3
\$\begingroup\$

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

\$\endgroup\$
5
  • \$\begingroup\$ Seems you used of the proteus program to simulate it. please testing it for real. \$\endgroup\$
    – Roh
    Commented Oct 9, 2013 at 13:50
  • \$\begingroup\$ What about your gnd connection to the MCU. \$\endgroup\$
    – Andy aka
    Commented Oct 9, 2013 at 13:57
  • \$\begingroup\$ 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? \$\endgroup\$
    – Nafees
    Commented Oct 9, 2013 at 14:39
  • \$\begingroup\$ Did you measure the voltage at pins 2, 7, 8, 3 and 6 ? \$\endgroup\$
    – Charles JOUBERT
    Commented Oct 9, 2013 at 15:24
  • \$\begingroup\$ Check how much current the motor draws at 6V. Maybe it draws more than the L293D can provide? \$\endgroup\$
    – JimmyB
    Commented Oct 9, 2013 at 15:29

1 Answer 1

Reset to default
1
\$\begingroup\$

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.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.