Transistor circuit

Here's how to use a TIP120 transistor to control higher voltage or higher current loads. This circuit will also work for an IRF520 MOSFET. The load could be a motor, or an ultrabright LED, or 50 LEDs you want to switch on (all at once) with one pin, or anything higher voltage DC. Maximum 60V, 5A... Continue Reading →

Relay circuit

Notice that in many relay circuits you will see a transistor used in addition to the relay. This is to ensure enough current is coming through to activate the relay. Often the Arduino can do this directly, but some relays require more current. More examples: SparkFun Controllable Power Outlet tutorial

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