03-06T19:51:28Z")
Okay I understand that. So using the code above , would it be possible to change the PWM frequency to 4kHz ---
**Author:** ![mrburnette](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/mrburnette/32/702556_2.png) [@mrburnette](https://forum.arduino.cc/u/mrburnette)\ **Post date:** [March 6, 2023, 8:31pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/7 "2023-03-06T20:31:42Z")
You may find this old paper of interest: [trans\_pe\_mar\_2004\_complete.pdf (utk.edu)](http://web.eecs.utk.edu/~tolbert/publications/trans_pe_mar_2004_complete.pdf) The backstory: [untitled (tinaja.com)](https://www.tinaja.com/glib/msintro1.pdf) ---
**Author:** ![pylon](https://avatars.discourse-cdn.com/v4/letter/p/59ef9b/32.png) [@pylon](https://forum.arduino.cc/u/pylon)\ **Post date:** [March 7, 2023, 6:49pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/8 "2023-03-07T18:49:14Z")
> [@taet17](#): > > So using the code above , would it be possible to change the PWM frequency to 4kHz No. that would result in a complete rewrite. The sinus wave wouldn't be that smoothed but much more squared. Why do you think you need that? ---
**Author:** ![taet17](https://avatars.discourse-cdn.com/v4/letter/t/b5e925/32.png) [@taet17](https://forum.arduino.cc/u/taet17)\ **Post date:** [March 9, 2023, 8:58pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/9 "2023-03-09T20:58:23Z")
At the output of the inverter I have an LCL filter that takes care of the square wave which is why I am using 4kHz . My project requires me to use 4kHz so that I can then filter the harmonics at the output. So I want to adjust the code above to meet the 4kHz requirements ---
**Author:** ![apf1979](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/apf1979/32/966781_2.png) [@apf1979](https://forum.arduino.cc/u/apf1979)\ **Post date:** [March 9, 2023, 9:34pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/10 "2023-03-09T21:34:52Z")
I had a similar idea once where I'd create a tone on one pin that would drive a transistor. Another pin would drive a PWM square wave signal going to a second transistor. The output would go through the two transistors in series (not a Darlington array) so there would be a PWM signal that has a frequency each time it's signal is high. IDK if that helps or generates any ideas. ---
**Author:** ![pylon](https://avatars.discourse-cdn.com/v4/letter/p/59ef9b/32.png) [@pylon](https://forum.arduino.cc/u/pylon)\ **Post date:** [March 13, 2023, 7:48pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/11 "2023-03-13T19:48:19Z")
> [@taet17](#): > > So I want to adjust the code above to meet the 4kHz requirements Feel free to change the PWM frequency to 4kHz and adapt the sine table. You then have to change the index values in the code too (i,j,k) to match the corresponding indices in your array. ---
**Author:** ![taet17](https://avatars.discourse-cdn.com/v4/letter/t/b5e925/32.png) [@taet17](https://forum.arduino.cc/u/taet17)\ **Post date:** [March 15, 2023, 5:41pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/12 "2023-03-15T17:41:28Z")
That is what I have been trying to do . Is there a way you can be able to assist ? ---
**Author:** ![pylon](https://avatars.discourse-cdn.com/v4/letter/p/59ef9b/32.png) [@pylon](https://forum.arduino.cc/u/pylon)\ **Post date:** [March 16, 2023, 11:43pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/13 "2023-03-16T23:43:14Z")
I think I did that in my last post. I won't do the programming for you but I gave you enough hints so you can do it yourself. You might have to study the datasheet and learn how PWM and timers work. And you have to understand how the current code works, otherwise modifying it will probably fail. ---
**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\ **Post date:** [September 12, 2023, 11:43pm UTC](https://forum.arduino.cc/t/3-phase-spwm-using-arduino-mega-my-target-fundamental-frequency-is-60hz-with-a-switching-frequency-of-1980hz/1096999/14 "2023-09-12T23:43:43Z")
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