Coil design, again

[Anonymous]

Hello again!
Would there be any gain to having a detector with the ability to accept different coil designs?
For example (I think) the sensitivity and depth is affected by coil windings, capacitance and all that talk. However, I don't know if coils of different windings/capacitance can be used on the same detector.
A post below I asked if a detector/coil design could incorporate "Plug and Play".
This would allow the detector to use radically different coils to optimize for smaller objects, different ground etc.
I could have 3 8" coils. 1 optimized for depth/ large objects, another for small objects, and a third optimized for pinpointing.
The detector would recognize which was plugged in, and change its setup.
Sound interesting? I am trying to get creative juices flowing, don't see a lot of design talk lately.
Neal

 

[Anonymous]

I wondered if you could have a VLF and a PI in one detector and just have switch to go back and forth. The advantage is to use the PI to gain max depth and then switch to VLF to help identify the target. Any thoughts on that one.

 

[Anonymous]

Hi Neal,
Actually there are quite a few coil designs out there already. Since this the PI forum, I will focus in that area.
Now, the main or basic coil is the mono coil which simply consists of one coil used as both the xmit and receive.
Then there is the DD coil, shaped like two D's facing opposite directions with their backs overlapping. In the DD design, one coil is the xmit and the other is the receive.
There is also one called the figure 8 coil which can be make with one coil shaped in a figure 8 or it can be a round or oval xmit coil and the receive coil is a separate a figure 8 design, or variation thereof, that fits inside the main xmit coil.
There is also the concentric coil which has a large xmit coil and a smaller receive coil basically centered within the larger coil.
Obviously, there can be variations of the general shapes of the above mentioned coil designs, meaning they can be round, oval, rectangular, etc. Also, there can be variations as to the general design of any of the above mentioned coils such as a DD with a large xmit and a small receive, a multi-coil figure 8 concept where there may be more then two receive coils, etc.
Now, each of the coil designs mentioned have a specific purpose or stated differently, different advantages and of course, disadvantages.
Can a detector be made to accept all the above mentioned coils? The answer is yes. However, because of the specific design of PI's, the coils have to electronically match so the PI works correctly.
If a person only wanted to find large objects, then the design isn't nearly as critical as other applications.
However, the design can become quite tricky when trying to design the various coils for a detector with very good sensitivity to items such as small gold objects
Reg

 

[Anonymous]

Jim,
Eric Foster more or less did this over twenty years ago with his PPD1 detector. One version of the Pulse Devil (still being tested) is also a PI - Discriminator. The detector never stops being a PI, it simply takes some extra measurements to obtain the discrimination information.
Most serious detector users agree that the only discrimination one should use should be limited to IDing or rejecting iron. Any more discrimination than this will without doubt lose you many good targets. an audio target ID is most likely the best way to go. All targets cause the audio level to increase in your headphones. Iron will cause a low tone and various conductive targets will cause higher tones. This method allows one to hear a coin next to a piece of iron.
Where in NC are you? I am in Charlotte, Dave. * * *

 

[Anonymous]

Thanks, Reg!
Our present state of design will not allow those different coils to work on the same detector.
You stated "Because of the specific design of PI's" Can a PI detector be made with the variables such as pulse strength, width, "flyback stuff" controlled by the computer, not chips?
I hear a lot of talk regarding this op-amp being better than xyz op-amp and other chips, so I realize now we need those specific chips, but is there any work on "variable format" replacements?
Thanks for the education!
Stumbling in the dark
Neal

 

[Anonymous]

Hi Neal,
Sorry if I didn't make my answer clear enough about different coils and their use on PI's.
You stated: "Our present state of design will not allow those different coils to work on the same detector". This is incorrect.
There are some PI's that will allow the use of many if not all of the coils mentioned in my earlier post. Many other PI's can be modified to use them.
I personally have built and tried several different coils including, the mono, the DD, the figure 8, and the concentric design, on my pseudo Goldquest. However, to do so, I had to modify my detector. Such a modification does require a fair amount of technical background and some test equipment, but it can be done using present designs.
Now to answer your question about whether several of the variables on a PI can be adjusted using a computer, again the answer is yes. In fact, a few manufacturers are doing something like this now.
Robert Hoolko has mentioned in previous posts that he is planning on doing basically what you asked also. In fact, he has already started on the design. You might want to go back and read through some of the previous posts by him.
Bascially, what is used is called a microcontroller, which can be thought of as a mini-computer on a chip that can perform or adjust many of the different functions you mentioned. The level of complexity you want to change will determine the specific chip you purchase.
Of course, one has to program the chip as well as layout the design for the switches, their functions, etc. In other words, there are microcontrollers built that can perfom many of the tasks you asked about, but they are not set up or programmed that way from the factory.
I hope this helps,
Reg