Dual Field Coil DIY project for PI Detector

[@martyjohnstone9362]

Hiya Alec,,Enjoyed your great explanation and detailed video on the Dual Field coil! Excellent work again! Regards, Marty

[@SurfDetector]

Hi Marty, Glad that you enjoyed it. I have been wanting to make a video for the Dual Field coil for a long time. Cheers.

[@RadioActiveDonats]

I just bought a Impulse 3 ready made board with LCD..is very interesting and cheap. The guy who make this says for 10" coil 0.4mm wire, 22 turns, 380uh, 2.3 ohm. But he is talking about mono coil. I really want to make your coil seems amazing. Can you please guide me what resistor do I need and how many turns for both coils. Your help would be very much appreciated.

[@SurfDetector]

Hi my friend. I am not familiar at all with the Impulse 3, I have never heard of the detector. I trust that you have an oscilloscope with which you can view the signal from your pre-amp. I cannot tell you what you need without a detector to hook up to I am afraid, I wish that it were that simple.

[@pixieloco]

Alrighty, I watched the video at least 7 times (ADHD over here 😅) but I have a few questions. the ruler you are using is in inches, right? but the inner diameter of the main coil is set as 122mm (4,8") on the calculator !? 🤔 do the diameter/turns/inductance of the big coil dictates the diameter/turns/inductance of the small one? let's say I have a main coil with a 200mm inner radius, 16 turns and an inductance of 350mH, how do I figure out the radius, turns and inductance of the second coil? is there any reference point? I thank you for this video, I built a Surf PI longboard and I just need to make the coil.

[@SurfDetector]

You need to calculate each coil independently with the knowledge that when two inductors are connected in series their total is the sum of the two. Good luck with your project. I am no longer active in metal detecting projects,

[@pixieloco]

@@SurfDetector thanks for the info, it really helps, and your other videos as well.

[@rafaelvillegas7425]

Saludos. Esta bobina dual aplica para el Detector Felezjoo PI?. Que mejoras esperaria percibir en la sensibilidad?

[@SurfDetector]

This coil will work as long as you match the inductance to the detector. The coil gives you better performance than a simple mono coil. Thank you for watching. Make sure that you watch my other videos on damping resistor use.

[@rafaelvillegas7425]

@@SurfDetector Perfecto Amigo, el Felezjoo trabaja bien con una bobina de 300 a 400microH, igual la resistencia de amortiguacion puedo ajustarla, ya tengo una bobina dual que hice con tubos pvc, hare mas pruebas de laboratorio con el osciloscopio y luego pruebas reales, me imagino que esa bobina dual debe ser mas sensible a metales mas pequeños que son casi invisibles para los detectores PI debido a su baja frecuencia pero me conformo si me ofrece mas estabilidad para objetivos pequeños no ferrosos.

[@m.sadeghyazdanpanah5857]

Hi Thanks for your great videos, Is this coil working with polones detector? i am going to make a polones and i want to make a coil like this video, and how should i calculate the coil size and turns and ohm and inductance? The circuit is as your polones Thanks in advance 🙏🙏💯

[@SurfDetector]

Yes this coil will work with the Polones. My video gives you all of the information about building the coil.

[@RadioActiveDonats]

Did you actually try this coil out on the beach? is it good in small gold and what is the depth at the beach? Thanks

[@SurfDetector]

Yes I have used this coil with both the Mini Pulse Plus as well as the crossbow detectors that I have built for projects. I think that the detector you are using is of as much importance as the coil especially if you are after gold, the dual field as I explain in the video has the smaller coil which helps with small targets as well as the larger. That being said I like the coil better than a typical mono coil. Nickels at the beach, probably 9" I think, although I don't really do depth tests like some others do. Thanks for watching and please subscribe.

[@mrongovia]

Is the copper foil connected somewhere? Is the coil wrapped with it and that's it? Thank you very much for your answer.

[@SurfDetector]

Hello my friend, welcome back again. Have you subscribed to my channel yet? The copper shields are connected as shown at 3:26 of the video.

[@mrongovia]

@@SurfDetector Subscription enabled :) thanks for the answer. I need to watch the material more carefully. My little daughters bother me a little bit :) Regards!

