ARADO 120 SCH& PCB

[aft_72005]

I made Arado in 2010, it had no problems in operation.
In your photo, you used thick foil, which reduces sensitivity.
Next, you should not close the foil completely on the entire coil and it should be partially open.

[profesor]

I made the arado 120b years ago. I had the original coil. But the depth was low. A 560pF variable capacitor is connected between the TX and RX coils. If you don't do this, the depth will be low and you cannot reset the detector.

[profesor]

https://www.amplifiedparts.com/produ...single-section

[nimalgr]

THNKS FOR YOUR ANSWERS.....THE FOIL FOR SHIELD IS FOR THE KITCHEN...VERY THIN AND WITH A 1CM DISTANCE FROM THE EDGES. THE FREQUENCY IS 4.680.I HAVE THE ORIGINAL AMETER AND I HAVE TRY THE ORIGINAL VARIABLE AIR CAPASITOR, BUT FOR THIS PCB I FOUND THAT A 220nF CAPACITOR PARALLEL ON THE RX COIL HELPS FOR CENTERING THE AMETER WITH VR1. I'II TRY TO
REMOVE THE FOIL FROM THE COILS. THE ONLY PROBLEM IS THE DEPTH AND THE LOW VOLUME FROM THE SPEAKER. ANY HELP FROM THE FORUM PLS? THANKS A LOT.

[nimalgr]

THE PROJECT FOR THE COIL IS 25CM DIAMETER WITH 0.3 WIRE. 160 TURNS FOR TX AND 205 TURNS FOR RX, AS ANDREAS POSTED MANY YEARS BEFORE.

[Pete61]

.....THE FOIL FOR SHIELD IS FOR THE KITCHEN...VERY THIN AND WITH A 1CM DISTANCE FROM THE EDGES.

You cant use anything that is seen by the metal detector.
This includes aluminium foil and even metal film with a plastic layer like coffee bags and cereal bags.

I use graphite powder mixed with wood floor varnish(polyurethane) in a 1:1 ratio by volume.
I use waxed lacing thread to tie the coil and wrap it with pvc electrical tape.
Then a layer of polypropylene spiral wrap and micropore bandage for the graphite varnish to stick to.
I strip some stranded copper cable, like cat5E or cat6, and graphite varnish it onto the shield.
Finally its resin and fiberglass to make the whole coil rigid.

[nimalgr]

I HAVE REMOVED THE ALUMINUM FOIL FROM THE COILS....ITS A LITTLE BETTER ABOUT THE DEPTH...THE AMETER WORKS PERFECT...FERROUS,NON FERROUS...AND THE SOUND COMES BETTER WITH A BUZZER. I THINK THAT A SMALLER COIL....ABOUT 20CM, WILL BE BETTER FOR THIS PCB.

[Pete61]

I HAVE REMOVED THE ALUMINUM FOIL FROM THE COILS....ITS A LITTLE BETTER ABOUT THE DEPTH...THE AMETER WORKS PERFECT...FERROUS,NON FERROUS...AND THE SOUND COMES BETTER WITH A BUZZER. I THINK THAT A SMALLER COIL....ABOUT 20CM, WILL BE BETTER FOR THIS PCB.

Its not about the size/ diameter of the coil, its about the frequency.
Both coils must be tuned to 4680Hz by adding or removing turns.

see post#5 by Andreas

If you want have "excellent" results, you should be manufacture coils with fine resonate - tune.
For this MD, you don't need at first step osciloscope, only a Freq-meter.
The "magic" frequency for this MD is oscilator work 4680Hz.
How we can this frequency of work?
Diametre Dcoil between 15-30cm is fine for this MD
Now a example. You have a form for make Dcoils diametre 25cm.
Put in this form 200turns copper-wire diametre 0,28-0,35mm. Diamtre copper-wire is not critical, but you cannot use <0,28 or >0,35. Now connect C19-Tx coil your Freq-meter. You see freq-meter example 3400Hz. You start now abstraction turns from Tx coil. In one point example -36turns you see Freq-meter 4680Hz. Thats all.
Only you should be know, how much turns abstraction, because the RXcoil should be have this formula. RXcoil(turns)=Txcoil(turns)+45turns. With this method, you have two excellent Dcoils for this MD
I think you understand well all steps for make easy this coils
best regards
Andreas

[nimalgr]

The frequency is exactly 4680 on tx and i have put 45 turns as the post of Andreas for rx coil.

[Pete61]

The frequency is exactly 4680 on tx and i have put 45 turns as the post of Andreas for rx coil.

All good then, Id double check the freq on the rx coil just to make sure, but maybe thats just me.

[nimalgr]

I CHECKED THE FREQ. ON TX COIL NOW AND IT IS 4,200....IT EAS 4.680 WHEN I HAD DONE THE TX COIL. DO YOU KNOW MY FRIEND HOW MANY TURNS MUST BE RX COIL, IF WE HAVE STANDARD THE TURNS OF TX COIL FOR 4.680. ANDREAS HAD SAID THAT MUST BE...TX TURNS+45. IS THATCORRECT?

[Pete61]

I CHECKED THE FREQ. ON TX COIL NOW AND IT IS 4,200....IT EAS 4.680 WHEN I HAD DONE THE TX COIL. DO YOU KNOW MY FRIEND HOW MANY TURNS MUST BE RX COIL, IF WE HAVE STANDARD THE TURNS OF TX COIL FOR 4.680. ANDREAS HAD SAID THAT MUST BE...TX TURNS+45. IS THATCORRECT?

Thats right yes, Tx + 45T

[nimalgr]

Pete61 I CONNECT ONLY THE TX COIL ON PCB AND PARALLEL CONNECT THE FMETER.....I PUT 4.650 THE FREQ.......AND AT TX TURNS PUT 45 TURNS PLUS AT RX COIL. DO YOU KNOW HOW I 'II SEE THE FREQUENCY OF RX COIL?THANKS

[Pete61]

Pete61 I CONNECT ONLY THE TX COIL ON PCB AND PARALLEL CONNECT THE FMETER.....I PUT 4.650 THE FREQ.......AND AT TX TURNS PUT 45 TURNS PLUS AT RX COIL. DO YOU KNOW HOW I 'II SEE THE FREQUENCY OF RX COIL?THANKS

From what Ive read, you connect the Rx coil and its capacitor to the TX position on the pcb to read its frequency. Then instead of adding or taking away Rx coil loops, you change the vari cap to get the right freq and then read the vari cap's value to choose a correct fixed cap for C17 or C18, which ever one it is.

I havent built one, so Im just forming an opinion based on what Ive read in these forums.


This quote from Andreas #32

C17,C18 you don't put now your PCB. After resonate Tx coil, you know if C17,C18 are right or not

#30

My method is simple for your all. After you build PCB , you must build a electronic-cap with range 50-300n. With this electronic-cap we can make a fine tune Rx coil.If you find this parts (example 101,5n) then replace with normal capacitor/capacitors and only difficult point is a "null" Tx/Rx. With this method we don't need variable capacitor between Tx/Rx
best regards

[nimalgr]

HAS ANYBODY A SCHEMATIC FOR ELECTRONIC-CAP PLS?