Spark Gap noise supression / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Spark Gap noise supression

1 2 next

Move Thread

LAN_403

Sulaiman

Sun Jul 15 2007, 07:32PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I am asking for ideas on how to 'silence' my static spark gap.

I am experimenting at low power (from 1W to 100W) with a spark gap Tesla coil
trying various hv generators (OBIT, Ignition Coil, and a couple of experimental invertors)
and MMCs and primary wire types, coupling. tuning etc.
with a selection of secondaries and toploads
General messing-about really.

I have made a static spark gap using tungsten rods and heatsinks that quenches quite well with no fan/forced air
(up to 20 kV and low power)
It's too noisy for continuous exposure so I'm going to 'silence' it.
I'm thinking just a wooden box with foam sponge or expanded polystyrene or some heavy cloth lining
I may have to add a fan, but I'd prefer not to.

Any advice please?

ShawnLG

Sun Jul 15 2007, 08:39PM

Registered Member #286 Joined: Mon Mar 06 2006, 04:52AM
Location:
Posts: 399

Sucker gaps have a low noize output.

HV Enthusiast

Sun Jul 15 2007, 08:55PM

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

Why? Most of the noise comes from the spark output on the coil itself anyways.

Sulaiman

Sun Jul 15 2007, 09:22PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Why? - because most of what I'm currently experimenting with is cheap/easy hv sources for SGTC use,
(CCPS-type invertors)
so mostly I use a 'dummy load' (tin can) in the primary
whilst investigating the various hvpsu handling of capacitor-charging and rf energy, transients etc.

Occasionally I move outside for a test with 'live' secondaries.
Rarely (but maybe more soon) I use a magnifier arrangement so the resonator is outside.

So I just want a simple quiet spark gap.
Nothing too technical - just easy, cheap, effective containment.
Must be accessible for occasional adjustments.
I only ask for comparative use of sound-proofing materials really - the box will almost certainly be wood due to cost/ease.

(My left ear already needs a hearing aid - I'd like to make the right ear last as long as possible)

P.S. The cheapest/easiest NST/OBIT substitute so far, that is rugged/reliable, is an Ignition Coil invertor.
I'm now trying ferrite-cored transformers, from pot-cores to 1" x 1" x 4" blocks glued together.
The large inverter gives too much power for my simple static gap so it will be part of an SSTC soon.

I'd 'publish' more of what I'm doing if I wasn't soooo lazy to make a web page.

Hazmatt_(The Underdog)

Sun Jul 15 2007, 10:20PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

You may want to have parts of your enclosure transparent for inspection of the gap itself, otherwise you won't be able to see what's happening with it unless you take it all apart.

ragnar

Mon Jul 16 2007, 12:16AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

'Leaded' sound-deadening cloth isn't cheap, but when properly layered is very effective, accoustically.

...

Mon Jul 16 2007, 01:37AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Just keep in mind that your gap is disapating a ton of power, and is making a variety of not so pleasant gases. You could probably get away with having 2 small holes hooked up to a little blower to purge fresh air in it...

ArcLight

Mon Jul 16 2007, 04:46AM

Registered Member #341 Joined: Thu Mar 23 2006, 07:41PM
Location: Northern Illinois, USA
Posts: 69

I don't claim to understand what you're doing or to fully understand coiling. I only offer my high voltage experiences in case there are any allegories that might be helpful.

On my first coil, the safety gap consisted of a plastic utility box and 3 carriage bolts to protect a 4-MOT stack. It worked fine until I covered the open side of the box with a piece of Plexiglas. What a mistake. The gap almost immediately began to power-arc and the coil quit running. Once I removed the plexi so the gap could breathe fresh air, it quit power-arcing and everything went back to working properly. I can only guess that the gases in the enclosure ionized and with no way to escape caused the gap to power arc.

As for the gap being noisy, I had a situation recently when I was adding a 15Kv, 30Ma transformer to my 15Kv, 60Ma power-supply. After adding the required extra capacitance, I had a (all too often) stupid moment and moved my primary tap the wrong direction. This caused the coil to be so out of tune that there was no output from the secondary, but what an incredible racket.

Before, when the coil was in tune, the gap sounded like an arc-welder (kind of a quiet hissing, spitting sound.) But with the coil so out of tune the gap just roared like an incredibly fast machine gun. It was truly amazing and somewhat frighting the amount of noise.

I'm guessing that being so out of tune caused the primary to be unable to transfer its energy to the secondary and that energy had to be dissipated someplace, and the gap was it.

Regards, ArcLight

Dr. Shark

Mon Jul 16 2007, 10:23AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Suliaman, I'd be very interested to hear more about what you are doing, so if you don't have the time to put it on the web, maybe you could start a thread about it here?

Re. the silenecing, you basically have two options. The first would be enclosing the gap in an airtight box, which would force you to keep runtimes very short, or to add a very elaborate water-cooling system. I think neither of these are feasible.

The second option would be a construction similar to a car exaust system or a firearm supressor, or in fact two of these added to the spark box: One to admit fresh air, and one on the exhaust side. Unfortunatley the sound will try to escape both ways.
A sinlencer like this could be constructed relatively easily e.g. from two copper tubes with lots of holes, and a tin can for containment. An image is worth a thousand words, so please look here

for what I mean.

A slightly simpler option would be to use a single pipe stuffed with e.g. steel wool, but I fear that this would create more backpressure than a simple blower could handle. Attaching a vacuum cleaner to suck air through would create as much noise as the spark gap itself.

Sulaiman

Thu Jul 19 2007, 02:58AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

It's really not very exciting, I am trying to design a 'noob' SGTC,
One of the major obstacles for me as a 'noob' was the HV source
I found it either difficult or too expensive to get a good NST
I also found it quite easy to 'kill' an NST
Although technically non-lethal an NST is (to me) quite a hazard to a 'noob'
OBITs are a little cheaper, but still easy to 'kill'
MOTs are lethal so I'm not even considering them.

So I am trying to come up with a simple SGTC that any 'noob' can build
with easily available parts, at a reasonable cost.

It also want it to be usable as a general purpose 'hv experimenter's' supply

I haven't got very far, so far an automobile ignition coil seems the best
( TV/monitor flybacks are also good but there are so many variations
and I don't want to answer the same questions too many times)
basically a 555, igbt and ignition coil in flyback mode.
Batteries are simplest, transformer/rectifier supplies give more power.
What I'm experimenting with at the moment is the hv diode(s)
how they hold up with a spark gap and the high frequency voltages.

Due to 'polyprojectitis' combined with being a pretty lazy guy, there's no end-date.
When/IF I get a good final design I'll definately 'publish' it.
(including the actual SGTC which will also need to be easy/cheap and matched to the hv source)

Any suggestions for a 'noob' hv supply are welcome.

1 2 next

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