[@SurfDetector]

@@mrongovia I am glad that you are watching my videos. Enjoy.

[@mrongovia]

@@SurfDetector Thanks to your help, I am already after the first pi detector tests. I was left with the coil shielding. I am not sure if my detector can be connected as shown in the movie. you can take a look at the diagram drive.google.com/file/d/1U7zvFrXCRcN5J-A60uZpwaKZC-nVmT-F/view?usp=drivesdk I will specify where I have doubts. Finally, I have three wires from the coil - the beginning of the coil, the end of the coil and the screen. My question is whether the detector lead to 3 wires? Or two? One option is to connect the coil end wire to the shield. The second option is the wires from the coil go their way and the screen to the negative pole of the battery - then three wires go to the detector. My doubt arises from the fact that in the case of the first option, I do not clearly see on the diagram which pole of the coil should be connected to the screen. Or maybe it doesn't matter?

[@SurfDetector]

I connect the shield to the RX lead of the coil. You need to look at your schematic to see how the Mosfet is positioned. The pulse from the Mosfet will of course be your TX side of the coil. I hope that helps.

[@Abedjuc_85]

Thank you for your helpful video's. I wanna know if the shield by using foil , reducing the ground sensitivity, as you know the Red soil decreasing the range of the detector . ? Thank you again

[@Abedjuc_85]

Is it helps. Or not?

[@SurfDetector]

Hello my friend, you wrap the coil to help shield it from EMI and also it helps to eliminate Ground Response

[@Abedjuc_85]

@@SurfDetector Ok thanks for reply. 🌹♥️

[@mattrowe1229]

so if you solder the joints or connections of the coil wires that go inside the coil, will they show up as targets maybe, or since you used heat shrink it protects it so they wont be detected by coil. or do you not solder and just twist together so theres just copper and no solder.

[@SurfDetector]

The connections are soldered. They do not present as targets.

[@mattrowe1229]

@@SurfDetector ok, thanks for your vids again i thought the iner coil was to be wound the opposite direction

[@SurfDetector]

These are two mono-coils which are in series with each other and wound in the same direction.

[@echocase9528]

Hello! Cool detailed video, thanks for it! How about efficiency of this coil?

[@SurfDetector]

The coil works well. It is based on the White DF coil.

[@emersonyepez1326]

Hola con esta bobina se logra más alcance en el pi polones??

[@SurfDetector]

It is a better coil than a regular mono-coil, It depends what you are looking for with your detector. I do not use the Polones, I only built it because so many people asked me for it.

[@ahmedoutlaw7923]

Hello surf detector thank you very much but i dont understand is the iner coil 10 turns or 20 turns ? Because you said 10 first of the video and 20 in another part of the video thank you

[@SurfDetector]

Hello my friend, I believe that it should be 10 turns but you should use the coil calculator to make sure as your size might not be the same radius.

[@Millzieeeee]

would i be able to use a thicker wrap of copper wire , to get better depths ? is that the whole difference on depth ? or am i missing something ? thanks

[@SurfDetector]

There is no one single factor that enables greater depth with a PI metal detector, you have among others, coil diameter, TX pulse width as well as PPS.

[@Millzieeeee]

@@SurfDetector could you not have just said, no , doing thicker copper wraps will not improve depth :')

[@Diyforlife474]

Sir... the green line on the diagram. Use insulated copper or use naked cooper

[@SurfDetector]

You could use either.

[@DavidALovingMPF102]

How much better are two coils than just one coil? How is that measured or determined? thanks.

[@SurfDetector]

Hello David, I would say that the determination would be made in a side by side comparison with a dual field coil versus a regular mono coil of the same diameter and inductance rating using an identical detector in a test garden. But then again, "horses for courses"

[@DavidALovingMPF102]

@@SurfDetector any deeper?

[@SurfDetector]

Very simply stated, the design is based around the concept that a smaller coil detects smaller objects better and a larger coil detects larger objects better. Depth is generally tied to the coil size.

[@delidigital8397]

Dear Surf Detector, First thank you for answering my question by email few weeks ago, I just built a concentric one, different radius, but mine is much more simple ( no dampling resistor, and no shield) and works great. difference is, the big coil is clockwise and the smaller one had to be anti-clockwise to get the 400mH (by the way is 400mH the target we have to be close to, what is yours?). So do you have any idea why? and what does those dampling stuff, and is the shield really necessary?

