Driving Bigger Loads (Motors, Lamps, and the Like)


Each of the pins on an Arduino board can only be used to power devices that use a very small amount of current, such as an LED.


If you try to drive something big like a motor or an incandescent lamp, the pin might stop working, and could permanently damage the microcontroller that is the heart of your Arduino.


To be safe, the current going through an Arduino I/O pin should be limited to 20 milliamps.


Don’t worry, though. There are a number of simple techniques that allow you to control devices that use much more current.


The trick is a bit like using a lever and fulcrum to lift a very heavy load.


By putting a long stick under a big stone and a fulcrum in the right place, you can pull down on the long end of the stick, and the short end, under the stone, has much more force.


You pull with a small force, and the mechanics of the lever apply a larger force to the stone.


In electronics, one way to do this is with a MOSFET.


A MOSFET is an electronic switch that can be controlled by a small current, but in turn can control a much larger current.


A MOSFET has three pins.


You can think of a MOSFET as a switch between two of its pins (the drain and source), which is controlled by a third pin (the gate).


It is a little like a light switch, where the gate is represented by the part you move to turn the light on and off.


A light switch is mechanical, so it is controlled by a finger, but a MOSFET is electronic, so it is controlled by a pin from your Arduino.


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Last-modified: 2021-11-23 (火) 09:53:42