Intro: Simplified Firefly Jar
This is my first instructable so be kind please. Please also keep in mind I'm not an electronics expert. I know just enough to not know what I'm doing.
I was inspired by photozz Fireflies - Analog version. I had two 555 timers but didn't have the cd4026b IC. Instead what I had was a sn7447an IC. Even with the help of photozz I still couldn't get it to work. So I started looking for a different way. I found the simplesit LED blinking circuit on http://www.cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html (note: any metteral taken from the above site is copyrighted to Dick Cappel) From there thru trial and error I designed my simplified Fireflies in a jar circuit. We will keep it simple and only do three LED's for now. Ime working on a 10 LED jar.
3 2N3904 NPN Transistors (Almost any other NPN or PNP from your junk box will work)
3 various resistors (I used 2-10K and a 1-1K resistor try different combos from the junk box)
3 100 ohm resisters (this one is a must or you MIGHT blow your LED's)
3 various capasters ( used 1-2200 UF 2-470 UF one 35V and one 16V try different combos.)
3 green surface mount LED (or any other color or kind)
1 Power supply of some sort. I used a Nokia Type ACP-7U. Out put is 3.7V DC at 340 mA I'm to cheap to buy batteries, and the cell phone for this charger became a dogs chew toy.
Various wires. the thiner the better.
1 mason jar. or some other type of inclouser.
Optional but nice.
DVM or AVM
Step 1: The Simple Cuircuit
When using the transistor only use the
emitter and collector. cut the base off or just bend it out of your way.
I will do a little cut and paste from the site I got the circuit from for those that are interested in why and how it works.
In this implementation, a common NPN transistor is used. In the circuit, a 1k resistor charged the 330 uf capacitor until the voltage became large enough to get the emitter-base junction to conduct. In the oscilloscope image, it can be seen that the peak voltage (yellow trace) was a little bit less than 9 volts. At this point transistor turned on quickly and partially discharged the 330 uf capacitor through the LED and the 100 Ohm current limiting resistor. The current wavform, which is the voltage drop across the 100 Ohm resistor, is shown in the blue trace on the scope image. Peak current was 26 milliamps, and the transistor continued to discharge the capacitor until conduction suddenly ceased at 60 milliamps. After the transistor stopped conducting, the capacitor began charging again, thus starting a new cycle.
To see oscilloscope image go to Simplest LED Flasher Circuit
What I did is no rocket science I used a common positive and a common negative and added more transistors. I also mixed and matched different combinations of resistors and capacitors so each LED blinks different then the others. In my mind the best blink fade in fade out combo is a 10K with a 2200 UF capacitor. it only blinks about once every three seconds but it looks more like a real firefly.
The image on this step is copyrighted by Richard Cappels at http://cappels.org/ , and is republished here with permission on this web page.
Step 2: Final Thoughts.
Sorry about the lack of pictures my camera is on the blink. As soon as I get some pictures I will post them.
I used a old mason jar and some very small gage wire to hang the surface mount LED's from. the circuit Is on a perfboard and hot glued in the top the over all effect is awesome except for the power supply wire running into the top. It will be replaced soon with a 2 small 3 volt batteries so the whole unit will be self contained. in addition to the batters it will also be getting a light sensing circuit to turn it on at dusk and off at dawn. I'm even going to put in a small cell phone vibrator to give the appearance of movement.
Remeber this is my first Instructable please be kind. I baleave Ive given credit to every one else work but if Ive forgot anybody please feel free to politely point it out to me and I will correct it.