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

[Goaty]

Bernt,
you can connect a LED directly to pin 7 of the controller. This was added as described in post #291.
This is a simple on/off detection indicator. You can attach an extra transistor here to drive more powerful LEDs - or a powerful buzzer ( to be heard underwater, even without headphones . When you attach the buzzer to the housing, the noise can be heard underwater).
A single hi-bright LED can be connected directly to the pin via a 470E resistor.

- Bernard

Hi Bernard
I would appreciate if you could provide further details on this - ie driver transistor circuit and piezo buzzer type.
I am in the process of modifying my snorkelling Pickini to add audio as I am finding the LED on the housing difficult to watch as well as swinging the coil underwater.
Thanks
Goaty

[F117]

Pin 7 of the PIC is a static detection pin: high (5V) = target / low (0V) = no target.
You can attach a buzzer/beeper with an extra transistor to the 12 V rail or in an identical way to the 5V rail.
The NPN transistor is not critical.
The resistor value can be 2K2 ... 10K (or more).

Something like this:



I connected a beeper once like this inside the housing for a dive version.
But when testing it in the 15 m dive tank, it kept beeping from the surface to the bottom because the tank itself is made of steel.
This was so annoying for other divers in the tank - it was really loud ! - that I removed it again and replaced with a cheap but bright flashlight that is pointed towards the coil through the transparent housing.
It lights up when a target is detected. Connected in the same way as attached image.

See also http://www.geotech1.com/forums/showt...708#post229708

[Goaty]

Thanks for the info Bernard.

The circuit diagram is just what I needed - When I get the piezo buzzers I ordered I will check their current draw and find a suitable transistor to handle it.
I will be getting 95dB piezos and hope these will be loud enough as I have to use earplugs when swimming/surfing nowadays due to chronic 'surfers ear'. Not sure what the medical term for this is but it is boney growths in the ear canals which are now almost totally blocked. I guess scuba divers could also suffer from this, especially in cold water.

I have been experimenting with getting sound out of my PVC pipe waterproof detector enclosure using a 105dB driver from a security alarm piezo 'screamer'. It is very loud but is two tone which is not really suitable for detecting. I have simply bonded the piezo disk onto the inside of the 2" PVC pipe cap using epoxy and the results seem promising.

BTW, I have had a hand in building 4 Pickinis to date. Two for myself (1 terrestrial and one diving) and another two with friends as their introduction to metal detectors. All have worked perfectly first up which is a testament to your design, so thank you.

Goaty

[nonkapo]

Dear Bernard,
Do you mind sharing info on the exact box model you use(basetech) as when going to the web site I get totally lost. Did not see info about the size either, probably cause the boxes are designed for particular phone/device. Thanks.

[F117]

It is Basetech 1310189. When you google it, you will find it on different websites
Not sure if "Basetech" is even the name of the manufacturer.
I bought it in Belgium at Conrad -- also available in Germany: https://www.conrad.de/de/werkzeugkas...e-1310189.html

http://www.produktinfo.conrad.com/da...r_nl_it_pl.pdf

[F117]

PICKINI V4 SHOP

You can now buy 2 items in the Pickini shop:

http://users.telenet.be/willaert/MD/...n/V4/shop.html

A programmed microcontroller:




A semi-kit consisting of PCB + all semiconductors, including the programmed microcontroller




This way, the microcontroller should be available to everyone.

- Bernard

[MartyJ1963]

Hiya Bernard,,,,Can you tell me what R21 is for on your new Revision - Pickini 2?,,,the 100k pot? Thanks. Regards,,,Marty

[F117]

Marty,

Pickini V2 is very old. The 100k pot is to set up the DC offset of the opamp and should be adjusted to 8 V.

With Pickini V4, this is adjusted automatically at startup.
Why would you like to build V2 ?

Regards,
- Bernard

[kosacid]

I have tried a few coils on this but I don't seem to be getting good depth only on large stuff I'm using a 8" coil, also any hints on making it more sensitive maybe a bit chatter, I can compile the c so is there a section I can try to make it sensitive, or make a coil that is better for this detector, I don't seem to get the results that others are getting, also dampening will that help ?

[F117]

There is some good info from Marty on the basket coil he used http://www.geotech1.com/forums/showt...870#post248870
And here is the coil I normally use - slightly larger than 8" http://users.telenet.be/willaert/MD/...n/V3/coil.html

The main difference is that the basket coil is a fast coil - very short flyback pulse - that is better for detecting gold. As Marty proved with his gold ring find.

In the software, you can decrease the value of DC_OFFSET_MARGIN that is now around 1V - that is the DC slicing level - volts below the steady state DC value of the flyback pulse.
If you make this value too small, you will get continuous chatter.
Do not use/test the detector indoors. This gives you a false impression of instability. Take it outside to test.
As for dampening: you could play with the 2 x 1K resistors in parallel. Never tried this as they seem to give good results on a "generic" 330 microHenry coil.

[MartyJ1963]

Hiya Bernard,,,I think I got a bit confused,,lol,,,I had a look on your website when you posted that you were selling 'Semi' kits because a few friends of mine were wanting a small, light weight detector with good sensitivity. They live on the other side of England from me so I recommended they build the Pickini. I'd never seen that 'Older' PCB (Pickini2) before so I thought it was a new version. Can you tell me where abouts on the Pickini 4 I would place the Oscope probes to check the Damping resistor please?,,I've not had any issues yet regarding the coils I use for the Pickini, but recently I made a better coil (8") that is more sensitive than the 300uh I use for it. It's a 3dss/260uh/16 strand wire - it's giving me nearly 14 inch depth on a the same ring I found with the Pickini 4 last year. I wanted to compare the the signals between what the 300uh give me and the new coil. P.S-Thanks for posting how to add the 'Vibration motor', my sister is totally deaf so I'm hoping she'll benefit from this. Thanks again Bernard. Regards,,,Marty

[MartyJ1963]

Hi again Bernard,,,,Regarding the 'Battery charger' circuit on your webpage, can I charge a 12v (3 x 18650 cells) battery pack with it? Thanks again. Marty

[F117]

Marty,
you can check the flyback signal at TP2 = pin8 and 9 of the microcontroller.
When you lower the damping = higher resistor value, you should see some ringing at the end of the flyback slope, when returning to steady state.
Make sure you divide the power over 2 1/4 W resistors in parallel - or a single 1/2 W resistor.
E.g. 2x 1K2 in parallel would give you 600 ohms instead of the 500 now.

Regards,
- Bernard

[kosacid]

probe pin 6 on op amp or diodes or the coil on x10

[MartyJ1963]

Hi Bernard,,,Thanks for info,,,,Can I use your Battery charger circuit to charge a 3x18650 cell 12v battery pack? Thanks again. Marty