True, but most tutorials involve a flyback transformer or chains of cap/resis to produce a steady arc. Im looking for something small/light enough to fit on a robot about the same size as the one in the video.
I don't see the size anywhere in the video and lots can be hidden by the tubes, but nevertheless... You're thinking of caps and diodes (A Greinacher multiplier), but that won't work, as the caps would have to be huge for making warm sparks at the gap size you require.
You need a transformer of some sorts and the more power and gap distance, the larger the transformer - however, using a high frequency, a fairly small ferrite core should do.
For the robot im working on power supply would be 12v 2400mah and spark gap would be 1/4 to 1/2 inch with a steady flow or high pulse rate i guess
Do you have any schematics in mind?
Nothing particular, but there's ample out there, if you don't wanna design it yourself.
Making a ½" spark is easy, making it a "warm" (high energy yellowish) spark takes a little extra - what is the purpose of the spark?
This will determine how "hot" the spark needs to be.
You can find tables for voltage vs. spark gap size vs. electrode diameter, but they'll tell you the bare minimum for a weak spark and if you want the spark to do something useful (like in a car motor, where it even has to spark under pressure), you need a good deal more.
A small ignition coil, or even better, an ignition transformer driven by a 555 and a power transistor will give you a steady pulse train that will seem
continuous from as low as 10..20Hz (it does growl at the spark frequency though)