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We used a few square inches of steel window screen held between 2
screwed together bars of aluminum. We combed the screen so it was very
pointy and stuck out.
On 09/29/15 22:07, David Speck wrote:
> OK, Matt,
>
> What do you use for a corona electrode?
>
> I'd suggest about 20 common pins through a strip of brass, directed
> toward the belt, as close as you can get to it without touching. Apply
> wax or epoxy to the back end of the strip to keep the majority of the
> corona at the pointy ends of the pins.
>
> Come to think of it, you could use a piece of Vector Strip board, a kind
> of prototype board that has a matrix of holes on 0.100" centers and a
> strip of copper in one direction. You would just put your common pins
> through the holes, line them up even, and solder them to the copper.
> That would be relatively quick and easy to fabricate.
>
> Dave
>
> On 9/29/2015 8:12 PM, msweeney23@xxxxxxxxx wrote:
>> Fyi the belt i use is approx. 2 inches wide and about 10 feet long. I
>> use belts homemade from latex resistance bands and they work great
>> with a plastic roller wrapped with electrical tape.
>>
>> With current humidity levels i can pull 20 inch 'sparks' from a 14
>> inch diameter collector. These sparks are not always fully complete
>> and often terminate into a plasma reaching 5 to 10 inches out from the
>> collector.
>>
>> ----- Reply message -----
>> From: "David Speck" <Dave@xxxxxxxxxxxxxxxx>
>> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
>> Subject: [TCML] Voltage/power dissapation drop across HV DC current
>> limiting resistors.
>> Date: Tue, Sep 29, 2015 6:27 PM
>>
>> Paula,
>>
>> MOTs are going in the wrong direction for this project. They have
>> relatively low output voltages, but very high output currents. A good
>> MOT can easily put out 500 mA into a short circuit, as they have only a
>> very small built in leakage inductance.
>>
>> You don't usually begin to see corona at less than 10 KV, so even
>> doubling a 2200 volt MOT would only give you 4400 volts, and the amount
>> of stored energy plus the high current capacity of the MOT would result
>> in a system with a much greater lethal potential than a rectified NST.
>>
>> Matt's project is looking for a moderately high voltage at a very small
>> current.
>>
>> I'm not sure how wide his belt is, or how efficient his corona
>> generating electrode is, but a milliamp or less at relative low voltage
>> would probably be entirely sufficient for his purposes.
>>
>> Dave
>>
>> On 9/28/2015 8:40 PM, Paula Lange wrote:
>>> What about two microwave oven transformers with diodes and Voltage
>>> doubling capacitors? That would give you plus and minus 4kv.
>>>
>>> msweeney23@xxxxxxxxx wrote:
>>>
>>>> I wish i could but i need both DC polarities :(
>>>>
>>>> I know an NST is totally overkill for this but outside of using an
>>>> old fkyback without the built in diode i dont see many options.
>>>>
>>>> Some 20 years ago i built this using a flyback from an old tube TV
>>>> running on 12DC but it was just a curiosity and i scrapped it when
>>>> building my first TC (at age 17 with no real knowledge building
>>>> plate glass capacitors - lucky i didnt kill myself).
>>>>
>>>> If i could find a cheap +/- HV DC generator id be happy. Could i use
>>>> a single polarity and somehow shift it down so i see a +/- half the
>>>> voltage?
>>>>
>>>> ----- Reply message -----
>>>> From: "David Speck" <Dave@xxxxxxxxxxxxxxxx>
>>>> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
>>>> Subject: [TCML] Voltage/power dissapation drop across HV DC current
>>>> limiting resistors.
>>>> Date: Mon, Sep 28, 2015 11:53 AM
>>>>
>>>> Matt,
>>>>
>>>> In today's eMail I received an offer from Goldmine Electronics for a 15
>>>> KV negative ion generator that runs off 12 VDC for $10. It's
>>>> intrinsically current limited, and you can lift it with two fingers
>>>> instead of two men and a boy like your NST corona generator.
>>>>
>>>> If the polarity is right for your application, then it would be a
>>>> simple
>>>> way to go. Special sale price ends 9/30. (No connection to seller,
>>>> but
>>>> a frequent buyer).
>>>>
>>>> http://www.goldmine-elec-products.com/prodinfo.asp?number=G20855
>>>>
>>>> Dave
>>>>
>>>> On 9/27/2015 9:51 PM, Matthew Sweeney wrote:
>>>>> No that is exactly correct. Another user mentioned that I should be
>>>>> careful
>>>>> using NST for VDG seemingly because there could be short down in
>>>>> the inside
>>>>> of the VDG to the HV brush, allowing potentially lethal currents up
>>>>> to the
>>>>> collector. I've not been able to confirm this exact reason - maybe
>>>>> someone
>>>>> else can chime in on this.
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>
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