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I am a beginner in Arduino.

I want to connect 2 motors to Arduino. Why do we require txhe motor shield? And if yes please explain why is it required? Also can I use an amplifier for the same.

Another question, I have SLAEX039 L293D Motor Shield. Does using this motor shield restrict arduino's pin usage? I mean we can't use the arduino pins if we use the motor shield right, can we?

Thank a lot

Yash Jain
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1 Answers1

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The core reason that we require motor shields is because the Arduino, on its own, cannot power a motor with its IO pins.

The digital IO pins on the AVR based Arduinos (such as the Uno) are only rated to supply up to 40mA of current at 5V - they are designed for signalling hardware, not driving loads such as motors, that can run to several Amps at higher voltages at peak loads.

Fortunately, there are devices that are designed to control heavy loads such as motors based on these logic level signals - we typically call these drivers. The L293D is such a driver, which connects to a logic device like the Arduino for signalling and then drives a motor from another supply.

While you can use a cheap, standalone L293D device on its own, it's often more convenient to use one carried on a shield, which correctly connects the driver as well as provides connectors for the external power and motor.

Ultimately, you don't require a shield, but you do need some form of driver to take the logic level signals from the Arduino, and shields are convenient ways of providing these.

http://www.ti.com/lit/ds/symlink/l293.pdf is a datasheet for a L293D device from TI, showing the various ways it can drive a motor based on the signals it receives.

Gareth Pulham
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  • So we can use amplifiers can't we? Thanks – Yash Jain Apr 15 '17 at 23:49
  • Amplifiers are a subset of drivers, that convert some form of signal into a proportionally larger signal. With the correct type of amplifier, you could drive a motor, but specific drivers are usually more effective. Do you have a specific driver in mind I can compare and contrast with the L293D? – Gareth Pulham Apr 15 '17 at 23:51
  • Nope, just an analog simple amplifier – Yash Jain Apr 15 '17 at 23:52
  • Ok, then let's consider the 741 operational amplifier. The 741 produces a voltage output based on the difference between the inverting and non-inverting inputs. We could tie the inverting input to 0V, and then by supplying 0/5V to the non-inverting input, we could output 0-Vs (the positive amplifier supply voltage). With this in mind, we can turn the motor on or off, but not backwards, and we end up constrained to a single motor, which probably wants to draw more current than the amplifier is designed to carry. Amplifiers are a type of driver, yes, but not the best type for motors. – Gareth Pulham Apr 15 '17 at 23:58
  • Ok. Thanks a lot Gareth Pulham – Yash Jain Apr 16 '17 at 00:00
  • Ok. Thanks a lot Gareth Pulham – Yash Jain Apr 16 '17 at 00:01