Whether you grew up with fireflies and miss seeing them around, want to add a little ambiance to your yard, or plan to add them to a holiday display, this easy project will yield a small cluster of fluttering fireflies. A firefly, maybe you called them lightning bugs, is simply a yellow LED at the end of a length of magnet wire. The magnet wire is very thin and virtually invisible at night. It also has the virtue of being springy which gives the LED a bouncy, jittery movement that resembles insects flying in a small group.
Materials List for Fire Fly Lights
By using 3 volt LEDs you can connect them directly to the 2 AA batteries without the need for a resistor. If you use different voltage LEDs, you will need to add a resistor between the battery and LEDs to compensate for the voltage difference.
Each LED will be wired directly to the battery pack leads; the wiring will be in parallel, as opposed to in series. You can connect as many LEDs to the battery pack as you like, however the more you connect, the more quickly the batteries will be exhausted. We wired together six LEDs, which made a small but nice cluster of fireflies, and it ran for about 48 hours on one set of batteries. Some advise against connecting LEDs in parallel and their reasons are valid. However, if the LEDs are identical, this method been tested to work well. However, you can connect the LEDs in series, which will increase battery life, but will also require a higher voltage source. Which also reminds me to mention that low voltage lighting systems can be used as a power source (12V) to power your fireflies. Add the voltage of the LEDs together to get as close to 12V as possible. Also, while we suggest these fireflies can be assembled without a resistor, best practices do call for a current limiting resistor. There are many tables and tools on the web to find the right size resistor for your circumstances. But the formula is essentially Supply voltage - combined LED voltage (when in series) / the wattage usually between .01 and .02 mA = Resistance value, (VS - VL) / I = R, which is rounded up to the nearest standard resistor value.
As we mentioned before, we used magnet wire to connect the fireflies. You can use any wire you like for this project, but the magnet wire gave the LED a very bouncy, jittery movement which required only the slightest of breezes to move. The effect was very realistic.
These fireflies are steady burning. Blinking LEDS tended to be too regular in their flash rate. A circuit can be created to cause a more random flash that more closely resembles a real firefly. However, we found that the LEDs, having a limited field of light dispersal, tended to move in and out of view simulating a flash. We also tried painting one side of the LED with opaque paint to create a similar flash in fireflies that didn't receive enough breeze to keep them moving very much.
Cut two lengths of magnet wire for each LED. Each set of LED wires should be a different length to keep the fireflies from bunching up. Strip about a quarter inch of insulation of each end of the magnet wire. The insulation is essentially painted onto the wire and so removal is accomplished by more or less scratching off the outer layer. Twist the wire around the lead on the LED and solder it in place. Mark which wire is connected to the longer lead on the LED (this is the anode and should be connected to + side of your battery), at the other end of the wire. Cut off any unnecessary length of the anode and cathode leads on the LED.
Cut two short lengths of shrink tubing and slip them over each wire and completely cover the LEDs leads. Use a hair dryer to heat the tubing so that it shrinks and seals itself around the leads and connection.
Gently twist the two wires together along their length.