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

[F117]

after some problems i thing it would better to remove this coils preset code lines, would cause less troubles

I understand your concern and you are right in a way that the calibration value ( = DC offset for the opamp ) that is stored in EEPROM may differ from one coil to another.
Actually, I never took this use case into account during the design, because I never change coils on the Pickini.
The main goal of storing the calibration values was to shorten the calibration time on the next startup.

If you are looking for a SW version that always starts the successive approximation from the middle value instead of the stored value, use this version:
http://users.telenet.be/willaert/MD/...Pickini4.0.hex

Calibration time may take a little longer but it will be coil independent.

[Goaty]

The 10 Ohm resistors in the diagram R14, R24, R19 and R21 should be considered as jumpers on the single sided board and can be omitted.
@ Goaty: if you really want to make a 1 to 1 comparison with your original build, you should also program your SMD version with v4.0 or 4.1.
Which could be difficult now that the chip is soldered to the board...

Looking forward to some scope images.
My gut feeling still tells me that there is something wrong with your automatic DC offset adjustment of the opamp after startup: the circuit around Q3.
This should be reflected in your waveform. When you measure it at pin 8/9 of the PIC (TP2 in the schematic), it should look something like this:

[ATTACH]49117[/ATTACH]

The noise on this signal is mainly coming from the scope backlight converter ( together with other EMI sources in my garage... ).

The signal in this picture will give a valid sensitivity setting between 1.5 and about 4.5 V. ( = comparator slicing level to measure the flyback pulse width ).
Below and above these tresholds, you will hear the error tone ( no flyback detected at the comparator output ) - with firmware version 4.2
With firmware version 4.1, the slicing level is fixed at about 0.5V below the max flyback voltage.

When the offset is not properly adjusted, the signal may be clipped to 5V, giving a much smaller slicing level adjustment range and less sensitivity.
The closer you bring the slicing level to the top of the flyback ( the "widest" part ), the more sensitive the detector will be for small changes.
Too close => instability.

Hi Bernard


Sorry about the long time in replying but in the meantime I have completely remade the smd version on a new PCB with mostly new components (except pic). I also re-programmed another pic with V4.0 & tried it on the original pcb – all produced the same problem.


I have measured voltages and waveforms on the new board and sketched them on the attached pdf along with the scope waveform at TP2 – analogue scope set set to 2v/div vert & 1mS/div horizontal. The black voltages & waveforms are without the coil attached, the red with the coil.


I would appreciate if you could have a look at them and perhaps suggest what to try next. My feeling is that leakage in the electrolytics could be contributing but have yet to try swapping them for tantalum's. I also found that R2 (470R) had a tendency to overheat and go o/c so I replaced it with a normal 1/4W TH type



SMD Pickini.pdf

[Hammerhead]

Hi Bernard I have watched your store I liked your offer at a reasonable price I want to buy the set But I want a favor from you Is it possible to replace irf740 + pc549 And put Instead of them Potmeter with on/off switch + The aluminum capacitor is not found in my country like them And I will be grateful for your generosity

[F117]

No problem. I will get back to you on Tuesday, as I am on holiday till then.

[Arionas]

Hi Bernard I have watched your store I liked your offer at a reasonable price I want to buy the set But I want a favor from you Is it possible to replace irf740 + pc549 And put Instead of them Potmeter with on/off switch + The aluminum capacitor is not found in my country like them[ATTACH]49561[/ATTACH][ATTACH]49562[/ATTACH] And I will be grateful for your generosity

[F117]

@Hammerhead : as Arionas illustrated: the 470 microFarad electrolytic capacitor does not need to be an aluminum housing.

@Goaty --- SMD build

Your waveform looks way too "slow" - too much damped - not high frequent enough, it should be a sharp flyback pulse.
The timebase on your scope is probably 1ms / division, - and vertically 5V / div ?

Something like this:



- it could be a very slow coil ? ( unlikely )
- C10 over the opamp = 4.7 picoFarad ( NOT nanoFarad) ? You can safely remove this capacitor.
- Damping resistor = 2 x 1K in parallel ?

[Goaty]

Hi Bernard
Thanks for your response with some suggestions.


In answer to your comments -


“- it could be a very slow coil ? ( unlikely )”
This coil has worked OK with 3 or 4 other Pickinis


“- C10 over the opamp = 4.7 picoFarad ( NOT nanoFarad) ? You can safely remove this capacitor.”
I removed C10 and it made no difference. It was in fact a 5pF smd cap as I could not find my 4.7’s.
“- Damping resistor = 2 x 1K in parallel ? “
These are definitely correct.


My analogue scope was set set to 2v/div vert & 1mS/div horizontal. “0 V” was the centre horizontal axis shown in the photo. With your scope photos I am not sure where the “0V” X axis is as I am not familiar with digital scopes.


