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I am trying to drive a 6V DC motor with an L293D driver and ATmega8 without PWM. The problem is, I am getting a very low speed while connecting the motor via L293D driver.But, It rotates well when I provide direct 6V DC supply to the motor.

I am using an external 6V source at the VS (motor supply) pin of the L293D but there is no improvement. The motor does not rotate until I turn the rotor by hand. What could be the problem? My code is here:

DDRB = 0xFF;
while(1)
{
  PORTB = 0B00000010;
  _delay_ms(20000);
}

My simulation design is here: Interfacing DC gear motor with Atmega8

Nafees
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  • Seems you used of the proteus program to simulate it. please testing it for real. – Roh Oct 09 '13 at 13:50
  • What about your gnd connection to the MCU. – Andy aka Oct 09 '13 at 13:57
  • I have simulated it. It rotates well in simulation mode. But, the problem occurred when i implemented it real.I have connected GND of ATmega8 perfectly. I am confused about unused L293D pins. Should i connect the unused pin with GND or keep it open? – Nafees Oct 09 '13 at 14:39
  • Did you measure the voltage at pins 2, 7, 8, 3 and 6 ? – Charles JOUBERT Oct 09 '13 at 15:24
  • Check how much current the motor draws at 6V. Maybe it draws more than the L293D can provide? – JimmyB Oct 09 '13 at 15:29

1 Answers1

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Here's what the L293D spec says: -

enter image description here

In red I've extrapolated what this means for a 6V battery supply. So, in a H bridge you can't really expect to put more than 3 or 4 volts onto your motor from a 6V supply. The device isn't modern and it isn't geared up for driving 6V motors from a 6V supply.

Also note the current drive capability of the device is 0.6A which is poor for driving any decent mechanical load.

Andy aka
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