Have you heard of something called a datasheet ?
There's a special HELL reserved for people who don't read datasheets. It's a world where nothing works and everything smokes as soon as you turn on the power.
If you're using an Arduino for the logic, split the power to go to your motor controller and the Arduino voltage in. The regulator on the Arduino will reduce the voltage to the 5V it needs, and that it will use to control the L293D.
LinusRJ: it only requires ,4A so I will need to use a resistor.
That doesn't sound like a real specification, and you will not need a resistor. See if you can get the correct info for your motor and ensure that it can be driven by the L293D. Also I suggest you find and understand some tutorials on using the L293D before proceeding - here's a link to one from Adafruit for example.
Also, the datasheet for the L293/L293D also includes important information you should know about the maximum current it can provide, and design requirements including heat sinks for high current use.
Good luck with your project, Geoff
You shouldn’t need a resistor in series with your motor leads. The L293 has two power pins. Make sure the one for the logic has 5V (Vss , pin-16) and another one for the motor power (Vs, pin-8) . Connect the 12V to pin-8.
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