LEDs are light-emitting diodes. They are specifically created to emit light, whether visible, infrared or near infrared. LEDs are polarised, which means that the way they are placed inside circuits is important. They are categorised by factors such as their colour, intensity, size, voltage and viewing angle. They are sensitive to current, and so must be used in series with a resistor to prevent their self-destruction. To calculate the value of the resistor needed with a 9-volt battery, use Ohm's Law. Ohm's Law is a formula where the resistance R is equal to the voltage V divided by the current I.
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Things you need
- Low-voltage LED
- LED datasheet
- 9-volt battery
- Jumper wires
Obtain the values for the LED voltage and maximum current. This may be done by reading them off of the LED datasheet or package.
Study Ohm's Law to calculate the minimum value for a current limiting resistor for an LED. It is R = (Voltage Source -- LED Voltage)/LED current.
Calculate the minimum value of the required resistance. For example, given a 9-volt battery, and a 2-volt LED with a maximum current of 30 ma, the required resistance R is (9 V -- 2 V)/0.03 A = 233 ohms. Note that milliamps must be converted to amps by dividing by 1000. Also, the absolute minimum R should be avoided; use a 240-ohm, 330-ohm or higher valued resistor instead.
Wire the 2-volt LED or another low-voltage one in series with a resistor and battery. First, attach the positive side of the battery to the breadboard, and connect one end of the resistor to this side. Connect the positive side of the LED to the free end of the resistor. Place the negative terminal of the LED to ground, and then also wire the negative side of the battery to ground. The LED will light.
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