Arduino metal detector?

[FoxyLab]

foxy pi is next my to do list

Thanks!

[bernte_one]

Hello Aleksej,

did you already draw a pcb layout for the latest version of schematic?

[useus]

Hello Aleksej,

did you already draw a pcb layout for the latest version of schematic?

I'm currently working on it, atmega328p directly on pcb, felezjoo pi style. I should be finished in two or three weekends

[bernte_one]

I'm currently working on it, atmega328p directly on pcb, felezjoo pi style. I should be finished in two or three weekends

sound very good, but the direct insertertion of an arduino nano into a circuit board could aslo be done by two lines of pin headers
and you still have the possibility to load uptades via usb and the price of an nano modul is cheaper compared to an atmega chips with additional parts around (power supply, etct.)

but equal, i am still intetested and can double check the layout if you need help

[useus]

sound very good, but the direct insertertion of an arduino nano into a circuit board could aslo be done by two lines of pin headers
and you still have the possibility to load uptades via usb and the price of an nano modul is cheaper compared to an atmega chips with additional parts around (power supply, etct.)

but equal, i am still intetested and can double check the layout if you need help

I'm working to power the circuit with a single 18V battery pack, I don't own Arduino nano but I have several atmega328p so I work on that also because it is the best solution for stability. However as soon as I finish it I load it on the forum, then anyone can modify it at will

[useus]

I have to double check everything but I'm already well underway. no ground fill on pcb since it works on two separate power supplies. (in the future I will work on single power supply)
I will probably insert 4 contact points to shield the pcb externally. to keep the pcb as small as possible i left only the holes for the connection of lcd, speaker, batteries and leds.


Note


1. 3600uF capacitor is made up of 2200 + 1000 + 470uF
2. I have not found lm385z on fritzing so from the drawing it is a transistor with a contact point not connected.
3. ANT are the contacts for the LCD connection and, next to the mosfet, one for any shield coil, all still to be renamed and I will have to draw a connection diagram.
4. vcc1 is speaker connection
5. need to add the external resistances of the leds



future updates


single power supply
avr isp connector
gnd fill
lcd, spk, leds connectors
led resistors on pcb

[FoxyLab]

Hello Aleksej,

did you already draw a pcb layout for the latest version of schematic?

Not, I am not a big fan of printed circuit boards. I am sure that the members of the forum will succeed even better.

I want to remind you that when building a metal detector, test firmware will help you, which, each time you press the button, gives one pulse to the coil and displays the received signal: FoxyPIv3_TST.ino.eightanaloginputs.hex

[FoxyLab]

I decided to numerically evaluate the stability of my metal detector - it turned out to be quite satisfactory: after 15 minutes of operation, the detection range of targets decreases by less than 4%.

[useus]

single 15V power supply works correctly with 7805CV with small heatsink.

L2 is not necessary if batteries with higher amperage (18650 or similar) are used


my configuration
NO nano, direct atmega328p-pu on breadboard testing circuit
3x 18650 BMS 12.6V + Boost converter set to 15.0V under load

[useus]

I decided to numerically evaluate the stability of my metal detector - it turned out to be quite satisfactory: after 15 minutes of operation, the detection range of targets decreases by less than 4%.

your stability problem is due to the type of batteries used, the stylus batteries you use (from what I saw on your site) have a low discharge value, for this reason it was unstable and you had to power the circuit and arduino separately.

using lithium or even lipo batteries that have a higher discharge current, the stability problem can be easily solved. Of course, a valid coil is also required

[useus]

new pcb version, everything should be correct, i consider it as final version.
Should there be any errors you are free to correct them or contact me to resolve them. unfortunately I have no way to print the pcb to test it, usually I rely on online services but before it arrives it takes a long time

added
GND fill
LCD connector
SND connector
LEDS resistances on pcb and connectors
Single +15V power
replaced UF5408 with 1N5819 (it should still work)
removed L2
note: lm385z silk is probably reversed, install correctly (follow foxypi scheme)

[FoxyLab]

your stability problem is due to the type of batteries used, the stylus batteries you use (from what I saw on your site) have a low discharge value, for this reason it was unstable and you had to power the circuit and arduino separately.

using lithium or even lipo batteries that have a higher discharge current, the stability problem can be easily solved. Of course, a valid coil is also required

Thanks for hint. You are right with this batts.
But 4% with 15 minutes is not big deal :-) And rebalance is "press btn -> 10 sec pause -> press btn -> READY".

[useus]

Thanks for hint. You are right with this batts.
But 4% with 15 minutes is not big deal :-) And rebalance is "press btn -> 10 sec pause -> press btn -> READY".

sure!


however, it is also a convenience factor, do you want to have only one rechargeable battery pack instead of two stylus battery packs to replace when they are discharged?

[6666]

Hi Foxylab, just wondering when you monitor the output of the LM358 with a CRO, what is the voltage range between the highs and lows of the signal ? thanks
like between arrows.

[FoxyLab]

Hi Foxylab, just wondering when you monitor the output of the LM358 with a CRO, what is the voltage range between the highs and lows of the signal ? thanks
like between arrows.

Hello!

Here are the signals at the ADC input - without a target (1), with a target (2). The upper horizontal line is the saturation of the ADC (voltage >= 1.235 V), then voltage gradually decreases to zero.