Help with building CCO?

[maikl]

I think the direction of winding as shown. Try a combination of both and will see the difference.When testing the detector in the vicinity should not be metal.Do you have Fédéré bed?

[maikl]

A crystal earpiece is used for sound
output. While a piezo sounder may be
used (without integral electronics),
this is not likely to offer good volume.
If the volume in the earpiece is too
high, use a suitable series resistor to
reduce it. An inductive sounder orearpiece is not recommended, because
it could overload IC2.18 ohm and 24 ohm impedance is much low.Try it with piezo as shown, impedance several thousand ohms (try different sizes of piezoelectric).

[TRX]

Post #14 http://www.geotech1.com/forums/showp...1&postcount=14

Here's another BB metal detector by the same author.There are more details for beginners.

I have a question, i lost something small in my backyard (size 300m2). The object is the size of a nail, made from steel, I need to sweep the area .

The schematic quoted from maikl (http://www.geotech1.com/forums/attac...2&d=1276694810 ) will it do the job ? Is is sensitive enough to detect such a small object ?


Thank you.

[maikl]

Post #14 http://www.geotech1.com/forums/showp...1&postcount=14




I have a question, i lost something small in my backyard (size 300m2). The object is the size of a nail, made from steel, I need to sweep the area .

The schematic quoted from maikl (http://www.geotech1.com/forums/attac...2&d=1276694810 ) will it do the job ? Is is sensitive enough to detect such a small object ?


Thank you.

Hi TRX."the size of a nail" how many millimeters? But regardless I think it could find "steel fingernail".

[TRX]

Haha.

~ 1cm/1cm

[maikl]

Haha.

~ 1cm/1cm

Can be safely.

[TRX]

The author says:

"Both the characteristics of IC1 and the inductance of the coil influence oscillator frequency, which lies around 260kHzwithout a Faraday shield. The Faraday shield approximately doubles the inductance of the coil, thus roughly halving the frequency." => ~ 130 kHz

"Wind the two search coils. They are 70 turns of 30SWG (0·315mm) enamelled copper wire on 120mm diameter formers."


If I use 0.21mm (35 swg)wire, how many turns do I need to make to achieve the same result ?

[maikl]

The author says:

"Both the characteristics of IC1 and the inductance of the coil influence oscillator frequency, which lies around 260kHzwithout a Faraday shield. The Faraday shield approximately doubles the inductance of the coil, thus roughly halving the frequency." => ~ 130 kHz

"Wind the two search coils. They are 70 turns of 30SWG (0·315mm) enamelled copper wire on 120mm diameter formers."


If I use 0.21mm (35 swg)wire, how many turns do I need to make to achieve the same result ?

70 turns of 0.315mm (120mm diameter) = inductance 1.522mH
67 turns of 0.210mm (120mm diameter) = inductance 1.528mH

[misko]

Nabiul, if your hobby is electronics, you should buy a ton of diodes 1N4148. They are very small and the most cheap diodes for signal processing.
However I posted an idea only. Since for me this is a BAD CIRCUIT, my advice is to try something better, like HOUNDOG. Here is an idea for modernisation of HOUNDOG.

hi mikebg.
I wonder if this plan works in practice.

[misko]

Nabiul, if your hobby is electronics, you should buy a ton of diodes 1N4148. They are very small and the most cheap diodes for signal processing.
However I posted an idea only. Since for me this is a BAD CIRCUIT, my advice is to try something better, like HOUNDOG. Here is an idea for modernisation of HOUNDOG.

However I posted an idea only. Since for me this is a BAD CIRCUIT, my advice is to try something better, like HOUNDOG. Here is an idea for modernisation of HOUNDOG.
hi mikebg.
I wonder if this plan works in practice.