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LAN_403

HV Enthusiast

Sat Feb 02 2008, 02:05AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

wrote ...

what type of screws or stand offs should I use for Type 1 PVC.

Actually, i chose Type 1 PVC since it is very easy to machine and low cost as well. You can actually drill / tap it just like aluminum. I use standard steel hardware.

wrote ...

My main concern is that i will have to drill all my holes and then put a machined screw though it which would be very time consuming. also do my stand offs need to be grounded as well?

Not that time consuming. Its only 4 holes i think. You can get self-tapping screws too. The (4) corner holes on the resonant driver board are connected to the internal ground plane. You only need to have one ground going to the
control board.

wrote ...

When the schematic refers to "ground" I am assuming it is not referring to the 3rd prong in the outlet of my house. I heard this was bad because the tesla could induce currents in other devices around the house like my plasma TV

Actually, i have never run a dedicated ground with my DRSSTCs, even the largest ones i've built. I always run earth ground to the 3rd prong on the outlet. Of course, anytime you hook up a Tesla coil to your power, you RISK damage to any other electronics wired on the same circuit. Its up to you to the way you ground your coil.

Just if you use a strike target, make sure to attach that directly to the ground where your secondary terminates. This helps maintain circular currents within that small loop during discharges. Otherwise, if your coil strikes the ceiling or other object nearby, it will find any path it can to make it back to the secondary and this means going through wiring in your house etc...

wrote ...

and looking at Figure 2-8 it looks like everything is grounded through the Resonant board... am I correct?

No. The only items grounded to earth are the secondary base, and the Resonant board. The resonant driver board is floating through the power transformer, so you need to ground the centertap for safety.

Wirenut

Sat Feb 02 2008, 02:31AM

Registered Member #141 Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96

Actually, i have never run a dedicated ground with my DRSSTCs, even the largest ones i've built. I always run earth ground to the 3rd prong on the outlet.

It's funny you mentioned this EVR, I did the same thing with my coil, but did not want to bring it up on the forum for fear of criticism. I have not fried any electronics in my house and I have run my coil merely feet away from my tv and 15 feet from my computer. Of course, if you're really paranoid, all you have to do is unplug any electronics on the same circuit to protect them.

Austin

Sat Feb 02 2008, 04:19AM

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

yes I got your PM Wire, Thanks for the tip even when faced with persecution

. I Just finished my primary circuit today, and will begin the strike rail probably tomorrow.

Daniel what did you mean by "The resonant driver board is floating through the power transformer, so you need to ground the centertap for safety?" Also do you sell board for the basic modulator mentioned in "DRSSTC : Building the Modern Day Tesla Coil." I can't afford the advanced modulator.

Will the tesla even run without some kind of external modulation? Or will it just resonate at its natural frequency?

Oh and one more question. is the terminal block mentioned in figure 2-11 just a way of connecting the power cord to all the peripherals without actually soldering them to their perspective boards? I don't actually think its talked about in the book, probably because its common knowledge to some people.

I ask a lot of questions but I like to make sure... Building a tesla is not something I want to "guess" on. Besides someone than myself may find this useful one day.

HV Enthusiast

Sat Feb 02 2008, 04:43AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

[quote]
yes I got your PM Wire, Thanks for the tip even when faced with persecution

. I Just finished my primary circuit today, and will begin the strike rail probably tomorrow.
[/quote]

Well, just remember, as with any tesla coil, there is always a risk in damaging electronic equipment. Best bet is to unplug anything sensitive.

wrote ...

Daniel what did you mean by "The resonant driver board is floating through the power transformer, so you need to ground the centertap for safety?" Also do you sell board for the basic modulator mentioned in "DRSSTC : Building the Modern Day Tesla Coil." I can't afford the advanced modulator.

The resonant driver board is powered via the small filament transformer which is isolated. If you don't ground the secondary side, no telling where the board is floating in reference to ground. So this is why we ground it - to ensure its tied to earth ground and safe to work on.

