ARMD (ARMRADIO based Metal Detector) VLF IB PROJECT

[BlackMorda]

I offer reverse software for the original HW QUASAR ARM 2.65M. Language C, IAR 8.2.
fake_265m.rar

[ArchibaldSTM]

Is there a compiled firmware? Not everyone can do this.

[ArchibaldSTM]

Is the project dead?

[moodz]

No it is not dead ... just 'parked' on the shelf. Some of the other guys are working on this but I have not heard anything. The code is working .. it can transmit and recieve and get a target IQ phase and amplitude etc

I also got a the dsp chain from this project working in Audioweaver working running in an STM32 F4 explorer ... however Audioweaver is so tied up in licencing and closed source core ... its really great for a school / uni project but not for real world use.

I moved some of the DSP concepts into an FPGA solution that was also on the "shelf" for about 10 years and that is now moving forward. The reasons for this are that the FPGA solution has a 24 bit ADC and the FPGA can do things that maybe a CPU cannot ( like lots of simultaneous things at once ferinstance ).

I will be coming back to this project as the FPGA may be over complex ... esp for hobbyists and I have a 32 bit ADC lined up for it if ( big if ) I can bring the ideas back from the FPGA to CPU land.

moodz

[moodz]

There is a lot of inspiration to be had from this book in regard to this project. Sadly out of print now .. it comes from a time when CPU memory was smaller and CPU clock speeds low so routines had to fairly nimble to cut the mustard. Written by smart guys at Sandia Labs. Full source in Fortran77 and straight C for every DSP function included on a floppy disk. Compiles nicely for CPUs like the STM32.

[ArchibaldSTM]

Thank you very much for your answer! We will wait......

[Mdtoday]

There is a lot of inspiration to be had from this book in regard to this project. Sadly out of print now .. it comes from a time when CPU memory was smaller and CPU clock speeds low so routines had to fairly nimble to cut the mustard. Written by smart guys at Sandia Labs. Full source in Fortran77 and straight C for every DSP function included on a floppy disk. Compiles nicely for CPUs like the STM32.

I have that book…must pull it out again, not sure if I still have the floppy, lot of gear still in boxes since we moved. Purchased it back in the mid 90s and I reckon I just about wore it out..great book.

[moodz]

I can send you the disk contents if required.

[Mdtoday]

I can send you the disk contents if required.

Thanks Moodz, that would be great, I will go through my project floppy archives when I find the box and drive just to be sure, however I binned a lot of gear during our move including floppy’s so chances are it went in the skip.
very kind of you to offer so thank you again.

cheers

[pechkata]

The coil is a minelab DD ... Its made for PI use and I believe the TX coil is wound with Litz wire. There is no capacitor across the coils ( like you may find in some VLF coils ).
Its a wide band low capacitance coil and the TX reactance at 8.33 Khz is about 15 ohms - 20 ohms and real ohms is 0.4 approx.

It develops 60 volts peak - peak across the coil @ 4 amps.

I should have quoted the IB leakage as 10 millivolts per amp ... so the unbalance at 4 amps is 40 millivolts not 10 millivolts. However 40 millivolts at 4 amps is OK for my application.

Below is pic of waveforms from the testbench ...

Yellow = TX clock
Pink = RX voltage ( 40 mv pp )
Light Blu = TX voltage ( 60 volts pp )
Dark Blu = TX current ( 400mV pp ) sensed by 0.1 ohm resistor in TX leg.

[pechkata]

[pechkata]

Probe range x10

[algan]

Update to make it clear how we switch the detector from PI to VLF mode.....

Hello, I would like to test the circuit, but I can't understand what the pulses on the inputs V7 and V8 should be. Can you write the parameters of the two pulses? Thank you.

[moodz]

V7 and V8 are square wave 180 degrees out of phase.

[moodz]

Make them 10 khz to start with.