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.
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.