felezjoo PI(the best pulse induction metal detector that I made until now)

[LUPENGR29`]

I finally received original lf357 from germany(ebay). tested with two coils.
Coil1: spider coil, 0.6mm copper bare wire, no shield, A301 B691 C785 1.6 ohm, 374uH, rg58 c/u



[ATTACH]48542[/ATTACH]
[ATTACH]48543[/ATTACH]
[ATTACH]48545[/ATTACH]

bs170 gate:
[ATTACH]48544[/ATTACH]

Coil2: bundle stranded insulated pvc tined copper, conductive cloth shield, A597 B733 C771 1.6ohm 361uH, rg58 c/u
[ATTACH]48546[/ATTACH]
[ATTACH]48547[/ATTACH]


I was expecting better performance for coil nr1, maybe i did something wrong... In both cases air detection depth for one coin is not bigger than 20cm.
What do you think about this measurements?

What resistor used for the 390ohm 2W ??? Metal oxide? or metal film?

[ionut_mtb]

What resistor used for the 390ohm 2W ??? Metal oxide? or metal film?

Metal Film Resistors - Through Hole 2watts 392ohms 1%

[marin2]

Hi everyone, it's been a long time.
I dusted off my felezjoo card to show you the spool with the LITZ thread.

[Suvabard]

I have no way to try it on the field until the end of the month, unfortunately I am injured and I cannot move, if there are substantial differences I will let you know even if I do not think there is a visible difference, before I had the values not perfect but very close (300 698 803). Value B I noticed that varies by changing impulse,
also the value C but is much more stable, the problem is that it also varies with A so I put a 470ohm potentiometer in place of R11 to be able to adjust it at will even changing the pulse value. I obtained the perfect C value using a coaxial cable,
unfortunately I can't tell you the model because nothing is written but looking at it I'm almost sure it's a RG58

What do these magic numbers actually represent?

[LUPENGR29`]

These number contains the sensitive-power-balance and more charactiristics of the coil... Different coil different numbers different LF different numbers again....

[ionut_mtb]

How should be connected corectly rg58 cable to board?

[SWL]

Soldering....

[ionut_mtb]

Soldering....

very smart, thank you. I’m referring on witch side should be connected the shield

[ivconic]

What do these magic numbers actually represent?

Time constants.

[Vadim18]

How should be connected corectly rg58 cable to board?

Hi ionut_mtb!
If i understand you properly, this may help.

[ionut_mtb]

Hi ionut_mtb!
If i understand you properly, this may help.
[ATTACH]48814[/ATTACH]
[ATTACH]48815[/ATTACH]

Thank’s, i was thinking the same. Yesterday i’ve noticed something interesting, after installing metal shield to the board i’ve managed to run the detector inside apartment at sensitivity 18 (usualy i can run it at max 12 indoor) and detection depth for 1euro was aprox 35cm.
Detector is more stable.

[Vadim18]

Ok, that's good result. Now you see how shielding affect to sensitivity.
If you have time to do some testing - try to put copper plate or mesh shield on top of MCU and bottom. Idealy the best way is to isolate all digital part with shield, cos MCU makes alot of random noise and interference.
Also, at least in theory, ferrite bead between op-amp (pin6) and MCU(pin23) will suppres noise coused by cross capacitance (nobody mentioned abouth it)


Nice experiments!

[useus]

Also, at least in theory, ferrite bead between op-amp (pin6) and MCU(pin23) will suppres noise coused by cross capacitance (nobody mentioned abouth it)


Nice experiments!

I'm interested, if someone has ferrite bead is able to do a test I would be happy to know the results

[ionut_mtb]

Ok, that's good result. Now you see how shielding affect to sensitivity.
If you have time to do some testing - try to put copper plate or mesh shield on top of MCU and bottom. Idealy the best way is to isolate all digital part with shield, cos MCU makes alot of random noise and interference.
Also, at least in theory, ferrite bead between op-amp (pin6) and MCU(pin23) will suppres noise coused by cross capacitance (nobody mentioned abouth it)

i think all the small things makes a difference in performance of a detector.

"Digital circuitry inside and outside the device generates EMI which might affect the accuracy of analog measurements. If conversion accuracy is critical, the noise level can be reduced by applying the following techniques: 1. Keep analog signal paths as short as possible. Make sure analog tracks run over the analog ground plane, and keep them well away from high-speed switching digital tracks. 1.1. The AVCC pin on the device should be connected to the digital VCC supply voltage via an LC network as shown in the figure below. 1.2. Use the ADC noise canceler function to reduce induced noise from the CPU. 1.3. If any ADC [3:0] port pins are used as digital outputs, it is essential that these do not switch while a conversion is in progress. However, using the 2-wire Interface (ADC4 and ADC5) will only affect the conversion on ADC4 and ADC5 and not the other ADC channels."



http://www.minelabmods.com/joomla3/i...-an-sd20002100

also post #6

https://www.geotech1.com/forums/show...highlight=bead

[SWL]

Hello! There is no backlight. On the circuit there is a resistance of 1 kOhm ... Shouldn't it be 100 Ohms? In the settings, the backlight level is 10.