The Motor sketch. One Direction ON-OFF DC Motor

Transcription

1 One Direction ON-OFF DC Motor The DC motor in your Arduino kit is the most basic of electric motors and is used in all types of hobby electronics. When current is passed through, it spins continuously in one direction until the current stops. Unless specifically marked with a + or -, DC motors have no polarity, meaning that you can swap the two wires over to reverse the direction of the motor. The Motor sketch You will need a simple control circuit to turn your motor on and off. You need: An Arduino Uno A breadboard A transistor A DC motor A diode A 2.2k ohm resistor Jump wires To power the motor, you need to send 5V through it and then on to ground. This voltage spins the motor, but you have control of it. To give your Arduino control of the motor s power, and therefore its rotation, you place a transistor just after the motor. The transistor is an electrically operated switch that can be activated by your Arduino s digital pins. In this example it is controlled by pin 9 on your Arduino, in the same way as an LED except that the transistor allows you the turn the motor circuit on and off.

2 This circuit works, but it still allows the chance of creating a reverse current because of the momentum of the motor as it slows down, or because the motor could be turned. If reverse current is generated, it travels from the negative side of the motor and tries to find the easiest route to ground. This route may be through the transistor or through the Arduino. You can t know for sure what will happen, so you need to provide a way to control this excess current. To be safe, you place a diode across the motor. The diode faces toward the source of the voltage, meaning that the voltage is forced through the motor, which is what you want. If current is generated in the opposite direction, it is now be blocked from flowing into the Arduino. If you place the diode the wrong way, the current bypasses the motor and you create a short circuit. The short circuit tries to ground all the available current and could break your USB port or at the very least, show a warning message, informing you that your USB port is drawing too much power.

3 Build the circuit as shown, and open a new Arduino sketch. Choose the Save button and save the sketch with a memorable name, such as mymotor, and then type the following code: void setup() Serial.begin(9600); pinmode(9, OUTPUT); void loop() int a; if(serial.available()) a=serial.read(); If(a==49) digitalwrite(9, HIGH); delay(1000); else(a==48) digitalwrite(9, LOW); delay(1000); One Direction Speed Control DC Motor Use the same setup and use the following sketch void setup() Serial.begin(9600); pinmode(9, OUTPUT); void loop() int a; if(serial.available()) a= Serial.parseInt(); analogwrite(9,a); delay(1000);

4 Controlling Direction of DC Motor A direct current, or DC, motor is the most common type of motor. DC motors normally have just two leads, one positive and one negative. If you connect these two leads directly to a battery, the motor will rotate. If you switch the leads, the motor will rotate in the opposite direction. To control the direction of the spin of DC motor, without changing the way that the leads are connected, you can use a circuit called an H-Bridge. An H bridge is an electronic circuit that can drive the motor in both directions. H-bridges are used in many different applications, one of the most common being to control motors in robots. It is called an H-bridge because it uses four transistors connected in such a way that the schematic diagram looks like an "H." Understanding the L298 module connections Consider the image match the numbers against the list below the image: 1. DC motor 1 + or stepper motor A+ 2. DC motor 1 - or stepper motor A V jumper remove this if using a supply voltage greater than 12V DC. This enables power to the onboard 5V regulator

5 4. Connect your motor supply voltage here, maximum of 35V DC. Remove 12V jumper if >12V DC 5. GND 6. 5V output if 12V jumper in place, ideal for powering your Arduino (etc) 7. DC motor 1 enable jumper. Leave this in place when using a stepper motor. Connect to PWM output for DC motor speed control. 8. IN1 9. IN2 10. IN3 11. IN4 12. DC motor 2 enable jumper. Leave this in place when using a stepper motor. Connect to PWM output for DC motor speed control 13. DC motor 2 + or stepper motor B+ 14. DC motor 2 - or stepper motor B- void setup() Serial.begin(9600); pinmode(4, OUTPUT); pinmode(5, OUTPUT); void loop() int a; if(serial.available()) a=serial.read(); If(a==49) digitalwrite(4, HIGH); digitalwrite(5, LOW); delay(1000); else(a==48) digitalwrite(4, LOW); digitalwrite(5, HIGH); delay(1000);

6 Controlling Speed and Direction of DC Motor // connect motor controller pins to Arduino digital pins // motor one int ena = 10; int in1 = 9; int in2 = 8; // motor two int enb = 5; int in3 = 7; int in4 = 6; void setup() // set all the motor control pins to outputs pinmode(ena, OUTPUT); pinmode(enb, OUTPUT); pinmode(in1, OUTPUT); pinmode(in2, OUTPUT); pinmode(in3, OUTPUT); pinmode(in4, OUTPUT); void demoone() // this function will run the motors in both directions at a fixed speed // turn on motor A digitalwrite(in1, HIGH); digitalwrite(in2, LOW); // set speed to 200 out of possible range 0~255 analogwrite(ena, 200); // turn on motor B digitalwrite(in3, HIGH); digitalwrite(in4, LOW); // set speed to 200 out of possible range 0~255 analogwrite(enb, 200); delay(2000);

7 // now change motor directions digitalwrite(in1, LOW); digitalwrite(in2, HIGH); digitalwrite(in3, LOW); digitalwrite(in4, HIGH); delay(2000); // now turn off motors digitalwrite(in1, LOW); digitalwrite(in2, LOW); digitalwrite(in3, LOW); digitalwrite(in4, LOW); void demotwo() // this function will run the motors across the range of possible speeds // note that maximum speed is determined by the motor itself and the operating voltage // the PWM values sent by analogwrite() are fractions of the maximum speed possible // by your hardware // turn on motors digitalwrite(in1, LOW); digitalwrite(in2, HIGH); digitalwrite(in3, LOW); digitalwrite(in4, HIGH); // accelerate from zero to maximum speed for (int i = 0; i < 256; i++) analogwrite(ena, i); analogwrite(enb, i); delay(20); // decelerate from maximum speed to zero for (int i = 255; i >= 0; --i)

8 analogwrite(ena, i); analogwrite(enb, i); delay(20); // now turn off motors digitalwrite(in1, LOW); digitalwrite(in2, LOW); digitalwrite(in3, LOW); digitalwrite(in4, LOW); void loop() demoone(); delay(1000); demotwo(); delay(1000);