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

[F117]

pickini v4 deferences with v1and2 and v3 is only in the hex file?and pcb and parts of v4 is the same as v1and2 and v3

Pickini V1 and V2 have the same PCB
V3 and V4 have a different PCB and different Microchip controller.

All 4 are based on the principle of temporal sampling, aka pulse-width measurement. As opposed to voltage sampling like all other classic PI detectors.

If you build one, try this V4.
This is the best one so far because it auto-adjusts itself after power-on.
The others require a manual adjustment of the opamp DC offset.

[mohammadreza1100]

Thank u bernard.what microchip can we use for replacement of 16f1824?

[F117]

what microchip can we use for replacement of 16f1824

Why not order this one ?
The source code is available and when you look into it, you will notice that many specific resources of this controller are used:
- internal oscillator
- timers
- EEPROM
- ADC
- DAC
- comparator
- PWM
-...
You could probably use its bigger brother the 16F1825, if that is an option at all.

[bernte_one]

you can find more Infos for diy coil housing from dfbowers here in Forum
the Shells are made of Polystyrol or abs plastic 1mm-2mm
all you Need is a Little box, a vacuum claner, a heater and a holder fram for the plastic Sheets

as postive form i used a coil Shell i ordered from bulgaria, fill it with epoxi, cut off the sidearms
thats all

in that way you can copy all coil forms, you dont Need to coil coil Forum by yourself from Wood
i tried often but my Wood cutting skills are not good

[nick holas]

hi all
hi bernard
hi bernte
i catch the virus too!!!!!
but i m cheater ,i ve made some mod on capacitor because i fed up waiting for aliexpress smd capacitor GRRRRRRR!!!
so now it s not 100% smd (maybe close to 70%! LOL)
look at my pcb ,on the left its a bikini to illustrate the detector (isn t it bernard???)

[bernte_one]

nice, but pay attention you have some broken tracks too
(i have problems with photo method my exposure was 30 sec to short and the etchant for the photo laquer was too strong)

just solder a wire on this places, for this it ake the cut off wires from normal resistor or the legs of To92 part

[F117]

@Nick: nice PCB with nice logo .
Looking forward to seeing it stuffed and working.

[mohammadreza1100]

Hi bernard.in my country there is no pic16f1824 avalaible.please help me what another micro i can use?pls tell me the micro numbers
Thanks a lot.

[württemberger]

https://www.aliexpress.com/store/328744

[bernte_one]

Hello Bernard,

can we improove the Performance from pickini
if we use the lm318 as dual stage amp ?

i made this simple mod at another pi detector and it results in 1/3 more sens to coin sized objects
i am not sure but i thhink the lm318 would work better as dual stage and with two additionel trimmers for Offset voltage
maybe i think wrong way

may somebody can try this ( with pickup pcb or so)

look at this dual op amp configuration
http://www.geotech1.com/forums/attac...chmentid=23505

[F117]

I have no idea if this dual opamp stage will lead to more sensitivity with temporal sampling - as opposed to voltage sampling.

I now start by adjusting the DC level of the amplified flyback pulse measured 200micros after the pulse with the onboard 10bit ADC -- this is about where you would sample the voltage normally.
With successive approximationof the opamp DC offset, the output level is set to about 3.5 V.
I then apply the slice level for the comparator about 0.5V lower than this voltage.
The DC offset of the opamp is regulated with the onboard 8bit DAC. The slice level is obtained by filtering the PWM output.
For more sensitivity with temporal sampling, we can accumulate multiple samples taken over time.
With a single sample voltage detector, the only way to gain sensitivity is by increasing the gain ( I think, not being an analog expert ).
A couple of years ago, I tried the schematic you refer to with an LM358 and never got it to work properly. I was looking for a complete DC coupled front end that could be easily adjusted with a single 0-5V DC voltage.

With Pickini V4, the main disadvantage of the AC coupling is that each adjustment step on the DC offset voltage needs some time (2-3s) for the opamp output to settle again.

My personal wet dream is a single chip ( PIC) PI detector, with a direct coupled logic gate FET switching the coil, and using the internal PIC comparator as opamp. There are PICs who have onboard opamps but I think they are not fast enough for this application..

- Bernard

[mohammadreza1100]

Hello bernard.i build the v4.pls say the value of sensitivity potentiometer and what is the usage of tp1 and tp2 and tp3?
Thank u.

[F117]

The sensitiviy potmeter is typically 4K7.
I used one with built-in on/off switch, but you can implement separate potmeter and switch if you like.
The value is not so critical, it may also be 10K. You just need to apply a sensitivity voltage between 0-5V at the input of the PIC.

The tp.. points in the schematic are test pins.
tp1: flyback pulse at the output of the internal comparator ( digital pulse that will change width when targets are applied)
tp2: amplified flyback pulse going into the PIC
tp3: ground -- to attach an oscilloscope or multimeter ground clamp
You don't need to stuff any pieces of bare wire into these PCB holes if you are not going to use them. I use them for debugging.

[mohammadreza1100]

Hello bernard again.i buy the pickit 2 programmer.but the software did not support pic16f1824.when i check i found there is no puc16f2824 in the micro list.how i can update the micro list?
Best regard

[nick holas]

hi all
hi bernard
hi bernte
hi mohammadreza1100 you have to put in PICkit 2 v2.61 software the pic16f1824 in his list (you have to replace/add one file in the soft) so the soft can recognize pic16f1824 (i found the tuto in a forum .google it, it ll be easy)

bernard look what microchip has send to me today!!!!!!!!! (foto!!pic16f628 and pic16f1824) its very cool to them ,no?
now just need lm318 smd and ......... power!!!

my pickini in DIP version don t work very good suddenly !!!!! once on tree it gives me false sound for coil and not very good deph(air test)!!!!! +/-10cm for 2€ ( will try to make some test later)