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

[Aziz]

Good outlook, Aziz.

From my point of view Tablet PC is almost ideal for real field use (it is hard to imagine to use Notebook in field)
But almost all Tablet PCs are based on Android platform.
How we can overcome this if you prefer only Windows for coding?

WM6, I'm specialised on Wintel platforms.

Unfortunately, I don't have a development platform for Android system. It's only a question of time & money
(even the Android SDK software is for free) . As I have already mentioned, the software is very trivial and can be ported to any real-time operating system platform.

Someone, who is specialized on Android systems could develop & sell it (would be a nice income.. ) .
Aziz

[Davor]

I'm also thinking of adding an RX-amplifier later (for the anti-interference coil configurations with superior sensitivity).

Actually you could run it as a real 4 quadrant Rx and greatly expand your choice of coils. Differential coils should give superior ground and noise cancellation.

[WM6]

The only critical part is the one-day computing Netbook/Tablet PC: allowing only 6-9 h of operating time duration.

Good outlook, Aziz.

From my point of view Tablet PC is almost ideal for real field use (it is hard to imagine to use Notebook in field)
But almost all Tablet PCs are based on Android platform.
How we can overcome this if you prefer only Windows for coding?

[Aziz]

Huh, something long awaited. How much "mA" with other version?

With the same set of batteries (4 x 1.3V = 5.2V): 18 mA.

You see, that the BJT transistors & base resistors do cause some losses. The mosfet variant is clearly an advantage.

The only critical part is the one-day computing Netbook/Tablet PC: allowing only 6-9 h of operating time duration.
------

I'm also thinking of adding an RX-amplifier later (for the anti-interference coil configurations with superior sensitivity). For this purpose, I'm going to steal some energy from the coil to make the step-up former for the bipolar op-amp power supply. It doesn't matter, when there is some load on the oscillator. I have the TX reference signal to compensate for all the (negative) actions happening.

Oh yes, a low voltage battery can generate enough voltage for the op-amps. I have to limit it even not to damage the op-amp.

Cheers,
Aziz

[WM6]

I have measured the power consumption of the n-ch mosfet version with 4 charged Ni-MH accus (4 x 1.3 V = 5.2 V). It consumes almost 9 mA. (Rough calculation: 1000 mAh/10mA = 100 h, 4 days long, yeah! )

Huh, something long awaited. How much "mA" with other version?

[Aziz]

Power Consumption Mosfet Version

Hi all,

I have measured the power consumption of the n-ch mosfet version with 4 charged Ni-MH accus (4 x 1.3 V = 5.2 V). It consumes almost 9 mA. (Rough calculation: 1000 mAh/10mA = 100 h, 4 days long, yeah! )
But it gives incredible high sensitivity and depth performance. The mosfet version runs more stable either.

The circuit is so small, that all parts can be placed either in the coil or at the bottom coil shaft nearby the coil. Yep, a SMD version would make it much smaller of course. The batteries can also be placed either in the coil shaft or somewhere mounted along the coil shaft (long 2 cell AA or AAA battery holder). Only the stereo line cable is going to the Netbook/Tablet PC (sound card input).

Preferred coil configurations (due to their simplicity):
- Double D/OO coil
- Omega coil
- Two-box coil
TX-coil: center-tapped, high Q (low resistance, 200 µH .. 500 µH total inductance, i.e. at both coils ends measured)
RX-coil: single ended (high inductance, 1 mH .. 10 mH)
Both shielded to GND.

I'm going to build another center-tapped TX coil using a cheap loudspeaker cable (twin-lead):
The forgotton Omega coil.

BTW, you can use the logic level n-ch mosfets too. They have a lower switch-on gate voltage. Some of them have a much lower switch-on resistance and should improve the efficiency further.

Cheers,
Aziz

[Davor]

Free to use & sell. Patenting not allowed!

I like this formulation!

[Aziz]

Nice simplicity Aziz. Congratulations.
Can you post supporting sound card programs too?
Without such program this is only dead idea. At least for me.

Hi WM6,

the sound card processing program (The VLF detector killer application *LOL*) must be written yet. I haven't been able to look at different open-source architectures freely available in the internet (I use my own software). But the requirements aren't critical: You just have to process both input lines (RX signal and TX reference) in real-time and do some detection sound onto the in-built sound card output.

Implementing the whole VLF technology in the DSP software is so much elegant. The published controller is a good platform for experimenting, education & learning.

When I find a good open-source platform, I could provide the code for it. The code is really trivial.
Oh yes!, the big players would hate me. It could eat all their profits. *LOL*

Aziz

[WM6]

Hi all,

I'm going to disclose two different VLF/LF Oscillator Detector Controllers now.
You don't need more parts. You don't need a complex circuit.
All you need is love!


1. NPN-BJT Version

Minimum voltage: 0.6 V (yeah!, that's a Joule-Thief *LOL* )
Maximum voltage: 4 x 1.5 V (6 V)

Reverse polarity protection:
The built-in reverse polarity protection is limitted to the max. Vebo voltage (5V specified). The typical values are higher (measured 8V .. 9V) so it is even protected to 6 V input voltage (4 x 1.5 V). Above Vebo, both transistors conduct and start to heat until they get damaged. Short time reverse polarity does not damage the circuit.

Recommended operating voltage: 1 - 2 Cells (1.5 V .. 3 V)


2. N-MOSFET Version

Minimum voltage: 2 V
Maximum voltage: 4 x 1.5 V (6 V)

Reverse polarity protection:
No built-in reverse polarity protection due to the inherent diodes in the mosfets. Both mosfets do conduct and start to heat until they get damaged. Use either a fuse or a series diode (1N5817) at the battery input. Short time reverse polarity does not damage the circuit.

