Practicum Report 3rd Microcontroller System

PRACTICUM REPORT: 3RD MICROCONTROLLER SYSTEM PWM ATMEGA 16 SUBMITTED BY : Michael Kurniawan 2018123456 ELECTRICAL ENGINEERING DEPARTMENT UNIVERSITY OF CINCINNATI 2022 I. PURPOSE OF THE EXPERIMENT In this experiment, students are expected to be able to run PWM on the atmega16 minimum system. II. THEORETICAL BASIS PWM is a control application which is a pulse width change technique. PWM pulse width modulation is applied to periodic signals that have a fixed frequency. The application of PWM is a periodic signal or has a fixed frequency that is used to control the intensity of the lights, motor speed, and electric heaters. The following is a digital signal with a high state width marked Thigh and a low state width marked Tlow: Figure 1. Example of a periodic signal The pulse change in question is a comparison change with the term duty cycle used to indicate this period with the formulation: 𝑇 𝐻𝑖𝑔ℎ Duty Cycle = 𝑃𝑒𝑟𝑖𝑜𝑑𝑒 x 100% When PWM signals with duty cycles of 25%, 50%, and 75% are applied to power control, the signals used are periodic handles that have on and off states. The on state means that the voltage is zero. If the duty cycle signal is below 100% at the load then in one period the load does not receive voltage. To run the PWM program, 3 timer register units are required, namely: A. Timer/counter control register ttcr to determine the PWM mode. B. Timer/counter register pcrp, used to determine the frequency modulation. C. Output compare register or OCR to determine its duty cycle value. In the atmega16 microcontroller, there are several PWM modes. The PWM mode that will be discussed is fast PWM mode. In fast PWM mode, the greater the OCR value, the greater the resulting duty cycle. The PWM output will be high logic after the top value is reached until the OCR value and then will be low logic until the top value is reached again. The working principle of the PWM phase can be seen in the following figure: Figure 2. working principle of PWM vase To calculate the working cycle, the formula is used: 𝑂𝐶𝑅 D = 1+𝑇𝑂𝑃 𝑥 100 To determine the PWM frequency is calculated by the formula: ƒ𝑐𝑙𝑜𝑐𝑘 ƒPWM=(𝑁𝑥(1+𝑇𝑂𝑃)) While to determine the PWM residution is used with the formula: R PWM = log (𝑇𝑂𝑃+1) 𝑙𝑜𝑔2 N is the prescaller factor (1,8,64,256 or 1024), and TOP is the highest value of the counter setting. Table 1. clock select Bit description CSO2 CSO1 CSO0 DESCRIPTION 0 0 0 NO CLOCK SOURCE 0 0 1 CLK I/O (NO PRESCALING) 0 1 0 CLK I/O/8 (FROM PRESCALING) 0 1 1 CLK I/O/64 (FROM PRESCALING) 1 0 0 CLK I/O/256 (FROM PRESCALING) 1 0 1 CLK I/O/1024 (FROM PRESCALING) 1 1 0 EXTERNAL CLOCK SOURCE ON TO PIN 1 1 1 EXTERNAL CLOCK SOURCE ON TO PIN Table 2.wave form generation mode bit description MODE WGMO1 WGMO0 TIMER/COUN (CTC0) TOP TER MODE OF UPDATE OF TCV0 OCR0 FLAG OPERATION SET-ON 0 0 0 NORMAL 0xff IMMEDIATE MAX 1 0 1 PWM, PHASE 0xff TOP BOTTOM OC IMMEDIATE MAX BOTTOM MAX CORRECT 2 1 0 CTC R0 3 1 1 FAST PWM 0xff Table 3.compare output mode, fast PWM mode COM01 COM00 DESCRIPTION 0 0 Normal port operation, OC0 disconnected 0 1 Reserved 1 0 Clear OC0 on campare match when up counting set OC0 at BOTTOM 1 III. 1 Set OC0 on compare match, clear OC0 at BOTTOM EXPERIMENTAL METHOD A. Tools and Materials: 1. ATMEGA 16 minimum system 2. USB ASP, 3. Jumper cable, 4. Project board, 5. LED, 6. Resistor 330 ohm 7. Mikro chip studio 8. Khazama 9. Zadig. B. Experiment Steps: 1. Prepare the lab tools and materials, then arrange the lab circuit as shown below: Figure 2. PWM experiment circuit 2. Make a program according to the experiments carried out IV. RESULTS AND DISCUSSION Coding programming: #define F_CPU 8000000L #include #include #include double duty = 0; int main (void) { DDRB = (1<100) { duty = 0 } } } ISR(TIMER0_COMP_Vect) { OCR0 = (duty/100)*255; } Explanation of program coding: 1. #define F_CPU 8000000L, defines a chip that works at a frequency of 8 MHz the frequency value is adjusted to the value of the crystal used 2. #include , enter the atmega input / output library 3. #include , access the delay library 4. #include , includes the atmega interrupt library 5. double duty = 0; declaration of double return duty 6. int main (void), the command that starts every language program code 7. DDRB = (1<100) duty = 0, after duty reaches 100 then the duty value will return to 0 and be incremented by 1 continuously 15. ISR(TIMER0_COMP_Vect), interruot service routine timer 0 16. OCR0 = (duty/100)*255; calculate OCR value So, in this code, the width of the high pulse will increase continuously until all PWM waves are full high then reset again at OCR0 and continue to experience the loop as above Figure 3. PWM coding Figure 4 PWM practicum results Figure 5 oscilloscope waveform of practicum results V. TASK Turn on the LED by using PWM phase correct mode with 8 bits for the waveform can use proteus or oscilloscope replacement. Program coding: #define F_CPU 8000000L #include #include #include double duty = 0; int main (void) { DDRB = 0x08; TCCR0 = (1<100) { duty = 0 } } } ISR(TIMER0_COMP_Vect) { OCR0 = (duty/100)*255; } Program explanation: 1. #define F_CPU 8000000L, defines a chip that works at a frequency of 8 mhz the frequency value is adjusted to the value of the crystal used 2. #include , enter the atmega input/output library 3. #include , access the delay library 4. #include , includes the atmega interrupt library 5. double duty = 0; declaration of double return duty 6. int main (void), the command that starts each language program code 7. DDRB = 0x08; initializes PORT B3 as an output written in decimal hex numbers. 8. TCCR0 = (1<100) duty = 0, after the duty reaches 100, the duty value will return to 0 and increase by 1 continuously. 16. ISR(TIMER0_COMP_Vect), interrupt service routine timer 0 17. OCR0 = (duty/100)*255; calculate the OCR value Figure 6 PWM phase correct coding Figure 7 PWM phase correct experiment results Figure 8 PWM phase correct experiment waveform results Figure 9 16 bit PWM phase correct coding result waveform VI. CONCLUSION In this module 3 experiment discusses PWM with changes in duty that increases from 0 to 100. The max OCR value on the microcontroller is 255 for 8 bits, to set the PWM mode used can set tccr 0 while the OCR wave formula = (duty/100) * 255.