what type of metal detector are these ?

[neptune]

VLF - very low frequency
PI - phase induction
BO - beat freq. oscillation

 

[Dragon Tamer]

I'm not an expert on metal detectors but I read up some info on them and it sounds like a VLF metal detector is the best way to go. I would sugest reading the site in the link, it describes the theory of operation and what the capabilities are; **broken link removed**

 

[neptune]

Thankyou but i think BFO systems are simple and easy to manufacture as this site has given.
but PI pulse induction system are very good discriminator then above two.

 

[Mr RB]

BFO can give really good performance from really poor hobby level hardware provided you have a knob to "trim" it. It only needs two really simple oscillators and can be made from a 556 timer or a few transistors.

 

[neptune]

BFO can give really good performance from really poor hobby level hardware provided you have a knob to "trim" it. It only needs two really simple oscillators and can be made from a 556 timer or a few transistors.

Hey i posted circuit using 555 timer, is that BFO system are there any other good circuits using 555 timer

 

[Sparky_s]

I read somewhere that the phase discriminator was useful to know what kind of metal the device detected. Each metal has different phase echoe (or something similar), so you can tune you metal detector to detect some specific metal.

 

[neptune]

I read somewhere that the phase discriminator was useful to know what kind of metal the device detected. Each metal has different phase echoe (or something similar), so you can tune you metal detector to detect some specific metal.

yes they are but they are very complex to make and Big, unless specified by customer nobody makes them ^^

 

[Mr RB]

Hey i posted circuit using 555 timer, is that BFO system are there any other good circuits using 555 timer

To make a "beat frequency oscillator" you really need 2 oscillators. That makes the "beat frequency" between the two different frequencies. One is from the coil's oscillator, that changes freq when metal comes near. The other is a reference oscillator that usually has a pot to let you "tune" it to make the beat.

You can use two 555 timers but it's just as easy and will sound nicer with transistor oscillators.

This link popped up at the top of a google search for "BFO metal detector using transistors";
http://www.easytreasure.co.uk/bfo.htm

**broken link removed**

It looks pretty good.

 

[neptune]

I looked at the link , its pretty childish or basic, would it work same as industrial type metal detector.
Also what are the specification for metal detector that makes it industrial grade or lower grade ?

 

[Mr RB]

I asked questions in your OTHER thread, please see there.

 

[Pommie]

A member here (Chemelec) has some useful information on his site and details of a pulse induction detector. See **broken link removed** also read some of the articles about how it works.

Mike.