Ardu motor shield Doesnt Work without cable connection

Development Boards Arduino
1

Hello, I am using a ardumoto, and have the program from sparkfun.

The program downloads using a serial cable, but it will not run without the serial cable being plugged in. I have a lithium backpack attached to it. I am using the Arduino Duemilanove. Please help. The code I am using is below:

//int pwm_a = 10; //PWM control for motor outputs 1 and 2 is on digital pin 10

int pwm_a = 3; //PWM control for motor outputs 1 and 2 is on digital pin 3

int pwm_b = 11; //PWM control for motor outputs 3 and 4 is on digital pin 11

int dir_a = 12; //direction control for motor outputs 1 and 2 is on digital pin 12

int dir_b = 13; //direction control for motor outputs 3 and 4 is on digital pin 13

void setup()

{

pinMode(pwm_a, OUTPUT); //Set control pins to be outputs

pinMode(pwm_b, OUTPUT);

pinMode(dir_a, OUTPUT);

pinMode(dir_b, OUTPUT);

analogWrite(pwm_a, 100); //set both motors to run at (100/255 = 39)% duty cycle (slow)

analogWrite(pwm_b, 100);

}

void loop()

{

digitalWrite(dir_a, LOW); //Set motor direction, 1 low, 2 high

digitalWrite(dir_b, LOW); //Set motor direction, 3 high, 4 low

delay(1000);

analogWrite(pwm_a, 255); //set both motors to run at 100% duty cycle (fast)

analogWrite(pwm_b, 255);

delay(1000);

digitalWrite(dir_a, HIGH); //Reverse motor direction, 1 high, 2 low

digitalWrite(dir_b, HIGH); //Reverse motor direction, 3 low, 4 high

delay(1000);

analogWrite(pwm_a, 100); //set both motors to run at (100/255 = 39)% duty cycle

analogWrite(pwm_b, 100);

delay(1000);

}

2

jayaneti,

I haven’t proofread your code, but if the system does nothing without the USB cable attached, then it’s probably a power problem, not a software problem. Here’re a few things to investigate:

  • - How many cells are there in the "lithium backpack"?
  • - What voltage are you providing to the Ardumoto? That is, when you are trying to run it, what is the voltage across the battery connection terminals?
  • - What voltage is there on the Vin, 5V, and 3V3 pins of the Duemilanove, both with and without the USB cable attached?
  • - Does removing the motors change the behavior? That is, if you disconnect the motors, what happens when you try to run?
  • - Which way is the Ardumoto's voltage selection jumper set?

    • Happy Hunting,

    Eric