Ok as part of my project for my mig/stick/tig on board 4x4 welder I have been looking at hf start for the tig mode.
I've seen designs some on this site about making a hf start unit, but all use neon sign trannys, not suitable for a mobile set as I dont have 240, so I've designed, well cobbled together a unit that does the job using 12v.
Heres a view of the output board.
You can see in the background the dc board, this is just a chopper which drives a car ignition coil with pwm, and at the front is the osc/spark gap board, the coupling trans is just 10 monitor cable suppressor ferrites held with heat shrink, and the windings placed on top, I didnt bother with doorknob caps I used 20 2kv caps to make 1 40kv cap, the spark gaps are made from scrap paxolin and the ends of 4.5mm tough drill bits.
I used the sig gen in the background to confirm the rf freq, it was close to my calculation at 1.4 Mhz.
Edit: I just tested this unit, I connected it to a ac output buzzbox, and the result was odd, there was a nice spark but the arc wouldnt maintain, I wonder if the hf start voltage needs to be sychronized to the output voltage waveform, shouldnt be a problem in the real application as it'll be dc.
I've seen designs some on this site about making a hf start unit, but all use neon sign trannys, not suitable for a mobile set as I dont have 240, so I've designed, well cobbled together a unit that does the job using 12v.
Heres a view of the output board.
You can see in the background the dc board, this is just a chopper which drives a car ignition coil with pwm, and at the front is the osc/spark gap board, the coupling trans is just 10 monitor cable suppressor ferrites held with heat shrink, and the windings placed on top, I didnt bother with doorknob caps I used 20 2kv caps to make 1 40kv cap, the spark gaps are made from scrap paxolin and the ends of 4.5mm tough drill bits.
I used the sig gen in the background to confirm the rf freq, it was close to my calculation at 1.4 Mhz.
Edit: I just tested this unit, I connected it to a ac output buzzbox, and the result was odd, there was a nice spark but the arc wouldnt maintain, I wonder if the hf start voltage needs to be sychronized to the output voltage waveform, shouldnt be a problem in the real application as it'll be dc.
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