At this stage I have run out of ideas so I think I will put it aside for a while and concentrate on putting one of the other working full size boards into the new waterproof housing I have been building. If I wait too long the sea water will start to get too cold for diving. Today I took the empty housing to one of the local jettys and lowered it into about 2-3m of water for 20 min. It came up completely dry so all good so far – now to put some ‘works’ in it!


Thanks again for your help.

[F117]

@Goaty:

The waveform should be between 0V and 5V as this is the input range of the analog comparator in the microcontroller.
The waveform is taken on pin 8/9 of the microcontroller.
In my pictures: 0V is at the bottom and 1V / div.
Your waveform looks too low-frequent. It should be a sharp spike, not a slope that takes about 500 microseconds to reach steady state again.
It should also have more amplitude. That is the reason why your sensitivity control is so limited.
Not much ideas left. Coupling capacitor C9 ?
Or disconnect the analog input of the microcontroller - remove R6 = 2K2 and measure the opamp output with the scope.
Opamp = LM318 ?

[bernte_one]

Has someone a modified hex file with longer pulse width maybe set to 150?s or 200?s

but based on V4 with activated piezo output for pin7 of the pic controller
want to test bigger 1m square coil and big caps at the end stage, 3.300?f or 4.700?f

or Bernard maybe you can provide such a hex file version for a little donation

[F117]

Here you go: Pickini v4.0 with 200 microsecond pulse width:
http://users.telenet.be/willaert/MD/pickini/software/v4/Pickini4.0_200.hex

[bernte_one]

hi Bernard, you are great.

I take that hex as soon as i return to home this evening

[SaltyDog]

Hi Bernard,

Intriguing build. I would like to try the hardware, but I really need to play with the software to try an optimize for small gold detecting ..
However, I only use Linux machines for development, so am struggling to find a compiler to build your code. I came across "sdcc" but does not like your code, can you suggest anything that will help me?

I know there is now an MPLAB for linux, perhaps an mplab version of the source would be good? Or is that too much work?

Many Thanks,
Bernard (snap!) Just call me Bernie to avoid confusion

[F117]

Hi Bernie,

My laptop also runs ubuntu natively.
I had to run a Win7 virtual machine in virtualbox to use the mikroC compiler.
I also run MPlab in this Win7 VM.
At the beginning of this project, some 4 years ago, I looked for a good microchip C compiler under Linux but didn't find any. Maybe in the mean time there are some available?
You will find that the C source code relies on some mikroC specific libraries eg Delay_ms, PWM2_Init, ...
This can also be overcome by implementing your own version of it - or an equivalent from another library.
Or download mikroC: https://www.mikroe.com/mikroc-pic
https://mikroc-pro-for-pic.software.....com/download/

[Qiaozhi]

Hi Bernie,

My laptop also runs ubuntu natively.
I had to run a Win7 virtual machine in virtualbox to use the mikroC compiler.
I also run MPlab in this Win7 VM.
At the beginning of this project, some 4 years ago, I looked for a good microchip C compiler under Linux but didn't find any. Maybe in the mean time there are some available?
You will find that the C source code relies on some mikroC specific libraries eg Delay_ms, PWM2_Init, ...
This can also be overcome by implementing your own version of it - or an equivalent from another library.
Or download mikroC: https://www.mikroe.com/mikroc-pic
https://mikroc-pro-for-pic.software.....com/download/

I have mikroC Pro for PIC (Version 7.6.0) on a Dell Latitude 5500 (with Windows 10) that's also used to to run MPLAB X IPE(Version 5.30), and Easy-PC (Version 23).
However, everything else such as emails, web browsing, LTSpice simulation, word processing, etc., is done on another laptop running Linux Mint (Version 18.1 Cinnamon).

There's a video on youtube where someone demonstrates mikroC Pro and Proteus software running in Ubuntu. There's no information about how this was achieved, so I assume it's running under WINE.

[waltr]

Hi Bernard,

Intriguing build. I would like to try the hardware, but I really need to play with the software to try an optimize for small gold detecting ..
However, I only use Linux machines for development, so am struggling to find a compiler to build your code. I came across "sdcc" but does not like your code, can you suggest anything that will help me?

I know there is now an MPLAB for linux, perhaps an mplab version of the source would be good? Or is that too much work?

Many Thanks,
Bernard (snap!) Just call me Bernie to avoid confusion

For PIC programming there is MPLAB X that will run on Windows, MAC and Linux.
https://www.microchip.com/mplab/mplab-x-ide

There is also the newer XC8,16 & 32 compilers for MPLAB X that are GCC based.
https://www.microchip.com/mplab/compilers

I have been running these Free versions for a while and they do work well.

MPLAB is old and only for windows.