![]() The following figures show the results (at 10Hz is poor, but acceptable) VALUES OF THE AMPLITUDE STEP OF THE SAWTOOTH WAVE, ACCORDING TO THE FREQUENCYĪ simulation of the full PWM output can be seen in the "pwm" tab of the worksheet. ![]() ![]() By trial and error method, all parameters had to be adjusted to respect these conditions (including the sine amplitude, 37, remember?). In this case, the challenges were: to find integer increments that produced good resolution in the tension variation And ensure that the amplitude of the saw is less than or equal to 255 (to fit into an 8-bit word) at all output frequencies. The variation behavior is inverse, that is, by increasing the wave amplitude, it will be reducing the output voltage. This is done by changing the step of increasing the timer interrupt 1 (variable STEP_SAW). To change the voltage, the option with less calculations in the microcontroller is to vary the amplitude of the sawtooth wave. VALUES TO BE RELOADED IN SINE´S TIMER, ACCORDING TO THE FREQUENCY For more details, refer to the spreadsheet and the 8051 manual, remembering that the timer is in mode 1. To change the output frequency simply adjust the sine wave refresh rate, ie change the reload value of the timer 0 interrupt counter (variables T_SIN_H and T_SIN_L, which represent the 16-bit word). I will show how these values were obtained (see the spreadsheet with the calculations on the "v-f" tab).įirst the frequency. ![]() ![]() It uses pre-calculated values to load the registers used in the routines, according to the desired output frequency. In this project, I tried to prevent the microcontroller from performing calculations for voltage and frequency variables. Some good articles explaining the speed control of induction motors via V / f strategy are available in: ![]()
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