Transformer Induction coil (COIL CONSTRUCTION)

[Bob S]

Mike's coil-3.jpg in Post 22 is the right way to do it. The two pickup coils, if properly balanced (bucking mode), will give a null signal unless a conducting ball rolls inside the pipe. It is important that the two pickup coils be symmetric about the excited coil. If necessary, the coils could be moved back and forth on the PVC pipe to get a null.

So this is the design I should be aiming for in order to obtain the best consistent signal?

Yes, IMHO.

Bob S

 

[jegues]

Also, how crucial is it that the two pick up coils are exactly identical? Will it make a huge difference if one pick up coil has more turns than the other?

Remember, the two pick up coils would be consisting of one 15m strand of very thin wire, it might be difficult to have the two coils be symmetric, no?

 

[Mike_In_Plano]

If your coils are off, you can scoot them closer or further with your thumb nail until you get a null. Or, you can use the orthogonal coil. I gaurantees a null simply by scotting it from left to right.

Mike

 

[Bob S]

If your coils are off, you can scoot them closer or further with your thumb nail until you get a null. Or, you can use the orthogonal coil. I gaurantees a null simply by scooting it from left to right.

The optimum design is probably a ~100-turn primary coil and two symmetric ~50 turn bucking pickup coils. The ideal location is with each pickup coil probably centered over each end of the excited coil, to maximally intercept the dipole field from a conducting (or magnetic) ball. This would require some electrostatic shielding between the excited and pickup coils, however, so probably starting out with Mike's end-to-end coil layout in coil-3.jpg is best. I suspect that the excitation frequency will be in the 20 kHz range. The optimum frequency will be when the skin depth is ~equal to the radius of the balls. If it is too high, you will not be able to discriminate between aluminum and steel balls, for example. Do you know whether the excitation is pulsed or CW?

Bob S.

 

[jegues]

The optimum design is probably a ~100-turn primary coil and two symmetric ~50 turn bucking pickup coils. The ideal location is with each pickup coil probably centered over each end of the excited coil, to maximally intercept the dipole field from a conducting (or magnetic) ball. This would require some electrostatic shielding between the excited and pickup coils, however, so probably starting out with Mike's end-to-end coil layout in coil-3.jpg is best. I suspect that the excitation frequency will be in the 20 kHz range. The optimum frequency will be when the skin depth is ~equal to the radius of the balls. If it is too high, you will not be able to discriminate between aluminum and steel balls, for example. Do you know whether the excitation is pulsed or CW?

Bob S.

Thanks again for your input Bob.

I'm not sure whether the excitation is pulsed or CW, I'm sure if I asked he would tell me but as of now we aren't given any detailed infromation about the circuit, just that it resembles a transformer.

We're going to be hopefully testing out coils out today so I'll let you know how our trial and error goes.