PICKINI V4 - an easy to build, self adjusting PI detector

[F117]

Check pin 3 of the PIC: does the sensitivity setting change with the potmeter between 0 - 5 V ?
When turning the sensitivity potmeter, does the DC offset at pin 3 of the opamp change ? ( only with SW version 4.2 )
DC at pin 4 of the opamp should really be 0V = GND.
Which SW version did you program: 4.0, 4.1 or 4.2 ?


http://users.telenet.be/willaert/MD/.../software.html

Maybe a picture of the board and coil could reveal something.

[Chiringo]

Sorry for the delay in answering I'm a little busy
The software version is 4.1 faster calibration
The potentiometer adjusts well from 0 to 5 volts on pin 3 of the pic
The plate is installed inside a glued box and with all the cables connected, so little detail will be appreciated
Cheers

[gurdal]

good day F117,
I want to use 8 ohm speakers in the circuit.
Can you send me the parts I need to add with a small diagram?

Best regards
Gurdal

[F117]

@Gurdal: you can use a generic NPN transistor to drive a speaker, like eg the audio on Felezjoo:



@Chiringo:
Does the calibration procedure at startup work normally?
You should hear the welcome sound, followed by a couple of ticks and then the detector should be ready.
This takes max 5s with v4.1 of the software.
If it takes longer, there is something wrong with the analog frontend: coil -> opamp.

[gurdal]

thank you very much F117,
I want to use it with 27cm coil.
coil thickness and resistance value,
damping resistor.
Can I catch the small coin 30 cm with the coil of the diameter I will use?
thanks a lot
Gurdal

[Chiringo]

Dear F117
I made a new pcb, I have exactly the same problem ... with LM318 it only detects 3-4cm from the coil at maximum sensitivity
I am using TL071 or LF356 and performance is good
Maybe badly programmed pic?
Cheers

[F117]

- Measure the DC level on the opamp pin 3. When you power the board you should see it change and end up around 7 to 8 V. But you should see it change after power on and remain steady afterward.
- The same DC variation should be observed after startup on the PIC pin 13 - but between 0-5V and in opposite polarity of pin of the opamp: when you see the voltage on pin 3 go up after startup, you should see the voltage on pin 13 of the PIC go down. This is the automatic offset calibration cycle after startup.

- Which layout did you use for the PCB?
- If you use the same coil for testing both PCBs, there may be something wrong with the coil.
Can you measure the coil inductance and resistance : 300-500 microHenry and around 1-3 Ohm ?

Do you have an oscilloscope ?
On pin 8 and 9 of the PIC you should see this waveform:


Or maybe a bad batch of LM318 ?

On this picture, you can see a close-up of the LM318 on one of my early boards - that work fine:

[F117]

Did you buy the LM318 on AliExpress ?
10 pcs for 2€ or even less?

[Chiringo]

Dear f117
I have LM318 from three different brands, one bought from aliexpress and two bought from different local stores
There is no difference between them
I still have low sensitivity
The pcb is the eagle of the official page of pickini 4
As soon as I have a little time I will do the checks that you suggest
Cheers

[Metalfree]

Dear f117
I tried the MD on the beach, excellent stability even with high mineralization perfect functioning.
On the other hand, the PicPoint does not work as it should, in practice once it has detected the metal it always sounds
even lifting the MD, should it work as non-motion I guess like other MD do?
Using the latest version of the software
Greetings

[F117]

The pinpoint button switches from motion to non-motion.
This means that new samples are no longer added to the slow running average reference value.
You place the coil away from the target and press the button there. The running average = reference is ground without metal target.
Keep the button pressed and move it over the target. There will be a difference between the stable reference and the target value -> target sound.
You can keep the coil over the target with the button pressed and the signal will not null out.
This is how the pin-point function is implemented. It allows you to hover over a target.
It has often helped me in determining the size of a target ( talking about bigger sizes here = WW1 artillery UXO)
You could also try to reduce the sensitivity before pinpointing.

[sbalio1]

Hi to all freinds tell me pleade i make pikini v4 it works but coil diden works . Why.

[jeep6789]

What are the advantages of detecting the width of counterattack pulse compared with its amplitude? Then where does the width of counterattack pulse start and end? Could you please give me a schematic diagram

[sbalio1]

I just buying pic16f1824 . I made this pinpointer but coil dident works i there is no sens . Iwell put my pcb.

[sbalio1]

hi i made like this pcb https://www14.0zz0.com/2022/04/11/01/507527140.jpg
https://www3.0zz0.com/2022/04/11/01/440374246.jpg but there is no sense coil