L293D: A notion to be cleared


IC L293D, is the Motor Driver IC, which is usually linked to Robotics Applications. Even if you tend to use this guy, few basic questions still arouse in the minds of budding Hobbyists; Like Why 2 supply pins on the IC, How much voltage can be given to the IC, Should I short all the Ground pins of the IC ?????? 

Here, I'll be explaining the Pin description of L293D and not the specifications or other technical details. You can refer datasheet for that. L293D datasheet click here.

To start with, any Microcontroller development Board works with a Max. of 5V, with a few hundreds of mA current. In case of ARDUINO Duemilanov:
DC Current per I/O: 40mA
DC Current for VCC & GND: 200mA 

Is this current sufficient enough to drive a everyday 12V, 200RPM DC motor ?
No. 

So what ?
Use a Motor Driver. 

Does it help ?
Yes. It converts low current to high, sufficient to drive a motor.




Pin Conections (Important: Even pro's tend to make mistake here)

Pin 1 & 9:
Pin 1 is Enable 1. Used for enabling working of Motor1 (IN1, IN2, OUT1, OUT2)
Pin 2 is Enable 2. Used for enabling working of Motor2 (IN3, IN4, OUT3, OUT4)

Pin 2, 7 & 10, 15:
Inputs for Motor. 
If pin 2 is +ve, pin 7 is -ve then motor Rotates in one direction. If Pin 2 is -ve, pin 7 is +ve then motor rotates in reverse direction.

Same explanation valid for Pin 10, 15.

Pin 16:
This is the Logic supply voltage for L293D. It should not exceed 7V (recommended rating). But can go Max. upto 36V.

Pin 8:
This is the Output supply voltage. We can give upto 36V (Max), depending on our output voltage requirement.

So, this explains why there are two supply pins on the IC. Pin 16 is usually provided for logic inputs to minimize the device power dissipation.

Pin 4, 5, 12, 13:
These pins are ground pins. They form an on-board Heatsink. Usually these pins are to be shorted  & connected to ground. But, I insist, take a multimeter and test the connectivity of these pins. THEY ARE INTERNALLY SHORTED. We need not short them again, it'll only increase the wire-do of your circuit.  

Please remember that Pin 8 & 16 are totally different. "Pin 8 is supply for left side, Pin 16 is supply for right side" is WRONG. 

Thanks,
Keep prototyping :)

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