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

[bernte_one]

ah ok thanks for showing

yesterday i try my pickini v4, i have seen that the last Firmware was already installed
work very good with high / low led indicator

if i install a vibro Motor into the stem grip it woul be a good silent and non visible Option for very secret threasure hunting

[nick holas]

hi bernte
hi F117
hi all
sorry for my long time answer (saddly lot of things change in my life, perhaps for better life?)
i haven t finished my smd pikini (lm318 still awaiting,smd capacitor too!!!!)
bernard your underwater pikini is fantastic!!!! maybe one day i ll make one or adapt smd pikini for underwater summer beach hunting
i ve finished an other PI MD witch look simple and promising but it don t work and don t have time and mind now to make it work so i m still awaiting too!!!!
have nice day

[reptooyep]

Hi,
I just come back to the project after few month (my daughter was born four month ago).
I made the through hole version with the latest firmware. It works pretty fine with my 3dss coil.
The board is too big to fit my waterproof pressurised enclosure so, i planned to make my own SMD version.
The problem is that i get a VERY bad sensitivity with SMD and i don't know why.
I've noticed that the 470ohms resistor next to the two diodes burn with 1/8 W SMD resistors, you need to put 1/4 TH resistor.
Where can i increase the sensitivity ? I tryed modifying the resistor bridge before the PIC input without success.
Thanks for help

[F117]

The damping resistor = 1K||1K = 470 ohm should be 2x 1/4 W in parallel or 470 ohm 1/2 W.

Sensitivity: does the sensitivity input from the potmeter work? 0V = minimum sensitivity - 5V = maximum senitivity ( in reality to be used on deserted beaches only ). A realistic value is around 1 - 3 V to test around the house.
Do NOT modify the resistive 1/2 divider!
Check the sensitivity input first. If this is for an underwater detector, you can set it to fixed value of around 2 V ( 3k3 + 2k2 between 5V and Gnd e.g. ). This way you don't have to make a hole for the potmeter in your housing and seal the potmeter,... Unless of course you know how to do this fool-proof ( or water-proof in this case ).

[reptooyep]

I took off the damping 1K resistor and replaced them by a 1/2W TH 390ohms one and the sensitivity is just perfect.
I also replaced the pot. by two resistors (55k - 33k) so, no problem with that.
I put a magnetic switch inside the case and when i turn it on, it does not want to turn off without the magnet. The switch is not made to drain 4V/55mA (measured in working order).
I want to make a switching circuit with a transistor but i don't know how to choose it, exept with the current value. Could a silicon NPN do the job ?

[F117]

I had the same experience with a light reed switch, intended to turn the detector on and off with an external magnet.
The inrush current from the batteries is too high.
The switch contacts are instantly welded together and the detector will never turn off again - after removing the magnet.

I had better results with a small 5V relay and a small but powerful neodymium magnet. When held close ( thickness of the housing) to the relay contacts, they make contact.
However, a more powerful reed relay should do this job better.

Your solution with the switching transistor looks OK to me, but I would still add a resistor from base to ground in the case of this NPN transistor. Also, I would put the load ( the detector ) at the collector side. Typically a PNP transistor is used with emitter at the battery plus, a pull up resistor from base to emitter and a pull down resistor in series with the magnetic switch to ground. When the switch is open, the base is pulled up to the emitter voltage and the transistor shuts down. The load would then be between collector and ground.

No idea if the remaining current, when the transistor is open, will drain the battery...

I am sure that people on this forum have better solutions than this. My best guess here is a reed relay that can handle the large rush-in current...

As you can see from previous pictures of my underwater version, I ended up placing the potmeter/switch combination inside the housing. This implies that you have to open it up and switch it on + set the sensitivity before each use.

Success !
- Bernard

[reptooyep]

Hi Bernard,
Your advices are great. I found an old relay i 've disassembled it to keep only the contacts and i've glued a small hard disc magnet piece on it.
On the case, i've glued a piece of electrical plastic trunk with another hard disc magnet and it works just fine.
I've added a QI charging unit and now, the last thing to do is the rod..
Thanks for help, i realy appreciate.

[reptooyep]

[F117]

Hi reptooyep,
Your setup looks very interesting!
Is that an inductive charger ?
Can you give some more info on these other parts?

[reptooyep]

Hi,
I've experimented inductive charger with a collpits oscillator and a 10 turns coil few month ago without good results.
I bought those QI charger on ebay for few $.
My setup is :
QI charger + charging circuit board, 4400mah liion 3,7v, dc to dc converter board.
I replace the input capacitor by a 4700uF cause the 12v output of the dc to dc board is too noisy.
Now, it's sealed for a long time.
Results in salt water will come this summer.i'll test it in the forest to find some beer caps ��

[F117]

Interesting battery / charger configuration.

My ultimate goal would be to re-use the search coil as charging receiver coil. Just flip a switch to connect the coil to the charger unit and place it on top of the base plate overnight ...

Correct me if I'm wrong:
On your picture, I can further identify the sliding magnet on this plastic side rail that switches the detector on/off. Nice !

What is the blue handle-like thing ?

Do you have a headphone connection ?

[reptooyep]

Good idea but not simple to manage. The emmiter charging coil must be the same size, you'll have to diy.
The blue thing is a wheel valve to pressurise the case.

[reptooyep]

I forgot to tell you about a problem with induction charger :
The emmiter and receiver coils must me at 3mm maximum.
I put an epoxy layer on my receiver coil and i must take off the transmitter case to make it work.
This wilm be a problem if using your detecting coil. The housing is too thick to work properly.

[ripsdevala]

Hi,
I've experimented inductive charger with a collpits oscillator and a 10 turns coil few month ago without good results.
I bought those QI charger on ebay for few $.
My setup is :
QI charger + charging circuit board, 4400mah liion 3,7v, dc to dc converter board.
I replace the input capacitor by a 4700uF cause the 12v output of the dc to dc board is too noisy.
Now, it's sealed for a long time.
Results in salt water will come this summer.i'll test it in the forest to find some beer caps ��

Good day repto, its been a while,
Im interesting with 4700uf caps trick, i use standart dc to dc converter to make 12v, what caps should i change, can i have a photo.

Thanks

[reptooyep]

Hi,
You're right, it's been a while but i'm a father for the 2nd time since 4 month.
The 4700 cap should replace the c2 before the 5v reg.
But you can put it wherever you want between 12v and GND.
Those dc to dc boards are pretty convenient and cheap. Viva China !!!
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