Whites Surf PI schematic

[daverave]

if i increase coil power will i get a few more inches of depth at the expense of battery consumption...or can i use a better first amp that is less noisy...if so what op amp you advise ????

[Tepco]

Variable coil power usually means varying pulse width, in this case varying R2 value, between pin 6 and 7 of 555. Increasing resistance will increase TX pulse width, and power consumption too, lowering it will produce shorter pulse, also frequency will be affected to some small degree. Exact timing can be calculated from 555 data sheet, or using numerous online calculators, like http://freespace.virgin.net/matt.wai...y/pinouts/555/ Better leave it as is, more effect can be achieved by varying minimal sampling delay, decreasing R25 value and adjusting R3 for minimal sampling time available for given coil. Suitable fast coil, and optimally adjusted dumping resistor R6 value is needed to best exploit this change, usually scope is necessary for optimal adjustment.

[daverave]

what components do i change so i can have a variable coil power control ????

[starmoml]

tanks

[Tepco]

ok.What is the maximum depth of the metal detector(surf pi)to a metal object 50 * 50 cm????

Once more, build delta pulse. Surf is completely unsuitable for detecting large objects deep and for large coils\frames, like 1x1m. It is designed for beach hunting, coins, jewelery, etc, with 20-25cm coils, with relatively slow sampling delays to ensure operation in salt water. With some modifications, faster coils and sampling, increased gain etc, can be fine for small gold too, but lacking ground balance, so can be problematic in most gold fields. Also, it is strictly “motion only” detector, useless with very large coils. Can be modified for static, but pulse parameters are not tailored for large and deep targets. Right tool for right job. Delta is simplest DIY solution, exactly made for this purpose. Forget ground balance, not relevant here, with large coil and slow sampling, ground signal will dissapear long before detector can measure it, pulse parameters are OK for large stuff, depth for 50x50cm with large coil is, well, more than you are willing to dig. For surf, with 25cm coil, something like 1.2m or so, depending on coil and adjustment. For delta issues, best to consult someone with more experience, like kt315 (aka 2N5551) for example.

[satdaveuk]

ok.What is the maximum depth of the metal detector(surf pi)to a metal object 50 * 50 cm????

The question you ask is like asking how long is a peace of string because its influenced by ground conditions and whats going on around you, some detectors handle heavy minerals etc better than others, so in affect one machine could perform better in one field and the other in the next field to it
Pumping up sensitivity with modifications to show better detection in air tests may look impressive to the novices but in real use you can actually end up with something that is near useless which I well proved with some of the modifications with the TGSL project many moons ago that were getting banded about, I have also proved it with many manufactured detectors over a period of time.
The only way to compare machines is have them working in the same location, detecting the same target in the same spot in the same ground, and that only proves that one machine worked better in that particular location on that type of target in those particular weather conditions on that particular day
Unless of course your trying to locate objects in the sky.
Regards

[starmoml]

ok.What is the maximum depth of the metal detector(surf pi)to a metal object 50 * 50 cm????

[maikl]

The Surf-PI has a self-adjusting threshold, so you need to keep the coil in motion. This will be difficult with a 1m x 1m coil.

Surf PI has a modification to non motion, but 1m x 1m...

[6666]

Encontre esta moneda de dolar con mi surf pi, alguen conoce esta moneda? se que es un dolar por lo que se puede leer, pero alguen sabe algo mas de esta moneda?(encontrada en Chile)
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Translated in google

"I found this dollar coin with my surf pi, alguen known this coin? is that it is a dollar that can be read, but alguen know something more about this coin? (found in Chile)"

[Qiaozhi]

The depth of this detector with loop 1*1???

The Surf-PI has a self-adjusting threshold, so you need to keep the coil in motion. This will be difficult with a 1m x 1m coil.

[starmoml]

The depth of this detector with loop 1*1???

[sukri01]

hi.. if i want to use 2 pcs 9v battery instead of 8 pcs 1.5 v.. can anyone show me the modification needed to do this.. thx..

[blizi]

Encontre esta moneda de dolar con mi surf pi, alguen conoce esta moneda? se que es un dolar por lo que se puede leer, pero alguen sabe algo mas de esta moneda?(encontrada en Chile)

[alonejax]

ok my friend
what's your ideal pi ?
thanks

[Qiaozhi]

thank you qiaozhi for replay
planning is mountain and f0r small & medium nuggets

In that case you need to decide whether an all-metal detector (such as a PI) is suitable for your application, or whether you need to discriminate against iron. If you decide on a PI, then you will need to construct a fast coil in order to detect small gold nuggets.