Questions on making big mono for gp 3000

[Righteous]

Hi i would like to make a big mono coil for a gp 3000 minelab about 30" 32" inches
as i have a few questions.
i belive : the smaller the coil the more windings
: the larger the coil the less windings
does any one know the amount of windings in other large coils eg. 18" 21" 24"25" coils ?
and what number of windings one would use for a 30/32 inch coil?
Also specifically what size and type of litz wire should i use ?
and does any one know what size is used in other large coils?

thank you for reading my post any and all feedback will be greatly Appreciated
Thanks Heaps Righteous

[ivconic]

....

I would like to help but i am a bit confused?
I have GP 3500 with mono coil...6.3 ohms resistance...nothing else...
On connector 3 pines wired togather, one separate and one giving those resistance with those 3...? But it is working fine!!!?
I can prepare photo and wire schematic if you want...if any help?
regards!

[ivconic]

.....

I didnt spoted this question before!
Well i'll repeat; resistance should be 6.3 ohms....thats all i know!

[Righteous]

ivconic photo and wire schematic would be a lot of help to me
if its not to much trouble
Thanks for you help
Righteous

[ivconic]

More complete datas...


Here's more complete datas;
i am to tired to shake my brain to get picture of inner wirements...a bit confused too, but here's what i found out;

[ivconic]

...

... this is 350mm mono coil...

[ivconic]

.....

Now i see photo is blur, so if you asking about values on right side of photo;
it is 0.6 Ohms...the rest is visible enough...
Anyeay if this helps than i'll be glad...
Regards!

p.s. this is 350mm coil, bought in Germany...

[Reg]

Ivonic,

I suspect your coil is not a mono and is a DD instead. I have attached a simple drawn pic of the coil connector. The numbers are the numbers on the connector and the connections are as you would see looking at the back of the connector.

Righteous and Ivonic,

If you look at the pic I attached, you will see several of the connector pins are tied together on the mono. Actually, only 2 and 4 are needed to be tied together on the mono. Although I think the pic is clear, I will note the black connections indicate connections to the shield of the coil coax for that winding. The black lead connects to one leg of the winding (s). I would keep the two coax shieldings separate in the coil wiring on a DD coil until they get to the plug. The red line is the lead for the transmit winding and the blue is the receive wire that goes from the center connector of the coax to the receive coil on the DD.

The different resistance readings you have on your coil are indicating the receive connectors are connected to a different winding.

Normally, the coil resistance of a mono coil is 0.8 ohms and the inductance is about 300 uh. On a mono, you shouldn't be reading the different resistances. In other words, you should read 0.8 ohms from pin 1 or 5 to pins 2, 3, or 4 on a mono coil.

Reg

[ivconic]

.....

I guess you have right !!!
I was confused from a start when measuring resistances..
Earlier i expected double D coil, but was confused with resistances i got!
Now i understand this a bit.
I was thinking to separate those coils and try it as double D? Is it possiblle without opening case? Are those connected in connector or in housing?
What do you think?
Since coil is brand new i didnt dare to open even connector...
What do you suggest?

[Reg]

Ivonic,

I think you can try the DD coil as either a DD or as a mono by just flipping a switch on the control box.

Now, I wouldn't try doing anything to the coil or the coil connector. Chances are, it might now work correctly after. They are extremely touchy.

Instead, I would try using the switch technique. What you should notice is only half of the coil will be active when you do switch to the mono mode. This will tell you which side is which. Also, it would be interesting to know if the Coiltek DD coil will work in the mono mode. Normally, the ML's are very temperamental and require a specific winding resistance to work. Coiltek seems to be using a different transmit resistance on their DD windings.

If you do try to use the coil in the mono mode, let us know how it works.

Reg

[Unregistered]

gp3000?
is not it PI and VLF system in one detector works alternately.
disc for shallow .and deep for big objects with oet disc.

so it is normal to see lots of wire inputs
okantex

[ivconic]

.....

Reg i know that!?
I wanted to split it to DD coil to experiment with other machines...let's say Delta Pulse or simillar...even to try to copy it..
But i still have reading 0.6ohms not 0.8ohms ?? Might be possible that my ohm metter is not calibrated well?
Anyway, thank you a lot for postin diagrams and show good will to help!
Best regards!

[Righteous]

Ivonic and Reg
thanks for your help and in put on this the info on the dd is of help also as i understand more about it.the diagrams rock !

Ivonic
to test the coil as dd or mono try this
gp 3500.at the front of the control box you have a dial that says "iron discriminate" turn this clockwise all the way round."NOT ALL METAL" select double d on coil switch.know pass over a small piece of gold say 2 grams or gold ring. the signal should be solid not broken.
know pass over a piece of metal iron and if the coil is a DD the signal will start and then break and start.alerting you to a ferrous object.
With minelabs the DD coil can discriminate and the mono carnt.
Also the discrimination is not always reliable as the coil does become over loaded eg. discriminate a 7 oz nugget and the detector will blank out i dont know why but it does ive seen this happen.
i hope this helps
thanks again Righteous

ps i wouldent void your warranty by opening you coil

[Righteous]

okantex
to my understanding it is only pi . to my knowlage
Thanks Mick

[Reg]

Reg i know that!?
I wanted to split it to DD coil to experiment with other machines...let's say Delta Pulse or simillar...even to try to copy it..
But i still have reading 0.6ohms not 0.8ohms ?? Might be possible that my ohm metter is not calibrated well?
Anyway, thank you a lot for postin diagrams and show good will to help!
Best regards!

First Ivconic, I need to apologize, I have been spelling your name incorrectly. It was a mistake on my part.

Now, you do not need to do anything to the coil to be able to use it on other detectors. You will need to modify the other detector input designs to allow for the use of a DD coil, though. Carl has done this on the newer HH boards.

So, once you modify the PI input and install a 5 pin connector like that used on the ML's, you can use the coil on any PI. The Coiltek has a built in damping resistor for the receive winding.

On the DD coils, Coiltek does not use a .8 ohm 300 uh transmit. They reduce this resistance down a little, so your reading of 0.6 ohm could be correct. I haven't tried to measure the coil I have apart. The 0.8 ohm resistance is only on the mono coils.

Hi Righteous,

The ML discrimination sucks in my opinion. Be careful because it can cause problems on large gold.

Now, when you try a DD coil on a different PI such as the HH or possibly the Delta Pulse, you will find you will get a strange signal from ferrous objects that are close to the surface. The signal will be reversed from that of gold or other non ferrous metal, meaning right down the center, the iron signal will be a negative response but will be a positive response on both sides of center. Thus, iron objects will give a double blip. On deeper iron objects, the double blip signal disappears but the signal is still wider than the signal from non ferrous objects.

Gold objects will only give a nice narrow positive blip that is obvious. However, if one listens carefully, they will hear the threshold drop a little on both sides of the center of the coil. This helps to make the signal more distinct and narrower.

Reg

PS, I have attached a pic of the inside of a Coiltek DD coil, so you can see the winding arrangement. Normally, the windings are covered with a conductive paper and can't see them. The conductive paper is the shielding. The second pic shows the top of the coil and what it looks like inside the housing. The dark gray surface is the conductive paper.