Introduction: LED Candle
We will build an LED candle and learn about simple electrical circuits. LED’s are light-emitting diodes. When current passes through them, they can glow in almost any color of visible light, and also infrared and ultraviolet. We will be using a type of LED called R-G-B. They have red, blue, and green emitting chips in the same housing along with a control chip. The control chip mixes the colors together and pulses them to make a nice visual effect. We will put three of these R-G-B LED’s in a translucent container to get even more vibrant visual effects. The whole “candle” is powered by two AA batteries.
Supplies
Step 1: Install Batteries
Make sure the battery holder switch is OFF. Then Install two AA batteries into the battery holder. Make sure the batteries are installed with the correct polarity. Usually the negative terminal of the battery (flat end) should press against a spring in the battery holder.
Step 2: Connect Power to the Breadboard
This step can be done later, but doing it now allows you to quickly check your assembly and make corrections if needed.
The steps that follow refer to grid points on the breadboard. If your breadboard grid happens to be numbered differently, don't worry, just use the photos as your guide and change the grid numbers as needed.
The red lead from the battery box should connect to J-11 on the breadboard. The black lead should connect to J-6.
TIP: We were trying to make these as easy as possible for novice summer camp students to assemble, so we soldered a 1 MEGOHM 1/2-Watt resistor shown in the photo between the battery holder leads. This allows one to easily make a solid, reliable connection to the breadboard, versus trying to insert the stranded wire from the battery holder. Since the resistor value is so large, it draws negligible current from the batteries.
Step 3: Plug LED #1 Into Breadboard
Insert one of the fast-flashing LED's (shorter legs) with its long leg (+) into G-8 and its short leg (-) into H-6. Then, insert one of the 100 ohm resistors between H-11 and H-8.
You should now have a complete circuit. Turn on the battery bow switch and verify that the LED lights up and flashes various colors. If not, check your connections and also make sure the LED is placed with the correct polarity. The shorted leg should be connected to the negative side of the battery.
After checking if the LED is in a complete circuit, turn OFF the battery.
Step 4: Plug LED #2 Into Breadboard
Insert one of the slow-flashing LED's (longer legs) between E-9 (longer leg = positive side) and G-6 (shorter leg = negative side). Connect a 100 ohm resistor between D-9 and G-11.
You should now have another complete circuit. Turn the battery ON and verify the new LED lights up and changes color slowly.
Once you have verified the LED is in a complete circuit, turn the battery OFF.
Step 5: Plug LED #3 Into Breadboard
Insert another fast-flashing LED (shorter legs) with its long leg (+) into E-8 and its short leg (-) into F-6. Insert a 100 ohm resistor between F-11 and C-8.
You should have another complete circuit. Turn on the battery and verify all three LED's light up.
Step 6: Final Assembly
Remove the paper from the bottom of the breadboard and stick it onto the side of the battery box that has the switch. DO NOT cover over the switch.
Now you can place the finished assembly into the translucent jar provided and enjoy the "LED Candle." You can carefully place the assembly down into the jar and screw on the lid, or if you prefer, you can place the assembly onto the jar lid first, then screw the jar onto it; that way you will get more light shining upwards.
