Let's made a PC-base metal detector with usb interface !!!

[Aziz]

Add-on Voltage Regulator Control Box Planned

Hi all,

to improve the detector stability and output power (drift due to battery voltage diminishing over time), I am planning to add an external simple and synchronized 18 V step-up SMPS add-on voltage regulator controller (fits into equal plastic case).

The clock timing will be fed through the voltage controller to the detector controller so the voltage controller can be synchrononized to the timings.

Power: Battery -> (input) Voltage controller (output) -> (input) Detector controller
Timing: Clock -> (input) Voltage controller (output) -> (input) Detector controller

The add-on box is just a nice to have feature and it isn't really required. Although it reduces the power efficiency, one can reduce the minimum battery input voltage below the 10 V mark (intended for 7.4 V Li-Ion cells).

Unfortunately, the mosfet driver IR2184 isn't working below approx. 10 V (~9.5 V) and the maximum input voltage is limitted to 18 V (absolute max: 20 V). But the circuit is protected against above 20 V. The diode 1N5817 breaks down at approx. 20 V, mosfet driver + mosfets will be protected by the 18 V zener diode. That's the reason, why the electrolytic caps must be all at least 25 V rating. The upper limit of 18 V is by far enough power for our purpose. But we might want to have the lower limit voltage input range.

Well, I like the modularized control box idea. The SMPS control box module will be added later. This is a good job to make the SMPS bread-board prototype to fill the 2-3 weeks of the PCB manufacturing and delivery time.

Cheers,

Aziz

[Aziz]

PCB Layout Fine Tuning

Hi all,

I'm doing the fine tuning of the PCB layout. It is almost finished. The design-rule-check (DRC) passes.

Some of the PCB manufacturers let make their PCB's in China. Unfortunately, it takes 2-3 weeks (cheap version). Perhaps, I should look for a Chinese PCB manufacturer.
*LOL*
Aziz

[Aziz]

PCB Manufacturing

Hi all,

does anybody know, where I can let make the PCB's cheap?
Preferably in Germany or EU (but not outside).

I have found Leiton (http://www.leiton.de/index.html) and WEdirekt (http://www.wedirekt.de/index.php) besides many others, which seem to be relatively cheap.

I want to spend approx. 50 - 120 EUR (incl. tax + shipment) and want as many PCB's as I can get for it.

Any tips to other cheap PCB manufacturing companies will be appreciated.
Thanks,
Aziz

[Aziz]

Nice design. Well arranged. Did you use auto-placer?

Hi WM6,

I think, Eagle isn't capable to support auto-placer. (Does anybody knows?)

My steps:
Manual placement, auto-router using a script file (with given order of nets) and final cosmetics made by me.

Yup, I like the new layout too.
Aziz

[WM6]

Hi all,

this is the preliminary version of the new 80 x 50 mm PCB. Haven't checked it yet.

Nice design. Well arranged. Did you use auto-placer?

[Aziz]

Preview of New PCB

Hi all,

this is the preliminary version of the new 80 x 50 mm PCB. Haven't checked it yet.
Cheers,
Aziz

PS:
WM6: Not required.

[WM6]

Hi all,

I have good news: the schematics fits into a 80 x 50 mm PCB size now.
Yeah!, I'm happy this time (it's getting cheaper now).

I have removed one TX buffer electrolytic capacitor and the two gate resistors and have achieved a reasonable layout by a re-arrangement (no vias).

Now optimizing the layout further. I will run a small prototype production series next month (at least 8 PCB's). So there is no reason to hurry up at the moment.

Aziz

Super Aziz. Probably this worth to start new tread.

[Aziz]

Small PCB's: Good News!

Hi all,

I have good news: the schematics fits into a 80 x 50 mm PCB size now.
Yeah!, I'm happy this time (it's getting cheaper now).

I have removed one TX buffer electrolytic capacitor and the two gate resistors and have achieved a reasonable layout by a re-arrangement (no vias).

Now optimizing the layout further. I will run a small prototype production series next month (at least 8 PCB's). So there is no reason to hurry up at the moment.

Aziz

[Aziz]

Plastic Case

Hi all,

BTW, I'm using the following cheap (half) plastic case:

http://www.reichelt.de/Kunststoff-Kleingehaeuse/SD-10-GR/index.html?;ACTION=3;LA=444;GROUP=C714;GROUPID=3355;ARTICLE=16993;START=0;SORT=artnr;OFFSET=16

There are two colors available: gray and black

Two of them makes a good and cheap controller case. The PCB is optimized for this case and is mounted via one 3 mm screw at the center position.

