Arduino metal detector?

[FoxyLab]

will reduce some current spikes at the signal path.

But why? During the flow of current through the coil and some time after disconnecting the ADC is not used. Well, then the inrush is simply nowhere to come from.

[Vadim18]

By the way, did anybody notice what delay insert lm358 in this circuit with slew rate of 0.6 v/us?

[Vadim18]

Pirat itself is also quite uniqe project, but I belive this project will be better.
By the way i discovered one intersting thing today.
I played with my BeagleBone (raspberrypi-like machine) where i used built in ADC input (with diode clamp protection offcorse), i used shielded wires and was unable to read any adc value until i put ferrite bead between ADC and PI detector. So i fink ferrite bead will help here too, as will reduce some current spikes at the signal path.

[FoxyLab]

Just for interest here is a link to simple TL072 project, which runs off a single 12 v supply, a 072 should plug into a lm358, but the results needs to be tested

http://alex---1967.narod.ru/PI_metal...arduino_u.html

Yes, "classic" PIRAT schematic.

[FoxyLab]

TL071 will run on single supply

Yes? Then i will simulate this OP in LTspice.

[6666]

Just for interest here is a link to simple TL072 project, which runs off a single 12 v supply, a 072 should plug into a lm358, but the results needs to be tested

http://alex---1967.narod.ru/PI_metal_detector_arduino_u.html

[6666]

Also we can use unused part of lm358 (or tl072), split amplifier into two stage with gain X28, and add high-pass filter with 100Hz cut off. Otput must be without any capacitors, becouse ADC has some input bias currents.
And If i not make mistakes, total gain wil be around 770.


How do you think about my idea?


ps: i may be wrong)
[ATTACH]48320[/ATTACH]

Thanks, interesting idea.

[6666]

I built a model of the entire power part of my metal detector for LTspice XVII:
FoxyPI_v3_tran.asc

You can play with the parameters and watch, for example, the voltage on the search coil (1), on the ADC input (2), the current in the coil (3):

Thanks, I got the asc file to work

[Vadim18]

Also we can use unused part of lm358 (or tl072), split amplifier into two stage with gain X28, and add high-pass filter with 100Hz cut off. Otput must be without any capacitors, becouse ADC has some input bias currents.
And If i not make mistakes, total gain wil be around 770.


How do you think about my idea?


ps: i may be wrong)

[Vadim18]

Now i understand you)
I checked tl071 in tinaTI and see no difference except that we need to try a new board layout.

[6666]

Thanks!!!
But TL071 is dual supply only? I dont want make negative voltage source, this contradicts the concept of maximum simplicity of the project.
Its T-34, not Pz.Kpfw. VI ;-) It works even without a PCB.
You probably haven't seen my VLF /very low frequency/ receiver :-)))
In addition, the ADC of ATmega328 is also not the height of perfection, so excessive care for one part of the project will be a discord :-)
Low frequency noise is bad of course, but that is big deal in outdoor finding? On the curves I do not see it.

TL071 will run on single supply

[FoxyLab]

Yes, thats why im wondering to! But in opposite shorter bandwidt will produce a less noise) Of course analog part of this detector is less good than digital, so simply placing ne5534 instead of lm358 will boost sensivity. Also high-pass RC filter with R10k and C 0.1 uf beetwen op amp and atmega will be nice, as it help to reduce low frequency noise. I think at nowedays lm358 is one of the best op amp for flicker noise generator project

FoxyLab make a nice project. At least simple and good as reference for comparsion.
Sory i forget about common mode voltage range limitation, ne5534 will not work here, tl071 will do.

Thanks!!!
But TL071 is dual supply only? I dont want make negative voltage source, this contradicts the concept of maximum simplicity of the project.
Its T-34, not Pz.Kpfw. VI ;-) It works even without a PCB.
You probably haven't seen my VLF /very low frequency/ receiver :-)))
In addition, the ADC of ATmega328 is also not the height of perfection, so excessive care for one part of the project will be a discord :-)
Low frequency noise is bad of course, but that is big deal in outdoor finding? On the curves I do not see it.

[useus]

Interesting challenge

I hope you will!

Maybe with nokia lcd it would be great!

[FoxyLab]

Congratulations for the project, I would be curious to try an adaptation of your software on the felezjoo pi circuit (same avr of your project, similar but different scheme but I think easily adaptable)

Interesting challenge

[FoxyLab]

Thanks!!!

The FoxyPI firmware version 3.5 is ready - FoxyPIv3_5.ino.eightanaloginputs.hex

What's new:
added the ability to adjust the display contrast using the CONTRAST item in the service menu

An example is small/normal/excessive contrast: