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

[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

[BC547]

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

[BC547]

- 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:

[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

[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

[BC547]

@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]

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

[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

[BC547]

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/pickini/pickini_en/V4/software.html

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

[Chiringo]

Good afternoon F117

With lm318 installed:

pin 1 8,62v
pin2 7,32v
pin 3 7,70v
pin 4 0,16v
pin 5 8,62v
pin 6 8,35v
pin 7 11,07v
pin 8 1,43v
barely detects 2 cm with the potentiometer of san butt sensitivity

[BC547]

Can you check the DC values on the opamp pins compared to the values here:

http://users.telenet.be/willaert/MD/pickini/pickini_en/V4/electronics.html

[Chiringo]

Hi all
I have sensitivity problems with lm318, I have tried several from different sources and it only detects a maximum of 5cm from the coil
If I put tl071 the sensitivity is acceptable but unstable
The best behavior I get with an old Motorola lf356
Someone who can clarify something for me about this?
Thank you and happy holidays

[useus]

is anyone able to convert the project to pic18f4520?
thank you

[gurdal]

Hello friends.
Today is a beautiful day.
Idx Pro and Pickini Got Good Results.
Thank you very much to those who contributed to the projects.

best regards

[Chiringo]

Solved the problem
Bad coil connection Now it's working
thanks Bernard