what is a servo motor shield in arduino? what is the key purpose for using it? I'm newbie in arduino and I've seen some briefings in websites which I couldn't understand, can somebody elaborate it to me?


Servos require power and PWM. Servo shields come in two main forms:

  1. Simple distribution
  2. Active control

The first kind just provides convenient 3-pin headers to the Ardino's PWM pins, and sometimes a dedicated power supply for powering the servos. They're simple and cheap, but can only provide as many servo ports as the Arduino has PWM pins.

The second kind, more expensive, has a PWM chip on it to provide many more PWM pins than the Arduino can natively provide. Again there is sometimes a power supply as well, along with the convenient 3-pin headers. You usually interface with this kind using either I2C or SPI. These are the ones people usually mean when they talk about a servo shield - a shield designed for powering and controlling many more servos than an Arduino by itself can manage.

Servo Motor Shields should not be confused with Motor Shields, which provide a number of H-Bridge drivers for powering and controlling (both the speed and direction) of a brushed DC motor.

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The dumb ones are basically distributors of power for the servo motors. There are more clever boards that offer the control of multiple servos (usually 10+) by communicating with the Arduino via some higher-than-PWM-level control (Like I2C) thus taking less pins from the Arduino than a dumb servo shield. Both kinds usually require a power supply to power the servos.


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  • He said "servo motor shield", not a DC motor driving shield. Very different thing. – Majenko Feb 18 '17 at 13:32
  • do you mean that using motor shields provides external power to servo? – Dharanendiran Feb 18 '17 at 13:35
  • @Majenko How does my answer suggest I am talking about a DC motor shield? Would you please elaborate? – Killer Rabbit of Caerbannog Feb 18 '17 at 14:14
  • "So, you need something that takes the signal from these pins and translate them into high current controls." - that is what a DC motor shield does. It's not what a servo motor shield does. You have perfectly described a H-bridge shield. – Majenko Feb 18 '17 at 14:15
  • @Dharanendiran Almost. A motor shield provides power to the servo/stepper motor but that power has to tome from somewhere, so to make a motor shield work you'll need a power supply to power the shield itself and you may need another power supply to power your Arduino. – Killer Rabbit of Caerbannog Feb 18 '17 at 14:18

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