Make Cool Gadgets From a Deceased Fluorescent Lamp




Do you have some deceased fluorescent lamps? If Yes, then you might still recycle some of its guts to fashion some simple yet usable circuits.

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Step 1: Car to Portable MP3 Player Power Supply

The first gadget is a 12 V to 1.8 V power supply, also known as step down or buck dc-dc converter. These type of SMPS (Switched Mode Power Supply) are very efficient in terms of energy loss by heat dissipation compared to the linear type (circuits like 7805, 7509, LM317, etc). This works under the principle of energy storage in a magnetic field and then just regulating the output voltage by means of duty cycle control on a PWM (Pulse Width Modulation).

Open up your lamp and look for a small ferrite core transformer (some brands might have two, so try different brands or sizes)

Step 2: MP3 PSU:Stuff You'll Need

Here is what you'll need:

-NE 555 (Timmer- oscillator IC)
-two 1N4001 or 1N4148 diodes or any similar (for low frequency)
-10k trimpot or potencimeter
-100n ceramic or polyester capacitor
-10n ceramic or polyester capacitor
-1000u X 25 V polarized capacitor
-Any N-Channel enhanced mode Mosfet for 5 A or greater current
-470 Ohm resistor
-A Schotsky diode (This is the most important item, since is should be a diode that can switch at high frequencies, thus the "fast recovery" tag) I got this from a deceased laptop power adaptor. They are very common.
-FROM YOUR LAMP, remove the xtransformed and if it is is still in goog shape, use it. If not, you can still use the core and rewind some 200 turns of magnet wire (30 or 32 AWG). Inductance of this coil should be in the mH range.

Step 3: Schematic

This is the schematic. 555 drives the Mosfet and it pulses current thru the inductor L and the load. Once Mosfet is off, the magnetic fiel collapses and a voltage with oposite polarity appears on L terminals, thus the Schotsky diode conducts this energy in the form of current to the load, but at the load the polarity remains unchanged. The resulting formula is this: Voutput=Vinput/Duty Cycle. Because power losses are like 15-20% you just need a small heat sink for the mosfet. Believe me, I had one linear converter using a LM317, and it got very hot, even though it had a large heat sink.

Step 4: End Result.

This is my version of the circuit.

Step 5: Adjust Your Output Voltage

Now, connect the NiCd to your dc-dc converter and adjust it to output 1.5 to 1.8 volts. Then power up your MP3 and fine tune it to get the full battery scale. This circuit will be able to charge your MP3 battery and at the same time power up your MP3.

Step 6: Joule Thief

This is a circuit that does the oppositte to the Buck converter, it "boosts up" the voltage, hence it is call Boost converter.

This circuit is known for its alias "Joule Thief". This is simply a self oscillating Boost DC-DC converter.

Using the toroidal ferrite core found on some flourescent lamps, you can wind the transformer needed for this gadget.

This is what you'll need:

-Any small signal NPN or PNP (bipolar transistor) like BC548.
-1k resistor
-A 1.5 V battery
-A led.
-The toroid from your lamp.
-1 meter long piece of magnet wire.

Step 7: Winding

Now bend your magnet wire in half and wind it around your toroid.
Cut the ends and using a Ohmmeter, identify the ends of L1 and L2.
Solder the end of L1 to the begginig of L2. So polarity on L1 and L2 are oposite. (for more detail go to these link:

This is how it works:

When the transistor conducts, current flows thru L1 and the the LED is off (fig. a). This creates a magnetic field on the coil and makes L2 shut off the transistor. When this happens (fig. b), the energy of the magnetic field induces a voltage on the coil called "back emf" and this ADDS up with the battery so you have 3 V or more (it like adding batteries in series).

Because this cycle occurs at high frequencies (kHz, depending on your inductor and transistor, etc), the LED seems to be all the time ON.

Step 8: Final Result

Here is how i just soldered it to a Alkaline battery.

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    70 Discussions


    Reply 9 years ago on Introduction

    True. People are just trying to scare others. Or are stupid. If people looked at the different levels of mercury in different objects, a CAN OF TUNA, will give you more mercury than a broken CFL. Assuming you don't eat the CFL, just exposed.


    Reply 10 years ago on Introduction

    Boy, I don't know - my neighborhood, myself, and all plant life within a 10 mile radius of my house died last week b/c one of my careless neighbors dropped one of these CFL bulbs and exposed us to the mercury.

    This was exactly the way "they" say it will happen!


    build a BOOMbobhill125

    Reply 10 years ago on Introduction

    sorry to say but mercury is not really the biggest threat to your health yes You really shouldn't mess around with it or break cfl bulbs or tubes. But mercury wont kill you. Oral thermometers all used to have it and most people (that I know)40 and older have broken mercury thermometers, even in their mouths ( accidently ). And they do not have any symptoms of mercury poisoning at all.


    9 years ago on Step 8

    Thanks for the tip. I never thought of looking inside a cfl for a toroid ring

    Sorry, I used a DOS version of ORCAD then printed them and scanned them. My old matrix printer is mechanically damaged. Freeware for electronic design are very limited in their libraries of symbols. Do you have a link to a good piece of freeware that has a good bunch of symbols?


    Thanks. By the way, I have all of Forrest Mims' Engineer's Mini-Notebooks, by Radio Shack. Forrest drew them all by hand, no typing, no CAD, just good old fashioned schematics. I think this series was his Masterpiece. So I try, in my own way, to emulate him. I don't like to use computers for everyting, except for programing, but computer drafting seems a bit constrining.


    Yes, your drawings are very similar to Forrest Mim's sensible schematics. I have many of his notebooks and value them.


    Great guy still living in TX with his family, Did you know he corrected NASA and a temperature calculation used in global warming with electronics he built on his farm? The joke at the nearest radio shack when parts are missing like LEDs is that the last guy in the store was him! I keep missing him lol


    Thanks for the clue. Because of what you said, I looked him up on the Internet. He has a couple of websites, and (which sells his books), as well as several science sites. Amazing guy.


    Reply 10 years ago on Step 3

    I had a look at dai, which I personally use for UML drawings. It seems to have all of the symbols which you need, and I find a pretty usable program.

    I have access to Illustrator through work, and i do a lot of technical drawings: Scientific figures, documentation for code and applications. In the situations where it is applicable (UML diagrams, electric circuits) it's my first choice application. It's simple and provides just the important features. This makes it quite efficient and easy to use for the kind of stuff I need to do.

    It's a really old school drawing program, orginally implemented under X-Windows, but it's recently been ported to Gnome. There is apparently a windows version:
    It is of course GPL'd.


    Reply 10 years ago on Step 3

    whoops, I should have proofread more closely. In the second paragraph, my intent was to say that DIA is my first choice application, rather than illustrator. I only whip out illustrator when I have to something kinda fancy.

    I use a software called ExpressSHC which has a bunch. it has all the symbols that you have on your schematic plus more. look it up on google. the download takes like 10 minutes but its free and works great. also, if your a really big electronic geek like me, the program automatically downloades a program called ExpressPCB. you link your schematic to it, send it to the site, and they send you a printed circuit board for it.....for a price of course. I used it to make a bunch of tv remote jammers (KipKay) and it's a lot easier to use than veroboard.

    mr smart

    9 years ago on Step 7

    is there a way to make this into a dc to dc high voltage transformer ?

    1 reply
    unknownpocketnerdmr smart

    Reply 9 years ago on Step 7

    Well, you'll need to do some calculations to guess the winding ratio. Or you can make a boost converter.


    10 years ago on Step 3

    i think you forget pin 6, it must be connected with pin 2