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

[Aziz]

Hi all,

I have soldered all circuit parts onto the bread-board now. It all fits well.
But I haven't choosen the gain of the amplifiers yet so I soldered IC socket pins to be able to change the gain quickly.

I'll wire the bread-board soon. Oh man!, the little beast is so cute. One can implement the "worlds best ground balancing and discrimination" on it. (Despite of the simplicity of the circuit.)

Aziz

[Aziz]

Nice.
Any suggestion for open source flavour?

Well, I'm for a C/C++ platform. And I prefer the Win32 (Windows) platform.

But hey, you could use any other platform as well.
The only task condition is:
- feed the input with clock timing (coming from the sound card)
- and process the pre-amp outputs (in real-time)

There are open-source sound card interface projects in the internet. So one can code the relevant parts and the whole frame work is available in the internet.
I have to look for a convenient one.

Cheers,
Aziz

[Davor]

Nice.
Any suggestion for open source flavour?

[Aziz]

Hi guys,

after the versatile (but very simple) reference hardware platform is finished, we could start the software coding competition. I'm planning to route a finalized PCB and maybe a small and limitted batch of manufactured PCB's.

How about open-source or open-binary projects (depending on the mode of operation)?

(Oh man!, it's the end of ... )

Cheers,
Aziz

[Aziz]

First Parts Placement

Hi,

you see the first (loose and not soldered) parts placement below. I have tried many different configurations but this seems to be more convenient. Unfortunately, I'm limitted to the plastic case. The evil screw in the middle drove me mad.

The big buffer caps makes a good shielding wall to the sensitive electronics area in case of the high voltage TEM TX mode. In the H-Bridge mode, the coil connector voltage isn't high.

I had to take a picture of the placement. You never know, if you drop the loose placement, you don't remember how it was before.

I like this little circuit, because its so ridiculous simple but it is working very well. And you won't find a voltage regulator there. Back to the roots and to the K.I.S.S.-principle.

In the couple of coming days, I'll solder and test it.

Cheers for now,
Aziz

PS: I'll publish the schematics and circuit spice files later!!!

[Aziz]

Power Supply Consumption

Hi,

I have measured the power supply consumption on one particular configuration:
TEM @6kHz PPS, 12 V battery:
15 mA: standby (no pulse clocks sent to the detector controller)
65 mA: full operation

Well, I have to live with the high power consumption.

Not bad. It is dependent on operating mode, frequency and the coil configuration of course. But the little circuit is capable to deliver much more juice if required. It can be operated from 10 V .. 18 V (max. 20 V).

Aziz

PS: Oh yes, the whole circuit fits into a small PCB and should fit into the small case as well.

[Aziz]

Can't wait... will you make a full MD with everything mounted for field testing?

-SB

Yes, I'll do it. I want to go treasure hunting this season.

That's a fine hobby for a retired person like me.

Aziz

[simonbaker]

Ok guys,

the dual op-amp NE5532 in the pre-amps works very nice and isn't bad for it's price and availability. Saved some more bucks now!

Two NE5532 will be used. The other one is regulating my virtual analog ground (power supply splitter).

It is convenient to use the pre-amp in the inverting mode. So I can feed in an induction balance compensation signal from the other sound card channel. The input impedances of the pre-amps are kept low (100 - 500 Ohms with high voltage clamping diodes).

I could fit the whole circuit into my small plastic case as the pre-amp PCB size is getting small now.

Cheers,
Aziz

PS: Ahhh, the end is coming..

Can't wait... will you make a full MD with everything mounted for field testing?

-SB

[Aziz]

NE5532 works!

Ok guys,

the dual op-amp NE5532 in the pre-amps works very nice and isn't bad for it's price and availability. Saved some more bucks now!

Two NE5532 will be used. The other one is regulating my virtual analog ground (power supply splitter).

It is convenient to use the pre-amp in the inverting mode. So I can feed in an induction balance compensation signal from the other sound card channel. The input impedances of the pre-amps are kept low (100 - 500 Ohms with high voltage clamping diodes).

I could fit the whole circuit into my small plastic case as the pre-amp PCB size is getting small now.

Cheers,
Aziz

PS: Ahhh, the end is coming..

[Aziz]

Hi all,


Trying different front-end amps now.
The LT1028 works fine but too much expensive (two of them used).

I will try the dual op-amp NE5532 and will see how it is going.

And I have six nice and small plastic cases, which should be used as well. So trying another bread-board to fit all the circuit parts into it (through-hole).

BTW, the whole circuit is sooooo ridiculous simple now:
- Power supply splitter (dual op-amp)
- Pulse clock detector/low-battery detector (dual comparator)
- Mosfet driver + transmitter (IR2184, one or two n-ch mosfets)
- Two-channel amplifier (two single op-amps or one dual op-amp)

The cost of the detector controller box should be less than 30 bucks.

That's all. We don't need more. But the detector is soooooo sensitive.

Aziz

Oh yes, it's the end of ...

[Aziz]

Hi all,

I have completely changed the last design. The PCB is totally obsolete. Particularly the mosfet driver IR2184 is gone. I'll use the most simple ones to be more flexible.
Aziz

*LOL#1*
Funny stuff. The IR2184 is being used again. I have managed it to run in the single low-side n-mosfet driver mode. The low-side is independent of the high-side driver. Bootstrapping can be disabled.

Very few changes makes from it a:
- full H-bridge driver
- TEM driver with unlimitted flyback voltage (the IR2184 isn't seeing the high voltage as the high side driver isn't completely working in this case)

*LOL#2*
Funny stuff again. Single output channel of the sound card controls the pulse width of the TX pulse now. The whole pulse logic is simplified. The whole circuit is simplified.

I'll continue shrinking and simplifying it.
Cheers,
Aziz

[simonbaker]

Hi all,

I finally catched the bargain:
http://www.norma-online.de/_a_/_ange...t-120307-45204_

I have missed this offer two times. Now got it today. All the three packages.
I'm happy!

Aziz

I know the feeling...

[Aziz]

Hi all,

I finally catched the bargain:
http://www.norma-online.de/_a_/_ange...t-120307-45204_

I have missed this offer two times. Now got it today. All the three packages.
I'm happy!

Aziz

[Aziz]

Hi all,

this is off-topic but very interesting:

http://www.kaggle.com/competitions

Look at this stuff:

http://www.heritagehealthprize.com/c/hhp

3,000,000 Grand Prize
and something valuable for the mankind.

I'm quite lucky at winning prizes. Last X-mas, I have won a math competition with 15 exercises (1 per day). I was the only one with no mistakes. Prize: 15 EUR.

Maybe I should try one of the competitions above. A real challenger.
MD stuff is soooo trivial.... no real challenge here...

Cheers,
Aziz

[Aziz]

Hi all,

I have completely changed the last design. The PCB is totally obsolete. Particularly the mosfet driver IR2184 is gone. I'll use the most simple ones to be more flexible.

And I have got real Australian hotrocks. Thanks to Ron for his effort, time and support. I appreciate it.


I'll work on the ground balancing problem. So it will delay everything.
Cheers,
Aziz