IR LED Driving with Arduino Timer

Other Hardware LEDs and Multiplexing
1

I have an IR LED that wants 1.4V at 40kHz. Since I can't change the amplitude of my timer, can I just drop a resistor in to acquire the 1.4V from the arduino to the LED? Will the timer then oscillate 40kHz at 1.4V instead of at 5V?

Thanks<

2

Yes a resistor in series with LED will drop voltage and will also limit the current through the LED which is an important function. When you know how much current you need you can calculate the resistor as

(5-1.4) / current in A) = Resistor in Ohms
e.g. if you need 10mA/0.010A = 3.6 / 0.01 = 360 Ohms

BTW if you want to be accurate the timer is still doing 5V but the LED only sees 1.4V of it.

Steve