[@SurfDetector]

What metal detector project are you working on? Coils should be shielded. You need to be matching your coil to your project. The coil oscillates as you can view with an oscilloscope at the pre-amp output. You want to critically damp the oscillations with the proper resistor. I suggest starting with a simple mono-coil and gain some experience with these concepts before trying concentric coils or DD

[@minekoiwa2971]

Hi, can you tell me what epoxy you use? My dual field coil is loose inside and when I hit it, it vibrates too much. I want to fill it with epoxy and kill its buoyancy too.

[@SurfDetector]

Hi Sergio, Welcome to my channel. Please subscribe. I use a slow cure casting resin to fill my coil shells. Is this for a DIY coil? www.amazon.com/Epoxy-Resin-Crystal-Tumblers-Graduated/dp/B0872SBPKD/ref=sr_1_39?crid=1BM1DB5KYEIX4&dchild=1&keywords=casting+resin&qid=1616064156&sprefix=casting%2Caps%2C189&sr=8-39

[@minekoiwa2971]

It is actually to fill in the dual field coil. I replaced one under warranty with the same problem, and now with whites out of business I don't see any other solution, I'll drill 2 holes in it and fill it with epoxy. I will make some coil for the TDI in the future. Thanks

[@machinadiabolika]

you can use spiral sheath it is more flexible than the split tube and thought to put the shielding to the mass just to see ..

[@SurfDetector]

I agree with you about the flexibility. The spiral tubing is much more flexible. What I used however is much cheaper :) One other thing as well. The solid tube makes a better base for the copper tape. The tape is very thin and easy to tear so it needs a good solid base.

[@jamiemarsden3823]

@Surf Detector Ihave a question before i continue watching the rest of this video lol the idea for my build is almost exactly the same as this.. are the 2 coild independant of each other and can you initiate them both together and if so how did you get around the external magnetic field to prevent it from detecting the inner field as a potential object find? thanks :)

[@SurfDetector]

Hi, Thanks for the comment and also for watching. I believe that the abstract from the patent should answer all of your questions. patents.google.com/patent/US7994789

[@jamiemarsden3823]

@@SurfDetector great all I need to do now is modify my already existing pre 1995* schematic lol the dampener was the key to a dual-centralized transmitter. Happy days now I can crack on with my build and go treasure hunting haha 😁

[@jamiemarsden3823]

@@SurfDetector I've been trying to come up with a different way for years is I ain't a fan of the crappy DD COILS lol

[@jamiemarsden3823]

@@SurfDetector lol I've just realised that patented design isn't for a dual centralized transmitter. That patented is for a dual-field end-to-end design. So serves no purpose on my question earlier on lol 🤔

[@jamiemarsden3823]

@@SurfDetector the design in this video helps me a lot though as it is almost exactly the same as my concept from 95* problem I have is realising an efficient way of utilising both, one or the other without interferences and/or false-positives etc 🤔

[@jeanmoisan6855]

super video !!!

[@SurfDetector]

Merci mon ami

[@jeanmoisan6855]

@@SurfDetector :-)

[@arabigamer1018]

hello sir can you tel please the size . the wire thickness .and number of turns for both coils thank's

[@SurfDetector]

Hello my friend all of that information is in the video. I used 24 AWG wire. The outer was I think 14 turns and I think the inner was 20. Please watch the video.

[@МистерХ-ы5у]

Hello! Could you add the pdf file of the metal detector you made to the description? And another question, is it necessary to wrap the coil with foil and for what?

[@SurfDetector]

Hello and welcome. The shield blocks the coil from picking up electrical noise and it helps to stop the coil from reacting to the ground when you are using low sampling delays. What pdf are you referring to? Which detector? Please subscribe to my channel. Thanks.

[@МистерХ-ы5у]

@@SurfDetector Thank you so much!

[@МистерХ-ы5у]

@@SurfDetector Usually, in the description under the video, many users leave pdf files of their devices with files in lay format. who did it themselves, so that others could do it. That is why I asked you about it. If there is any information, please discard.

