L293 Motor driver difficulty

Discussion in 'The Projects Forum' started by spiked, Jul 14, 2010.

  1. spiked

    Thread Starter New Member

    Jul 14, 2010
    4
    0
    So I'm building a line following robot that is directly wired from the Atmega8 to a L293 motor driver chip and then obviously to some motors.

    The Atmega8 is sending manual PWM signal to the L293 driver on the forward pins. By that I mean I have code like:

    void motor_pacer();{

    ticked++

    if( ticked <= duty_cycle)

    PORTD |= LEFT_FORWARD;

    else if(ticked <= period)

    PORTD &= ~LEFT_FORWARD;

    else

    ticked=0;

    }

    All other pins on the L293 are logic low. Except obviously for the 2 Vcc pins which are supplied by a 6V battery and also for one enable.

    Without the L293 motor driver in all the voltages are showing what I expect. Importantly the enable to one motor is high while the enable pin to the other is low and PWM is being sent to one forward pin. However when I insert the L293 motor driver in both motors switch on and the voltage on both enable pins has become high.

    How do I fix this?

    Thanks
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    No schematic?
    No information on the motors?

    That's why you haven't received any responses.
     
  3. spiked

    Thread Starter New Member

    Jul 14, 2010
    4
    0
    This is the motor driver schematic, all the in and en pins go directly to the atmega8
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    1N400x diodes are not suitable for the application.

    You need fast-recovery diodes.
     
  5. spiked

    Thread Starter New Member

    Jul 14, 2010
    4
    0
    Are they required at all?
    Or can I just remove them?
     
  6. spiked

    Thread Starter New Member

    Jul 14, 2010
    4
    0
    So I've removed diodes because the only reason they were in was to limit voltage.
    However I stil have the same problem.
    From my last schematic there was a change in that I have pull down resistors on the input pin. I've attached a new diagram
     
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