Inside the 4" BH nugget coil

[Ed in SoDak]

Took a hacksaw blade and cut just through the case, then popped it open and picked out the foam. I scraped off some insulation to trace the wiring. What gets me are the little, loose-wound "tuning" loops and loose wad of wire in the center.

I had two coils, so why not?

-Ed

 

[silversmith]

Wow, interesting...........Thanks!

 

[jimjimmyjames]

Ed, I have been enjoying your adventures into coils. Nice work! James

 

[skyhy]

I think I can make a 10inch(or bigger) DD Coil to fit my Bounty Hunter,made one years ago for another detector I had and it worked great.
I have the same wires at the plug end of the factory coil (I changed the plug and socket to a screw lock microphone,the facotory one was just too loose for me).
I was wondering if you could post the track of the wires so I know which are going to the transmit/receive coil etc?
Cheers Stewart

 

[ronaldj2]

Doesn't look like rocket science, but somebody makes them work really well.

 

[Ed in SoDak]

Here's a simplified wiring diagram of the 4-inch coil. The five cable wires are numbered to correspond with those on the plug, as seen in the second pic.

The inner coil is colored green. It connects to Pin 1 (red cable wire) and Pin 2 (black cable wire).

The outer and middle coils are colored red. They are wound from a single length of wire, but wound in two sections. It thus consists of two windings with a space between them of about a half-inch. Electrically, they would be considered as two series-wound loops with an air gap. The smaller half is wound tightly against the green coil. The large half of the red loop begins at Pin 4 (white cable wire). At its end, it wraps around itself, then heads to the center of the coil. There, a small hank of wire is in a loose oval shape and seems almost randomly wrapped about the center of the oval. From here, the red coil continues with the smaller half of its winding. The smaller loop ends at Pin 3 (gray cable wire). Additionally, the red coils are paralleled by two capacitors. a .22 uf and a "223" (.022 uf). At the point where the wires exit the outer jacket of the cable, the gray wire is stripped of insulation so it contacts the cable's shield.

Finally, a short length of red-colored wire (drawn in yellow for clarity) is connected to Pin 5 (green cable wire) and randomly wraps loosely around the inner green and middle red coils. After a few turns, the wire dead-ends without a connection to its far end. I did not see the green cable wire connected inside the detector either, so I don't know the purpose of this wire that is apparently not actually connected into the circuit. I may have to open up the Time Ranger again and see if I missed something.

-Ed

 

[jimjimmyjames]

From an electrical engineering standpoint. Wire #5 must be a "drain" wire. The drain wire is only landed on one end of an installation and it helps take care of interference and induced voltages on low voltage signal applications(like metal detecting).

 

[edjcox]

Very interesting. Would be really interesting to get a field strength perspective of the coils. Wonder if the bundle in the center serve as a means of focusing the field smehow to make the field center centric.

Thanks.

 

[Ed in SoDak]

I've been working on a set of pages on Bounty Hunter detectors, and just put it up tonight. Here's the "tech" page: http://www.whiteriverprep.com/vintage/ArticlesTipsAndTech/bhtech.html

There's a lot of info to add, but I have the basic framework up and working.

I recently did some coil field experiments, using time exposures of waving an LED over the coil. They're kinda rough, but I see some potential. The experiments were all done with the 8" coil. It might be interesting indeed to see what differences there are between other coils and differing machines. I posted the info on Findmall, and included it on my new site.

-Ed

 

[skyhy]

Ok just to clarify the outside red coil is the transmit coil
The inner green coil is the receive coil
The red coil wound outside the receive is the bucking coil...the transmit and bucking are in series but are provided with a siginal of opposite polarity to give a null...the capacictors are there to tune the coils.
For fine tuning in the factory up to a quater of a turn in the transmit-bucking coil setup can make a big difference so I guess that is the loose wire seen in the middle.