[@SurfDetector]

@@МистерХ-ы5у Hello my friend. almost all of my detector projects are based on information from the Geotech Forum. Please share my videos with your friends who might be interested. Thanks.

[@cranegantry868]

@@SurfDetector Do you mean long sampling delays which I suppose would mean the pulse rate from the transmitter is slow??

[@bilalhajji9473]

Thank you Mr alec 👌 I have a question please. did you print the coil housing ?

[@SurfDetector]

Hello Bilal, I did not. The housing was vacuum formed by one of the Geotech Forum members.

[@bilalhajji9473]

@@SurfDetector thank you for your reply 🙏

[@jeanpierretayeh]

Dear surf detector I have a very interesting coil project I’m planning on doing but I am very lacking in expertise would love to get a few pointers if you don’t mind. I just need to send you the info please advise on how to reach you sincerely J.P

[@SurfDetector]

Hello my friend, I don't have time for projects at this time as I am too busy with my real job. I suggest that you go to the Geotech Forum. There you should find some people to assist.

[@jeanpierretayeh]

@@SurfDetector i appreciate your reply sir and still hope we may communicate one day at least to get on the right track and i wish you great success in your career endeavours

[@musaameril7067]

Hi!! How to make large coil sir?? Any idea for 70cm diameter coil,how many turns we cn do?

[@SurfDetector]

What inductance coil are you trying to build? Once you know the Inductance then you just use the coil calculator like I show in my videos my friend.

[@22koga]

So that was 2 coils on 1 PI channel ? Also what type of resistors are those that you are using for damping ?

[@SurfDetector]

This is 2 mono coils in series. The connection as is clearly shown in the video is the same as a single mono. In this video I am using 2 watt metal oxide resistors for damping. Thanks for watching.

[@22koga]

Thank you !

[@maglintemarlo1918]

What size of magnetic wire you use for that coil sir

[@SurfDetector]

I used #24AWG wire. You will get better performance if the wire has PTFE insulation

[@stargalacticfederation]

can you please send me the link of the coil calculator tester so I can purchase one for myself

[@SurfDetector]

Just Google LCR Meter and you will get many choices.

[@MysticMCWizard]

Hi. I built the surf 1.2 pi circuit back in 2015 along with a dual field coil as you have here. But without the shielding or the damping resistors. I got great detection but I also got a ringing on the coil .. I've since found out this is due to my lack of damping resistors in the circuit. I know that the coil on this circuit is to have a resistance of approx 1.3ohms and inductance of approx 260-290uH the inductance is fine but I'm not sure how to calculate the damping resistors values.. any ideas?

[@SurfDetector]

You need to connect each part of the dual coil up to the TX portion of the PI machine that you are using along with a damping resistor jig and monitor the output of your pre-amp with an oscilloscope. I have a 2 video playlist on the damping resistor subject on my channel.

[@MysticMCWizard]

@@SurfDetector yes, I've just watched them thanks. Unfortunately I do not have an oscilloscope.. (I was tuning thebdetector using silverdogs instructions). But I didn't realise at the time that the dual coil needed to be tuned using damping resistors when I first built my dual coil .. I originally thought it wad just a tuning issue regards the threshold level. But the ringing made it very difficult to tune accurately.. I just recently read a post in a forum which someone replied to me regarding a patent then I noticed my mistake. I believe that it it approx 1ohm per uH for each of the coils .. my outer coil is 128uH and my inner is 144uH my biggest concern though was increasing the resistance of the coil.. but looking at the diagram again the path of least resistance is still through the coil. So my 1.3ohms across the coil will not change .. my thought is that the 1st damping resistors has to be big enough for the total of the two coils and the second is just enough resistance for the second smaller coil.. so in my case r1 would be approx 272 ohms and the second 144 ohms .. is this approx correct as compared to your findings on your build?

[@SurfDetector]

Unfortunately the only way that you are going to be able to properly match the damping resistors to the coil is by seeing the ringing with a scope. You can use this formula however the scope method is much more accurate in my experience, R d = ⁢ L π ⁢ ⁢ C

[@MysticMCWizard]

@@SurfDetector I noticed you have built the wave2 portable oscilloscope.. is it any good? Considering getting one for myself .. I cannot justify spending £250-£300 on a 2 channel laboratory oscilloscope just to be used on a £50 project.

