How to Design a Simple LED Circuit

by J.T. Barett

    A simple light-emitting diode circuit is an excellent first project in electronics, as it illustrates the use of electrical current and gives you practical experience handling components. The circuit uses a switch to control a 20-milliamp current, turning a light-emitting diode on and off. The LED is a solid-state device that produces light from a small current; the circuit employs a resistor to limit the current, preventing the LED from burning out. This circuit is completely safe, as it uses a 9-volt battery for power. You can build the circuit in less than 20 minutes.

    Step 1

    Cut the 6-inch piece of 22-gauge wire into two segments of 3 inches each. Strip about 1 inch of insulation from one end of each wire and 1/2 inch from the opposite end. Stripping the wire reveals the bare metal conductor.

    Step 2

    Tightly wrap the 1-inch bare end of one of the wires around one lug of the pushbutton switch. Wrap the 1-inch bare end of the remaining wire around the second lug. Crimp the wires in place on the lugs with the long-nose pliers. The switch now has two wires attached, ready to connect to the circuit.

    Step 3

    Examine the prototype breadboard; notice it has a grid of holes arranged into rows and columns. Holes within the same column are electrically connected; holes in the same row are electrically insulated from one another. You build circuits by plugging wires into the holes, using the columns to create connections.

    Step 4

    Insert one lead of the resistor into a breadboard hole. Insert the other lead into a different column in the breadboard. You may want to use a hole two or three columns over so the resistor fits in the breadboard. Resistor leads usually take a firm push to seat in a breadboard hole.

    Step 5

    Set the LED's anode lead into a breadboard hole so it shares the same column as one of the resistor leads. Insert the cathode lead into an unshared column in the breadboard.

    Step 6

    Insert the bare end of the 9-volt battery clip's black wire into a hole in the same column as the LED's cathode. Insert the battery clip's red wire into an unshared column.

    Step 7

    Set one of the switch's bare wire ends so it shares the column with the red battery clip wire. Note that one of the resistor's leads occupies an unshared column. Insert the remaining switch wire into this column. Snap the 9-volt battery into the clip. This completes the circuit.

    Step 8

    Press the button. The LED lights up.

    Warnings

    • If you put the LED in backward, it will not light. This does not harm the component or the circuit; the LED blocks current when it's wired in reverse. Double-check the LED's connections if the circuit doesn't work.

    Required Items

    • 6-inch length of 22-gauge solid wire
    • Wire strippers
    • Normally open, SPST pushbutton switch
    • Long-nose pliers
    • Prototype breadboard
    • 5mm light-emitting diode, any color
    • 470-ohm, 1/4-watt resistor
    • 9-volt battery snap connector
    • 9-volt battery

    About the Author

    Chicago native J.T. Barett has a Bachelor of Science in physics from Northeastern Illinois University and has been writing since 1991. He has contributed to "Foresight Update," a nanotechnology newsletter from the Foresight Institute. He also contributed to the book, "Nanotechnology: Molecular Speculations on Global Abundance."

    Photo Credits

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