LEDs, an acronym for Light Emitting Diodes, can be wired in many different ways. How you decide to wire your LEDs depends on your power supply limitations and the number of LEDs in your design. Either way, the fastest and easiest way to wire a LED circuit is to use a LED wiring and schematic generator. These generators not only calculate out the values of the current limiting resistors you'll need, but also produce a detailed schematic and wiring diagram for you to follow.
LEDs are tiny lights that require a very low voltage and current to light; often as little as 1.5 Volts and 10 milliamperes. Look on your manufacturer's LED's data sheet and find these operating specifications. Specifically, look for the LED's forward voltage rating and forward current rating. Also look at the other LED specifications and find out their significance. The more you know the better position you will be in to troubleshoot your circuit.
Maximum power supply voltage
Multiply the number of LEDs you will use by the forward voltage rating of your LED to determine the maximum power supply voltage. For your first design, use two LEDs to increase your chance the circuit will work correctly. Circuits with fewer components are also easier to troubleshoot.
Circuit design and wiring arrangement
Use the LED schematic generator and enter in the information that the generator requests. For the source voltage, enter in the maximum voltage level you previously calculated. Then, enter in the diode forward voltage, the diode forward current and the number of LEDs in your design. Generate the schematic and wiring diagrams.
Note how many resistors are required, their resistance values and wattage ratings. Pay special attention to the overall power that your circuit requires. Make circuit calculations that will assure you that the circuit design is correct and safe to use. Also consider ways to redesign the circuit for lower power.
Finally, select the wiring diagram check box and select "design my array." Now, print the resulting wiring diagram. Study the wiring diagram and compare it to the schematic diagram. You should notice a one-to-one correlation between the two.
Wiring the LED circuit
Examine your LED data sheet and determine which LED lead is the cathode and which is the anode. Connect the power supply, resistors and LED using the diagrams as a guide. Ensure that the actual anode and cathode connections are the same as in the diagrams. If your anode and cathode connections are reversed, your LEDs will not light.
Applying power and troubleshooting
Slowly increase the voltage level of your power supply. Stop raising the voltage when the LEDs light or when you reach the voltage level you calculated. If your LEDs do not light when you reach the maximum voltage level, turn off your power supply. Then, recheck your connections and the value of each resistor. Also check to see if the anode and cathode of each LED are connected correctly.
Reconsider the LED specifications. Specifically, consider the tolerance ranges of the specifications. Factor these tolerances into your design calculations. Also measure the forward voltage and current measurements for each individual LED that you are using. Compare these results with the data sheet's specifications.