[@SurfDetector]

I built the Wave 2 just for fun. I would not use it to build a project.

[@tomhabokita8818]

Hello very good 😀

[@SurfDetector]

Thanks for watching and I hope you subscribe

[@nourddin1692]

شكرا لك.

[@SurfDetector]

You are welcome. I am glad that you liked the video. Please subscribe.

[@RadioActiveDonats]

The small coil resistor is 510 Ohm, what value is the other resistor for the both coils ?

[@SurfDetector]

Hi my friend, thanks for your interest in the video. I do not have that coil and PI available for me to look. When building these DIY coils it is important to hook them up to a PI machine and watch the pre-amp wave form in order to correctly calculate what the damping resistor for your particular coil will be. That goes for the inner coil damping resistor as well. Just because I used 510 ohms doesn't mean that will be ideal for everyone's coil. The oscilloscope is essential.

[@RadioActiveDonats]

@@SurfDetector I just got a oscilloscope but I'm not sure where to hook it up. I wish you could show everything on this videos :(

[@SurfDetector]

The ground clip will connect to the ground reference on your PCB and the probe will be on the output pin of your pre-amp. Without a schematic of the PI that you are working on, I cannot tell you what pin that will be for you. In this video I show the connections for the Crossbow PI kzbin.info/www/bejne/rXfHlZiad71_bJY

[@David_11111]

yay ..not sure about this, but may say more about me than you :)

[@SurfDetector]

This style of coil is quite good. At some point I shall do another one with better wire.

[@hip408]

do you have a link for the coil calculator ?

[@SurfDetector]

You need to go to the coil section of the Geotech Forum.

[@oussamaboudaoudi436]

Does the spider coil work with Voodoo?

[@SurfDetector]

No it does not. The book on the Voodoo project explains what you need.

[@arifinilham7626]

Kalo pengen lebih dalam gimana cara nya serr

[@African_farmer]

Hello sir please I bought pi board it detect metal and silver but gold no detection can you help me?

[@SurfDetector]

Hello my friend, You say that you bought a PI board. What PI board did you buy?

[@African_farmer]

@@SurfDetector this board sir from ebay kzbin.info/www/bejne/i4vYdX57hKt2rtU

[@SurfDetector]

@@African_farmer You should try to reduce the sample delay, that might help you to detect gold slightly better.

[@Ostaz-Hekaia]

Coil calculator link please

[@SurfDetector]

Here you go: www.geotech1.com/forums/showthread.php?17909-Coil-Calculator

[@johnpaulanderson8630]

Folded mono and parallel coil will be less complicated with just a single damping resistor.

[@SurfDetector]

The Dual Field coil fits very nicely into the same style coil shell as a concentric and therefore is easier to make for me. Thanks for watching. Happy Hunting.

[@johnpaulanderson8630]

@@SurfDetector putting two coils in parallel will be a dual field as well.

[@SurfDetector]

It would not be a dual field in accordance to the Whites patent

[@emersonsilvadeoliveira4525]

Esquisito 😂

[@shamy6346]

لماذا تلف قصدير على الوشيعه المعذره

[@SurfDetector]

Hello my friend, you wrap the coil to help shield it from EMI and also it helps to eliminate Ground Response.

[@shamy6346]

You are creative, sir. Thank you. Excuse me. Is the sensitivity deficient? I still suffer from the problem of stability

[@SurfDetector]

Are you asking about the sensitivity of the coil? What detector are you using?

[@someone-wv8uh]

That work also for idx pro??

[@SurfDetector]

Hello my friend. The IDX is a VLF machine. The Dual Field coil in my video is for a Pulse Induction machine. Thanks for watching.

[@someone-wv8uh]

@@SurfDetector What is the best coil for idx pro...

[@someone-wv8uh]

@@SurfDetector can i get you mobile number please

[@SurfDetector]

@@someone-wv8uh I have never built an IDX Pro. My interests lie mostly in Pulse Induction as you can see from my channel.

[@someone-wv8uh]

@@SurfDetector can i get you mobile number...

[@n5sdm]

Please script it out.....the constant pausing in speech after three ot four words is terrible.

[@SurfDetector]

Hello and thank you for taking the time to comment. Sorry that the video wasn't more to your liking.