You also could use a bigger case and could mount the external usb sound card into it too (disassemble it and mount the sound card PCB). You can save some space, weigth and connectors, if you wire it directly. You have than the pure USB metal detector controller!

Aziz

[Aziz]

PCB

Hi all,

it seems, that I could fit 4 PCB's into a 160x100 mm board size. Re-arranging saves more PCB space too and it would make the PCB in the production phase cheaper.

Let's wait and see how the single 80x50 mm board goes and let decide later, which one should be followed.

Please, be patient.
Cheers,
Aziz

[Aziz]

Aziz ..good work ...if you are not releasing the code ..I dont blame you ...but could you release screen shots of code in action with different targets ??

moodz.

Hi moodz,

my own detector software contains very sensible algorithms (to much sensible to the patent trolls ), which I'm not going to share (yet).

The "code" is an experimental bunch of software algorithms (lab & analysing software). I want to develop a minimal software solution soon. Maybe a well-known open-source platform as a frame work, which I can share with you easily (minimal work overhead).

Well, it depends on the patent trolls and greedy players. When I get upset, I'll publish much much more to make their greedy business totally kaput!

Aziz

[moodz]

Hi all,

you will find the very trivial schematics below in the pdf-file just to give you an impression of how simple it is. Note, it is a preliminary version only. (Open issues haven't been fixed yet.)

It seems, I need a two layer PCB to fit all the parts into the restricted PCB area, which is fixed to the plastic case I have. I will work on an optimal PCB layout next time. Please, be patient.

Cheers,
Aziz

Aziz ..good work ...if you are not releasing the code ..I dont blame you ...but could you release screen shots of code in action with different targets ??

moodz.

[Aziz]

Hi Aziz,

Sounds like a good reason to go for the through-hole components as you have!

Hmmmm a netbook with a good sound card hey?

What programs would you recommend for making the program for the laptop detector? Last programming I did on a pc(for pc programs) was using turbo pascal 8, and that was just database stuff so nothing flash there!

Cheers Mick

Hi Mick,

Well, the netbook is damn cheap (>200 EUR). We can use it (at least, I'm using it). There will be new tablet PC's available soon. Very likely not as cheap as the netbooks. But hey, they are getting cheaper and cheaper (and smarter too). The netbook battery lasts for one day prospecting with ease (8 h).

We don't need whistles and bells in the software. One can use any programming platform.
I'm using the Win32 SDK platform with the C/C++ compiler (Microsoft Visual C/C++).

The detector software isn't much time-critical (a lot of reserve there). We have a buffered transmission (CLK + compensation signal) and buffered reception to meet the real-time criteria. Some sound card interfaces provide a direct interface to the sound card to lower the latency time (like ASIO interface). The signal output sound can be made unbuffered to achieve a fast response (low latency).

I probably will support a push-button to trigger a ground balance in the software. This can be achieved by several means:
- feeding a low frequency signal into the pre-amp (via compensation input)
- shorting the pre-amp output by a push button switch
The software can easily detect the GB request and can perform a GB sequence. More isn't necessary. Switch on and go!!!

Later, a GPS unit can track your search area and can make a ground mineralization map. You will directly see the mineral patches or veins.

We can do a lot more with the PC type computers!!!

Aziz

[Aziz]

Goal: 80mm x 50 mm PCB

Hi all,

I'm trying to reduce the circuit complexity further so I can get four PCB boards onto one 160 mm x 100 mm EURO size board. This is very important to me as I can save a lot of money by the PCB manufacturing. The width of the PC board is already fitting into 80 mm. Let's work on the 50 mm height now.

The circuit isn't critical and we can leave some big capacitors and some resistors.
- reducing the transmitter buffer capacitors (overkill not necessary)
- removing one buffer capacitor (overkill not necessary)
- removing the gate resistors (not required)
- re-arranging the layout to use more space

If I can achieve a 80 mm x 50 mm PCB layout, I would be happy. Let's look, how good the coil connector and the mosfet's fits into a 50 mm PCB height.

Aziz

[Mechanic]

Hi Aziz,

Sounds like a good reason to go for the through-hole components as you have!

Hmmmm a netbook with a good sound card hey?

What programs would you recommend for making the program for the laptop detector? Last programming I did on a pc(for pc programs) was using turbo pascal 8, and that was just database stuff so nothing flash there!

Cheers Mick