When using Light Emitting Diodes it is strongly recommended that a resistor is placed in series with the LED to limit the current and prevent heating up and damage. Suggested resistor values to use are shown below. These values are not critical but for guidance only. Cathode (-) This is the shorter connector. There is also a flat side on the LED which corresponds to the negative termminal. IF max. Maximum forward current i.e. maximum recommended current passing through the LED when connected correctly VF typ. Typical forward voltage VF max. Maximum recommended forward voltage VR max. Maximum recommended reverse voltage – not a problem if connected the right way round!