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

[Aziz]

Hello friends,

did you see this?

http://www.recursion.jp/avrcdc/

The cheapest RS232 <-> USB 1.1 converter solution. The 8 dil chip with ATtiny45 makes it perfect. You don't need any FT232RL chips anymore (quite expensive and lots of ultra tiny pins to solder).

Aziz

[Aziz]

Look at this:

AVR309: Software Universal Serial Bus (USB)
Documentation:

http://www.atmel.com/dyn/resources/prod_documents/doc2556.pdf

Software (driver, firmware, etc):

http://www.atmel.com/dyn/resources/prod_documents/AVR309.zip

This implementation has 32 bytes FIFO for the USART. The microcontroller can be bus powered and the two RXD/TXD lines must be opto isolated to the main microcontroller (powered on negative supply rail referred to ground). This seems well documented and easy to make for this project.

Aziz

[simonbaker]

Thanks Aziz, these are great references for all kinds of applications.

-SB

[Aziz]

Hi all,

found finally a good usb solution. The only drawback is I have to find a free useable VID/PID without licensing this. F.u.ck the expensive usb licensing! The USB-RS232 converter chips are due to this fact quite expensive.

I am not convinced about the usb licensing policy. I will use the RS232 implementation until I find a better solution.
Aziz

[Aziz]

Hi all,

now the PGA, integrator and S&H stages are finished but not tested yet. I will continue with a very simple coil driver and preamp. Pay attention to the red S&H caps (rectangle blocks)! They are FKP-2 types (from WIMA).

Aziz

[Ismael]

Hi Aziz, if you are interested, I have been using BascomAVR since it was first produced and the forum there has a lot of useful information and sample code. The beauty of this IDE is you can mix and match ASM within the code and can use just about any ISP etc. They have really developed into quite a large community envolving even video interfaces and networking, bluetooth you name it they've done it. Also the author Mark is quite happy to help and so are most of the users. The link is:http://www.mcselec.com/ I have found this to make a lot of work (programming wise) quite easy. Anyway worth a look.

Regards Ismael
http://www.minelabmods.com

[Aziz]

Hi Ismael,

Hi Aziz, if you are interested, I have been using BascomAVR since it was first produced and the forum there has a lot of useful information and sample code. The beauty of this IDE is you can mix and match ASM within the code and can use just about any ISP etc. They have really developed into quite a large community envolving even video interfaces and networking, bluetooth you name it they've done it. Also the author Mark is quite happy to help and so are most of the users. The link is:http://www.mcselec.com/ I have found this to make a lot of work (programming wise) quite easy. Anyway worth a look.

Regards Ismael
http://www.minelabmods.com

thanks for your hint. But I do not use the "basic" programming language anymore since I studied software engineering. The fact is: I hate basic.

The firmware code is trivial but time critical. As a consequence of this, I even avoid using "C". I probably will mix assembler and C later.

Regards,
Aziz

[Ismael]

Quite understand the BASIC bit, not so much that just some of the hardware and implementations of different architects might be of use. Might be worth checking out anyhow...

[Aziz]

Hello friends,

the last module (basic coil driver and preamplifier) is finished now and is ready for starting with the software coding (see below). Now the development will go very slowly as I have to make more tests and software coding. I also have arrived the state, where I need an oscilloscope to go on. This will slow things until I can get one in the coming weeks. Till then, the development will go almost "blind" or with sophisticated measurement methods (without scope).

I will replace this module with a better preamplifier later. I just need a reference for the improved version.

Aziz

[simonbaker]

Hello friends,

the last module (basic coil driver and preamplifier) is finished now and is ready for starting with the software coding (see below). Now the development will go very slowly as I have to make more tests and software coding. I also have arrived the state, where I need an oscilloscope to go on. This will slow things until I can get one in the coming weeks. Till then, the development will go almost "blind" or with sophisticated measurement methods (without scope).

I will replace this module with a better preamplifier later. I just need a reference for the improved version.

Aziz

Hi Aziz:

I like your prototyping techniques and have a question: why are some resistors, diodes etc. mounted on little gray terminal blocks and some directly into the board? And what are those little gray terminal blocks called, where do you get them?

Thanks,

-SB

[Aziz]

Hi simonbaker,

Hi Aziz:

I like your prototyping techniques and have a question: why are some resistors, diodes etc. mounted on little gray terminal blocks and some directly into the board? And what are those little gray terminal blocks called, where do you get them?

Thanks,

-SB

I don't like desoldering parts. The PCB board gets worst on every soldering and desoldering action. All parts, which might be changed in the prototyping are mounted on a precision DIP IC socket pins. I bought many of 40 pin DIP IC sockets and cut them into peaces of 3 (for transistors) or any array combination. Single pin peaces will be used for single resistors or other parts.

This makes changing of parts quickly possible by removing the part from the DIP pins without desoldering them. Fixed parts (no change necessary) will be soldered directly to the board.

The MOSFET and diode are using a different connector socket (also cut into necessary number of pins) due to thicker wire diameter.

Aziz

[Aziz]

Hi all,

the power consumption of the design meets the < 200 mA limit including the damping resistors and 4 active LED's (but not the TX pulse power). It was a good invest to the DC/DC charge pump, which draws ca. 50 mA at the moment. I took the higher current rated TL082 in the S&H because I haven't any TL072 left. The TL072 are drawing less current and have better performance.

Aziz

[simonbaker]

Hi simonbaker,



I don't like desoldering parts. The PCB board gets worst on every soldering and desoldering action. All parts, which might be changed in the prototyping are mounted on a precision DIP IC socket pins. I bought many of 40 pin DIP IC sockets and cut them into peaces of 3 (for transistors) or any array combination. Single pin peaces will be used for single resistors or other parts.

This makes changing of parts quickly possible by removing the part from the DIP pins without desoldering them. Fixed parts (no change necessary) will be soldered directly to the board.

The MOSFET and diode are using a different connector socket (also cut into necessary number of pins) due to thicker wire diameter.

Aziz

Very nice technique!

Thanks.

-SB

[Aziz]

Hi all,

as you can see (below), the hardware overhead is quite big. But it doesn't matter for the experiments I have planned.
Now, the very big part of the project starts: the soul of the detector (firmware, PC software). So I might be offline for a while.

I will continue as soon as I am feeling better (had a relapse of my tooth problem).

Take care,
Aziz

[Qiaozhi]

Hi all,

as you can see (below), the hardware overhead is quite big. But it doesn't matter for the experiments I have planned.
Now, the very big part of the project starts: the soul of the detector (firmware, PC software). So I might be offline for a while.

I will continue as soon as I am feeling better (had a relapse of my tooth problem).

Take care,
Aziz

I think you should call this detector "Frankenstein", as it's turning into a monster.
But hopefully it won't try to kill its creator.