problem in dc motor need a push to start

Hi, I'm making this obstacle collision avoidance robot and I'm having a problem in the dc motor, I used this motor (FA-130 Tamiya motor). I'm not using a motor shield, I'm using this L293D ic to drive the motor with input 4x 1.2V panasonic rechargable battery 2400mah. I need to spin the motor first before it runs own its own.

That is because you are not supplying it with enough current / voltage. Use 1.5V batteries or another 1.2V one.

Any chance of some schematics?

Some things to note:

  1. The motor is a 3V motor, 4 1.2V batteries is 4.8V.
  2. The stall current is 2.1A - that is how much current is needed to get it moving from stationary

Is there any load on the motor, or is it just free-running?

i use this schematic

4x 1.2v battery is enough right? i tried using 9V battery with 350mah its working fine but so fast not good for my project.

4x 1.2v battery is enough right?

Want me to say it again, no.
According to the data sheet Vs has to be at least the same value as Vss. In your case it is less.

i use this schematic

That is not a schematic, that is a physical layout diagram and as such is useless for talking about the circuit.
You have no diodes, while that will not stop it from working it will cause problems / damage to the other components in the circuit.

Grumpy_Mike:

4x 1.2v battery is enough right?

Want me to say it again, no.
According to the data sheet Vs has to be at least the same value as Vss. In your case it is less.

i use this schematic

That is not a schematic, that is a physical layout diagram and as such is useless for talking about the circuit.
You have no diodes, while that will not stop it from working it will cause problems / damage to the other components in the circuit.

where should i place the diode. i thought it has a diode already.

where should i place the diode.

See page 2 of the data sheet.

L293D has a very big voltage drop (your case could be > 3 V) at high current.

We have one thread, the drive IC has 0.03 V voltage drop at 2.1 A. (make sure meet power voltage required, PWM, reduce the motor voltage when you do.)

http://forum.arduino.cc/index.php?topic=169717.0

majenko:
Any chance of some schematics?

Some things to note:

  1. The motor is a 3V motor, 4 1.2V batteries is 4.8V.

And the L298 will lose 2.5V or more, its not a great choice for low voltage motors.

  1. The stall current is 2.1A - that is how much current is needed to get it moving from stationary

Stall current is the current it takes when the motor is prevented from running (rotor locked in place) and
its given its nominal voltage in full. Its equal to nominal voltage / winding resistance.

The current needed to get it running from stationary should be about the same as the no-load current,
this is due to frictional losses mainly.
(or if under load it depends on the nature of the load).

Is there any load on the motor, or is it just free-running?