RE: [TCML] RE: Switching on for the first time

["Stephen J. Hobley" <shobley@xxxxxxxxxx>]

Yes you're right, that was an error on my part...
 
10Meg 1/2 watt, not 100K...
 
Thanks for letting me know.
 
We think the gap is the weakest link - basically it's just a spark gap and a blower about 1" away from it - nothing is guiding the airflow. I will take a picture and post it soon.
 
Steve
 
 
Stephen Hobley Photography
www.stephenhobley.com
317 201 4281
 
The Laser Harp Project - www.stephenhobley.com/build

________________________________

From: tesla-bounces@xxxxxxxxxx on behalf of Lau, Gary
Sent: Mon 7/28/2008 10:30 AM
To: Tesla Coil Mailing List
Subject: [TCML] RE: Switching on for the first time



If you really are using 100K bleeder resistors across each MMC cap, that's a problem.  The recommended value is 10Meg on each cap.  The lower value that you use will be wasting an inordinate amount of the NST's available power.

I calculate that each resistor would dissipate 5.6 Watts if the total string saw 12kV RMS.  Your resistors look to be 1/2 Watt units, so they would be smoking hot and not long for this world if they are 100K units, so please be clear.

Beyond resolving the resistor thing, optimizing the gap (overall geometry, airflow, width) often has substantial payoff.  A photo of what you're using would be useful.

All simulation and equipment-based primary tuning methods take a back seat to experimentally trying each primary tap and comparing results.  Longest sparks is all that matters!

For future thoughts, a larger toroid, higher inductance secondary (thinner wire w/ more turns), comparably higher inductance primary and possibly higher cap value (you could use fewer caps in your string - as few as 9 if you don't need your MMC to last forever) may all help.

Please note that the work "quench" is too often used incorrectly on this List.  Quenching is not synonymous with blowing on the gap.  Airflow through the gap will usually improve performance, up to a point, but does not necessarily improve quenching.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Stephen J. Hobley
> Sent: Monday, July 28, 2008 9:45 AM
> To: Tesla Coil Mailing List
> Subject: [TCML] Switching on for the first time
>
> We did the final assemble and checks on our Tesla coil on Saturday night, we
> rolled it out into the back yard and switched it on...
>
> Nothing is as scary as that first time...
>
> And...
>
> http://www.stephenhobley.com/Tesla.jpg
>
> Nothing exploded, imploded, melted, smoked or fried...
>
> First off, a big big thank you to all the people on the list for helping us to get this coil
> going. We never would have finished the project without you...
>
> We were able to tease 7" sparks out of the toroid with the safety 'wand'. We tapped
> the primary on the recommendation of Teslamap - but we're not trying to fool
> ourselves that this thing is tuned. We just built the oscillator tuner based on the 555
> chip and we're going to try and tune it properly.
>
> The static gap is quenched with a tough little AC blower and set to about 0.18
> inches. After operating for about 30 seconds the tungsten electrodes did not see
> very warm at all.
>
> So after getting the tuning as perfect as we can, what should we examine next?
>
> * Height of the secondary from the primary?
> * Height of the toroid from the secondary
> * Spark gap distance / more quenching?
> * Addition of a rotary gap? (this is NST based, and so I'm not sure if this is safe...)
>
> Our setup is:
>
> Variac -> RF filter -> NST (12Kv) -> Terry Filter -> Static gap -> MMC (16 series
> with 100K bleeders) -> 0.25 copper tubing primary (15 degrees 12 turns total) -> 4"
> 24 gauge wire secondary (19.5 coil height) -> 12" / 3" spun toroid.
>
> Thanks again!
> Steve Hobley and Pete Kuhns

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