PICKINI - an easy to build PI detector

[F117]

Hi Mike,
I programmed a V2 board with the file that is available on my website and did some more tests.
First: a picture of the test setup:


Close up of the board
There is a jumper underneath the big elco !!




The only difference with the layout on the website is that the damping resistor across the coil is a single 470E resistor instead of 2x1K parallel.

I also measured some values:

Resistance across the coil connections - no coil attached and unit switched off: 461 Ohm.

DC voltages:
L1: 11.97 VDC
L2: 11.94 VDC

Opamp:

pin 1: 9.46 VDC - pin 5: 9.46 VDC
pin 2: 7.98 VDC - pin 6: 8.65 VDC
pin 3: 7.98VDC - pin 7: 11.90 VDC
pin 4: 0 VDC - pin 8: 1.39 VDC


Microcontroller: -- with sensitivity potmeter almost at minimum

pin 1: 5.06 VDC - pin 14: 0 VDC
pin 2: 0 VDC - pin 13: 0.41 VDC
pin 3: 0 VDC - pin 12 : 2.90 VDC
pin 4: 5.05 VDC - pin 11: 0 VDC
pin 5: 4.96VDC - pin 10: 0-5VDC tick
pin 6: 0VDC - pin 9: 4.32VDC
pin 7: 0VDC - pin 8: 4.32VDC

Hope this helps.
Again: inside the house with an unshielded coil like the one in the test setup, I can only turn up the sensitivity very little.
It's only on the beach that the sensitivity can be cranked up without disturbances.

Best regards,
- Bernard

[mikejr0046]

Got them both to work but I don't why. Well #1, I checked the coil ohms only 220 pulled the resistors both were 1k??? Replaced the two diodes and the two resistors hooked it back up it started to tone again went with the meter to check voltage when I hit # 10 the meter was 0 to 5 and the tone stopped.Fixed. Number 2 coil ohms ok, touching bottom of opamp it went dead. Some where along the way it seems I killed the 316 I had a TLO71 & 81 still had the tone replaced 2 caps by the opamp no luck. I had ordered 16f616 but the only crystal I had was a16mhz from arduino projects, put it in, programed the pic still the tone. I had a LM301 in my collection of stuff did not know what it was to lazy or mad to look it up lets let the smoke out. Put it in, turned it on, got the tone again started with the meter again hit #10 again tone gone. They both must have known the hammer was about to fall. Thanks for all your help and patience. Mike in MN.

[F117]

I had ordered 16f616 but the only crystal I had was a16mhz from arduino projects

to get the timing right: the Xtal with a 16F616 should really be 20MHz. It may work with a 16 MHz Xtal, but the resolution will drop, the pulse width will be longer than 100 uS, the pulse frequency will be slower and the audio tone will be lower...

Some where along the way it seems I killed the 316 I had a TLO71 & 81

The only other opamp I tried besides the LM318 is a CA3140, which gives a rail-to-rail signal output. For the application here we don't really need this feature.
Anyway, glad to here there is some progress.

One other thing you may try to deal with coil parameters that are different:
- place the coil well away from any metal on a stable surface (so that it doesn't move)
- turn the unit on, with the sensitivity potmeter at minimum
- if the detection tone does not stop: slightly turn the 8V adjustment trimmer in one or the other direction.
- If this doesn't make a difference, return it to 8.0V

Best regards,
- Bernard

[Schatztaucher]

"finished" now i have to make some tests with different coils before i make a video.....

[F117]

Nice work ! Looking a lot better than the builds I did so far, but then again, my mechanical skills are limited...
Best regards,
- Bernard

[Schatztaucher]

thanks bernard! and also thanks for your excellent project!

[mikejr0046]

Bernard this is the one with the 16f616. Seems to work OK waiting for the snow to melt. Tens minutes after I made the video it started to snow again. Put the video on youtube,first time hope I can link it.

[F117]

Hi Mike,

Great build and nice video
Some good design features too:
- switch between pinpointer coil and search coil
- separate, removable battery pack - you can take a spare one in your backpack

Hopefully spring will kick in soon and get rid of the snow.

Best regards,
- Bernard

[johnandles]

My build so far..
Pic has been programmed.
About to power up before inserting Ic's.
Check power supply etc
Cheer John

[WM6]

Excellent project Bernard, thank you.
Congratulations to all builders on finalisation, especially Schatzsucher on his great work.

Bernard, can you say something about power consumption?

[F117]

Bernard, can you say something about power consumption?

@WM6: Thank you, Please have a look here: http://users.telenet.be/willaert/MD/...technical.html
90 - 130 mA depending on the sensitivity potmeter setting. The pulse frequency changes with the sensitivity setting -> current consumption changes.

@john: looking good
The 100 nF ceramic decoupling capacitors look smaller than the housings I am used to, but if they have the correct value, go ahead !
It just surprises me that there is not much difference between the 4p7 feedback capacitor housing and the decoupling capacitors...
Just make sure it's not 100pf instead of 100nf !

One other tip: you can use the wire jumper that is located underneath the large elco at the coil side to secure the capacitor to the board by routing the jumper over the capacitor housing

Best regards,
- Bernard

[johnandles]

@john: looking good
The 100 nF ceramic decoupling capacitors look smaller than the housings I am used to, but if they have the correct value, go ahead !
It just surprises me that there is not much difference between the 4p7 feedback capacitor housing and the decoupling capacitors...
Just make sure it's not 100pf instead of 100nf !

One other tip: you can use the wire jumper that is located underneath the large elco at the coil side to secure the capacitor to the board by routing the jumper over the capacitor housing

Hi Bernard, the caps 100pf have a 104 stamped on them.
The 4p7 has 4.7.
I didn't put them through my cap meter,but I will ..just in case.
I also substituted the electros C9 and C7 for Tantalum..that's what I had in my parts box,
It also seems in line with Blind squirrel.
I used hot melt glue to hold the larger caps
Best regards,
Thanks for your reply
Regards
John

[F117]

Hi Bernard, the caps 100pf have a 104 stamped on them.

104 = 100000pF = 100nF

[WM6]

104 = 100000pF = 100nF

yes, in other words:

104 = 10 + 4x0 = 10+0000 = 100000 pF

this way:

103 = 10 + 3x0 = 10+000 = 10000 pF

102 = 10 + 2x0 = 10+00 = 1000 pF


F117 thanks for info about consumption - it is very acceptable.

[F117]

Some evolutionary pictures of my latest build - elbow crutch + low-cost carbon fishing rod - combined with spray paint experiments on camo patterns.
The outcome is a "dune snake" pattern - although I've never seen a snake in the dunes...


Have fun,
- Bernard