Monday, December 15, 2014

H Bridge Circuit

I have constructed my own h bridge circuit to control the speed and direction of 12V dc motor. With the H-bridge I can control dc motor forward and backward using two wires, and the speed is controlled by a third wire witch is connected to a pwm signal.
Basic Operation Of The H-Bridge:
The basic circuit of the H-bridge is simply contains a dc voltage source,4 switches and load as shown in the following figure:
h bridge
Now, if S1 and S4 are ON (S2 and S3 must be OFF) the current will flow from positive to negative across the motor and the motor will run at the forward direction.
h bridge
If S2 and S3 are ON (S1 and S4must be OFF) the current will flow according to the following diagram and our motor will have backward direction:
h bridge
In our circuit we are going to use mosfets as switches.
2 X IRF4905 (P-type)
2 X IRF3205 (N-type)
The full circuit is shown in the following figure:
IN1 & IN2 to control the direction of the motor
If IN1 = IN2 = 0 the motor is at OFF state (1 means 5V and 0 gnd)
If IN1 =1 & IN2 = 0 forward direction
If IN1 =0 & IN2 = 1 backward direction
Note that IN1 & IN2 must not equal to 1 at the same time.
PWM pin is connected to a pwm signal. If pwm = 1 means full speed.
h bridge circuit dc motor control