How to Wire Resistor Load in LED Lights

Resistors' ohmic values are color-coded on their bodies.
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LED (light emitting diode) lights are low-current electronic components. As such, they cannot be connected directly to a typical household battery without running the risk of burning out from too much current. To prevent a single LED (or chain of LEDs) from burning out, a resistor load is placed in the circuit to limit the amount of current that flows through the LED(s). Typical LEDs operate within a range of a few milliamps of current and under 3 volts of direct current power from a battery. A resistor load of approximately 100 ohms will prevent a common 5 mm red LED from burning out.

    Tin a 100-ohm resistor and a red LED by melting solder over their leads.

    Solder one lead of the resistor to the short lead of the red LED. Resistors are non-polar, so either end will do. LEDs, however, are polar; therefore, polarity must be observed in the connections. The short lead of the LED is the cathode (negative) lead.

    Solder one end of a copper wire to the remaining resistor lead. Solder one end of a second copper wire to the long lead of the red LED. The long lead is the cathode (positive) lead of the LED.

    Hold the negative side LED/copper wire to the negative terminal of a 1.5 to 3.0 volt battery. Hold the positive side LED/copper wire to the positive terminal of the battery. The red LED will light and will not burn out.

    Things You'll Need

    • 100-ohm resistor
    • 1.5- to 3.0-volt battery
    • 5 mm red LED rated at 28 milliamps
    • Rosin core solder
    • Soldering iron
    • 2 6-inch lengths of copper wire

    Tips

    • Vary the values of resistor used. Larger resistors will cause the LED to glow dimmer. Smaller resistors will cause the LED to glow brighter. However, too small of a resistor (or too large of a battery) will cause the LED to get hot and burn out.

    Warnings

    • Soldering irons are hot enough to cause severe 3rd degree burns; use with caution when soldering.

      Avoid breathing in the fumes from the melting solder. Solder fumes contain traces of lead, a known neurotoxin.

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