measuring the current of the Dc motor

[MarkT]

The ACS712 30A current sensor will not be useful for measuring small currents (the L293D can only
handle small currents).

For small currents a simple shunt resistor in the ground-return from the motor driver is all you need
to measure current.

[koronus]

The ACS712 30A current sensor will not be useful for measuring small currents (the L293D can only
handle small currents).

For small currents a simple shunt resistor in the ground-return from the motor driver is all you need
to measure current.

ok thank you so much

[koronus]

and how much(ohms) must be  the value of the resistor?

[MarkT]

What current maximum?  How much voltage do you mind losing?  How much heat can you afford to dissipate?
From such considerations use Ohm's law to calculate the shunt resistor value that works for you.