Eddy Currents

Cenlasoft

Hello,
I made a proto type of an eddy current tester. I am using the basic stamp II to read the output. It works. My question is:
Does any one know how to create a 40 to 50 khz AC signal which can be sent to an inductor coil? I found a 555 time circuit, but the ac out included a transformer and the output was too high.
Thanks,
Curtis
·

stamptrol

Curtis,

Can you show us the link to the 555 circuit? It can't be too big a transformer if the 555 is driving it. Shouldn't be too expensive to rewind or replace the transformer to bring it within the required range.

What are you testing?

Cheers,

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tom Sisk

http://www.siskconsult.com
·

Cenlasoft

Attached is the circuit I found. I am testing various metals like Al, Cu for thickness of corrosion layers.

Thanks, Curtis

Beau Schwabe

Cenlasoft,
With that particular schematic, it's going to be very frequency dependent to get optimal results... C4,L1, and T1 form a resonant circuit that will have some peak frequency value.· The downside is that any loading on T1 will change the optimal resonant frequency and the output will be diminished.
"My question is: Does any one know how to create a 40 to 50 khz AC signal which can be sent to an inductor coil?"
The short answer would be yes, but in order to do so, we need to know what the inductor value is that you are currently using, and what that part of your circuit looks·like.... Also,·a better description on what goals you are expecting might also be helpful.· What·will you be using this for?·
·

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe

IC Layout Engineer
Parallax, Inc.

LoopyByteloose

If you need a sine wave, does it remain one frequency or is it adjusted. I don't think the inverter design is really helpful as the frequency of the sine wave is a lot lower and the wave shape is far less critical.

Try here for some basic reading about tank circuits and oscillator circuits.

http://www.phy.davidson.edu/instrumentation/NEETS.htm

You can use a crystal, a VCO, or a lot of things to generate a good sine wave. Even the 555 in some fashion might be you final choice. Then the question would be merely how to amplify it and optimize the impedance match to the coil that is the final stage. Do you have a lot of different coils to test? If so, a range of parameters would need specification.

So, one needs to know what that final coil is like and then design your power amplifier to adjust to such characteristics.

How exactly do you plan to measure the eddy currents? Is this some kind of non-destructive testing? What and where is the material that is producing the eddy currents?

The Propeller can nicely synthesize wave forms for you.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).

Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan

Post Edited (Kramer) : 7/26/2008 4:39:06 PM GMT