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EMP BOX - TEST RESULTS - CALCULATOR AND LED CONNECTED TO A COIL...

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Slava

Wed Nov 11 2015, 03:48PM

Registered Member #518 Joined: Tue Feb 13 2007, 05:20AM
Location: New York
Posts: 168

More results are in! ...

check out videos on page

I tested 3 designs... I am torn between two of them...

One of them can light an LED farther and resets a calculator, the other puts random digits on a calculator... but the LED range is less...

Any thoughts?

004

hen918

Wed Nov 11 2015, 06:39PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

Try adjusting the length of the spark gap and post results.
Thanks

Slava

Wed Nov 11 2015, 07:00PM

Registered Member #518 Joined: Tue Feb 13 2007, 05:20AM
Location: New York
Posts: 168

I made an error, .. the coil diameters are different.

10 TURN = 5.5cm coil form

5 TURN= 8.0cm coil form

008

In this test I used coils with the same diameter. Got different results. My power supply is running off of batteries, so try not to compare new results to old ones.

Sulaiman

Wed Nov 11 2015, 08:30PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

NICE PROJECT

try a better spark gap, 'pointy' spark gap electrodes are (in my opinion) rubbish compared to large radius electrodes
(e.g. the back of two metal spoons or any curved objects), the gap will need to be MUCH smaller.

I suspect that for a given power supply / supply of power
the greatest range will be achieved by fewer but larger energy 'pulses' per second rather than many small ones
that means more capacitance and/or voltage ( E = 0.5 x C x V^2 )

The number of turns and diameter of the coil will have multiple effects;
. larger coils transmit farther
. fewer turns decreases 'Q' and increase frequency and peak current, stressing the spark gap, capacitors and wire more
. higher frequencies are likely to induce more interference than lower frequencies (use higher voltage / lower capacitance)

Having transmit and receive coils in the same plane as in your video has sometimes worked better for me than axially
circular coils tend to have a uniform field, square coils may work better in this case.

also, having a 'spare' high voltage generator and capacitors helps ;)

Slava

Wed Nov 11 2015, 08:38PM

Registered Member #518 Joined: Tue Feb 13 2007, 05:20AM
Location: New York
Posts: 168

Thanks for the tip. Right now I'm using screws as the gap... I redid my web page btw..

I need to figure out what setup is best... I'm surprised it works with other power supplies...

I built an EMP box long time ago and it turned out that the spark gap and resonant LC didn't do anything, all the RF came right from the power supply. I hate this because I have no control over it.

With this setup I tried different power supplies and it worked with all of them.

Signification

Thu Nov 12 2015, 02:10PM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

IIRC, I got best results on an old coil coupling experiment that used a stationary round coil with a square coil as the distant "fine tune" element. I even used the degauss coil from a TV with some success (remove the "varistor" ??). I didn't try variation of the winding turns or caps (should have) then--just alignment effects for what I had.
Better be "careful" here...

Slava

Thu Nov 12 2015, 04:15PM

Registered Member #518 Joined: Tue Feb 13 2007, 05:20AM
Location: New York
Posts: 168

When I get home from class, I want to try a 20 turn coil...

Signification

Thu Nov 12 2015, 04:45PM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

Slava wrote ...

When I get home from class, I want to try a 20 turn coil...

I have more comments in mind, but it seems if you waited a bit longer between posts, you, I, and others, could get more information per post which will benefit all, do you plan on trying square or rectangular coil combinations, perhaps of certain dimensional ratios
...more later...

Slava

Thu Nov 12 2015, 06:44PM

Registered Member #518 Joined: Tue Feb 13 2007, 05:20AM
Location: New York
Posts: 168

Just tested, 3 turn coil and 20 turn coil...

008

Two inaccuracies in my test...

1) hard to tell when the led turned off
2) long alagator clips may throw off readings for low number of turns

Signification

Thu Nov 12 2015, 07:31PM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

There's a maxima. An LC circuit can be represented mathematically. Simple differentiation can find the maxima patterns.

Can you fire a single pulse and capture it on a scope? You're looking for the maximum peak of an exponentially decaying sinusoidal...for starters...

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