# H Bridge is reducing the RPM withing 2 seconds

Joined Dec 24, 2011
84
Dear All Have a nice day

I make a H bridge using IR2104 bootstrap and I used four IRFP150N MOSFET( N Channel )
It is working

The issue is
It has IN1 and IN 2 pins to control

When IN1 = HIGH and IN2 = LOW

Motor is rotating and withing the two seconds RPM is reduced by certain amount at that time we can see little hum by the motor ( Vibration )
whine I give the PWM pulse the motor is rotating it's max RPM
SD pin is always HIGH
Vs capacitor is 1uF 50v

#### AlbertHall

Joined Jun 4, 2014
10,780
If there is no PWM signal - the bridge is in a fixed state - then there are no pulses to work the bootstrap to generate the voltage needed for the upper MOSFETs to turn fully on.
For this to work there must be comtinuous pulses.

Joined Dec 24, 2011
84
If there is no PWM signal - the bridge is in a fixed state - then there are no pulses to work the bootstrap to generate the voltage needed for the upper MOSFETs to turn fully on.
For this to work there must be comtinuous pulses.

This is the code
Code:
void loop() {

forw();

delay(10000);

bacw();

delay(10000);

}

void forw() {

digitalWrite(in1, HIGH);

digitalWrite(in2, LOW);

}

void bacw() {

digitalWrite(in1, LOW);

digitalWrite(in2, HIGH);

}

#### Irving

Joined Jan 30, 2016
1,070
IR2104 isn't really suitable for H-bridge motor control as it only implements a dependant 1/2 bridge driver. For motor control as you require, you need independant control of top and bottom channels on both sides of the bridge. A IR2110 is a better device for your needs. There are various ways to configure this, but a common solution is to apply PWM to the top driver on one side and a high level to the low driver on the opposing side.