Whites Surf PI schematic

[homefire]

"
But I'm still looking for the answer if it's normal to get a response while tilting coil?
I tested this out on two different locations."

With that detector Yes. Your causing a Variation in the Ground Signal.

[Koala]

if it's normal to get a response while tilting coil?
I tested this out on two different locations.

over normal fields

Once ground balanced properly. You can swing however you like and it will not sound.

There should be no difference between swinging flat or like pendulum. Swinging through tall grass or over wet concrete paving slabs.

When I test my first homemade coils on my nice flat law and they have been okay but as soon as I tried them on real fields they were rubbish

To be able to pick out faint signals your coil has to run very quite.


You should be able to swing it round in a circle above your head without it sounding. It also should not make a sound if you jiggle it up and down. As long as your windings are well potted and the shield is working.

[Qubic]

Single thread carbon fibre resistance measured:
1.5m ~ 244 ohms (just about enugh for 20cm dia coil to come around)
1m ~ 185 ohms
10 cm ~ 28 ohms
1 cm ~ 8 ohms

It is difficult to get good contact because it is so loose material. If thread is twisted and visually be campared to wire (copper core) it's cross-section is slightly less than awg 24.
If you need anything else let me know.

But I'm still looking for the answer if it's normal to get a response while tilting coil?
I tested this out on two different locations.

[Qubic]

No problem. I'll measure as soon as I get back home...

[Koala]

In have some 2mm carbon sheet. It is not conductive on the surface but 30 ohms per square if you sand the surface off.

[6666]

I tried and warp carbon fibres around the coil and It did the job great I think.

Thats interesting can you measure any DC resistance along the threads ?

[Qubic]

Hello!

Question:
Is it normal for surf 1.2 to give a response, when coil is lifted high above the ground, away from metal objects, holding it parallel to the ground and then tilt it in any direction, while tilitng it gives a sound response?
If it's parallel to ground I can move it around, lower or lift it without response.

Coil is 20cm, 300uH, 1.4ohm, magnet wire 0.56mm. I put over a shrinkinh tube for some extra spacing. But later I find out that this setup is wery prone to static elecrticity - tuching it gave a response and when trying to set up decent treshold cuircuit started motorizing beep beep...
I figure that out while was trying to find out what will happened it I add some shielding. Alu foil did solve treshold problem but my coil was just a bit too bulky and foil wasnt a good choice because the reduction of detection was to great.
So I tried and warp carbon fibres around the coil and It did the job great I think. Calm treshold and no more respons if I tuch the coil. Going back crazy if I disconeted it.
I used six threads puled out from fabric.
Olso tried to wound a new coil using utp cat6 24 awg cable and I gues it's much better choice. Did not add shield yet and it works fine without it on bench top for now.
Otherwise I get good response if air test at 25 cm for one euro coin, same for 5g 14k gold ring with both coils...
And I dont have o-scope...

[RH-Lightning]

Hi everyone,
tested some coils today, outside.

cat5 24cm diameter coil gave me 27cm stable on 1 euro coin, 1,9 Ohm winding, whole board consumption is 50mA.
copper wire 22 cm diameter coil gave me 25cm stable on 1 euro coin, 1,4 Ohm winding, whole board consumption is 62mA.
I used 150Ohm impedance headphones.

cat5 coil is actually looking good. Judging by the low consumption, there is still room for power. I'll experiment with damping.

[RH-Lightning]

here is the scope pic to the previous post.
the coil is now nice and tidy, but the results are still the same, low sensitivity. another thing is that the board is dead silent even in the heavy EMI environment with max Tune.

[RH-Lightning]

Thanks for the info.
I am using a high quality stranded cat5. As I have done it only for the proof of concept, I have left long ends on windings.
Coil cable is good quality RG85, overall (1,8m cable + coil) resistance is 2,2Ohm.

I'll redo it and post the results.

[Koala]

Someone did try with cat5 think it was on here but may have been a different forum. From memory results with cheap cable was very poor. With proper cable results were no better than using enamelled copper wire. Also the join was critical too much solder affected the performance.

[RH-Lightning]

Has anyone tried to use a Cat5 cable for coil windings with Surf PI? If yes, what are the results?

On russian forums this type of coil is popular for good results and very easy to build. Instruction how to build: http://www.metdet.ru/korsina2.htm
Basically, it is an easy to do "basket coil" with low parasitic capacitance.

I've built the 9.5 inch coil and tested indoor, the results are not spectacular. I could only get about 15cm for a 50 cent euro coin. Maybe the coil is overdumped, I'll post the scope pics later.

[peppe30679]

Hello guys. I almost finished my Surfmaster PI
I want to know how to make headphones: I bought some anti-noise headphones and i think to use 2 passive buzzer (piezoelectric) connecting in parallel....It's possible for you? There are other alternatives?
Thanks
PS: excuse me for my bad english

[paku]

Yea bro i using my eye scope!,and sharp Knife and multimetar probe

Thank Bro i will find that tools now at electronic shop!

[seadoggy]

bro do you fix using scope or using sand scope ? hakhakah

Yea bro i using my eye scope!,and sharp Knife and multimetar probe