Arc (Poulsen) Oscillator Tesla Coil Ideas - Page 1
Forum section: electronics / projects

author: Cyberdragon
author_rank: Super Contributor
timestamp: April 16, 2018, 09:17:26 pm
content: I can only find one ancient mention of someone trying to use an arc (Poulsen) oscillator for a Tesla coil. All the links are long dead.https://www.pupman.com/listarchives/1999/August/msg00155.htmlYou would obviously have to have knowledge of machining your own parts (as it would probably be better than trying to cobble off the shelf stuff), and vacuum chambers if anyone wants to tackle it. But I'm more interested in the circuit design. The post said there was a "brilliant find", but I'm not sure if that was an actual coil schematic or just Poulsen info in general. It's long gone now regardless (there's still Poulsen info out there though).You'll need a HVDC source first, but however you achieve that probably doesn't matter as long as it's clean enough. As for the coil drive itself, there's several ways you could do it. The first would be a traditional Poulsen circuit with a series tuned primary and secondary as a Tesla coil. Another is an interesting circuit I found called the Collins telephone system based on autotransformers.Unlike a traditional Telsa coil, there would be no primary or secondary, just an oscillator coil and an output coil, which you could probably wind to get pretty high voltages (would this effect the tuning since it's directly coupled?).I'm not sure what that "resonance tube" component is, a vacuum capacitor or another spark gap?You would also need an amplifier on that transformer modulation input, as you would need a strong enough drive to hear anything in the arc. You could probably just build an amp around that transformer as it's output transformer.Any other ideas?

author: dmills
author_rank: Super Contributor
timestamp: April 16, 2018, 10:18:12 pm
content: I built a Poulsen set in my misspent youth.Mine ran in a mostly hydrogen atmosphere from thermal dissociation of alcohol, arc electrodes were carbon rods, and I used a ballast resistor instead of the magnetic regulation that that drawing has. The RF is not what you would call clean.I don't think it would do well for a tesla coil of the autotransformer sort, you really want loose coupling to get that to work well.The tech is cool and very, very steampunk, but there are much easier ways to do the job, an old Russian external anode RF power Tetrode springs to mind as being cheap, high power, high voltage, robust and easy to make honk.Regards, Dan.

author: Cyberdragon
author_rank: Super Contributor
timestamp: April 17, 2018, 06:00:21 am
content: You're supposed to use the coils, it was standard. If you just used a ballast, of course the output will be dirty, it's not an arc lamp. The coils keep the arc stable as well as regulating the power, they're essential for stable operation.The thing about spark gap coils is they can get really high powered. And they also just tend to quite and not explode if they fail (unless a component was underrated), especially in this case, as the arc would go out making it open circuit. It's about building a better spark gap coil, not a tube coil.That circuit would work, but it wouldn't be Tesla coil, it would be an Oudin coil. In fact, the circuit is nearly identicle (principle wise).

author: dmills
author_rank: Super Contributor
timestamp: April 17, 2018, 10:40:31 am
content: My Playing was pre internet and I had materials sourcing issues with the soft iron cores I would have needed for the magnet structure, and I was a child with no access to a machine shop.The magnets are a neat way to stabilise the arc voltage, without the gross inefficiency of a ballast resistance, but are not absolutely required for CW operation.73 Dan.

author: Cyberdragon
author_rank: Super Contributor
timestamp: April 17, 2018, 06:33:55 pm
content: You'll get CW oscillation with just a ballast, but it won't be clean or overly stable.The rotary electrode and an auto igniter would be totally optional though, probably only useful if you were using it for stage/event shows like Arc Attack or something where you would need reliable operation.The "resonance tube" component appears to be a gas discharge tube used as a tuning indicator for the coil.http://g3ynh.info/zdocs/magnetics/appendix/self_res/gallery.htmlIn that case, it's entirely optional, but could probably be implemented pretty easy with just a small florescent lamp or something.