Re: [TCML] VDG pickups (was Ignition coil driver)

[David Boyle <twoten@xxxxxxxxx>]

Exactly. I built a big one for a science center and used a 10kv charger
from a photocopier. On dry days 4 foot sparks were common. We tried a
1/4 horse motor, but it couldn't push the charged belt into the ball,
then a 1/2 horse, same thing. Finally I used a 1 hp motor and within 2
or 3 seconds our long haired blond TA was a full sunburst of upright hair.



On 12/24/15 04:57, Teslalabor wrote:
> Hello,
> 
> it seems that only self-exited van de graaf generators are built by you
> folks. Why not use an external DC source (10-20kV) and spray the charge
> on the belt, like all big generators do the job? Wouldn't that be much
> easier to realize than dealing with triboelectric scale and humidity
> problems?
> 
> Regards,
> Stefan
> 
> ----- Original Message ----- From: "ExtremeElectronics.co.uk"
> <tesla@xxxxxxxxxxxxxxxxxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Wednesday, December 23, 2015 3:36 PM
> Subject: Re: [TCML] VDG pickups (was Ignition coil driver)
> 
> 
>> Doug,
>>     Looking at the triboelectric scale for Polyethylene its near the
>> -ve end, so contact with neoprene you will get a charge build up,
>> although that should be counteracted by a similar charge build up at
>> the other end, so the net gain would/should be zero.
>>
>> I agree about the spark losses. I always thought they were negligible,
>> but now  I think of it they could be quite large, especially if the
>> gap from belt to collector is large. But the resistance of the sheet
>> must be quite large, so I would expect losses there too.
>>
>> I can see how these would work for the neutralisers in a Wimshurst,
>> but not for the collectors in either machine, as they are to collect
>> surface charge, pushed out towards the collectors by the opposing
>> charge on the roller or other plate of the Wimshurst and not in full
>> contact.
>>
>> Do you use the film for both collectors and neutralisers  in your
>> wimshurst? Are they both in full contact with the disks
>>
>>     Derek
>>
>>
>>
>> On 23-Dec-15 1:38 PM, doug wrote:
>>> Derek, I am sorry, I do not know the tribo property's of the plastic.
>>> Here is my theory on why it works so well;
>>> With the pickups sitting a little away from the belt you can see
>>> little sparks passing, that is energy, like a spark gap. With the
>>> pickup point in contact with the belt there is no charge dissipated
>>> from jumping the gap.
>>> I could be wrong on this theory, all I know is that it works!
>>> I use the same stuff on my Wimshurst machines in contact with the
>>> discs with great success.
>>> Here is the link to my source>>
>>> http://www.all-spec.com/products/65-18.html
>>> Doug
>>>
>>> -----Original Message----- From: ExtremeElectronics.co.uk
>>> Sent: Wednesday, December 23, 2015 2:51 AM
>>> To: Tesla Coil Mailing List
>>> Subject: Re: [TCML] VDG pickups (was Ignition coil driver)
>>>
>>> Doug,
>>>     So the film is actually touching the belt?
>>>
>>>  If so, then you are adding another place for charge separation, as
>>> well as collection. Any idea where on the tribo electric scale the
>>> conductive film sits?
>>> Would that account for the extra current ?
>>>
>>>     Derek
>>>
>>>
>>> On 22-Dec-15 10:55 PM, doug wrote:
>>>> Hi Derek; What you see is conductive plastic film riding on the
>>>> rollers attached with copper tape, rollers are PVC and aluminum tape
>>>> covered acrylic. I did do comparisons, plastic film produced 30%
>>>> more current. Belt Is neoprene.
>>>> Doug
>>>> -----Original Message----- From: ExtremeElectronics.co.uk
>>>> Sent: Tuesday, December 22, 2015 4:52 PM
>>>> To: Tesla Coil Mailing List
>>>> Subject: Re: [TCML] VDG pickups (was Ignition coil driver)
>>>>
>>>> Doug,
>>>>     From what I can see from the videos, you are using a thin piece of
>>>> copper for your pickup. Have you done any comparison between that,
>>>> wires
>>>> or gauze. Do you see an increase in current or voltage ?
>>>>     What is the composition of your rollers and belt ?
>>>>
>>>>     Derek
>>>>
>>>> On 22-Dec-15 2:34 PM, doug wrote:
>>>>> Hello Derek;
>>>>> Thank you for your comments and including a link to my youtube
>>>>> video. I have included a link to my youtube page so you can take a
>>>>> look at some of my VanDeGraaff projects. I think all VDG builders
>>>>> are using the wire or screen type pickups on their VDG’s, I have
>>>>> found something MUCH better. You can see it in operation in some of
>>>>> my videos.
>>>>> https://www.youtube.com/user/dr043042#p/u
>>>>> https://www.youtube.com/watch?v=YCWAH-J091c
>>>>> https://www.youtube.com/watch?v=uoS7sOy2Src
>>>>>
>>>>> Thank you again, Doug J.
>>>>>
>>>>> -----Original Message----- From: ExtremeElectronics.co.uk
>>>>> Sent: Friday, December 18, 2015 11:35 AM
>>>>> To: Tesla Coil Mailing List
>>>>> Subject: Re: [TCML] Ignition coil driver
>>>>>
>>>>> You can get about 300W from 8 of them though..
>>>>>
>>>>> http://www.extremeelectronics.co.uk/electronic/v8-tesla-engine/
>>>>>
>>>>>     Derek
>>>>>
>>>>>
>>>>>
>>>>> On 18-Dec-15 2:30 PM, Jim Lux wrote:
>>>>>> On 12/18/15 4:39 AM, doug wrote:
>>>>>>> Hello; I am looking for some information concerning Ignition coil
>>>>>>> HV supplies. I am using 120V mains through a light dimmer and
>>>>>>> wonder if there is something better and more robust than the
>>>>>>> dimmer? This Ignition coil HV supply will be a dual coil setup
>>>>>>> using a 25.0uf/370VAC motor run Cap.
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Not as cheap..
>>>>>>
>>>>>> any of the standard capacitor discharge electronic ignitions
>>>>>> basically put 400V pulses into the coil to generate HV.
>>>>>>
>>>>>> 6000 RPM in a 8 cylinder engine is 200 Hz
>>>>>>
>>>>>> typical energy per "pulse" is 100 mJ so 200 Hz is 20 W
>>>>>>
>>>>>>
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