Cow Digestor Simulator

Initial Design and Specification

Based on torque and speed requirements needed to stir a viscous substance similar to honey, a 19.1V DC motor was selected during the initial design phase. It operated at a max speed of 373 RPM, delivering 202 RPM under continuous torque of 16 in.-oz.

Testing and Prototyping

• Identified discrepancies between set and actual RPM during motor testing.
• Realigned the motor shaft and optimized bearing configurations to reduce friction.

Electrical Adjustments

• Discovered the motor was receiving 24V instead of 19.1V.
• Installed a DC-DC step-down converter to supply the correct voltage.
• Resolved wiring inconsistencies and improved signal reliability.

Troubleshooting

• Used a stop-motion camera to record motor rotation and calculate RPM via frame-by-frame analysis.
• Mapped RPM to microcontroller effort levels for precise performance tracking.

Results

Successfully minimized the discrepancy between set and actual RPM through iterative mechanical and electrical improvements, ensuring stable and reliable motor operation.

Code Implementation

The Arduino code below was used to read and display real-time motor speed on a 16x2 LCD, enabling accurate monitoring and control.

#include <LiquidCrystal_I2C.h>
LCD_I2C lcd(0x27); // For a 16 chars and 2 line display

int in1 = 8; // Declaring where the module is wired
int in2 = 9;
int ConA = 10; // PWM DI/DO pin
int speed1;

void setup() {
    Serial.begin(9600);
    lcd.begin();
    lcd.backlight();
    lcd.print("RPM: ");
    pinMode(in1, OUTPUT);
    pinMode(in2, OUTPUT); 
    pinMode(ConA, OUTPUT);
}

void loop() {
    digitalWrite(in1, LOW);
    digitalWrite(in2, HIGH);

    speed1 = analogRead(A0);
    speed1 = map(speed1, 0, 1023, 0, 255);
    analogWrite(ConA, speed1); // Inject value to motor

    if (speed1 < 90) {
        speed1 = 0;
    } else if (speed1 > 253) {
        speed1 = 160;
    } else {
        speed1 = map(speed1, 90, 255, 25, 160);
    }

    Serial.println(speed1);

    lcd.setCursor(5, 0);
    if (speed1 < 100) {
        lcd.print(" ");
    }
    if (speed1 < 10) {
        lcd.print(" ");
    }
    lcd.print(speed1);
}
                        

Code Explanation

• Libraries & Initialization: Uses LCD_I2C to control the display.
• Setup: Initializes pins and LCD screen.
• Loop: Reads analog input, maps it to PWM, updates display and serial output.

Challenges and Solutions

Motor speed discrepancies were addressed through real-time monitoring and fine-tuned adjustments, resulting in improved reliability and performance consistency.