complete project

[IBGold]

I can supply the PCB component overlay and circuit and you are correct no solder mask on the Prototype boards and the supplier in Melbourne is where I get my boards from the power/supply board will I think be about a month or so away.

Regards, Ian. VK5KIB

Hi Ian, thank you for the generous offer, will take that up with you pending Tinkerer's approval.

I had a look on the net and found a reasonable priced supplier in Melbourne i think. Asking price for that size board around $5.00 each.

Not an issue with creating my own vias. Just wanting to know, will i receive the overlay parts placement documents if created or would i have to figure it out by comparing the schematic with the board......i am assuming there will be no solder mask.

How far off is the power supply PCB? Would most likely wait for that too.

Tomorrow i am digging out all my electronic parts and equipment, from storage, shed, garage etc. Got parts all over the place., so unorganized due to reno's.

Thanks again, all of this pending permission.

Regards Sid

[satdaveuk]

Hi Tinkerer
Im also looking forward to seeing your two projects, if you or anyone here has sorted layfiles for it would be interested in making my own pcb for it to get the ball rolling so to speak.
Will the hex files be flash type or do we need to write them?
Anyways thank you very much for all your hard work put into this project.

Regards
Dave

[Tinkerer]

Hi Tinkerer
Im also looking forward to seeing your two projects, if you or anyone here has sorted layfiles for it would be interested in making my own pcb for it to get the ball rolling so to speak.
Will the hex files be flash type or do we need to write them?
Anyways thank you very much for all your hard work put into this project.

Regards
Dave

There will be DESIGNSPARK PCB and Gerber files eventually, but there is still some work needed on that.

You can download the DESIGNSPARK software for free: http://www.designspark.com/ and give it a try yourself.

Tinkerer

[Tinkerer]

TINKERERS_SB_NM

Here is the RX of the TINKERERS_SB_NM.

SB_NM stands for SIMPLE BASIC NON MOTION.

This detector would be good for underwater use or very large coils and other uses where it is not practical to sweep the coil at a specific sweep speed.

A very simple design, no frills, bells and whistles, but deep searching, sensitive and reasonable iron discrimination.

Enjoy

Tinkerer

[Tinkerer]

TINKERERS_SB_NM_PSU&TX

Below is the schematic of the TINKERERS_SB_NM_PSU&TX.

So we have now a complete metal detector design.

Tinkerer

[sido]

Hi Ian, thank you for that. Will shortly get in touch with you early next week. My small work bench is slowly taking shape now, just about up and running, bar a few test gear missing (still in storage).

Hi Tinkerer, thanks for posting the schematics. Looks interesting. Ground balancing could be a issue here, but worth a try. Will look into them soon.

BTW, will be offline for a few days, because my network provider (Voda) decided again to do some network changes here in Melbourne and not to happy. Time for a new provider me thinks. Talk to you all soon.

Regards Sido

[pelanj]

Hi Tinkerer,
I was thinking about the audio options and if I wanted to have the audio I have described in one of my posts, it would need another PIC programmed to just convert the samples to audio. For the front end part, you need precise timing. The audio needs much less computations, but at the same time, it needs to be precise anyway. Is it acceptable that the detetor would have a PIC for timing and another PIC for audio processing?

[Tinkerer]

Hi Tinkerer,
I was thinking about the audio options and if I wanted to have the audio I have described in one of my posts, it would need another PIC programmed to just convert the samples to audio. For the front end part, you need precise timing. The audio needs much less computations, but at the same time, it needs to be precise anyway. Is it acceptable that the detetor would have a PIC for timing and another PIC for audio processing?

Hi pelanj,

thanks for the feedback.

PIC's are cheap. There is no problem of using 2. For just the timing, I can also change to a smaller, cheaper PIC.

It might be a good idea for you to breadboard the RX board above. For the TX you will need to solder the Mosfet, because it runs with about 4.5A at several hundred Volt, but all the rest runs OK on a breadboard.
The RX circuit has an audio, but the audio response is not as good as I would like it to have.
The human ear is sensitive to slight changes in the pitch, but for good target recognition we need about 2 cents of change.
For a 500Hz center audio frequency, this means we want about 10 to 20Hz change in frequency for 10 to 20mV of minimum target response.

Now, it is easy to make a window comparator that switches the audio ON at 10 or 20mV, but that results in a lot of noise or falsing, when the audio switches ON and OFF, every time some noise peaks above that level.

