I found it hard to get consistent current & brightness with varying battery voltage. A 24 volt battery can be expected to go from 20 volts flat to 30 volts at full charge current.
My circuit is very stable in this regard. Only the frequency seems to vary with voltage.
I think choice of fet (gate switch-on voltage) would be critical to get this circuit working on 12 volts. I've previously used bipolar transistors, in a TO-92 case, running off 9 or 12 volts to power lcd backlights. But thats a very low power level.
I expect, though haven't tested it, that this circuit would work well with a TIP41C, after choosing the right value of base resistor.
One last point I noticed; it takes a second or two for the tube to initially fire, after switch on, during which the current draw is about 1.5 amps.
Amanda
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