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Jonathan Dennis

Thu Aug 20 2009, 07:01PM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Yes, in these photos I elevated the secondary. NO, I could not get continuity from toroid to ground rod, but I COULD from the bottom of the secondary windings to the ground rod. If you look in the pictures you can see the wire from the bottom of the secondary connecting to a small screw. On the under side of this wooden deck, the grounding wire is clamped to the screw, and runs to ground. I thought perhaps I couldn't get continuity THROUGH the secondary windings because the wire is so small (28 Gauge). The pics were the best I could do without getting dangerously close. Without dimming the lights, the flashovers were invisible.

Austin

Thu Aug 20 2009, 08:45PM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

I don't understand, you only tested the continuity from the BOTTOM of your secondary wire to the stake in the ground?

Did you try checking the continuity from the bottom of the secondary to the top of the secondary and then from the bottom of the secondary to the toroid. How did you calculate the size of your toroid? ummm try adding a breakout point if indeed the secondary is connected to the toroid.

These are obvious suggestions but I make no assumptions when helping people troubleshoot stuff. because we all know what happens when you ASS-U-ME.

also i don't think a 3 foot steel stake in the ground is a good ground but perhaps someone else can confirm th

cheers

Jonathan Dennis

Thu Aug 20 2009, 09:39PM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Ok, I tested continuity from bottom of secondary to ground rod and the connection is good. However I'm not getting continuity from the bottom of the secondary to the top, my voltmeter beeps when there is continuity. Instead of beeping random numbers popped up around .030 I don't know what this means, I assumed there was continuity but the wire was so small and so long that the voltmeter couldn't get a clear reading, therefore it did not beep to indicate a good connection.

Myke

Thu Aug 20 2009, 09:46PM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

The wire in the secondary is probably too long (too high of a resistance) for your meter to consider it a complete connection. try measuring the resistance of the secondary and see if it gives you a constant reading.

I would say that 3 feet into the ground isn't enough... I think you can get grounding rods from a hardware store like ACE or home depot that are 6-8 feet long and are copper.

Jonathan Dennis

Thu Aug 20 2009, 09:50PM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

How much money though? I'm broke, just payed for my tuition. My dad has tons of steel poles laying around his greenhouses, I need to try and make something I already have work.

Herr Zapp

Thu Aug 20 2009, 11:36PM

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

JD -

STOP!!!

If you can't measure continuity from your toroid to your ground rod, you need to find out why, before you go chasing any other issues. Something is very wrong!!!

Your coil CANNOT operate with this open circuit condition. This "open circuit" condition means one of the following:

1. Your secondary wire is not electrically connected to ground;
2. You have a break somewhere in your secondary wire;
3. Your secondary wire is not actually connected to the topload.
4. You made the continuity measurement incorrectly.

First, verify that you are making the continuity measurement properly. Your Tesla coil design program should tell you what the expected DC resistance of your secondary is, based on the wire gage and the total length of wire used. If your program doesn't provide a DC resistance value, it will tell you the total length of wire required. Look up the resistance of #28 AWG magnet wire, and you can calculate the DC resistance of the secondary. Knowing the expected resistance of the secondary will allow you to select the correct resistance range on your multimeter to use when making the continuity check. If you use the wrong range, you may get an incorrect continuity reading.

(If your secondary was actually built to the specifications you posted earlier, 4" dia X 20" long, #28 awg wire, this will have a DC resistance of around 325 ohms.)

When you say you verified continuity from the bottom of the secondary winding to the ground rod, how exactly did you make this measurement? Did you just check between the ground rod and the "screw" the secondary wire is supposedly attached to? If you did, it's possible that you only checked the continuity of the ground wire, from the rod to the screw. If you made the measurement from ground rod to screw, you can disconnect the secondary wire from the screw and it WILL NOT change your test results. That's why I specifically said to check continuity from ground rod to toroid.

If your secondary wire is not actually grounded, you can get secondary arcing EXACTLY like is shown in your video.

If your secondary wire is not actually connected to your topload, the coil will be RADICALLY out of tune, and you may get all kinds of unusual behaviour, including strange arcing in odd locations.

(By the way, what technique did you remove the enamel insulation from the secondary wire, where you connected it to the grounding screw, and to the topload? I have seen first-time coilers "forget" to remove the insulation on magnet wire, and end up with a secondary coil that's completely isolated from the rest of the system.)

Regards,
Herr zapp

Coronafix

Thu Aug 20 2009, 11:45PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Hi Jon, from your vid I see racing arcs. This is usually a sign of overcoupling, but along with the pictures of your primary/secondary setup I would say it isn't that. The coupling appears to be quite loose.
One thing I definately see is that your ground rod is a galvanised bolt which is a poor choice. If you have some copper pipe, this will be better. Or i understand that a ground rod can be bought for quite cheap, which is a copper coated steel stake. (Oh, Myke has mentioned this)
My ground is very rocky here so i've got the copper in the ground not very far, but I have connected it to my shed which is a big steel counterpoise essentially.
You can try raising the secondary up some more to stop the racing sparks, but to get efficiency you'll have to nail the real problem.
Can you tell us about your coil? # of turns, power input.

Austin

Thu Aug 20 2009, 11:52PM

Registered Member #1169 Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251

I just hope JD doesn't hurt himself....

Myke

Fri Aug 21 2009, 12:14AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

I noticed those things that looked like racing sparks but I then thought they were artifacts from the camera's CCD. The sparks might be bright enough to saturate other parts of their columns. You can see this in many videos of arcs so I didn't think much of it. You could try to rotate the camera by 90 degrees so that the sec looks horizontal in the video or just say if there are any small sparks racing across the secondary. As said before though, racing sparks usually appear near the tops of secondaries and not near the bottom.

Jonathan Dennis

Fri Aug 21 2009, 05:11AM

Registered Member #2153 Joined: Wed Jun 03 2009, 03:19PM
Location:
Posts: 69

Ok, I'll calculate the resistance of the secondary and check it. It's 4"x25" btw. To remove the enamel, I took semi-rough sandpaper and gently rubbed the ends of secondary wire until it was bare. When I checked continuity, I checked from the end of the secondary wire that connects to the screw, to the ground. Not from the screw to the ground. So, could the problem be a very poor grounding rod? Or do you think it's a bad secondary? Like I said earlier, I thought I couldn't get continuity from bottom of secondary to toroid because of the resistance and length of the tiny 28 gauge wire. If the problem is the secondary, it's going to take a while to fix, because I go off to college in 2 days. If it's the grounding rod, I can move it to a less rocky location, and I can use a copper pipe I have. It's 2.5' long. I hope that is long enough.

P.S. thanks for your concern Austin, but I NEVER screw around with HV, I check EVERYTHING with voltmeter before I touch it. I know there is always a chance, but I do everything in my power to get that chance to 0%!

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