Transformer Induction coil (COIL CONSTRUCTION)

In summary, the conversation discussed creating an efficient induction coil for a circuit that imitates a transformer. The circuit is given two very thin strips of wire which can be used to create a primary and secondary coil. A ball passing through the coil(s) will generate a numerical output based on the strength of the sensed magnetic signal. The main question was how to build the coil(s) in the most effective and efficient way without changing the signal threshold. Various suggestions were given, including using standard epoxy or bondable wire to hold the coil shape, and using a twist-tie or beeswax to temporarily hold the coils in place. The conversation also touched on the possibility of using a scope and signal generator to demonstrate the coils' operation and changing the
  • #36
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.
jegues said:
So this is the design I should be aiming for in order to obtain the best consistent signal?
Yes, IMHO.

Bob S
 
Engineering news on Phys.org
  • #37
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?
 
  • #38
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
 
  • #39
Mike_In_Plano said:
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.
 
  • #40
Bob S said:
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.
 
Back
Top