Surf Pi Build + inbuilt pinpointer

[pberrett]

Hi all

I own a Tracker IV and an Aldi detector but like all people who gets toys I find myself wanting a bigger toy.

So I've ordered the surf pi kit which I am going to build.

http://www.adrianandgenese.com/blog...ulse-induction-metal-detector-from-a-diy-kit/

http://www.silverdog.co.uk/shop/index.php?route=product/product&product_id=76

From what I've read this detector can detect to a depth or 12 inches (30 cm) in contrast to my current detectors which can do about half that.

I have a bit of electronics building experience and I am a ham radio operator (vk3pb). I also cohost an electronics/ham radio show called Amateurlogic which can be downloaded off the internet or found at Youtube. So I plan to do this build as one of my segments and you'll be able to see how I put it together and whether it works or not. I've already ordered the kit.

I have one idea I'd like to throw out there which may or may not have been implemented previously.

A very useful device to have when hunting on the beach is a pinpointer. From what I can see its just basically a metal detector in a small package. So my idea is to build my surf pi metal detector but put a switch between my coil and the electronics box. By activating the switch instead of the electronics being connected to the coil they would instead be connected to a second cable which would run to another smaller coil inside a pinpointer casing. The pinpointer would ride on a bracket on the metal detector pole and when you find something in the sand you merely flick the switch, grab the pinpointer and look around in the sand. Effectively the circuitry would be used for both the main coil and the pinpointer. I don't think that having a small cable running from the pinpointer to the detector would be a great inconvenience.

Thoughts?

Peter

 

[Ramjet]

Looks like an interesting project.
Looking forward to following your progress

Cheers

Ramjet

 

[kleinman98]

Hi all

I own a Tracker IV and an Aldi detector but like all people who gets toys I find myself wanting a bigger toy.

So I've ordered the surf pi kit which I am going to build.

http://www.adrianandgenese.com/blog...ulse-induction-metal-detector-from-a-diy-kit/

http://www.silverdog.co.uk/shop/index.php?route=product/product&product_id=76

From what I've read this detector can detect to a depth or 12 inches (30 cm) in contrast to my current detectors which can do about half that.

I have a bit of electronics building experience and I am a ham radio operator (vk3pb). I also cohost an electronics/ham radio show called Amateurlogic which can be downloaded off the internet or found at Youtube. So I plan to do this build as one of my segments and you'll be able to see how I put it together and whether it works or not. I've already ordered the kit.

I have one idea I'd like to throw out there which may or may not have been implemented previously.

A very useful device to have when hunting on the beach is a pinpointer. From what I can see its just basically a metal detector in a small package. So my idea is to build my surf pi metal detector but put a switch between my coil and the electronics box. By activating the switch instead of the electronics being connected to the coil they would instead be connected to a second cable which would run to another smaller coil inside a pinpointer casing. The pinpointer would ride on a bracket on the metal detector pole and when you find something in the sand you merely flick the switch, grab the pinpointer and look around in the sand. Effectively the circuitry would be used for both the main coil and the pinpointer. I don't think that having a small cable running from the pinpointer to the detector would be a great inconvenience.

Thoughts?

Peter

Good luck with it. Please let us know how you go with it. I am also interested in building one eventually.

 

[Shane]

I wonder if the two coils will interfere with each other?

 

[pberrett]

I wonder if the two coils will interfere with each other?

It shouldn't because the switch will only connect one coil at a time and the two will be kept separate.

It remains to be seen whether it would actually work however.

cheers Peter

 

[Shane]

I was thinking more from the perspective of each coil being metallic and interfering with the other.

 

[kleinman98]

I was thinking more from the perspective of each coil being metallic and interfering with the other.

I think you should be ok if nothing moves around ei pinpointer and cables and it is kept high on the shaft. Hey good on ya for trying. Cant wait to see it.

 

[OZDigger]

This ebay add addresses the approach you are speculating about.
http://www.ebay.com.au/itm/1-x11-Co...21326815544?pt=AU_Gadgets&hash=item4ad0921938

I understand that Detector Pro had a similar system as well.

Please keep the forum updated with your progress.

 

[Ben78]

Coiltek used to make a pointer for GPX's too.

You need to keep the pointer coil in the same plane as the primary coil - ie attached to the shaft. When you make your pointer coil you'll need to use a ferrite rod wrapped in wire to get the inductance to the ~300uH it needs to be.

My Surf PI goes deeper than 12", essentially the same detector as a Whites Surfmaster. You get zero discrimination. Also you can use coils made for GP/GPX on it.

 

[pberrett]

Coiltek used to make a pointer for GPX's too.

You need to keep the pointer coil in the same plane as the primary coil - ie attached to the shaft. When you make your pointer coil you'll need to use a ferrite rod wrapped in wire to get the inductance to the ~300uH it needs to be.

