Science Buddies: "Ask an Expert"

I built my coil mounted my relay my problem is it still does not work. I have 14 wraps on my primary and 900 wraps on my secondary is this the problem? I have tried 6 volt 12 volt even a 12 volt car battery. can you help me Please?

Can you point me to something that describes what you built?

Transformers require alternating current or at least changing current to get the magnetic field built up and then collapse to induce voltage in the secondary.

Is whatever you are using as an oscillator or interrupter changing states?

12v * 900 / 14 = 771v

This isn't enough voltage to break down an air gap of even 1/64th of an inch even with high relative humidity (a few degress of temperature above the dew point).

Paschen's Law for air, and gaps on the order of a millimeter, the breakdown is roughly a linear function of the gap length: V = 30pd + 1.35 kV, where d is in centimeters, and p is in atmospheres.

Hope this helps, if not, I need more knowledge about what you built.

Craig_Bridge wrote:Can you point me to something that describes what you built?

Transformers require alternating current or at least changing current to get the magnetic field built up and then collapse to induce voltage in the secondary.

Is whatever you are using as an oscillator or interrupter changing states?

12v * 900 / 14 = 771v

This isn't enough voltage to break down an air gap of even 1/64th of an inch even with high relative humidity (a few degress of temperature above the dew point).

Paschen's Law for air, and gaps on the order of a millimeter, the breakdown is roughly a linear function of the gap length: V = 30pd + 1.35 kV, where d is in centimeters, and p is in atmospheres.

Hope this helps, if not, I need more knowledge about what you built.

I believe the project is the science buddies project at:
https://www.sciencebuddies.org/mentorin ... ?from=Home

Louise

In looking at the link Louise posted, there is a statement

A ratio of 750–1000 is a good place to start. In order not to exceed the power rating of the current-limiting resistor, the ratio of turns (secondary:primary) should not exceed 1000:1.

Looking at the recommended starting point, 14 * 750:1 = 10,500 turns; at 6v * 750 = 4.5Kv which above the 1.4KV by about a factor of three.

So you are going to need in the neighborhood of 3000 turns or about 3 times as many secondary turns for a 14 turn primary.

This assumes that your Neef vibrator is vibrating.