How to Build the Basic LED Circuit
Circuits are the building blocks of electronics projects. You need several parts in order to build a basic LED circuit. Here is a list of those parts:
Four 1.5-volt AA batteries (make sure they’re fresh)
One four-battery holder (for AA batteries)
One battery clip
(identified by a red-red-red stripe pattern and then a gold or silver stripe)
One red LED (any size)
Three insulated alligator clips or one solderless breadboard
Insert the batteries into the battery holder, observing the polarity markers, and attach the battery clip. The battery holder is wired to connect the four batteries end-to-end, creating a battery pack that supplies 4 x 1.5 = 6 volts via the wires extending from the clip.
Before you build the circuit, you may want to use your multimeter to verify the voltage of your battery pack and the value of your resistor (especially if you’re not sure of their values).
Set your multimeter to measure DC voltage, hold the black (negative) multimeter probe to the black lead coming out of the battery pack, and hold the red (positive) multimeter probe to the red lead coming out of the battery pack. You should get a reading of at least 6 volts, because fresh batteries supply a higher voltage than their rating. If the reading is much less than 6 volts, remove the batteries and check each one individually.
To check the resistor value, switch your multimeter selector to measure ohms, and touch one multimeter lead to each side of the resistor (it doesn’t matter which way). Verify that the resistor value is roughly 2.2
You can build the LED circuit by using alligator clips to connect the components or by using a solderless breadboard to make the connections.
Building the circuit with alligator clips
Use the alligator clips to make connections in the circuit, as shown. Note that the orientation of the resistor doesn’t matter, but the orientation of the LED does matter. You connect the longer lead of the LED to the resistor, and the shorter lead of the LED to the negative side (black wire) of your battery pack. When you make your final connection, the LED should glow.
If you connect an LED the wrong way, it won’t light and it might become damaged.
Building the circuit with a solderless breadboard
The following two figures show the circuit set up on a solderless breadboard. A solderless breadboard makes connections between holes so that all you have to do is insert components in the right places. On the left and right sides of the breadboard, all the holes in each column are connected to each other. In each of the two center sections of the breadboard, the five holes in each row are all connected to each other.
As you set up the circuit on the breadboard, remember that it doesn’t matter how you orient the resistor, but be sure to orient the LED so that the shorter lead is connected to the negative side of the battery pack. If you clip the leads to make your circuit neater, remember to keep track of which lead was shorter to begin with. You use a short jumper wire in your trimmed circuit to connect the resistor to the LED.