Andy Flind MFD.

[Geo]

Yes but it must detect the quartz watch....

[abdou2014]

Does this LRL have the ability to detect a test field 1 year old ?

[Geo]

I don't know.
some years ago i tried an cryfton at a ancient place (where some other lrls gives signals) without results.
Also with my mfd i found some very small objects but nothing else....

[abdou2014]

What are the changes that increases the sensitivity , I can not detect a watch ?

[Geo]

Maybe you have bad calibration or bad preamplifier...

[abdou2014]

I do not think everything is OK, preamp first 2N2222 and the second bc238 HFE 700. I noticed: when I leave the first LED on, and I adjust the buzzer Off, the LRL more sensitive than all LEDs off . I need help Mr Geo!

[Geo]

Can you give details of coil and frequency???
do you have potentiometer at preampl output??

[abdou2014]

[abdou2014]

Coil 2X30 turns + Pot 5K pream .

[Geo]

Originally Posted by abdou2014

Coil 2X30 turns + Pot 5K pream .

What do you mean 2x30???

[abdou2014]

Like This .

[ASHIL]

Originally Posted by abdou2014

ANDY WITH DIGITAL DISPLAY

Hi My friend
Can you put this circuit and digital Display`s in here? But if not Personal

[Geo]

Originally Posted by abdou2014

Like This .

Why you use 2 coils????

Who is the coils diameter??

[abdou2014]

The diameter of the coil is 16 cm. with 30 turns I detect the transmitter at 1 meter, 2X30 I detect at 2 meters . frequency 80 Khz .if it's wrong what's to change ???

[Geo]

I don't know more....
Now about calibration you must calibrate it so the first led to be on (light) and just little before the 2nd led turn on.

[abdou2014]

is those winding are necessary, and what is their detail ?

what are the changes to detect a watch, I do not think that will detect anything without

reaching this sensitivity ?

[Geo]

If the gain is ok then you must receive the watch (at least if you touch the watch to the coil).
Do you have oscilloscope and signal generator to test the MFD???

The small coils at Cryfton don't do anything. Constructor use them with gold sample and try to catch the phenomenon. He says that this small coils with gold paper is gold filter. Anyway, averyone can say it as he like.....
For me 30 turns are enough, just tune them at 80Khz.

[Geo]

Here a photo from my Andy Flind's MFD as lrl

[abdou2014]

is there a difference between the coil location :
the coil below the PCB and in front of 12 cm ?
the coil is it shielded ?

[Geo]

No it is not shielded.
The distance is a small secret: lol :: cool :.
So ..... if the coil is near to pcb and to buzzer, then when the buzzer beeps there is feedback to the coil, and all leds turn on and beeps continuely.
If coil is far then .... NO problem.
This Trick is a present for you ...

[abdou2014]

Thank you Geo , to be precise, this inconvenience is caused only by the buzzer, or even the PCB ?

[Geo]

As i remember, from buzzer and coil

[abdou2014]

so I remove the buzzer to keep my design , I think it's the speed that made Andy flind MFD particular ?

[Geo]

It is a good way... but if you will see problems remember to move the coil.

[abdou2014]

there is a remark that I would like to have some explanation :
there is OBMD builder that used all regulator 100mA, the small,
and others who have used the 100mA just in the ANDY LM 358, and the others all a big regulator 1A, is there a diference and what is the right choice ???