The 555 FireFly





Introduction: The 555 FireFly

About: I started taking things apart when I was 6 started putting them back together at 8 and they actually worked again when I was 10 or 11...
What is the 555 firefly? It is a 555 circuit that blinks an LED. But, not any LED. The LED is a UV led dipped in Glow In The Dark (GITD) paint. The end result is that the UV light excites the paint resulting in it glowing and then fading out like a real fire fly does. This project started as an offshoot of a couple of my recent experiments with UV lasers taken from an HD DVD player and general playing around with stuff that lights up or glows. There are a couple of cool projects out there that use UV LED's in a matrix to “paint” on GITD material, making Persistence of Vision more organic looking. I started researching GITD stuff and came up with the following information: Zinc Sulfide is the original GITD material and then there is Strontium Aluminate, which is brighter and has a much longer persistence. You might think that Strontium Aluminate is immediately better but that depends on what you are trying to achieve. Having the glow fade faster might actually be useful depending on what you are trying to do. I had some GITD paint based on Strontium Aluminate from a previous project (one that didn’t actually work as well as I wanted due to the long persistence.) So I had an idea... Dip a UV led into the GITD paint and see what happens... The result was pretty cool and all I needed for a stand alone cool little project was something to turn it on briefly and then off for a while. Enter the 555 timer. These guys have been around a long time, I used to build stuff with them in my teens. To make it simple I didn't even use a PC board and chose the ultimate point to point wiring method. Here is a little video of the 555 firefly in action.
I will mail a UV LED dipped into GITD paint to the first five people who correctly identify the music in the video! Send me a private message if you know.

General Info on GITD:
General Phosphorescence 
Zinc Sulfide  
Strontium Aluminate  

Step 1: Lets Build It!

The Parts List:

  • Needle Nose Pliers
  • Diagonal Cutters
  • Round Nose Pliers
  • Soldering Iron
  • “Third Hand” helping holder

The first thing to do is to make the GITD LED's. I bent the (+) lead (the longer one) into a little loop so I could hang it to drip dry after dipping. Next time I think I would use masking tape and rig up something that I could stick the LED to so it can drip and dry. The way I did it, they tend to swing around and can stick to each other if they get to close. Give them about 24 hours to fully dry. While they are drying lets build the circuit. 

Step 2: The Circuit

Take the 555 timer IC and bend the leads straight. We are going to mount all the components on the leads. See the schematic for a layout of how it will all look. Cut and bend the leads for the 1 Meg resistor so that you can mount it as shown between pins 7 and 8. Solder the resistor to the 555. Now take the 22K resistor and connect it to Pin 6 and 7 using the same technique. Flip the 555 over and using an extra piece of lead from the resistors, make a connection between Pin 2 to Pin 6. Coming back to the front, form the 49 ohm resistor as shown and connect to Pin 3 leaving the other lead straight up to connect to the LED. The way the 555 works, the output stays high for a time based on the 1M resistor plus the 22K resistor as the capacitor charges, then goes low for a short time based on the 22K resistor discharging the capacitor. To get the LED to be off most of the time and on for a short time, we connect the cathode to the output of the 555 and the anode to the + supply. Now connect the LED between the 49 ohm resistor and pin 8 of the 555. The Capacitor is next and goes between pin 1 (-) and Pin 2 (+). We are using an electrolytic capacitor that is polarized. There is a nice stripe on it identifying the (-) lead. OK now for the value. In the video I used a 4.7 uF one to make it flash faster. For a real firefly effect, use a between a 22uF and a 68uF for a longer time between flashes. If you make several of these, use different value capacitors to mix it up a bit. I ordered 25 555's to make a batch. Finally, solder short wires for taping to the batteries. Red for (+) to Pin 8 and Black for (-) to Pin 1. Before powering it up, double check your wiring, which should be easy to do as you can see everything.

