Problem with motor driver shield

Question

I have recently bought a L293D shield and 2 BO motors. Whenever I connect the motors to the shield it makes a beeping noise. I searched online and found that I need to change PWM frequency but I know nothing about it and anyone please tell me about the PWM frequency and how to change it.

I have used almost every sketch found online but condition remains same. I am using 9V battery as External power supply and it is absolutely new. Please help me.

• Chris Stratton: Motor driving 101: 1) Do not use 9v batteries, they are for low current circuits not motors. 2) Do not use the antique and horribly lossy L293 or L298.
• user43728: Then what should I use to drive motors from arduino @Chris Stratton
• Chris Stratton: Probably an FET bridge. Which one depends on the motor specs, for some small motors the TB6612FNG can be good.

Answer 1

Acting as a conduit for Google: Arduino Change PWM Frequency shows me:

https://playground.arduino.cc/Code/PwmFrequency

Which has the following example function:

/**
 * Divides a given PWM pin frequency by a divisor.
 * 
 * The resulting frequency is equal to the base frequency divided by
 * the given divisor:
 * - Base frequencies:
 * o The base frequency for pins 3, 9, 10, and 11 is 31250 Hz.
 * o The base frequency for pins 5 and 6 is 62500 Hz.
 * - Divisors:
 * o The divisors available on pins 5, 6, 9 and 10 are: 1, 8, 64,
 * 256, and 1024.
 * o The divisors available on pins 3 and 11 are: 1, 8, 32, 64,
 * 128, 256, and 1024.
 * 
 * PWM frequencies are tied together in pairs of pins. If one in a
 * pair is changed, the other is also changed to match:
 * - Pins 5 and 6 are paired on timer0
 * - Pins 9 and 10 are paired on timer1
 * - Pins 3 and 11 are paired on timer2
 * 
 * Note that this function will have side effects on anything else
 * that uses timers:
 * - Changes on pins 3, 5, 6, or 11 may cause the delay() and
 * millis() functions to stop working. Other timing-related
 * functions may also be affected.
 * - Changes on pins 9 or 10 will cause the Servo library to function
 * incorrectly.
 * 
 * Thanks to macegr of the Arduino forums for his documentation of the
 * PWM frequency divisors. His post can be viewed at:
 * http://forum.arduino.cc/index.php?topic=16612#msg121031
 */
void setPwmFrequency(int pin, int divisor) {
 byte mode;
 if(pin == 5 || pin == 6 || pin == 9 || pin == 10) {
 switch(divisor) {
 case 1: mode = 0x01; break;
 case 8: mode = 0x02; break;
 case 64: mode = 0x03; break;
 case 256: mode = 0x04; break;
 case 1024: mode = 0x05; break;
 default: return;
 }
 if(pin == 5 || pin == 6) {
 TCCR0B = TCCR0B & 0b11111000 | mode;
 } else {
 TCCR1B = TCCR1B & 0b11111000 | mode;
 }
 } else if(pin == 3 || pin == 11) {
 switch(divisor) {
 case 1: mode = 0x01; break;
 case 8: mode = 0x02; break;
 case 32: mode = 0x03; break;
 case 64: mode = 0x04; break;
 case 128: mode = 0x05; break;
 case 256: mode = 0x06; break;
 case 1024: mode = 0x07; break;
 default: return;
 }
 TCCR2B = TCCR2B & 0b11111000 | mode;
 }
}

And numerous results from this SE community also:

https://www.google.com/search?q=arduino+change+PWM+frequency+site:arduino.stackexchange.com

Which note methods for calculating/setting specific frequencies and pitfalls and side-effects of making such changes.