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LED Calculator

Calculate Resistor Value for LEDLED Battery circuit

A LED cannot be connected directly to a battery but requires a resistor that limits the flow through the diode. The amount of power that may flow through the diode depends on the individual diode and is indicated in the diode’s data sheet for the diode.

Typically, the maximum power intensity must be about 20 MA.

This is achieved with a resistance of 470 Ω if the battery is 9v –
Ohms law: 9v/470Ω = 0,019A = 19 mA. The calculation is approximate.

Voltage Supply


LED forward voltage

LED current


in milliamps

Resistor value (R1)

Wattage (R1)

     
Typical LED Forward Voltages

Red

1.98v

1.96v

Green

1.94v

1.92v

Yellow

1.90v

1.92v

Blue

2.76v

2.78v

White

2.78v

2.76v

Pink

2.84v

2.84v

Ultraviolet

3.10v

3.16v

What is a LED – Light Emitting Diode

LED anode cathode

The LED is a diode that emits light when power is running through it. It is widely used as a light signal instead of an ordinary bulb – for example, To indicate if an appliance is switched on or off.

LEDs are available in different colours and sizes-but the classic LED is red with a diameter of 5 mm.
Just like the regular diode, there can only be flow between the anode and cathode and not the other way around. It is therefore important to turn the LED correctly into a circuit.
You can tell the difference between the two legs because one leg is longer than the other. The leg that goes to the LED’s anode (+) is longer than the leg of the LED’s cathode (shorter).

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