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Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
Hey,
Thanks for the quick reply. I will leave it as is then, should be good for my new SGTC, (The older one was driven by a single 2n3055 and was making 5cm arcs with crappy caps) I am quite hopeful of this one.
I should be getting my MMC caps this week. Will update my thread in the Tesla Coil section with the results. Thanks to everyone who helped with tuning!
Yeah unfortunately it is a PC PSU, I am thinking of going up to my attic and riping apart some of the PC's left over from my overclocking days and just paralleling the power supplies.
BTW, how do switching power supplies respond to being put in series, sorry if it is a dumb question, somehow it doesn't seem to feasible to me.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
brtaman wrote ...
BTW, how do switching power supplies respond to being put in series, sorry if it is a dumb question, somehow it doesn't seem to feasible to me.
AFAIK the outputs are grounded to the case which is grounded to mains Earth. So seriesing the outputs is basically making a short. You might have luck with detaching the earth connection on one of the PSUs, but I'm no expert on this.
Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
Hey,
Yeah that is what I was thinking, I remember reading a post somewhere on the internets of some guy who supposedly wired them series, it always seemed like a stretch to me.
But, never hurts to ask, especially on a forum with so many EE's (Electrical Experts) :).
Registered Member #1956
Joined: Wed Feb 04 2009, 01:22PM
Location: Jersey City
Posts: 172
brtaman
PC psu's arranged in series are common on amateur radio as they need a lot of current at low voltages, as 40 A at 15 V.... Some folks even put four in series and parallel to get 24 V at higher current. There are a few sites explaining how to do that: It's the cheapest way to do it but the whole thing looks like crap using different old used psu's...
Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
tobias wrote ...
brtaman
PC psu's arranged in series are common on amateur radio as they need a lot of current at low voltages, as 40 A at 15 V.... Some folks even put four in series and parallel to get 24 V at higher current. There are a few sites explaining how to do that: It's the cheapest way to do it but the whole thing looks like crap using different old used psu's...
Very nice. Thanks for the link, my Google searches ended up with no real useful info.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Dr. Kilovolt, what is your opinion for SGTC use. Should I go for good resonance (like before) or just for brute power like now?
Thanks, uzzors, I am on 3+3 turns though, you think it would be better even lower? I am pretty happy with the way it is now because before the white arc would turn into purple much sooner and would then expand. With this version it just keeps on going in white + the arc seems much thicker?
EDIT: One thing I noticed during tests, even though the PSU is rated at 15amp@12v, when I draw the arc out and the ciruit starts drawing 10amp there is a noticeable decline in fan speed insinuating a voltage drop on the 12v rail?
I can remember some pretty good small SGTC's made with flybacks. I think they make a great and inexpensive beginner tesla coil project, just take care not to destroy your flyback. 100W is plenty of power for a small SGTC (up to like 5*20cm secondary or so). The flyback's output impedance is rather high compared to most TC power supplies, hence a correspondingly high surge impedance of the primary tank is required. That means a lot of primary turns (30+) and a small, high voltage cap.
A small rotary gap also seems to perform better than a static, but I think the static would work well too with enough airflow.
I wanted to try this myself but never got around getting an adequate flyback for it yet...
Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
Thanks marko for the suggestions.
Well I got my caps today...and the TC is a killer :D a 20cm lighting bolt (only 1), just like this video but with only one really long spark (it is burning up my crap secondary, good one is drying. I will post a video later tonight (its poker night today and I am already running late). I cant believe the performance :D
It works best with only 3 primary turns though!? MMC is 18kV 2.2nF It is a beast with only 10 minutes of tuning. :P Can't wait to show you guys.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
I would personally suggest making your own HV transformer, with an LOPT core. Less voltage, but that might be a good thing.
LOPT's secondaries will die very quick in Tesla coil use, but since homemade ones are normally lower voltage, they aren't always being pushed so close to the limit. I could push 700 watts into my homemade one continuously, and the arcs where large. around 6kv and maybe 120ma (just judging by the arc starting distance and i took the current from that and the wattage)
Just rectify with a string of UF4007's, preferably each with a 1kv or higher rated capacitor of some nanofarads in parallel with each diode.
Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
Hey,
Back from poker night, I don't think I have had worse hands in all my years of playing. -.- Oh well, such is life. :)
Arcstarted, yeah I agree the flyback in the SGTC circuit gets quite hot with only 5-10 minutes of runtime, I think I am going to need spare flybacks on stand-by. :) Your idea is interesting, I will talk to you on MSN hopefully you will be able to instruct me.
Few words before you watch the video. The table is a mess. The SGTC was thrown together in 1h using SGTC v1 parts (had to hurry). I spent 10 minutes tuning the coil, basically I adjusted only the windings. I am still using the junk secondary (you can see sparks flying from its top)
Specs:
18kV 2.2nF MMC 6x1 inch secondary 3 1/4 winds on primary (WTH?) 6cm sphere torroid
Well here is the promised video.
Some of the sparks are longer than the secondary!? I am happy but the coil is chaotic needs a couple days of tunning. I think a bigger toroid is in order.
EDIT: Marko, thanks for the suggestion, currently I am using a static sucker gap but the rotary is almost 40% complete. I like rotary mainly because of the "cool" factor in the ability to set BPS, not to mention the performance increase.
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Finished up ZVS need advice.
