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Questions On Electrostatic Charge Generator

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Benji

Mon Dec 24 2007, 12:07AM

Registered Member #1189 Joined: Sun Dec 23 2007, 11:29PM
Location:
Posts: 2

Hello friends,

I am currently doing a school project where I need to create an electrostatic charge generator to pick up small and lightweight objects such as a piece of paper of about 30 grams each. I am currently having difficulty in finding experimental data and/or equations/formulas on the minimum amount of volt and charge my electrostatic charge generator will need to generate in order to pick up a piece of paper. I've tried the web, school professors and currently focusing on searching my college libraries but without much luck.

I have never built any type of electrostatic charger before, so knowing the initial design parameters would really help out. Does anyone here have any clue or pointers on how to find out what equations or experimental data that I can use to determine the voltage or charge needed? Or perhaps an estimate based on experience on the parameters needed to achieve the lifting force?

Thanks,
Benji

Spedy

Mon Dec 24 2007, 01:40AM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

I;m pretty sure a 30 g piece of paper is beyond the range of electrostatic force.

I've always had a fun time using a simple PVC pipe generator to pick up little ripped-up paper bits that are around 4 square centimeters. For this all you need is a length of pvc (3-4 feet is a good length) and a rough paper towel. You rub the pipe with the paper towel then use the pipe to pick up the little paper bits. Btw, if it's too humid it won;t work..

I think if you are making the project yourself, like the teacher isn;t saying "find a way to pick up 30g of paper using static electricity", you should set more realistic goals.

I would make an electrostatic precipitator. Basically, make a good electrostatic machine like a Van de Graaff, or maybe a dirod. Then, find an old jar like a mayo jar and clean it so there's no label on it or mayo in it.

Then, take a small piece of metal pipe, (copper is easier), like 1/4" diameter and 2" long, and cut one end so it is sharp. Now, cut a hole in the top of the jar's lid so you can put the piece of pipe in it, and glue it in.

Connect one electrode of your electrostatic generator to the copper pipe somehow. Fill the jar with smoke through the pipe.

Now, when you turn on the generator, all the smoke should disappear. This demonstrates electrostatic precipitation.

Hope this helps.

DrZoidberg

Mon Dec 24 2007, 12:03PM

Registered Member #350 Joined: Mon Mar 27 2006, 05:14PM
Location:
Posts: 106

That's easy. Take a metal plate that's as big as the piece of paper, then glue some plastic foil on the metal plate.
You then place the foil covered plate on the piece of paper. Paper is slightly conductive. So you can say the metal plate and the paper form two plates of a capacitor.
Then you have to make sure the paper is grounded. For that it could lay on a metal table or even just a wooden table since wood is slightly conductive too as long as there is no insulating varnish on it.
The force on the paper is equal to the electric field strength times the charge stored in the "capacitor" divided by 2.
Let's assume the plastic foil is 0.1 mm thick, the dielectric constant is 2 and the paper has an area of 0.2 m^2.
The capacity is 8.85*10^-12 As/Vm * 0.2m^2 / 0.1mm * 2 =35.5nF
Let's say you apply 1000V. Then the field strength is 1000V / 0.1mm = 10,000,000V/m.
The charge is 35.5nF * 1000V = 35.5uAs.
So the force should then be 35.5uAs * 10,000,000 V/m / 2 = 177.5 N = 17.75kg.

A little more then the force you needed.
Theoretically 40V should be sufficient here but at 40V the paper and the wooden table are probably not conductive enough. So I would use a few hundred volt.

Attracting the paper from a distance is alot more difficult. You'd need a big VDG and also the paper would need to be electrically charged which can be achieved by simply grounding it while it's close to the VDG. VDG's will also attract uncharged pieces of paper but not if it's that big and heavy.

flannelhead

Tue Dec 25 2007, 04:00PM

Registered Member #952 Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388

You could also try an ion generator. These are kinda easy to build. For an example look at my creation: http://4hv.org/e107_plugins/forum/forum_viewtopic.php?30389. Or look here where I got inspired: http://www.freeinfosociety.com/site.php?postnum=250

Benji

Tue Dec 25 2007, 09:46PM

Registered Member #1189 Joined: Sun Dec 23 2007, 11:29PM
Location:
Posts: 2

Yeah the project I had in mind requires attracting a paper from a short distance probably around 5 cm or so.

The project's theme is randomly set by my second yr engineering prof and I happened to get the electrostatic theme so I just came up with a crazy idea (that might turn up to be completely impractical as it is crazy) to aid printers in lifting up papers onto the printing tray to reduce moving parts by using perhaps the previously mentioned ion generator... since no moving parts requires less maintenance I figured. This is a very silly application of electrostatic the more I think about it, but first I need to create a contraption that can lift something light from a small distance and THEN think of some application where it can be of use :P

Thanks a lot for the great tips guys! I have yet to finalize what the project will be to my prof so I'll look into all your suggestions and do some more feasibility studies on my first idea.

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