I am trying to use L293D with relay to power a 12V DC motor. Can I use arduino's 5V to provide L293D inputs 4 and 8 such as in the drawing? Or do I need to use a separate source, e.g. a power module?

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  • I have to ask... why the relay...?!
    – Majenko
    Mar 10 '19 at 16:07
  • @Majenko I am following the guide elegoo.com/tutorial/… page 150. Say I wanted to power some other device, with AC current, I would need a relay anyway.
    – leosenko
    Mar 10 '19 at 17:07
  • 1
    That "guide" seems completely pointless. Nothing more than a demonstration of what a relay is. Throw that whole thing away. You don't want to use a relay to control a DC motor, especially when you already have a motor driver chip, and the previous "guide" shows you how to use it. Why they included that relay thing in there is anyone's guess. Yes, if you wanted to control something AC, or very high voltage, then a relay would be used. You wouldn't use a motor driver to control it though - you'd just use a simple transistor.
    – Majenko
    Mar 10 '19 at 17:50

it looks like that motor controller chip has separate logic level and motor power inputs.

VCC1, at pin 16, is a low current logic level power input. You should be able to drive that from the Arduino's power supply.

VCC2, at pin 8 is the motor power input. You should NOT drive that from your Arduino's power supply. You should have a separate power supply for that (+5V with enough current for all the motors you are powering - 600mA is the max that chip can drive for a single motor, so a 1A power supply for VCC2 would be fine.

It looks like you are feeding the Arduino's +5V line into VCC2. DON'T DO THAT.

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