Troy Shadow X5 Homebrew Coil Problem

[Naildigger]

Hello there,

I built my own DD-Coil for my X5. But there are still some problems, which cannot be solved.
The coil is shielded by Graphite-Spray, and connected to the Ground Sig of the RX Coil.
The Problem that appears, is, that the coil is totally noisy !!! You can sweep it above the ground, and everything is just fine, but when you touch a leaf, or grass or anything else it produces a false signal. Even if you lay it to the ground, and just touch one of the Metal Switches, or the Rod or anything else conductive on that machine, it produces false signals. I used no other parts but the coils in that DD-Coil. The coils are 100% the same inductance (and of course Resistance) like the Original Troy coils.
I Used no additional C´s or R´s.
Has anyone an Idea, what the reason for the strange behavior of the coil might be ?

Best Reagrds,

Naildigger

[Reg]

Re: Troy Shadow X5 Homebrew Coil Problem

Hi Naildigger,

The symptoms are that of a coil that is not shielded. I would double check to be sure the connection to the shielding is functional.

Shielding should be applied to the inside of both the top and bottom of the housing and a connection made to both. You might try adding a second connection to each part on the opposite side of where the first connection is also. If there are gaps in the shielding spray, then there may be a "break" in the shielding. This can happen because the spray doesn't like to stick evenly to plastic.

There is a minimum amount of shielding necessary also, so there is a possibility there is too little spray, but before adding any more, I would double check the connection to the shielding and to the ground lead back to the pc board. My guess is this connection isn't correct.

Care has to be taken to avoid too much shielding also. This can reduce the sensitivity plus cause false signals if the plastic housing can move at all. If the shielding is too thick, the shielding can be detected if there is movement between the shielding and the windings. However, this doesn't sound like your problem at this time.

Reg

[Naildigger]

Re: Troy Shadow X5 Homebrew Coil Problem

Hi Reg,

that´s what I thought after my first coil !!!
It has to be something with the shielding...
Then, after building 3 of them, looking very carefully to do the shielding thing the right way, I don´t think this anymore...
I could measure about 50 - 500 K-Ohm between the Plug (RX-Shielding wire) and the Coil Shielding at any point of the shielding. This should be enough to short-circuit the electrostatic currents. There are no gaps, and the Housing also cannot be moved.
And, if it would be the housing, would the detector react to a touch to the switches ??? Or the rod ??? That´s what makes me wonder...

Best Regards,

Manuel; Naildigger

[Reg]

Re: Troy Shadow X5 Homebrew Coil Problem

Hi Manuel,

If your lower value mentioned is 50K, this sounds a little low. I forgot just what was recommended but I think George Payne mentioned something like 10K per inch resistance worked well.

Now, just where does the RX shielding connect? Does it connect directly to either the ground or the + power supply of the pc board?

Is there a different "common" that can be used to ground the shielding? If so, I would try it instead to see if that makes a difference.

Finally, do you have some distance between the windings and the shielding? If not, you might try placing something like short pieces of rubber tubing around the wiring to suspend it away from the shielding a little.

Reg

[Naildigger]

Re: Troy Shadow X5 Homebrew Coil Problem

Hi Reg,

I don´t know if the resistance of the shielding is critical... But that´s an interesting point. I will check this...

There are 2 different Ground Signals on that machine. One for TX and one for RX. Neither oft them is connected to Battery Minus ! I asked in another Thread where to connect Coil Shielding... The answer was RX-GND.

I already tried TX GND, but without success !!!

Yes I have distance between Coil and Shielding. I use a tube, which you wind around the coil. This also has the positive Side-Effect, that the Inductance doesn´t change, when it´s filled up with epoxy. Because it´s already compressed...

Another User sent me a Tip by mail. It said, that on DD-Coils only the RX-Coil should be shielded, with a small gap, because otherwise it would be a closed loop.... I usually shielded the whole coil !!! I Sprayed the inside of the Housing, layed in the coils, nulled them, fixed them, and then I covered the Coils with epoxy. After taht I Sprayed some more graphite onto the surface of the epoxy, which has a measurable contact to the connected RX-Shield Wire. After that I filled up the housing with epoxy...

Maybe now anyone sees a mistake I made.

Any Suggestions ?

Manuel; Naildigger

[Reg]

Re: Troy Shadow X5 Homebrew Coil Problem

Hi Manuel,

I am not so sure about just shielding the rec winding. If the transmit winding is part of the resonant circuit, then I suspect it will have an effect. If the transmit is a driven device, it might not be so critical. In either case, I would shield it anyway.

I would try more shielding spray next.

One way to tell if the shielding is marginal is to wave your hand close to the coil. If you get a relatively strong signal from your hand, you probably need a little more shielding.

However, if the sensitivity is extreme on the detector, then this trick is sort of nulled since there usually is some pickup of the hand.

In any case, you might try the factory coil to see how well it detects your hand, and then compare the built coils. This is a crude method, but it might give you an idea of how close your shielding is to what is on the factory coil.

Reg

[MagnumPi]

Much lower ohm value I like is 200-800 ohms across coil shield layers

make sure you use a wire within wire rcv and tx cable like I guess video cable (cheap)like old gold bug coils. In other words the the gound for Tx would wrap Tx feed same on rcv. You can use foil type cables of the past but it is nioseier and not as sensitive on the fine tune set up.
Ps. Reg has good advice for the experimentter

Happy Trails
MagnumPI



Home of the Crazy Boys

[Don Bowers]

Re: Troy Shadow X5 Homebrew Coil Problem

Just a thought.. Does the X5 coils have any internal capacitors like the Whites coils?

If you feed a square wave into an X5 coil and don't dampen the ring, what will the frequency be? That's how I tuned my tesla coils.
(www.hometown.aol.com/dobybowers/index.html)

Don

[MagnumPi]

depending on the grade of the graphite shield somtimes it helps to

Put a coat of depthane over the shied to protect it from any chemical break down from various potting methods be sure to allow hard cure before proceeding. Just a thought, hope you do well in your expeiments.

MAG