Help on a coil for a DFX

[thevacantface]

Hi all,

Total newb here and maybe trying to bite off way more than I can chew with this project after reading a bunch of the threads here. I do tend to be a quick study though and hopefully can get this underway with a quick tutorial and some guidance. Go ahead and throw complex concepts and terms at me, I'll do the leg work to figure out what they mean.

Anyway, have a DFX and I'm wanting to experiment with some custom coils and it seems the people here will most likely have the answers because they are way smarter than I. I get the two concentric coils idea, but was never that great with electrical theory.
How does one determine the number of wraps for each of these coils?

Also, can someone let me know a little more about Faraday shielding? Specifically how it is done, why there needs to be a gap left, and optimization.

Next, I see from some other discussions of white's coils there are other electronic components within the coil housing. What are these components, and what do they do?

The machine uses a five pin type connector. What is the fifth pins function? And am I even correct in thinking that two of the pins go to the TX and two go to the RX?

And lastly for the moment, when it comes to DD type coils are there actually four loops? Or do they just use a double mono loop? Depending on the answer, I may look for some more explanation on this.

Thank you much for any help you can provide, I really hope I can get this figured out and if I do, I'll definitely be posting the results.

-Neil

[Skippy]

Whoa, that's a lot of Q's, and a lot of biting and chewing to do... Plenty of studying this forum should give some answers, but here's a few pointers.The fifth pin I believe is the electrostatic shield; the components are capacitors, to tune the TX and RX coils; several faraday screen methods exist, see the forum discussions, without a gap you have a shorted turn coil, a bad idea for definite; unless you like being very experimental, I'd ensure the TX and RX coils have inductance AND resistance values close to the original coil; DD coils normally have two coils, one TX and one TX, this forum has several guides on their construction.Best of luck.

[satdaveuk]

Hi
Like you im looking to build coils for the DFX
Lets hope we get a speedy responce
All i like to know is the frequency the TX and RX works at how many windings aprox, Gauge of wire to build a 8x10DD coil, far as the capacitors i can work that out after construction.
Regards

[thevacantface]

I'm back after a long hiatus and still looking for info

Well I've decided to go with a DD coil, seems a little easier.

Anyway, how are the number of turns required determined for each coil? That is, how do wire thickness, size of coil, length of wire used have an effect on the coil?

Next could someone describe what is required for nulling the coil and process if needed at all.

And my last question for the moment is what direction should the coils be wound? Clockwise, counter, opposing? And should they simply overlap or wound interlocking?

[satdaveuk]

Well I've decided to go with a DD coil, seems a little easier.

Anyway, how are the number of turns required determined for each coil? That is, how do wire thickness, size of coil, length of wire used have an effect on the coil?

Next could someone describe what is required for nulling the coil and process if needed at all.

And my last question for the moment is what direction should the coils be wound? Clockwise, counter, opposing? And should they simply overlap or wound interlocking?

Far as a DD coils both can be wound clockwise or counter clockwise but keep them the same and make sure you mark your starts and finsh
If you go into the TGSL forum and download the final zip files you will see some very good tips on coil nulling, although we do differ a bit on are aproach.
Far as working out your coil inductance/resistance there is a coil calculator on here in the coil section which will give you a ruff Idea, but read all posts because alot of us have had in depth discutions on coil making over a very long time.
What you most certainly need is a good accurate inductance meter to get your final turns and at the very least a good quality multimeter, if you have not got these your wasting your time and money on wire etc.
I personaly do final settings with a scope but many on here have had reasonable results without one.
Let us no how you get on with it.
Regards
.

[John in NC]

Okay here we go. For a DFX coil the RX values are 37 Ohms and 14.05 m Henries, and it is connected to pins 1 and 2. The TX values are 2.9 Ohms and .555 m Henries, and it is connected to pins 4 and 5. Pin 3 is extra and not used. In the cables that have a plastic connector with a metal screw ring there are only 4 wires. The cables with the ALL metal connector has five wires, but pin 3 is still not used. (Knowing about the extra wire is only important if you are trying to keep weight down). Whites uses 22 gauge coated copper wire for the TX coil. I think they use 30 gauge for the RX coil, but I have used 32 gauge with success. Now for the size of the coil, the number of turns determines both the resistance and the inductance. For example the RX coil may take 50 turns to get to .555 mH but will only give a resistance of 1 Ohm. In this case you would have to add a series 1.9 Ohm resister to get to the value of 2.9 Ohms. (These are not real values). To find out how many turns, you have to wind and measure. (I like to overwind a bit, measure, and then back off winds to get to the correct value). The inductance is certainly more important than the resistance. The values of RX and TX are important if you want to phase shift between the two coils to be close enough to give you correct VDI numbers. You may have to tweek these values slightly, and add some small capacitance to get the phase shift correct. This venture will take time, trial and error, and more time. Usually it is only worth the effort if you are trying to build a coil that is not available on the market. Hope this helps you out.