Problems with my tesla coil (FIXED PICS!) / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Problems with my tesla coil (FIXED PICS!)

1 2 next

Move Thread

LAN_403

magnet18

Thu Sept 08 2011, 08:43PM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

OK, I plug it in, it go BRRRRT angrilly, spark gap starts firing, and nothing happens...
I put a fluorescent tube on top of the toroid, and it just lights up oh-so faintly.

Does this mean that I have to tune it?

Dr. ISOTOP

Thu Sept 08 2011, 08:55PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Yes.

magnet18

Thu Sept 08 2011, 09:03PM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

Should I try moving it every quarter turn, whole turn, half turn, or what?
How sensitive is it?

Hey, Would using a steel grounding rod, and having it about 10 feet away make a difference?
Also, I just noticed that I was getting strikes from the primary to the bottom of the secondary, what would cause that?

magnet18

Fri Sept 09 2011, 12:56AM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

OK, I noticed some carona coming off the foil of my bottle cap, and when making a video I think my camera picked up arcing on the secondary.

And then there's the occasional arc from the bottom of the secondary to the primary, which I believe is either the result of poor grounding, or back emf when I turn it off (it only does it when I let go of the switch)

I think I can do a better job with the shlack on the secondary, and put the bottles of the cap in a bucket of oil.

I also think I might be losing some energy into the wood that serves as the primary coilform, so I plan to re-do the primary using plasti, and also design it with the same amount of inductance in less wire, so I will have some left on the outside for tuning.

Am I missing something?

lightlinked

Fri Sept 09 2011, 01:27AM

Registered Member #2087 Joined: Tue Apr 21 2009, 08:32AM
Location:
Posts: 115

for the arc over to the primary you can move the secondary higher. is your secondary coated with epoxy or varnish?
have you measured the capacitance of your bottle cap with a meter?

Dr. ISOTOP

Fri Sept 09 2011, 01:27AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

(1) VERY sensitive
(2) Over-coupling
(3) Tune first, then optimize your construction

Also, wtf TRIPLE post??? There _is_ an edit button, ya know ;)

magnet18

Fri Sept 09 2011, 01:41AM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

Promised picture-

Scratch the bit about the secondary arcing, trick of the camera

There IS arcing to the primary however, so I'll move the secondary higher to reduce coupling and just get it farther away.

I don't have a capacitance meter

getting one soon, $$$ or not. Same for a decent scope.

So, since I lack a decent scope at the moment, I just have to move it an inch, power it up, repeat until it magically works?

(sorry bout the tripple post... I got carried away)

Herr Zapp

Fri Sept 09 2011, 07:39AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

M18 -

1. By itself, a steel grounding rod is not a problem, but what's the diameter, how deeply is it buried in the ground, and what kind of ground is it buried in? Damp soil is fine, dry sand or dry rocky soil is bad.
2. 10' is further than ideal, since the inductance of that 10' of ground wire is the same as adding X number of turns to your secondary that you probably have NOT included in your secondary resonant frequency calculations. Can you move the coil closer to the ground rod for initial testing, using a much shorter lead?
3. Assuming that you have reasonable clearance (say 3/4" to 1-1/4") from the OD of your secondary to the ID of your primary, arcing here is frequently a sign that your secondary is not actually grounded. Carefully re-check all your connections between the bottom turn of your secondary and the ground rod. Also make sure that there are no points or sharp edges anywhere on any metal surface on the inner turn of your primary or the outside of your secondary.
4. For tuning, initially move in 1/4 turn increments. If all else is OK, you should easily see either an increase or decrease in output as you move inward or outward on the primary. If you've "swept" the entire primary and haven't seen a clear increase or decrease in output, you may be so far out of tune that you can't achieve resonance with your current configuration. Add or subtract capacitance (tank cap) and again search for the tap point that gives best performance.

If all else fails, build Terry Fritz' "Tesla Tuner" (

, or borrow an oscilloscope and signal generator to measure the actual resonant frequency of both primary and secondary circuits, and adjust as necessary

Herr Zapp

magnet18

Fri Sept 09 2011, 02:44PM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

The diameter is 3/8", and it's buried about 3 feet, soft wet clay in my moms flower bed, she was thrilled.

I will try to move it closer, hopefully it's not raining, because I don't want to get my coil all wet (been raining for like 3 days

)

Right, there are sharp edges AND it's less than 3/4" away... mainly because of the hose clamp I used to attach the lead. Ima fix that... it scares me.

I think I shall build one of those tuners, thanks for that link

If I increase the capacitance in the primary it reduces the required inductance in the primary coil for the same resonant frequency, correct?
What do I need to worry about if my cap is LTR?

magnet18

Sat Sept 10 2011, 06:25PM

Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location:

Posts: 624

OK, when trying to tune the primary, the tuner only lights up when i have it turned as far as possible...
It worked fine for my secondary, saying it was about 350khz-ish, but when I try the primary it says I have a frequency of like 10khz, no matter how much I decrease the capacitance to try to raise it...

Could this be because of the saltwater capacitors?

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob