DIY LED Fixture

Forward Voltage
Forward voltage is the minimum voltage required for the LED to emit light. A typical high power LED used in reef lighting has a 3V (volt) forward voltage. It may be referred to a Vf on a datasheet. The forward voltage is summed when wiring emitters in series and remains the same when wiring in parallel. For example, three emitters in series will require a power source that outputs at least 9V (3 x 3V) and three emitters in parallel will require at least 3V.