Step 3: Powering It Up and Use:

Powering It Up And Use:

Take two CR2032 cells and put them on top of each other to make one 6-Volt cell. Yes, it kinda sucks to have to use two, but as I write this my prototype has been running for 48 hours straight. And form deal extreme they are pretty inexpensive. Great for throwies too! Using the electrical tape wrap the (+) and (-) leads to the appropriate terminals of the battery and tape it all together just like a throwie. In fact, you just made an LED glowie!

These are great for kids and hiding around the house in closets. They also look cool at night. I am going to build a bunch to use for outdoor decorations.

Step 4: Taking It Further

Taking it Further:

As I already had the GITD paint and it is rather expensive I began to search for less expensive alternatives. And, I know there are a lot of other very cool things that I could do with these LED's. If you put a bunch in a row and scanned them you would have a very cool and organic looking Larson Scanner without having to pwm the levels. I ordered enough to build an Matrix of them that should show some interesting patterns. I will write that up when I get the parts and build it. I also ordered 4 oz of Zinc Sulfide based GITD powder from the link below. I am going to experiment with making my own GITD paint to dip the LED's in. Just coating the LED with clear nail polish and dipping it into the powder worked pretty good.

GITD Powder 

have fun blinking and glowing.


If you were wondering what I had the Economy Green GITD paint from it was this: And, the price has gone up!



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    28 Discussions

    Is there a way to attach multiple LED lights to make them blink at different times. Or would this require a board like the ATTiny45?

    Thank you. I came up with a better method for dipping the UV LED's Stay tuned!


    This is a GREAT idea, thanks! Very cool alternative to the PIC/AVR methods.

    One of those things that I wish I'd thought of myself!

    3 replies

    Do you have Pin 2 and 6 connected together? That is needed for the 555 to work as a bi-stable multivibrator (oscillator)


    Just connect pin 4 and pin 8. It is necessary to connect both of them to the +of power supply.

    hello.need a little help here in the process of making this blinky but I cant seem to get it work.i made 2 of these things one on a pref board and one with freehand soldering.i used the exact same components except for a 47ohm resistor instead of a 49 o.i tried using different capacitors too (4.7uf , 10uf , 100uf) but no luck :'(


    Well, its been 3 years. Did anyone guess the music? I love it and would like to know the track & artist.....

    Great idea about dipping the UV LED in the phosphoresent paint, by the way :-)

    1 reply

    The song is : Dassic - Hedgehopper V3.0 from a Future Music CD (came with the Magazine from November 1998 issue. Glad you like it! I have some more idea for great instructables. Just not enough time!


    The 1Mohm resistor sets the speed. The 47-100 ohm resistor is current limiting resistor for the LED.


    3 replies

    I use a Weller temperature controlled soldering station. About 15 years old at this point. I also use Kester 63-37 solder with water soluble flux. Easy to clean up.

    Okay so I've been trying to build this circuit for a little while and I noticed that you're using a LM555 as opposed to the NE555 which is what I'm using. Do you know if that makes a difference? The LED only blinks on after I take off the power. Also where did you find a 49ohm? The closest I've been able is a 47ohm. Other than that it's a cool circuit.

    1 reply

    Hey, a 47 ohm will work just fine. I believe the LM555 is made by National Semiconductor and the NE555 is by Interstil or Fairchild semiconductor. Both are equivalent. my 49 ohm is a 1% that I had lying around from many moons ago.


    Great idea for using uv leds. I've been playing around with placing electronics in clear resin (joule thief was my first try). It's pretty easy if you get the resin that mixes in a 1:1 ratio. The stuff that comes in a can and has a catalyst that you mix on a 1:10 ratio has a very strong chemical smell, but it will cure to a bubble free mold. the 1:1 resins don't smell nearly as bad, but they are thicker, so you have to use pressure to get the bubbles out while it cures (or stir very carefully). Leaving the bubbles in can have a very cool effect though.

    1 reply