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Offline CorneliusTopic starter
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« on: November 09, 2009, 09:32:19 am »
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This is a full schematic of a BFO Discriminating metal detector .  As you can see it consists out of two  oscillators .   Fs is about 120 KHz while Fr is  four times as high at about 480 KHz .  You can use any frquency you want as long as  Fr is four times Fs . You may try to use a  cristal to get a steady Fr . This is all up to you and how handy you are . The oscillator Fs is using an adjustable capacitor  . Take a good one out of an old radio or something . You may use a regular capacitor to bring the adjustable capacitor in the limits you are seeking for . ( mount the regular capacitor  parallel to the main capacitor ) .  On the two sided PCB , you first work on the solder -side of the print . ( leave the other copper side untouched ) . You drill the  solder-side first .  After that you carefully remove the copper from the other side where it is needed . You can use a small drill bit to do this (  use a wood -drill ) . The coils is made from  0.5 mm enameled cu wire .  45 windings  . Diameter 16.5 cm .   The leds will run in two directions  . To the left and to the right .  You set the variable capacitor to the point where the led are at rest  ( only one is burning )  . If there is any metal underneeth the coil the leds will start to move . One way for ferrous metals the other way for gold or silver  .     Cornelius
Part two .  Cornelius
Sorry guys it was impossible to post the other parts to this schematic  . This turns out to become a lousy forum if you cannot post a simple schematic anymore !!!!!!  Cornelius ( if you are interested  I can  E-Mail the rest to you )   
Part two. Cornelius

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Offline xavier
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« Reply #1 on: November 09, 2009, 02:28:26 pm »
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Hi Cornelius

Yes yes yes please send as I am very interested to make one for experimenting purposes .You will find my E-Mail in my profile thanks a lot it's the kind of thing that I am all way's looking for. Cheesy

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Xavier


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So many questions so little time

Offline CorneliusTopic starter
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« Reply #2 on: November 09, 2009, 03:29:22 pm »
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Xavier . As you probably know by now I have built and designed quite a few detectors . Although my idea is now to keep on going with PI detectors I must say that this BFO detector is a very nice unit . As long as you keep the two oscillators  as stipulated  ,  Fs x Fr = 1 to 4 , you can have a lot of fun with this detector . Now don't get me wrong  it is not a toy . It is a real metal detector  . I will send the whole schematic to you by E-Mail  . Regards  Cornelius

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Offline mdiede57
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« Reply #3 on: November 10, 2009, 02:13:33 am »
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can you send me a copy of the full schematic, also?  Thanks

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Offline CorneliusTopic starter
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« Reply #4 on: November 10, 2009, 04:52:53 am »
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mdiede57 . The schematics are in your mailbox . Have fun with them  .  Cornelius

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Offline technos
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« Reply #5 on: December 12, 2009, 05:18:03 pm »
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I honestly do not think there is any such thing as a "discriminating bfo" unless you are discriminating between ferrous/non ferrous only. They tend to be set off by any hot rock there is (or swamping out real targets with a hot rock). I'm not saying there can't be, just that I've never seen one. I think they belong in pinpointer circuits imho.

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Offline xavier
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« Reply #6 on: December 13, 2009, 05:52:27 am »
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Hi Technos

I think that you should build this BFO it may just surprise you. As for the discriminating part of it you are right it will tell you if it is ferrous on non ferrous but that is a sort of a discriminating device as you can choose to dig or not to dig.  Smiley

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So many questions so little time

Offline CorneliusTopic starter
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« Reply #7 on: December 13, 2009, 06:20:39 am »
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Xavier  I think I did not put the both sides of the pcb on the net . Here they are  Cornelius

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Offline xavier
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« Reply #8 on: December 13, 2009, 08:10:54 am »
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Hi Cornelius

As you had a problem last time to post it you sent the schematics to my E-Mail so I do have all the PCB lay out however it?s good that you have posted them as there may be someone else interested in it. I have got it going but not to my satisfaction as I seem to have a problem with my I-meter  Cry and I?m also busy with my VLF detector (starting to work very well) Great so I did not have a look at what?s up with the meter but will be getting to it soon. That is why I have not let you know yet how it was performing. I hope to get to it this coming week.

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So many questions so little time

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« Reply #9 on: December 13, 2009, 10:14:50 am »
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Xavier . Yes I sure hope we can help somebody else with these schematics . In the discrimination mode the led travel from left to right or from right to left . You adjust the detector by turning the variable- capacitor till the leds stay motion-less . As soon as you neer the target the leds start moving . Either to the left or to the right  for ferrous or non ferrous materials .  Cornelius

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