What's your opinions on basic home buildable BFO detectors for pinpointing?

[mashersmasher]

I know BFO is the most dated and least capable metal detecting technology but i'm wondering if, should I build a simple one, it would be an effective for use as a pinpointer given that the range of a pinpointer is less of an issue than in a full sized detector. I ask because i've found a pretty cheep to build and simple one online that even has a PCB layout

http://www.easytreasure.co.uk/bfo.htm

Also if this is a not so good design can anyone recommend me a simple PI or VLF pinpointer that has a PCB layout?

[Skippy]

Did you miss this?http://www.easytreasure.co.uk/probe.htm

[mashersmasher]

Did you miss this?http://www.easytreasure.co.uk/probe.htm

Well for one it has a pic and i don't have a pic programmer. I have arduinos but I don't see a schematic and don't want to pay for it

[Carl-NC]

BFO is probably the simplest pinpointer you can build, and should work just fine. Most pinpointers use a loaded-loop oscillator design, which is similar to BFO in sensitivity.

[satdaveuk]

Hi
Good subject
Over the years ive built many a design of pinpointers right up to recently with a pic chip 876, but still keep coming back to the BFO type.
Infact funny enough was only thinking the other day wether with new components available maybe its worth having a look to make/design a new full blown metal detector using the BFO format, as the tech seems to have been left on the shelf.

Regards

[satdaveuk]

Did you miss this?http://www.easytreasure.co.uk/probe.htm

Hi Skippy
The Sherlock they show on there is underated if put in a better housing, then tweeked up is better than the pic pinpointer.

Regards

[Skippy]

Yes, Sherlock/Scanmaster probes work adequately, I have one, fairly modified, of course. But the adjuster knob IS one of the weak points, I broke mine several times - a tiny plastic spigot supporting the lower end of the shaft snaps off if the knob is knocked. I replaced it with a steel pin, and also glued a protection guard onto the case, next to the knob, made from scrap ABS. They are also not remotely water-resistant.
Regarding the treasureland PIC probe, you don't need a PIC programmer, you buy the pre-programmed device.
Also, there is the Scarborough-designed BFO mini-pinpointer published in EPE magazine, which you should be able to find on-line (PDF of the entire magazine).

[satdaveuk]

Yes, Sherlock/Scanmaster probes work adequately, I have one, fairly modified, of course. But the adjuster knob IS one of the weak points, I broke mine several times - a tiny plastic spigot supporting the lower end of the shaft snaps off if the knob is knocked. I replaced it with a steel pin, and also glued a protection guard onto the case, next to the knob, made from scrap ABS. They are also not remotely water-resistant.
Regarding the treasureland PIC probe, you don't need a PIC programmer, you buy the pre-programmed device.
Also, there is the Scarborough-designed BFO mini-pinpointer published in EPE magazine, which you should be able to find on-line (PDF of the entire magazine).

which year was that cause i may have made it at somepoint

[satdaveuk]

Heres a easy cheap pic probe, from micro examples got flash hex code plus c files if anyone interested.

[Skippy]

Dave, it was July 2003 EPE magazine. I have prototyped it, it does work, but I did improve it a bit. Despite it's simple appearance, it's a job to get it working, both oscillators drift, but not in a matching way, of course. The RC oscillator is sensitive to stray capacitance/hand pickup.

[mashersmasher]

Heres a easy cheap pic probe, from micro examples got flash hex code plus c files if anyone interested.

Is that just a collpitts oscillator being read by a pic?

[Skippy]

Yes, it's an LC in place of a crystal, the website mentioned on the circuit gives basic details, plus the C code for the in-depth info.

http://www.micro-examples.com/articles/index.php/PicoDetector