My Surf PI goes deeper than 12", essentially the same detector as a Whites Surfmaster. You get zero discrimination. Also you can use coils made for GP/GPX on it.

Thanks Ben

That's great information. I have a spare ferrite rod lying around I can use. I wonder what kind of cable to use?

Anyway that aside here's the latest. My kit arrived today so this weekend will be spend soldering. I'll just start with the metal detector but include a switch and 2 jacks so that I can add the pinpointer later.

 

[pberrett]

By the way I see there are no instructions included but I'm sure they'll be online somewhere.

cheers Peter

 

[pberrett]

Coiltek used to make a pointer for GPX's too.

You need to keep the pointer coil in the same plane as the primary coil - ie attached to the shaft. When you make your pointer coil you'll need to use a ferrite rod wrapped in wire to get the inductance to the ~300uH it needs to be.

My Surf PI goes deeper than 12", essentially the same detector as a Whites Surfmaster. You get zero discrimination. Also you can use coils made for GP/GPX on it.

Ben

I have a couple of questions regarding your comments above.

1. Does a surf pi need 300uH inductance?

2. How did you wind your coil?

3. Have you experimented with different types of coils and if so what works best?

4. What do you mean by zero discrimination? Are you saying it cant discriminate at all?

Thanks Peter

 

[TenOunce Tone]

Good luck Pete. Interesting to see how the electronics handlesvthe changes in coil sizes.

Cheers, Tone

 

[Ben78]

Ben

I have a couple of questions regarding your comments above.

1. Does a surf pi need 300uH inductance? Yeah about that, could be mH though?? It's not exact there is a lot of room to move on that.

2. How did you wind your coil? Made a few types, Made a plywood form and wrapped the wire on that, use cup hooks in a board and wrap on that etc

3. Have you experimented with different types of coils and if so what works best? Yeah, mono round coils get the best depth but I have done a 11x8 elliptical and a 11" spiral. The spiral had great sensitivity to small objects and good depth too. Tesoro use spiral coils on their PI machines.

4. What do you mean by zero discrimination? Are you saying it cant discriminate at all? Yep, no discrimination at all. You can disc out tiny bits of foil by turning the delay up, but then you lose the smaller bits of gold jewellery and still get the rusty jetty bolts 2' deep...

Thanks Peter

 

[gcause]

Hi Peter,

Good luck with the build. I built mine a year or so ago. Here's the link hope this helps:

http://golddetecting.4umer.net/t6394-grant-s-diy-pi-detector

Regards,

Grant

 

[pberrett]

I finished off the electronics for the Surf Pi last night as well as the coil.

Its working fine and can detect, using the coil I have built, Gold to a depth of about 22-23 cm.

I'm just about to head out to Jaycar to get a JIffy box for the electronics and I'll pick up some more wire to try out different coils designs. I'm pretty happy with the build so far although I do note that the main transistor does get pretty hot.

I can really recommend the kit - its great fun to build.

cheers Peter

 

[Ben78]

Jaycar has some nice pelican style waterproof boxes. I wish the electronics were on a square PCB rather than the ridiculously long one they did put it on...

 

[gcause]

The other kit I built from that same place in the UK is the Baracuda PI it is supposed to be more sensitive than the SurfPI and has a more square circuit board that fits more easily in most cases.

However as per my link above neither of these could handle the mineralised ground out at Warwick' Thane and Canal creek goldfields.

They just don't have any ground balance to counter it. They should work just fine in the local parks though.

Also check out the geoforum for answers on why the chipset heats up as there have been a few modifications made since the kits were produced.

Good luck with your build.

 

[Rompingdog]

Hello all.
I've just finished knocking up the surf Pi kit and to pberret, if your main transistor is getting quite hot, hunt about for a dry or incomplete joint somewhere. I cooked the first kit I had due to a dodgy joint, but the second kit I built I left on soak test for three hours and the transistor never even broke sweat. In terms of a coil, just make a 20cm circle using 26SWG resin coated copper for twenty or twenty two turns and that will work fine. Cable from the coil to the board is bog standard speaker wire with the inside end of the coil to the positive leg of the connector on the board.
Be sure to adjust pin six of the 553 IC to zero volts (takes a bit of very delicate turning of the pot screw to achieve this) and then twiddle (technical term) with the delay until it appears to be right.
Then it's just a case of bunging the lot into a suitable box. The coil I have encased in between the plastic lids of paint tins and sealed it up with Aquasure sealant of the type used to repair dry suit leaks etc. So long as the lids are of the right diameter, it doesn't matter on cosmetic looks.
I get my coil to "see" a small coin at about 25cm in air tests, which may equate to 18cm or so in the ground.
I just built it to see if I could and use a Gold Bug 2 for actually finding gold.
Just a tanners worth and hope it helps someone.
Dave

 

[pberrett]

I picked up this nice case today in Rockby Electronics surplus store.You can see the switch I installed to switch between the coil and the pinpointer. More photos to follow.