Introduction: A Simple, Low Voltage Inverter for Fluorescent Lamps Up to 15 Watt

About: I am a high school student in Cairns, Queensland. Most of the time I am either at school, sleeping, doing stuff on my computer, making circuits of some kind or messing with 240v

Thankyou to Burak Incepinar for letting me document his design. This is his website if you want to check out more awesome designs.

This Instructable will help you run any fluorescent light off low voltages, It has been tested to run Compact Fluorescent Lights and Fluorescent tubes up to 15 watt.

Step 1: Parts

Things you will need:
  • 25mm x 20mm x 5mm ferrite core.
  • AWG28 (~0.3mm) Magnet wire.
  • AWG32 (0.2mm) Magnet wire.
  • 2x 22nF unpolarised capacitor, I used ones out of a camera flash.
  • 22 ohm resistor (red red black gold) OR a variable resistor.
  • 470 ohm resistor (yellow violet brown gold) OR a variable resistor.
  • A BD243C or similar NPN transistor.
  • A fluorescent light to drive.
  • A battery or power supply of your choice.

Step 2: Dismantling the Ferrite-cored Transformer

Try to pull the two "E" cores apart. Usually they have a little glue between them which makes it extremely hard to dismantle without breaking the ferrite core. Mine broke at the ends which still gave me space to wind/unwind it.

If your ferrite core breaks at the end, You can usually glue them back together with little performance degradation.

Step 3: Wind the Transformer

The hardest step if you can't count to 250...

Use AWG28 (~0.3mm) wire to form primary and feedback windings and AWG32 (0.2mm) wire to form secondary. Make out a smooth winding for maximum performance and easy fitting. Place primary and feedback windings on opposite sides of the frame. Primary winding will run over on feedback in this case but it is not so important. It also isn't important in which direction the windings are made, you just have to change two wires' places to make circuit work, But for a problem less first run and make the transformer to fit on the PCB right, follow these instructions:

Start by numbering the four slots on your transformer 1, 2, 3 and 4. Start by winding the feedback. Put wire at slot two (leaving a bit of wire free to connect to the pins easily) and wind 18 cycles clockwise, When done put the wire in slot three. Start on slot 4 for primary, wind 25-30 cycles clockwise and end in slot 1.

Wind secondary with AWG32 wire and wind 250 cycles turns from the other end of the transformer

If you make a mistake at this point or just confused, it does not matter at all. Allow wires came out 2cm or more long from the frame, then you will be able to swap feedback (or primary) connections in case of wrong phase polarity.

Step 4: Put the Transformer Back Together

Put your transformer back together, Making sure that if you broke the core that it goes back together the right way.

There should be thin spacers made out of adhesive tapes, between the contact points of core parts. If you got your ferrite core with this spacers on it, do not remove them. If there isn't any spacers, you can use very thin adhesive tape to make them. If you don't use any, performance of the transformer will be degraded. You should manually move two core parts relative to each other in order to find the best operating point which can be determined from the brightness of the lamp.

Step 5: Make the Driver Circuit

WARNING, Only use the driver circuit when there is a fluorescent tube connected to the output or you can damage your transistor.

Using the schematic, Put together the driver circuit, You should use a breadboard at first to make sure everything works because it is very hard to trouble shoot a part on a PCB.

Once tested and working, you can make a PCB for it using the included PCB layout, Change it to match your transformer.

Step 6: Is Your Circuit Not Working?

If it isn't try:

  • Reversing the feedback wires
  • Check all your connections
  • Does your transistor work, If not get a new one.
  • Has your circuit got power, If not, FIX IT!

Enjoy the pics of the 12 volt driven fluorescent lights.

F8T5 tubes can be easily light up with the inverter. Just take this advice: as the tubes get old, they draw more current from the inverter. So always use a tube that lights up well and consumes less current.

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