Matchless metal detector

[der_fisherman]

OK guys, I think this has gone far enough.
Please read the Basic Rules of the Forums ->
http://www.geotech1.com/forums/showthread.php?t=10526

In particular, the part where it says:
"Criticism should be relevant and constructive. If you disagree with something, state your case, and move on."

It's time to move on.

Fully correct, thanks for the timely intervention.

regards

Andy

[satdaveuk]

I thought it was actually quite funny young Tim trying to walk before he can crawl and then theres Andy been the older wiser fatherly figure basically smacking his bum for been a naughty boy.
Theres a old saying... you cant put a old head on young shoulders.

Regards to all

[6666]

Davor did you ever complete this project ?

[Davor]

No. I kinda skipped a step.

I made several sims of a search head consisting of 2 identical IB coils that would oscillate at ~10kHz apart, and with ground compensation. Fun part is that it is quite easy to achieve such compensation over a large frequency span using a very simple network. The 10kHz difference is tackled with a PLL in a slow loop filter for motion compensation, and a notch audio filter that provides silence in the absence of targets and also a phase reference for PLL to make it happen without excessive knobology. In essence - plug and play. The best of all, it would also provide some discrimination.

Perhaps this winter...

[wadea]

Nicolae, for more sensitivity you need more amplification of RX signal, ie instead transistor you should use an opamp.

For the present try attached transistor circuit with better stability of operating point relative to threshold of comparator. When battery voltage changes, it will maintain better collector voltage as half of supply voltage.

You can also increase TX power. For this purpose you should use NE556 instead ICM7556 and should reduce resistance connected in series with TX coil.

Hi I am trying to build the matchless metal detector but unfortunately I can't find ICM7556 only I got NE556N and the owner of this diagram said " do not use
NE556E by the way" _which I do not why cause they are all dual timers_ is there any changes can be made to make it work. Do I use different coils as Mr. Nicolae did or should I reduce tx resistor from 680 to 300 ! I don t now your help is very appreciate .regards

[der_fisherman]

Finding an equivalent to the ICM7556

Hi I am trying to build the matchless metal detector but unfortunately I can't find ICM7556 only I got NE556N and the owner of this diagram said " do not use
NE556E by the way" _which I do not why cause they are all dual timers_ is there any changes can be made to make it work. Do I use different coils as Mr. Nicolae did or should I reduce tx resistor from 680 to 300 ! I don t now your help is very appreciate .regards

Which is correct as the ICM version is a low power version and although the NE556 may work, it will use up your battery power much quicker than the low power ICM version as well as producing big voltage spikes that will make a metal detector unusable.

But there are other manufacturers of low power, pin compatible versions, like the TS556 for example.

To help in your search, download and read the following, checking that any device you find is pin compatible:-
http://html.alldatasheet.com/html-pd...1/ICM7555.html

The TS556 data sheet can be found here:-
http://www.st.com/web/catalog/sense_...errer=70032480

I leave it up to you to check pins etc., but it is not the only low power version around. The TS556 has some other good points like suppression of spikes that no sensitive electronics EVER needs, especially a metal detector.

The earlier versions (NE556 for example) were notorious for their hungry current requirements and damaging spike propagation.

I hope this helps you further.

If you have "local" sourcing problems, let us know where you are and how we can get some chips to you by mail.

Regards

Andy

[nick_f]

Hi I am trying to build the matchless metal detector but unfortunately I can't find ICM7556 only I got NE556N and the owner of this diagram said " do not use
NE556E by the way" _which I do not why cause they are all dual timers_ is there any changes can be made to make it work. Do I use different coils as Mr. Nicolae did or should I reduce tx resistor from 680 to 300 ! I don t now your help is very appreciate .regards

Hi Wadea,
I haven't tried to use standard 555 or 556 instead of the CMOS ones. You can try them and if you have an oscilloscope you can check the waveforms and compare the performance against the one I made. Probably it won't work or it won't work as well as with the CMOS version. If you are able to buy components from the internet, the web site www.futurlec.com (or www.futurlec.com.au if you are in Australia) sells ICM7556 for $0.95 and LMC555CN for $0.47 a piece - but you will need two of them (and $4 shipping for Australia). It takes a long time for them to arrive (I usually order more parts and I receive them in about a month). The difference between CMOS and standard timers is in their technology (I believe there is much higher input impedances for CMOS).

PS - I see Andy already replied and he appears to know better the advantages and disadvantages of using standard vs CMOS chips.

Regards,
Nicolae

[6666]

If you are going to try standard 556, put a 100uF cap across the DC supply pins, right at the chip.

[der_fisherman]

NE555 and NE556 Timers

If I remember correctly, the original NE555 and -6 were first made in 1971 by Signetics. It is I believe the oldest chip, still in production.

I have used hundreds of them over the years.....they make a Billion per year, still!!

For more detailed info's look here:-

http://en.wikipedia.org/wiki/555_timer_IC

Have fun!

Andy

[wadea]

Thanks very much for your responds .indeed thisforum is the best.

1. [*=left]I live in Yemen and even if I try buying from internet it cost a lot to shipping to here and when I read the reply of Mr. mikebg
   o That he say "for more power of tx coil usene556 and reduce the resistor" I was very optimistic that it may works.
   May be I start looking in some RF junk devicesand if I am lucky maybe I find a used one.
   Thanks again for your help

Regards

[der_fisherman]

May I suggest that you don't try using the original parts (ones marked NExxx for example). I think that you will find that they simply do not work as you wish.
If you were a professional electronics design person for example, you might be able to fix most problems other than the current consumption.
Making something that does not work correctly improves your knowledge, but is very, very frustrating........
Use your time, money and knowledge to source the correct parts, maybe a friend that travels could bring you a handful (they are very, very cheap!)
Best of luck.
Andy
PS. The Last time I was in the Yemen (1963 or 4), I got a hand grenade thrown into my Taxi, we (a colleague was with me) luckily had both rear windows open and it sailed in one window and out the other and we were 50 yards or so further on when it exploded and killed two people on the side of the road. The Taxi driver almost **** his pants! (Luckily I had already emptied my front and rear end!!!)

Another colleague had a hand grenade thrown into his Taxi, but the person that threw it had not removed the pin! He brought it back on board and got into minor trouble with the ship's commander.....He had it disarmed by a colleague of mine (a dangerous procedure as they can easily go off as you remove the detonator. It is basically similar to a match striking and burning!) and emptied and kept it as a souvenir. In the RN, we normally did not remove detonators, we just had a fun afternoon throwing them in the English channel, the same for the underwater anti diver charges, which are basically "BIG" grenades, in a thin aluminium case.

[jlsilicon]

Anybody think of Connecting this to the Arduino
- to display the result and / or improve the Speaker Output Tones ?

[dbanner]

This little circuit works very well for such simplicity. And if the coils are properly balanced, it ignores iron.
Big problem is stability- you constantly have to be fine tuning every so often to maintain maximum sensitivity.
I built circuit using ordinary 556 chip and it worked fine.

[jlsilicon]

Great little project by Scarborough - he has given us good projects.
I found this project inspiring (and other projects of his) when I was young,
- now my daughter is building it.

[jlsilicon]

Does a VReg fix the Stability ?