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

[F117]

@666:
library: con-wago-508
device ( 3 pins) : W237-3E
device ( 2 pins) : W237-02P

[6666]

@666:
library: con-wago-508
device ( 3 pins) : W237-3E
device ( 2 pins) : W237-02P

Thanks

[F117]

@moorejl57:
Earth Field Effect in voltage sampling is countermeasured by taking 2 samples - one much later than the other and subtracting the 2 samples.
With pulse width measurement, there is only 1 sample.
In this design, the samples are accumulated and go through a low pass filter = running average.
Both the number of accumulated samples and the running average array size are influenced by the sensitivity setting.
The source code is available here if you are interested or have any tips to improve it : http://users.telenet.be/willaert/MD/.../v4/Pickini4.c

[filos]

Is it possible to increase the power of your device ..

[F117]

@ filos

To increase "the power" you probably mean: apply a longer pulse to the FET ?
At the moment this is fixed to 100 microseconds.
If you can build the source code for the PIC yourself, it should be obvious to change this setting:

#define TX_PULSE_WIDTH 100 // TX pulse width in microseconds

The only time I increased this to 200 microseconds was for a 1m x 1m square coil to detect WW1 unexploded ordnance here in Flanders Fields.
These grenades are typically 30-50 cm long and 10-20 cm diameter iron shell that can easily be detected well over 1 m in depth, resulting in a lot of digging. Well... I detect and mark suspicious targets and other people do the digging. There are still thousands - nobody knows exactly how many - of these things buried here.
Increasing the pulse width to 200 microseconds instead of 100 also doubles the current consumption.

Here is the square coil setup - on plastic wheels from a small child bicycle - and some "treasures" retrieved with it ...



Control box - hip mounted with 12V Li Ion battery mounted under the PCB:
The pinpoint pushbutton was replaced by a switch because I needed both hands to pull the cart.



Some finds - a large grenade + unexploded detonator:



A nice collection of finds from a piece of farmland that was going to be plowed for the very first time in 100 years.
It used to be a pasture for cows. As a farmer, you don't want the plow to run over the detonator of one of these :



In my experience: increasing the power results in a lot of deep digging - and a lot of back ache in the end.
A soda can burried on the beach gives a clear signal on 1m depth with the standard settings ( depending on your coil of course ).
So, - no thanks - I don't need more power...

[filos]

If pi pulse width is 100 ms. , a little golden thing, sees your device 8-10cm. then with a width of 250ms. will see 10-15cm.

[sinclairuser]

If pi pulse width is 100 ms. , a little golden thing, sees your device 8-10cm. then with a width of 250ms. will see 10-15cm.

oh filos, if only it was that simple.

[waltr]

If pi pulse width is 100 ms. , a little golden thing, sees your device 8-10cm. then with a width of 250ms. will see 10-15cm.

Do you mean us (micro second) not milli-second?

oh filos, if only it was that simple.

Correct. Also for low TC targets increasing the TX pulse time does NOT increase the target response. Small gold object have low (short) TCs and a 50us pulse will fully excite them.
On the other hand, long TC objects will give a larger response with longer TX pulse. Silver coins, for example, respond best with a >200us pulse.

[sinclairuser]

hi all i'm currently tinkering around with the pickini, in my cap stash i have 3300uf 50v elcos, 3300uf 25v and 2200uf 16v,
but not 2200uf 25v, so what do you all think should i use 3300 25v or2200 16v?.
normally i would use the 3300uf at 25v, instead of 2200uf 16v better to use a slightly bigger cap than a lower voltage version.
but reading through the thread turn on inrush current can be a problem here, will the extra capacitance be a problem, or will a 16v 2200uf cap be ok?.
thanks,
aly.

[F117]

16V is a little low with a 12V supply. I would use the 3300 uF / 35V.
Inrush current will be larger, but as long as you use a solid mechanical on/off switch or something similar combined with the sensitiivity potmeter, this should not be a problem.
The only time I experienced this as an issue was with a reed relay as on/off switch. After one cycle, the contacts were welded solid.

[sinclairuser]

thanks bernard.

[bernte_one]

nice finds, in germany some people do big fireworks for sylvester from that stuff

[dbanner]

hi all i'm currently tinkering around with the pickini, in my cap stash i have 3300uf 50v elcos, 3300uf 25v and 2200uf 16v,
but not 2200uf 25v, so what do you all think should i use 3300 25v or2200 16v?.
normally i would use the 3300uf at 25v, instead of 2200uf 16v better to use a slightly bigger cap than a lower voltage version.
but reading through the thread turn on inrush current can be a problem here, will the extra capacitance be a problem, or will a 16v 2200uf cap be ok?.
thanks,
aly.

There is a little circuit(about 5 components) which provides a soft start upon switch on. Maybe it will be good for use here or for some other circuit. It slowly charges the capacitor thus limiting inrush current. If used in conjunction with regulator....well have a look:

[F117]

Another option to limit the inrush current passively is an NTC thermistor between the battery and the circuit.
At startup = normal temperature ( 25 C) it has a relatively high resistance to limit the inrush current and as current is flowing through it, resistance will decrease.
As described here e.g. : http://www.farnell.com/datasheets/18...SAAEgJgHPD_BwE

[sinclairuser]

There is a little circuit(about 5 components) which provides a soft start upon switch on. Maybe it will be good for use here or for some other circuit. It slowly charges the capacitor thus limiting inrush current. If used in conjunction with regulator....well have a look:

thanks DB,

thanks bernard,

aly.