The analog audio on the TINKERERS_SB_NM, has a floating center frequency. The ear can easily distinguish the downward change in pitch for iron targets and upward change for gold, while the center frequency follows the ground between manual ground balance.

If we could do something similar, digitally, we would have something good.
And of course, the analog circuit above, does not vary the volume with target, and that would make it so much better.

Tinkerer

[mickstv]

Hi Tinkerer, certainly looks good mate. One thing I picked up on which may cause problems are the LDO's if they are standard 78L05 and 79L05 they normally have a minimum input voltage requirement, normally about 2 volts above the rated output, any less and they won't regulate correctly.



Cheers
Mick

[Midas]

Hi Tinkerer, certainly looks good mate. One thing I picked up on which may cause problems are the LDO's if they are standard 78L05 and 79L05 they normally have a minimum input voltage requirement, normally about 2 volts above the rated output, any less and they won't regulate correctly.



Cheers
Mick

Hi Mick,
That's true but there are plenty of 5v LDO's with drop outs of less than 1v. Element 14 has 430 of them The -5v isn't as common but they still have 10 with dropouts of only 0.5v-0.6v.

Hi Tinkerer,
Thanks a lot for posting your new design. I've learnt heaps from your schematics.
I was wondering whats the purpose of the high pass filters on the sample lines?

Midas

[mickstv]

Hi Mick,
That's true but there are plenty of 5v LDO's with drop outs of less than 1v. Element 14 has 430 of them The -5v isn't as common but they still have 10 with dropouts of only 0.5v-0.6v.

Hi Tinkerer,
Thanks a lot for posting your new design. I've learnt heaps from your schematics.
I was wondering whats the purpose of the high pass filters on the sample lines?

Midas

Thanks Midas. Obviously I didn't look hard enough the last time I ordered some. LOL



Mick

[Tinkerer]

Thanks Midas. Obviously I didn't look hard enough the last time I ordered some. LOL



Mick

Thanks for the feedback, Mick.

This is the most basic I can go with a design, so obviously there are many things that can be improved.
For example, you can use a low noise LDO and you can add a regulator to the TX supply.

Better parts will give better results, like the CD4066, is just the cheapest analog switch, but there are many much better ones available, and so on.

Tinkerer

[Tinkerer]

Hi Mick,
That's true but there are plenty of 5v LDO's with drop outs of less than 1v. Element 14 has 430 of them The -5v isn't as common but they still have 10 with dropouts of only 0.5v-0.6v.

Hi Tinkerer,
Thanks a lot for posting your new design. I've learnt heaps from your schematics.
I was wondering whats the purpose of the high pass filters on the sample lines?

Midas

Thanks for the feedback, Midas.

Adding filters before the pre-amp, seems a good idea, we do really not want to amplify the noise coming form the coil.

The input is coming from a differential RX coil. Adding a low pass filter for common mode noise and a low pass filter for differential mode noise, reduces the bandwidth to the minimum necessary.
The minimum will depend on the intended targets. If we want to look for very small hypodermic needles, we need to keep the fo above 500kHz.
In other words, we eliminate all the noise above the desired target response frequency, or maybe we should call it Tau, since it is a single decay curve.

By the way, do not use these filters on a traditional PI. It will not work.

Tinkerer

[mickstv]

Thanks for the feedback, Mick.

This is the most basic I can go with a design, so obviously there are many things that can be improved.
For example, you can use a low noise LDO and you can add a regulator to the TX supply.

Better parts will give better results, like the CD4066, is just the cheapest analog switch, but there are many much better ones available, and so on.

Tinkerer

Hi Tinkerer, no worries. Just wondering if you could post up some specific details for the coil ie:- diameter + turns ratio etc. Will it be suited to smaller coils 8 to 12"



Cheers
Mick

[Tinkerer]

Pinpointer or underwater detector?

Now that we have a new design on the table, we can decide what we could do with it.

For example, we could make a very powerful pinpointer.

Or we could make a very deep searching relic detector.

Or we could make a very deep searching underwater detector.

All these specific purpose detectors have one thing in common. They work well in non motion mode.

For each one of these purposes, specific changes in the design will need to be made, but the basics can remain the same.


And of course, I will post very soon, a motion detector model too.

The next step will be a detector that can be switched between motion and non motion.

With this new technology, the possible variations seem endless.

IT IS A WHOLE NEW HORIZON IN METAL DETECTORS!!!!!!!!!!!!

Tinkerer