Website? For metal detectors? No, I do not know any, it might confuse me.
I design my own, but if you want simple, like BFO, I can give you something, in fact I uploaded an circuit, that I got from a member in Argentina... its an old design, fairly simple, and I improved it, redesigned it for 30 kHz, which is VLF, or was until the 5 kHz ones started appearing, I would call them ELF (Extra Low Frequency)
I kind of modernized it for the average available transistors, 2N2222 (NPN) and 2N3906 (PNP) I rearranged the coils so one end was grounded, this cut out a lot of unnecessary parts so now the search coil goes through coax to thhe oscillator with no chance of shorting the battery.
Coils will be hard to do, because you need a lot of fine insulated wire. But I suggested making the coil form from 1/2 inch soft copper pipe, split around the outside. This makes a coil form and a shield. the coax braid has to be wired to the copper pipe so the copper is grounded.
What I can do is type up directions, for the coils, and upload them to you, as well.
You can get transistors and other stuff from old TVs, just be careful of the picture tube, because it may have a 20,000 volt charge, still on it and the glass is LEAD glass so it has to be disposed of , safely.
I will upload the schematic which is in poor shape, try to print it and if you need to, pencil in the faint stuff. I will redo it and make it darker, but meanwhile, you have something.
Note, the wires may seem to cross but there is no connection except where ther is a big dot. The original was terrible.
The LCR bridge (it has limits) can use a 2N2222 type as it is similar enough.... it is designed to put a potentiometer (10k) from the green binding post, to a black one then a coil or resistor or a capacitor (0.0016 ufd smallest) from the red binding post to the other black binding post. The oscillator should be set to 10,000 Hertz. It will measure coils from about 500 uHYs to 155, 000 uHYs and capacitors from 0.0016 ufd to 1.55 ufd., suitable for VLF detectors.
Plug in a set of Mono 16 ohm phones and turn the potentiometer until the tone disappears, or the DVM reads zero. Then measure the pot. and this equals the resistance, if a resistor, and impedance if a cap or coil. You have to know the formula for converting impedance to capacitance or inductance. But it is simple. I will include some simple calculator formulas with the coil data.
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« Last Edit: August 14, 2009, 04:30:05 am by goldigger »