Posted by : AVINASH CHAKRAVARTHI Wednesday, 18 September 2013

have u ever wonder,how we can control robots to move right left straight  back.with out using steering in bots. i'll show u how we can control the direction of the bots .first we need to know abt h-brige.lets do that.


As you can see in the image, the circuit has four switches S1, S2, S3 and S4. Turning these switches ON and OFF can drive a motor in different ways.
  1. Turning on Switches S1 and S2 makes the motor rotate clockwise
  2. Turning on Switches S2 and S3 makes the motor rotate anti-clockwise

  1. Turning on Switches S1 and S2 will stop the motor (Brakes)
  2. Turning off all the switches gives the motor a free wheel drive
  3. Lastly turning on S1& S3 at the same time or S2 & S4 at the same time shorts your entire circuit. So, do not attempt this
  • HOW TO CONSTRUCT H-bridges for DC motors:

  1. type 1:-(4 inputs to control 1 motor)
H-bridges can be built from scratch using relays, mosfets, field effect transistors (FET), bi-polar junction transistors (BJT), etc. But if your current requirement is not too high and all you need is a single package which does the job of driving a small DC motor in two directions, then all you need is a L293D IC

A,B,C,D can be connected to micro controller and we can control the motors according to the program.
simple push switch connected between pt A and B and gnd ...similarly rest of the pt .by pushing the switches we can control the direction of the motor`

2.   type 2:-( 2 inputs to control 1 motor)

just by two switches we can control clock wise and anticlockwise rotation of the motors
3.    type 3:-( 4 inputs to control 2 motor)

Construction using l293d ic (4 inputs controlling 2 motors) :

L293D construction is similar to the h-bridge controlling 2 motors but using l293d is more preferable as it was so easy and occupies very few space in circuit
here pin 13 ,pin 12,pin 11,pin 10 are synonymous to pin A,B,C,D in above H-bridge controlling 2 motors
google for the datasheet of the L293D ic for more information.

how to control servo motors: 

servos works based on pwm(pulse width modulation)
so it requires the pulses along with voltage.the best way to control the servo are using the 555 timmer.(click the link to know abt 555 timmer).

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