# Problem with motor driver shield

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.

• 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. Mar 14, 2018 at 3:44
• Then what should I use to drive motors from arduino @Chris Stratton Mar 14, 2018 at 3:46
• Probably an FET bridge. Which one depends on the motor specs, for some small motors the TB6612FNG can be good. Mar 14, 2018 at 6:51

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: