New Homebrew Metal Detector

[ivconic]

Regards...

Regards !
When finishing i'll post some reports here...

[ivconic]

It is working !!!


Hi again Zisme !
I've just finished this PI. It works fine from the very start.
I just did'nt make coil you posted here yet. I tried detector with
some scrap coils, already have here. Although it is not mach, it works
almost fine with it!!!
For example: 1.5cm brass coin it can detect on 20cm distance ,
with 21cm diameter coil,with 31 windings and 0.7mm wire gauge.
I am not thrill with this result but of course the presented coil is not
suitable for it,not proper. So, i decided to make your spiral coil,and
only one thing is buging me. You mentioned 9.5 in diam. But,looking
at your coil i keep wandering what of the two axis here(on my picture)
should be 9.5 in.Inner or outer? If you started with first winding from
inner, how did you knew in advance,that it's gonna end just on 9.5 in?
If not, than otherwise you must started from outer point on 9.5in circle
wound from outer to inner axis? This i ask cose want to make exact coil
as yours, due to very good results you posted here.Many thanks in advance!
By the way, IRF is calm and cool, no noise, and power consumption is 24mA
without detection(no sound) and 98mA with full detection(loud sound)...
All presets are working just fine, also 2 potentiometers also...
What to say!? Nice project and working at once! No problems at all!
Congratulations!
best regards!
P.S.
waiting for hints about coil...

[ivconic]

More...


I forgot to mention very important thing !!!
Instead of 3.5xxx quartz i put 3.663 MHz quartz.Also instead 27p i put 30p capacitor...
The freq. is 225Hz. I think it is even better cose could be a bit more sensitive on
small items - who knows? Those jumpers can be arranged some other way to obtain
different freq. i suppose.... I do not have right now any manufacturer aplication here,
so if you want, may post here inner composition of i.c. with all jumper presets available.
I was thinking to add some switches instead jumpers, so i can choose working freq. by it,
later, without opening box or rearranging jumpers.What do you think? It brings to me a
bunch of new ideas right now...!
Anyway, the fact is that this device is much simplier than Delta Pulse, which i prefered
so far, so if gain with it even close results like with D.P. i will "switch" on it in the
future....
Last step is to "establish" the proper coil for it.
I am waiting for you hints, and later i am gonna start making some coils here...ha,ha,ha!
regards


P.S.

Also i omited low drop reg. and connect it straight to 12v accu, 1.3A...
No big use from low drop if you use powerfull accu, only have to add 4700mF
and all is "singing" nice...

[zisme]

I forgot to mention very important thing !!!
Instead of 3.5xxx quartz i put 3.663 MHz quartz.Also instead 27p i put 30p capacitor...
The freq. is 225Hz. I think it is even better cose could be a bit more sensitive on
small items - who knows? Those jumpers can be arranged some other way to obtain
different freq. i suppose.... I do not have right now any manufacturer aplication here,
so if you want, may post here inner composition of i.c. with all jumper presets available.
I was thinking to add some switches instead jumpers, so i can choose working freq. by it,
later, without opening box or rearranging jumpers.What do you think? It brings to me a
bunch of new ideas right now...!
Anyway, the fact is that this device is much simplier than Delta Pulse, which i prefered
so far, so if gain with it even close results like with D.P. i will "switch" on it in the
future....
Last step is to "establish" the proper coil for it.
I am waiting for you hints, and later i am gonna start making some coils here...ha,ha,ha!
regards


P.S.

Also i omited low drop reg. and connect it straight to 12v accu, 1.3A...
No big use from low drop if you use powerfull accu, only have to add 4700mF
and all is "singing" nice...

Nice Job! I am amazed you are operating it without any regulator! You guys are already improving it!

I really enjoy hearing from folks like you that are having as much fun with this project as I have had.

Sorry for leaving out the inside diameter of the coil. The I.D. is 5.75 inches. I made a coil winding jig with a center disk that's 5.75 inches in diameter and wound it outward untill I had the number of turns I needed. It just happened to come out at 9.5 inches O.D. so that's what size housing I then built for it. I have added the coil I.D. to the webpage.

As for the frequency selection jumpers, I have added a chart on my website that shows all the possible jumper configurations and the resulting frequencies out with a 3.579545 mHz. crystal.

Glad you like the circuit,

Mike

[ivconic]

Thanks..


Thank You very much. I'll visit your site again and update news...
Right now i am experimenting with coils... I 'll report here any news on that subject..
regards!

[ivconic]

Same results ...


I made a several coils yesterday and today. Experimenting and gain no better
results yet. Still best result is coin detection from 20-23cm with coils 24 diamm.
I do not see some differences, no matter number of windings, from 20 to 40... IRF 740 is still cool.No problems with apparatus at all, only could'nt
match better coil so far....
The same problem i had with Delta Pulse at the time.But solved later with some modifications. I made spiral coil, started as told here, but windings finished much before 9.5 in...!? WIre gauge is proper...
Although i noticed a slice better performances of spiral than conventional coil. But very slice.....1cm more on the coin...
Still experimenting...
See you later..

[zisme]

I made a several coils yesterday and today. Experimenting and gain no better
results yet. Still best result is coin detection from 20-23cm with coils 24 diamm.
I do not see some differences, no matter number of windings, from 20 to 40... IRF 740 is still cool.No problems with apparatus at all, only could'nt
match better coil so far....
The same problem i had with Delta Pulse at the time.But solved later with some modifications. I made spiral coil, started as told here, but windings finished much before 9.5 in...!? WIre gauge is proper...
Although i noticed a slice better performances of spiral than conventional coil. But very slice.....1cm more on the coin...
Still experimenting...
See you later..

One thing I noticed is that you said you were getting about 225 Hz. out with the substitute crystal you installed. When I did the math, I came up with 111.7858887 Hz. which is about half of what you are getting which means the your oscillator appears to be operating at twice what it should be. I don't know if this makes any difference or not in the range you are getting, but in troubleshooting, you should start with the original frequency of about 100 Hz just to rule that aspect out. If the oscillator is running at twice it's frequency, you might try playing with the value of C3 or just try to get hold of the correct crystal. These are common color-burst crystals that you can get for as little as 10 cents each.

I checked the wire gauge and coil again and it's correct. The spiral winding is close-wound with no gaps. If you are not getting the diameter, go to a larger gauge wire. In fact, this should increase the Q and maybe improve your results.

I assume you have experimented with all of the timing adjustments. These should be fine tuned to get the best results from a given coil.

Also, another difference between your detector and mine is the current draw. My detector draws much more current than yours which means it's putting more current into the coil. Of course, mine is running at 109 Hz. too.
You said you left out the voltage regulator, what is your input voltage? If you drop below 12 volts, the range starts to drop off quickly.

Again, thanks for the feedback and good luck.

Keep us posted,

Mike

[Geo]

Hi Ivconic. If you still work with D.P then i can send you the manual. I found it.
Btw I believe that for big objects 100hz is better than 400 hz
Regards

[ivconic]

inches....

:confused:
Hi Zisme !
It appears that some harmonic became stronger than main pulse.Why? Well,i guess,i put
some of the filtering component bad!I had to check them all over again, some of them
not new, i used a lot of scrap components( i have tons of them)...
You are right about C3.
Also crystal is not hard to obtain.I just used first nearby i found.
About wire...i might be wrong. It's so hard for me to manage with all those standards..
Is it awg, swg or bwg standard you are talking about? Let's measure in mm's for a while.

Wire #20 could be 0,81mm(awg) or 0,89mm(bwg) or 0,92mm(swg).....
The former is 5.75 in as you said. It means 14,605cm in my language and mind (since i am
european and it's so hard for me to think in inches).
27 turns of wire on 14,605cm former should give us:
- 16,792 cm or 6,61 inches spiral coil diamm. respecting AWG or
- 17,008 cm or 6,71 inches spiral coil diamm. respecting BWG or
- 17,089 cm or 6,72 inches spiral coil diamm. respecting SWG standard.
Anyway, it ends on some bellow 7 inches, but not on 9,5 inches !!!???
You said 27 turns, but it will take much more to reach 9,5 inches with #20 wire by any
standard.Or maybe you started with 27 turns and continued while got some good results?
Anyway,if it's possible,(it would be so help for me), to measure wire you used in mm's
and reply here or detailed explain your coil, since results you posted here are very good!
The very best regards to you, and thank's in advance!

.................................................. .......

Geo...
"Hi Ivconic. If you still work with D.P then i can send you the manual. I found it."
Yes Geo. I made another DP and it is working much better than first one.I am so glad.
It shows that Delta Pulse (or XR 71, whatever) is very good,nice and usefull detector.
The second one i made is so good that reaches PulseStar II performances! So Pulse Star II
is "history" now! I am gonna sell it as soon as possible.For those money i can make over the
15 Delta Pulses more!Why keeping "dead" capital at home !?
Do you have that manual scanned? If file is not bigger than a few mbytes, than o.k. send
it.
Best regards to you Geo

[ivconic]

Always forgot....


One more thing....
Your results:
U.S. penny: 12 to 15 inches......30,48cm to 38,1cm
U.S. nickel: 9.5 to 10 inches....24,13cm to 25,4cm
Car.............................121,92cm to 152,4cm
I can tell you that those results on coins are excellent, with such small coil!
But on car, result is average....
I would like to gain such results on coins, with my home-made detector, and
such a small coil diamm.
THE REAL THING, WHEN PROSPECTING COINS, IS TO USE AS SMALLER COIL AS POSSIBLE,
DUE TO SPEND LESS TIME ON PINPOINTING,ALSO AVOID POSSIBILITY TO DAMAGE ITEM
WHEN DIGGING....
My Delta PUlse, with 42cm coil is detecting coins from 20 to 27cm, but car
(Wolksvagen Golf II) it can detect over the 200 cm.....
With 75cm coil, very poor on coins(20cm...27cm) but on car over the 300cm !
.................................................. ............
Now back to your post....
"Also, another difference between your detector and mine is the current draw. My
detector draws much more current than yours which means it's putting more current
into the coil. Of course, mine is running at 109 Hz. too."
I guess, it should be oposite. Higher freq. - draws much more current!
Also thick wire in coil...But, thick wire and lower freq. are suitable when prospecting
big items at high depths.I want to prospect coins and small items at lower depths up to
45-60cm , no more.That's why i am experimenting so much with PI's...Also i have a few
of IB's(some of them very good), but PI's are my favorites!
"You said you left out the voltage regulator, what is your input voltage? If you drop
below 12 volts, the range starts to drop off quickly"
Voltage is 13,6 volts. Straight from accu. 6 Ah.. I left out v.reg. and add 11000 microF
capacitor,cose wanted to use heavy duty accu, which sometimes can vary from 13.xx to
12.xx volts and i guess than in some conditions, that low drop can cause some problems on
the field.
Also it is much safer now to experiment with higher voltages, up to 18 volts...only have
to "isolate" IC's fedding from driving voltage, by using some small reg. in that rail. But
it will open this project for much more improvements and lead us to whole new project.
I do respect this project of yours, cose it is small,simple and very usable! I am planing
to keep it as it is,pack in some small box and use it in places where bigger machines
not suitable for handling( holes,caves,pipes,etc....).
But also, i can aprove your case, where, you put another type of accu's, and , of course
it is much better to use v.reg....I can agree on that 100%...
"...Again, thanks for the feedback and good luck..."
No, friend ! THANK YOU, for sharing with us, here, your schematic and project,hints...
Also showing a good will to help!
best regards

[zisme]

[quote=ivconic]:confused:
Hi Zisme !
It appears that some harmonic became stronger than main pulse.Why? Well,i guess,i put
some of the filtering component bad!I had to check them all over again, some of them
not new, i used a lot of scrap components( i have tons of them)...
You are right about C3.
Also crystal is not hard to obtain.I just used first nearby i found.
About wire...i might be wrong. It's so hard for me to manage with all those standards..
Is it awg, swg or bwg standard you are talking about? Let's measure in mm's for a while.

Wire #20 could be 0,81mm(awg) or 0,89mm(bwg) or 0,92mm(swg).....
The former is 5.75 in as you said. It means 14,605cm in my language and mind (since i am
european and it's so hard for me to think in inches).
27 turns of wire on 14,605cm former should give us:
- 16,792 cm or 6,61 inches spiral coil diamm. respecting AWG or
- 17,008 cm or 6,71 inches spiral coil diamm. respecting BWG or
- 17,089 cm or 6,72 inches spiral coil diamm. respecting SWG standard.
Anyway, it ends on some bellow 7 inches, but not on 9,5 inches !!!???
You said 27 turns, but it will take much more to reach 9,5 inches with #20 wire by any
standard.Or maybe you started with 27 turns and continued while got some good results?
Anyway,if it's possible,(it would be so help for me), to measure wire you used in mm's
and reply here or detailed explain your coil, since results you posted here are very good!
The very best regards to you, and thank's in advance!

.................................................. .......

I must be getting SEE-NILE!!! I took the coil apart and measured the winding again, and the inside diameter is 6.5 inches! I had been measuring my coil winder inner form, but I forgot that I did remove some of the inner turns because I ended up with too much inductance. Sorry, sorry, sorry....about that. I have corrected the measurements on the website. Thanks to you for being persistant about it. I measured the diameter of the wire with my dial caliper which came out to .043 inch.

Hope this helps with your coils and again, thanks for finding this,

Mike

[ivconic]

Even more confused !!??

:confused:
Now i am even more confused...But first thanks for replying me.If i am to persistant and buging you, it's quite alright to tell me. Due to real wish to
make that coil i just have to bug you more...
Your latest post confused me more. According to your measures it will take approx. 69 turns to reach 9.5 inches, with the .043in wire! Not 27.
I 've been visited your site and no changes there,no updates yet.
Anyway,inner former is now right and known, so i am gonna start all over again to wind that coil.It is so interesting to me to try to gain your results.
If inner is 6.5 inches and outer is 9.5, for windings 3 inches are left.Divide 3
inches with .043 and you'll get some 69 turns.O.K. we do not need to be so
neat, let's say from 65 to 70 turns !!!???
It is too much i guess!
O.K. i will wait your opinion on that.
best regards

[zisme]

:confused:
Now i am even more confused...But first thanks for replying me.If i am to persistant and buging you, it's quite alright to tell me. Due to real wish to
make that coil i just have to bug you more...
Your latest post confused me more. According to your measures it will take approx. 69 turns to reach 9.5 inches, with the .043in wire! Not 27.
I 've been visited your site and no changes there,no updates yet.
Anyway,inner former is now right and known, so i am gonna start all over again to wind that coil.It is so interesting to me to try to gain your results.
If inner is 6.5 inches and outer is 9.5, for windings 3 inches are left.Divide 3
inches with .043 and you'll get some 69 turns.O.K. we do not need to be so
neat, let's say from 65 to 70 turns !!!???
It is too much i guess!
O.K. i will wait your opinion on that.
best regards

9.5 minus 6.5 equals 3 is correct, but you forgot to divide by 2 to get the radius of windings which is 1.5. Then dividing 1.5 by .043 gives you 34.88 turns if wound absolutely tight. However, my windings are not very perfect, so it came out to 27 turns. Given the error in measuring the diameter of the wire and consistancy of the enamaled wire, I say that's probably pretty close.

The update to the website was a new picture of the coil with the correct dimentions on it.

Thanks again and never think you are bugging me.

Glad to help,

Mike

[ivconic]

ivconic is now SEE-NILE!!!


Ha,ha,ha,ha......but of course! Stupid me! Yesterday i checked your answer
and reply "on the fly" here, without much of brains, i guess.
You are right now! Thank you being good help.
It is correct now. I am going to fix some coils here....


best regards

[Seeker]

Hi Zisme,
I think it is better to use avalanche transistor, then mosfet .

Best regards