I'm studying H-Bridge for DC-motors. I have a 9V battery, DC-motor (9v), Arduino Nano and L293D. I follow Jeremy Blooms Book about Arduino. Well, the system works perfectly with PC connected. When I turn off the PC and connect to the battery only, it doesn't work at all. The system should work only with 9V battery.

```const uint8_t EN = 10;
const uint8_t MC1 = 8;
const uint8_t MC2 = 7;
const uint8_t POT = 0;

uint16_t velocity = 0;
uint16_t PWM = 0;

void forward(uint16_t);
void reverse(uint16_t);
void brake();

void setup(){
 Serial.begin(9600);
 pinMode(EN, OUTPUT);
 pinMode(MC1, OUTPUT);
 pinMode(MC2, OUTPUT);
 brake();
}

void loop(){
 Serial.println(PWM);
 PWM = analogRead(POT);
 if (PWM > 562){
 velocity = map(PWM, 563, 1023, 0, 255);
 forward(velocity);
 }
 if (PWM < 462){
 velocity = map(PWM, 461, 0, 0, 255);
 reverse(velocity);
 }
}

void forward(uint16_t speedValue){
 digitalWrite(EN, LOW);
 digitalWrite(MC1, HIGH);
 digitalWrite(MC2, LOW);
 analogWrite(EN, speedValue);
}

void reverse(uint16_t speedValue){
 digitalWrite(EN, LOW);
 digitalWrite(MC1, LOW);
 digitalWrite(MC2, HIGH);
 analogWrite(EN, speedValue);
}

void brake(){
 digitalWrite(EN, LOW);
 digitalWrite(MC1, LOW);
 digitalWrite(MC2, LOW);
 digitalWrite(EN, HIGH);
}```

A0 pin is used for Rotate sensor (PWM)

[![The circuit][1]][1]


 [1]: https://i.sstatic.net/GliSw.png