complete project

[Tinkerer]

Thank you Mick. This looks like a very useful circuit.

We all agree that a good audio can help a lot in making the detecting enjoyable. It is also very important for discerning targets.
I propose we make a joint effort to produce a fully developed circuit and then a small PCB "shield" that can then be added to all sorts of detectors.

For this to work we will need to establish some sort of standard.

Opinions???

[6666]

Thanks Mick

[mickstv]

Hi Tinkerer, here's a present for you "the circuit below". I've just finished it and added it to my PI detector. It should work for the TEM as well.

In my PI the circuit outputs slight threshold level until a target is detected and given the timing I use it produced a higher pitch for fast TC targets, with a volume level increase. Whereas long TC targets produce a lower pitch, with a volume level increase. Also the higher/lower pitch is variable dependent on target type and how close it is to the coil.


This isn't the complete circuit missing, are things like bypass caps and volume control etc.

[6666]

Thanks Davor
I will try and look at your post attachments when the forum is running correctly just getting messages saying ERROR 403 - FORBIDDEN

[Davor]

You can see it from here on http://www.geotech1.com/forums/showt...241#post168241 ... provided you can see pictures on the forum. Some further improvements are in the following posts. There is also a demonstration of this contraption acting as a DSB modulator.
I also started making a PCB layout for a prototype (activity I'm not particularly fond of) and somehow didn't make it yet.

[6666]

The vco? I used an old 4046

Hi yes, thats the one.

I'm about to implement my audio modulator that converts DC target response to sinus

Thats interesting news Davor, any more details please, this area does not get much attention.

[Tinkerer]

I'm about to implement my audio modulator that converts DC target response to sinus in a span of about an octave and completely proportional. Simulation sound is nice and I'm itching to try it in RL. It sounds very non-irritating, and it performs as a real 4 quadrant multiplier, a real balanced modulator.

This sounds very interesting. Sine wave is so much kinder to the ear. How much power does it consume? Can we see a circuit?

[Davor]

I'm about to implement my audio modulator that converts DC target response to sinus in a span of about an octave and completely proportional. Simulation sound is nice and I'm itching to try it in RL. It sounds very non-irritating, and it performs as a real 4 quadrant multiplier, a real balanced modulator.

[Tinkerer]

Hi Tinkerer
do you have any audio files online which give a demo of your vco audio ?

I lost practically everything. The laptop and the external hard disk ceased to work. They stole the coils out of the boxes I shipped and destroyed whatever they could destroy. I am left with a box full of parts, all mixed up, since they emptied about half the sorting boxes into one big box.

It is nearly back to zero. The best repository is what is on the TINKERER IB-PI FORUM, here.

So, up to a new start.

The vco? I used an old 4046. The center frequency, with the frequency going high on gold and low on iron seemed a good idea.

Bugs recently posed a better version with the same IC. It might be a good idea to try his circuit. I wonder if he let's us post it here?

The 4046 has another feature that he is not using. That is the enable pin. Controlling the enable pin with the PIC, to avoid the squeel at start-up or to establish a no audio noise band might be useful.

Since we start from scratch, let's kick some ideas around.............

[6666]

Hi Tinkerer
do you have any audio files online which give a demo of your vco audio ?

[Tinkerer]

It has been a long time, but finally I can get back to my hobby of tinkering with metal detector design.
The TINKERERS design still looks interesting. I want to spend more time on it. One of the interesting parts of it, is the possibility of classifying the targets to their TC, or time constants.
Could we use the time constant for Ground Balance? It seems that the aggressive ground has a relatively constant time constant, while the desired targets have a very wide variety of time constants (TC).
With PI detectors, the targets as well as the ground respond with signal amplitude as well as with a TC.

How can we separate the target amplitude from the target TC? This will be the first project.

I have an idea..... maybe there are some other ideas out there?
Anyone? Any ideas?
Let's hear...

[Qiaozhi]

Hi Tinkerer et al,

I have wanted a metal detector for many years, and have resolved that it is time to think about building one. (I built a Jaycar kit once, but it was oversimplified and was just too painful in the field, requiring continuous adjustment). I've been reading through this and other pages on GeoTech forums, and I have to say it's been quite an education!

Congrats on all the development work you guys have put in. I only wish I could bring something to the table, but you are operating way over my head!

Perhaps you need to read Inside the METAL DETECTOR - Published September 2012

[tmiller1079]

Hi Tinkerer et al,

I have wanted a metal detector for many years, and have resolved that it is time to think about building one. (I built a Jaycar kit once, but it was oversimplified and was just too painful in the field, requiring continuous adjustment). I've been reading through this and other pages on GeoTech forums, and I have to say it's been quite an education!

Congrats on all the development work you guys have put in. I only wish I could bring something to the table, but you are operating way over my head!

[mschmahl]

And Video 3 With bigger Goldcoin 22mm

[mschmahl]

Video 2 with small Goldcoin 10mm