Capacitor in DC Motor Circuit – What is the Use of a Capacitor in a DC Motor Circuit?

arduinocomponent-selectioncomponentsdc motorelectrolytic-capacitor

I'm trying to understand all the components I need in order to drive a DC motor through an Arduino.
I saw this circuit below, which has a capacitor (other sources show same circuit but without the capacitor).

I understand that the resistor is a pull-down to evacuate residual electricity when switching off the MOSFET and the Diode to not to damage the circuit when powering off the motor (as this one will produce electricity at that moment).

But what's the role of the capacitor?

Arduino DC Motor with capacitor

Image source

Best Answer

The circuit is rubbish. Apart from it being drawn as a cartoon of a wiring diagram, if you look closely, the GND pin on the UNO is connected to the drain pin of an unspecified (could be P ch or N ch) MOSFET. The power supply negative connection does not reach the UNO at all.

The resistor is placed between drain and gate is highly likely to also be in error.

The only conclusion is that the circuit was drawn by someone with little knowledge and has therefore no merit hence, to try and fathom out why the electrolytic capacitor is placed across the motor is of little point.

Stick to proper symbolic circuit diagrams from reputable sources.

If you read the user comments at the bottom of the page you linked you'll see that other folk have also pointed out several errors in the diagrams. Sites like that are basically an insult to engineering but, as a beginner, you are not to realize this so you have my sympathy.

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