How to Build a Simple, Efficient, 16w 12v Fluorescent Inverter With AC Output.

Introduction: How to Build a Simple, Efficient, 16w 12v Fluorescent Inverter With AC Output.

This inverter will drive any fluorescent lamp between 8w and 20w but works best with 16w tubes. It preheats the electrodes and keeps them heated while running. This inverter can be dimmed by reducing the input voltage e.g a pulse width modulator with smoothing capacitor. In this instructable I will show you how to build one of these inverters.

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Step 1: The Schematic Diagram


The electrode connected to the secondary is not heating.
Increase the value of C3.

The electrode connected to the transistor is not heating.
Decrease the value of R3. If this does not fix the problem replace Q3.

Little or no output and lots of heat, drawing lots of current.
Decrease the value of C2 and shorten air gap in core (transformer covered in next step), check feedback winding polarity. If this does not fix the problem replace Q1 and Q2.

Lamp fails to strike at 12v input, ends glowing brightly.
Decrease the value of C4.

Step 2: Winding the Transformer

First wind secondary winding on a bobbin of about 2.5cm x 2.5cm x 1.5cm.

Wind the heater winding over the secondary winding. you can start from the top or bottom.

Next insulate with PVC tape.

Then wind the first half primary starting from the bottom to top then sharply fold down back to the bottom.

Now wind the second half of the primary starting from the bottom to top and sharply folding down once again.

Wind the feedback winding the same way then insulate it all with PVC tape.

Insert the cores with a 1mm air gap.

Step 3: The Final Test

Give it a test by attaching the circuit with no tube connected to a variable power supply and slowly turning it up to 12v while observing the current draw. The current should be at around 200mA under no load and at about 1.5A under full load. If it shoots up to something silly reverse the polarity of the feedback winding to see if that fixes it.

Step 4: The Finished Board

Pictures of the finished board. Some components are mounted under the transformer to save space

Step 5: The Finished Product

The circuit built into a lantern.

The first picture shows it starting and the second shows it on.

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    6 Discussions


    5 years ago on Introduction

    Very nice!

    Would 2N3055 or TIP31C transistors be able to replace the two 2SD882 transistors?


    Reply 5 years ago on Introduction

    Yes, just replace R1 and R2 with 120R rated at least 1/2w. The on voltage drop of these transistors is higher than that of the 2sd882 so they may need a heatsink. There in no way of reducing the heat dissipation from them other than using a different transistor.


    Reply 5 years ago on Introduction

    Ok! Thanks for the fast reply! I will use two TIP31C transistor on two heat sink instead of using transistor insulators. for the resistors i will connect two 240 ohm resistor of 1/4W in derivation to get 120 ohm and 1/2W of max power.

    Thanks again jonathanmlang! :-)



    8 years ago on Introduction

    winding the transformer makes me live in agony


    Reply 8 years ago on Introduction

    Well I thought that too until I thought of using a standard drill clamped in a vice sideways with a wire bobbin placed over a screw in the work bench. Much easier!

    Put a long screw through the transformer bobbin with washers at both sides then place a nut on the end but DON'T tighten it too much of your transformer bobbin may split! Place the protruding end of the screw in the drill and begin winding!


    Reply 8 years ago on Introduction

    yeah i've been using this method for some time. but still... i find it difficult to do. i prefer the long hand wound method. it gives best results. but if i have over 200turns i use the drill method