Tag Archives: Atmel

Driving an Infrared Led directly from an Arduino Pin

logobutton200x200A common question asked on forums is one about – Driving an Infrared Led directly from an Arduino pin.  Although the answer may be obvious to anyone with at least a basic knowledge of Ohm’s Law, many are confused about how to choose a resistor value for optimum performance. Often, there is a debate about whether a resistor is required at all, given that the AVR pins are rated to deliver an absolute maximum of 40mA on a pin. (Note: All of the quoted specs in the data sheet are for test conditions of up to 20mA on a pin). Of course there are better ways to drive an IR LED with a transistor circuit or even a constant current circuit. However, in this post we consider only the direct drive circuit using a current limiting resistor, as illustrated in the diagram down below.
Make sure to read the caveats at the end of this post.

Analysis of Voltage & Current for Infrared Led driven by Arduino
Analysis of Voltage & Current for Infrared Led driven by Arduino

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