Recommended operating voltage: 2 Cells (3 V)

I have built both circuits and they work really fine. The n-mosfet variant is more power efficient, which I like to use it. I'll show you the pictures of the circuits soon.

Notice: The (+) connection of the battery is connected to ground (GND)!

Disclaimer:
Free to use & sell. Patenting not allowed!


Cheers,
Aziz

Nice simplicity Aziz. Congratulations.
Can you post supporting sound card programs too?
Without such program this is only dead idea. At least for me.

[Aziz]

The KISS Artwork: VLF/LF Oscillator Detector Controller

Hi all,

I'm going to disclose two different VLF/LF Oscillator Detector Controllers now.
You don't need more parts. You don't need a complex circuit.
All you need is love!


1. NPN-BJT Version

Minimum voltage: 0.6 V (yeah!, that's a Joule-Thief *LOL* )
Maximum voltage: 4 x 1.5 V (6 V)

Reverse polarity protection:
The built-in reverse polarity protection is limitted to the max. Vebo voltage (5V specified). The typical values are higher (measured 8V .. 9V) so it is even protected to 6 V input voltage (4 x 1.5 V). Above Vebo, both transistors conduct and start to heat until they get damaged. Short time reverse polarity does not damage the circuit.

Recommended operating voltage: 1 - 2 Cells (1.5 V .. 3 V)

Schematics:


Spice File:
SingleFrequencyOsc-VLF-1-4CellArtwork-npn-03.zip

2. N-MOSFET Version

Minimum voltage: 2 V
Maximum voltage: 4 x 1.5 V (6 V)

Reverse polarity protection:
No built-in reverse polarity protection due to the inherent diodes in the mosfets. Both mosfets do conduct and start to heat until they get damaged. Use either a fuse or a series diode (1N5817) at the battery input. Short time reverse polarity does not damage the circuit.

Recommended operating voltage: 2 Cells (3 V)

Schematics:


I have built both circuits and they work really fine. The n-mosfet variant is more power efficient, which I like to use it. I'll show you the pictures of the circuits soon.

Notice: The (+) connection of the battery is connected to ground (GND)!

Disclaimer:
Free to use & sell. Patenting not allowed!


Cheers,
Aziz

[Aziz]

Sounds like quite a challenge! Hope you get over your influenza. I guess you forgot to watch your cussing here! Slow learner?

No PJ, it is a very trivial job (can't be seen as a challenge). And da'**** cct works. Minimalism & KISS-principle at best.
A $5 circuit + coil (DIY) + Netbook/Tablet/Laptop = It's the end of <you know what>...
*LOL*

-----------------------
Specs of power consumption:
1.5 V cell: 5 mA

I like the battery solution because, it makes the need for a second sound card obsolete. The in-built sound card of the Netbook/Tablet can be used.

Cheers,
Aziz

[PATCHES JUNIOR]

Hi all,

the "MadLabs Inc."(c)(r)(tm) is starting an artwork competition. Just for fun of course.


Goal:
Exploiting the KISS-principle to the maximum limit.

The VLF/LF Oscillator Detector Controller

Features:
- minimum amount of parts
- minimum amount of space (placed in the coil *LOL*)
- single battery cell (0.6V .. 1.5V, yep!, it's a Joule-Thief *LOL*)
- in-built battery polarity protection
- high power efficient (long operating duration)
- good detection depth performance *LOL*

Be prepared to be surprised.

More to come on this channel...
(I'll give you some time to think of and myself to get rid off of the **** influenza .. )

Cheers,
Aziz

Sounds like quite a challenge! Hope you get over your influenza. I guess you forgot to watch your cussing here! Slow learner?

[Aziz]

Artwork Competition

Hi all,

the "MadLabs Inc."(c)(r)(tm) is starting an artwork competition. Just for fun of course.


Goal:
Exploiting the KISS-principle to the maximum limit.

The VLF/LF Oscillator Detector Controller

Features:
- minimum amount of parts
- minimum amount of space (placed in the coil *LOL*)
- single battery cell (0.6V .. 1.5V, yep!, it's a Joule-Thief *LOL*)
- in-built battery polarity protection
- high power efficient (long operating duration)
- good detection depth performance *LOL*

Be prepared to be surprised.

More to come on this channel...
(I'll give you some time to think of and myself to get rid off of the **** influenza .. )

Cheers,
Aziz

[Aziz]

Hi all,

after being knocked out by influenza recently (still continues) I'm back with more experiences found on the new cross-coupled LC oscillator.

- the oscillator frequency is slightly dependent on the supply voltage (parasitic capacitances becoming relevant: transistors and zener diode).
- more harmonic distortion at higher frequency ranges.
- temperature dependency (particularly on the transistors)
- phase noise & frequency instability

All these effects doesn't really matter in the DSP domain. Everything can be compensated by processing the TX reference signal. This awesome cross-coupled LC oscillator doesn't require any regulation in my DSP application.

I can even go up to 45 kHz operating frequency (48 kHz limit at 96 kHz sampling rate). It gives magnificient sensitivity & performance with the simplest VLF controller solution.

Cheers,
Aziz

[Davor]

Actually I did some sims and they revealed to me that you either go completely dressed, or completely nude. The worst case is having it half way through. I also found that shield is not nearly as bad as I thought, but it does hurt high R targets a bit, and it must be applied equally on both Rx and Tx to really work.
I'm still a firm believer in a FKK coil choice. Of course, with all the perks and trimmings that go with it.