Help!! Making A electro Static field meter,

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Help!! Making A electro Static field meter,

Post by project-reveal » Thu Jun 10, 2010 4:08 pm

Hello, All, i have been making a simple circit which is made to monitor electrostatic **van de graaf produces**

here is what i have done,

I Got a battery clip, Connected the red lead from the battery clip to the middle wire of the FET,
then Bent the gate wire Upwards in the air. *ride hand side wire*
then conected the remaining wire to the + long wire of the LED,
then the - wire of the LED to the Black wire of the battery clip,

Put battery in and it works bingo...

However, On a site im looking it it says this.

"On a low-humidity day and with a 1/2 meter antenna wire, its little LED-light will respond strongly when someone combs their hair at a distance of five meters or more."

The humidity reading of our test was at 58.0 - 60.07

the light should turn off. when a elctro field is around.

And the filed length from running a comb through hair, then putting the comb close to the wire is 6 cm away the LED turns off.. then 7 - 8cm it faids back on.

This is no 5 meters... Lol.

I did use a soldering iron..

Any help please.

This is for a ghost hunting project :D

Thanks... and btw i dont know nothing much about electronics.


Lee steer

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Bob Scott
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Re: Help!! Making A electro Static field meter,

Post by Bob Scott » Thu Jun 10, 2010 5:57 pm

Maybe you could go to a seance and get advice from the ghost of the late Mr. Van de Graaf directly.

Good luck with your quest!
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Re: Help!! Making A electro Static field meter,

Post by dyarker » Thu Jun 10, 2010 11:10 pm

If that humidity reading is percent relative, then it NOT a low humidity day.
Dale Y

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Re: Help!! Making A electro Static field meter,

Post by jimmy101 » Sat Jun 12, 2010 2:12 pm

Ya, 60% humidity is anything but low. The page is probably referring to something more like January in the Midwest where inside humidity might be as low as 15%.

I take it this is the basic jFET-9V battery-LED setup for detecting electrostatic fields?

You might get better sensitivity if you remember that what it is detecting is the field difference between the metal shell of the battery and the "antenna" lead of the FET (the one that isn't connected to anything). So you want the "antenna" as far from the battery as possible and you want the imaginary line from the battery to the "antenna" to be perpendicular to the EMF (static) source. So you want that imaginary line pointing towards your source, for example, a TV screen.

Also, it helps (or least the thing behaves more consistently) if you "zero" the detector by touching the battery shell and the "antenna" with your bare hands. That'll set both ends of the detector to the same relative potential. Careful though, if you didn't include the 1 Meg ohm or so resistor on the "antenna" and if you generate a spark when you touch the device you will instantly cook the jFET.

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