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

Stefan.
Initially I decided to go with the traditional build. Id had my fill of electronics and wanted something different (I then built a uP speed control for the motor) 

    So,  hair dryer v High voltage supply.
I've thought about it, but I'd need to change my bottom roller to Aluminum. I don't have the workshop tools to make another crowned roller. The last two rollers were machined for me, so it will have to wait until someone with a lathe owes me a favour..
I would be interested to see if the performance (other than reliability) is any better. 

Derek

On 24-Dec-15 9:57 AM, 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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