Wednesday, 25 December 2013

H Bridge simulation in NI multisim

H Bridge configuration has many applications in controlling a motor. Generally, a motor can be either switched ON or OFF(uni directional rotation) based on the needs and the direction of rotation depends on the polarity. But, in the field of Robotics and Medical applications, a single motor must have the ability to rotate in two directions(clockwise and anti clockwise). For this purpose, an H bridge configuration is preferred. As the name indicates, the circuit will be in the shape of alphabet “H”. The motor is made to rotate in two directions by changing the polarity of the motor.

Look at the following connections, 
Here, the direction of rotation of the motor varies with the change in its polarity. A simulation of the above schematic is shown below,

A combination of these two schematic gives a H Bridge circuit and the switching between polarities is done using the transistors(electronic switches) as shown below,

From the above circuit, it can be seen that when the switches(SW1 and SW3) closed, the motor will be in one polarity and when the switches(SW2 and SW4) are closed while the other switches are open, the motor will be in another polarity. And this is how an H Bridge circuit works and the transistors are used as the switches.  Below shown is the simulation of the H Bridge circuit in NI multisim,

Here, when the gate is ON, the MOSFET is turned ON, hence forms a closed circuit and the motor receives the polarity based on the above explanations. 

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