12V Fluorescent Tube Inverters
Here are 2 designs:-
Very Easy Fluorescent Tube Inverter Circuit 12 DC to 220 AC 6 -20 W
(Modification from Eric ON4CBL)
Tune 1M for +-10 KHz, and maximum efficiency / resonance from transformer.
Tune 4k7 for desired current / brightness.
Heatsink TIP 41 for currents > 300 ma.
From Chrissi ZR6CPB
From : VK3EUB.#MEL.VIC.AUS.OC (Brian)
This circuit appeared in silicon chip mag October 1999 page75
This fluorescent light inverter uses just one transistor
and a transformer wound on a ferrite rod. The clever component is the
transformer, it performs 3 functions. Firstly, it acts as a feedback component
for the transistor to create an oscillator circuit. Secondly, it provides
a high voltage (over 2KV) to strike the fluorescent tube and thirdly it
supplies energy to keep the tube illuminated.
The transformer has 3 windings. The 20 turn primary is switched by the
BD681 and the resulting primary voltage of around 24V peak to peak (plus
considerable spikes) is stepped up in the 960 turn secondary. Positive
feedback is applied from the third winding to the base of the BD681 to
ensure that the circuit oscillates continuously.
The ferrite core of the transformer is an antenna rod from a transistor
radio. You can use a slab antenna but I chose to use an antenna rod 6cm
long and 9mm in diameter.
The primary winding is the first to be wound, on 45mm of the rod, using
20 turns of 0.5mm diameter enamelled copper wire. Use grease-proof paper
as the interlayer insulation. The second winding is the feedback winding
and consists of 6 turns of 0.3mm wire wound in a spiral fashion so that
it lies over the full length of the primary winding.
The secondary winding consists of 960 turns of the 0.3mm wire. The feedback
winding must be connected the right way around so that the BD681 gets
positive feedback. When first powered up, connect the 3 ohm safety resistor
in the positive line and connect the feedback winding. Then turn the circuit
on and off very quickly and if the fluorescent tube does not come on immediately,
the feedback winding is the wrong way around. The safety resistor allows
a limited current to flow through the circuit and the BD681 will not be
damaged.
Once the correct feedback connection has been established and the fluorescent
light comes on correctly, remove the 3 ohm resistor and the circuit is
ready to use. However, you must not use the circuit without the fluorescent
tube connected because it provides loading for the transformer and has
a damping effect on the spike voltages to the transistor's collector each
time it switches off.
By J Draper, Glenview, Queensland Australia.
/QSL
73 De John, G8MNY @ GB7CIP
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