Don't sell the basic modulators. They are simple to build though. Just a 555 timer chip is needed and a few parts.

wrote ...

Will the tesla even run without some kind of external modulation? Or will it just resonate at its natural frequency?

Without an external modulator, the tesla coil will not run. The input to the gate driver ICs are pulled low, so in the absenve of a modulator signal, they will be forever disabled.
Also, the modulator is necessary to ensure the system is "pulsed" and running a very low duty cycle. If you just pulled the external modulator up to high and run the coil CW (continuous), you'd most certainlky blow up quite
a number of components.

wrote ...

Oh and one more question. is the terminal block mentioned in figure 2-11 just a way of connecting the power cord to all the peripherals without actually soldering them to their perspective boards? I don't actually think its talked about in the book, probably because its common knowledge to some people.

Yes

Austin

Sat Feb 02 2008, 07:09AM

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

Since I am on the subject of grounding things..... what prevents the user from being electrocuted while using an external modulator? Coax cables have conductive material in it, so what would happen if an arc struck the cable connected to the modulator?

----->

Wirenut

Sat Feb 02 2008, 07:29AM

Registered Member #141 Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96

Coax cables have conductive material in it, so what would happen if an arc struck the cable connected to the modulator?

The co-ax cable has a grounded shield, so any arc connecting to it would be conducted to ground. Also, the modulator box is plastic. I also aim my breakout point to the side and no arcs have come close to hitting it. If an arc did hit it, I think it might kill the modulator - I've noticed that it is very sensitive to the rf or em field from the coil. If I'm closer than about 7 feet, the coil's output drops dramatically, especially if I hold the modulator in a manner that makes the board parallel to the coil. The advanced modulator design has 2 bnc jacks, and if I'm too close to the coil and I touch one of the bnc output jacks, I can feel a small shock from it. Nothing painful, but it's definitely there.

Austin

Sat Feb 02 2008, 07:34AM

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

I was thinking about making my modulator out of something metallic for better shielding would this be a bad idea?

Wirenut

Sat Feb 02 2008, 07:41AM

Registered Member #141 Joined: Sat Feb 11 2006, 01:14PM
Location: Southern California
Posts: 96

I was thinking about making my modulator out of something metallic for better shielding would this be a bad idea?

Maybe some others here can share their experiences. On one hand, metallic objects near a running coil can have currents induced in them making touching them uncomfortable, on the other hand, yes the shielding should be better, and with my coil, the induced current problem goes away as long as I'm more than about 7 feet away. If you already have a metal enclosure planned, I'd say go ahead with it - it'll probably be ok, and you can change it later if it's not without too much trouble.

HV Enthusiast

Sat Feb 02 2008, 07:47PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Austin wrote ...

Since I am on the subject of grounding things..... what prevents the user from being electrocuted while using an external modulator? Coax cables have conductive material in it, so what would happen if an arc struck the cable connected to the modulator?

----->

With a DRSSTC, you basically position a break-out point on the toroid to the side where you want arcs to propogate. Doing this, you can route the interrupter cable on the opposite side away from the arcs and shouldn't have any problem. However, you can never eliminate any electrical hazard risk with a Tesla coil so you need to proceed understanding the risks involved. When i run a DRSSTC, my interrupter is usually on the ground and i have minimal contact with it, also my cables are routed in such a way where the arcs never strike in the area where the cable runs.

However, even more dangerous would be the primary circuit coupling into resonant driver board and putting full DC bus voltage on the interrupter. Hence, the NEED to properly earth ground the floating modulator control board!!!

Austin

Sun Feb 03 2008, 02:42AM

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

The primary and base of the coil are done.... well almost, I ran into a snag. The books states that I only need 10-24 machined screws to bolt the primary and the strike rails into the board however the strike rail supports have an 8-32 tap dimension in the schematic. I'm assuming Daniel ment to say "8-32 falt head phillips machine screw, 1" length, stainless steel" instead of "10-24 flat head phillips machine screw, 1" length, stainless steel" in table 3-6. Any comments Daniel? Should I go ahead an order some of those screws?

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